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Wang Y, Liang P, Lan F, Wu H, Lisowski L, Gu M, Hu S, Kay MA, Urnov FD, Shinnawi R, Gold JD, Gepstein L, Wu JC. Genome editing of isogenic human induced pluripotent stem cells recapitulates long QT phenotype for drug testing. J Am Coll Cardiol 2014; 64:451-9. [PMID: 25082577 DOI: 10.1016/j.jacc.2014.04.057] [Citation(s) in RCA: 118] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Revised: 04/07/2014] [Accepted: 04/30/2014] [Indexed: 12/22/2022]
Abstract
BACKGROUND Human induced pluripotent stem cells (iPSCs) play an important role in disease modeling and drug testing. However, the current methods are time-consuming and lack an isogenic control. OBJECTIVES This study sought to establish an efficient technology to generate human PSC-based disease models with isogenic control. METHODS The ion channel genes KCNQ1 and KCNH2 with dominant negative mutations causing long QT syndrome types 1 and 2, respectively, were stably integrated into a safe harbor AAVS1 locus using zinc finger nuclease technology. RESULTS Patch-clamp recording revealed that the edited iPSC-derived cardiomyocytes (iPSC-CMs) displayed characteristic long QT syndrome phenotype and significant prolongation of the action potential duration compared with the unedited control cells. Finally, addition of nifedipine (L-type calcium channel blocker) or pinacidil (KATP-channel opener) shortened the action potential duration of iPSC-CMs, confirming the validity of isogenic iPSC lines for drug testing in the future. CONCLUSIONS Our study demonstrates that iPSC-CM-based disease models can be rapidly generated by overexpression of dominant negative gene mutants.
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Affiliation(s)
- Yongming Wang
- Department of Medicine, Division of Cardiology, Stanford University School of Medicine, Stanford, California; Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, California; State Key Laboratory of Genetic Engineering, Fudan University, Shanghai, China
| | - Ping Liang
- Department of Medicine, Division of Cardiology, Stanford University School of Medicine, Stanford, California; Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, California; Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, California
| | - Feng Lan
- Department of Medicine, Division of Cardiology, Stanford University School of Medicine, Stanford, California; Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, California; Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, California
| | - Haodi Wu
- Department of Medicine, Division of Cardiology, Stanford University School of Medicine, Stanford, California; Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, California; Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, California
| | - Leszek Lisowski
- Departments of Pediatrics and Genetics, Stanford University School of Medicine, Stanford, California
| | - Mingxia Gu
- Department of Medicine, Division of Cardiology, Stanford University School of Medicine, Stanford, California; Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, California; Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, California
| | - Shijun Hu
- Department of Medicine, Division of Cardiology, Stanford University School of Medicine, Stanford, California; Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, California; Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, California
| | - Mark A Kay
- Departments of Pediatrics and Genetics, Stanford University School of Medicine, Stanford, California
| | | | - Rami Shinnawi
- Rambam Medical Center, Technion, Israel Institute of Technology, Haifa, Israel
| | - Joseph D Gold
- Department of Medicine, Division of Cardiology, Stanford University School of Medicine, Stanford, California; Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, California
| | - Lior Gepstein
- Rambam Medical Center, Technion, Israel Institute of Technology, Haifa, Israel
| | - Joseph C Wu
- Department of Medicine, Division of Cardiology, Stanford University School of Medicine, Stanford, California; Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, California; Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, California.
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Moshal KS, Zhang Z, Roder K, Kim TY, Cooper L, Patedakis Litvinov B, Lu Y, Reddy V, Terentyev D, Choi BR, Koren G. Progesterone modulates SERCA2a expression and function in rabbit cardiomyocytes. Am J Physiol Cell Physiol 2014; 307:C1050-7. [PMID: 25252951 DOI: 10.1152/ajpcell.00127.2014] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
We recently showed that progesterone treatment abolished arrhythmias and sudden cardiac death in a transgenic rabbit model of long QT syndrome type 2 (LQT2). Moreover, levels of cardiac sarco(endo)plasmic reticulum Ca(2+)-ATPase type 2a (SERCA2a) were upregulated in LQT2 heart extracts. We hypothesized that progesterone treatment upregulated SERCA2a expression, thereby reducing Ca(2+)-dependent arrhythmias in LQT2 rabbits. We therefore investigated the effect of progesterone on SERCA2a regulation in isolated cardiomyocytes. Cardiomyocytes from neonatal (3- to 5-day-old) rabbits were isolated, cultured, and treated with progesterone and other pharmacological agents. Immunoblotting was performed on total cell lysates and sarcoplasmic reticulum-enriched membrane fractions for protein abundance, and mRNA transcripts were quantified using real-time PCR. The effect of progesterone on baseline Ca(2+) transients and Ca(2+) clearance was determined using digital imaging. Progesterone treatment increased the total pool of SERCA2a protein by slowing its degradation. Using various pharmacological inhibitors of degradation pathways, we showed that progesterone-associated degradation of SERCA2a involves ubiquitination, and progesterone significantly decreases the levels of ubiquitin-tagged SERCA2a polypeptides. Our digital imaging data revealed that progesterone significantly shortened the decay and duration of Ca(2+) transients. Progesterone treatment increases protein levels and activity of SERCA2a. Progesterone stabilizes SERCA2a, in part, by decreasing the ubiquitination level of SERCA2a polypeptides.
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Affiliation(s)
- Karni S Moshal
- Cardiovascular Research Center, Division of Cardiology, Department of Medicine, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island
| | - Zhe Zhang
- Cardiovascular Research Center, Division of Cardiology, Department of Medicine, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island
| | - Karim Roder
- Cardiovascular Research Center, Division of Cardiology, Department of Medicine, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island
| | - Tae Yun Kim
- Cardiovascular Research Center, Division of Cardiology, Department of Medicine, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island
| | - Leroy Cooper
- Cardiovascular Research Center, Division of Cardiology, Department of Medicine, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island
| | - Bogdan Patedakis Litvinov
- Cardiovascular Research Center, Division of Cardiology, Department of Medicine, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island
| | - Yichun Lu
- Cardiovascular Research Center, Division of Cardiology, Department of Medicine, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island
| | - Vishal Reddy
- Cardiovascular Research Center, Division of Cardiology, Department of Medicine, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island
| | - Dmitry Terentyev
- Cardiovascular Research Center, Division of Cardiology, Department of Medicine, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island
| | - Bum-Rak Choi
- Cardiovascular Research Center, Division of Cardiology, Department of Medicine, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island
| | - Gideon Koren
- Cardiovascular Research Center, Division of Cardiology, Department of Medicine, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island
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403
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Terentyev D, Rees CM, Li W, Cooper LL, Jindal HK, Peng X, Lu Y, Terentyeva R, Odening KE, Daley J, Bist K, Choi BR, Karma A, Koren G. Hyperphosphorylation of RyRs underlies triggered activity in transgenic rabbit model of LQT2 syndrome. Circ Res 2014; 115:919-28. [PMID: 25249569 DOI: 10.1161/circresaha.115.305146] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
RATIONALE Loss-of-function mutations in human ether go-go (HERG) potassium channels underlie long QT syndrome type 2 (LQT2) and are associated with fatal ventricular tachyarrhythmia. Previously, most studies focused on plasma membrane-related pathways involved in arrhythmogenesis in long QT syndrome, whereas proarrhythmic changes in intracellular Ca(2+) handling remained unexplored. OBJECTIVE We investigated the remodeling of Ca(2+) homeostasis in ventricular cardiomyocytes derived from transgenic rabbit model of LQT2 to determine whether these changes contribute to triggered activity in the form of early after depolarizations (EADs). METHODS AND RESULTS Confocal Ca(2+) imaging revealed decrease in amplitude of Ca(2+) transients and sarcoplasmic reticulum Ca(2+) content in LQT2 myocytes. Experiments using sarcoplasmic reticulum-entrapped Ca(2+) indicator demonstrated enhanced ryanodine receptor (RyR)-mediated sarcoplasmic reticulum Ca(2+) leak in LQT2 cells. Western blot analyses showed increased phosphorylation of RyR in LQT2 myocytes versus controls. Coimmunoprecipitation experiments demonstrated loss of protein phosphatases type 1 and type 2 from the RyR complex. Stimulation of LQT2 cells with β-adrenergic agonist isoproterenol resulted in prolongation of the plateau of action potentials accompanied by aberrant Ca(2+) releases and EADs, which were abolished by inhibition of Ca(2+)/calmodulin-dependent protein kinase type 2. Computer simulations showed that late aberrant Ca(2+) releases caused by RyR hyperactivity promote EADs and underlie the enhanced triggered activity through increased forward mode of Na(+)/Ca(2+) exchanger type 1. CONCLUSIONS Hyperactive, hyperphosphorylated RyRs because of reduced local phosphatase activity enhance triggered activity in LQT2 syndrome. EADs are promoted by aberrant RyR-mediated Ca(2+) releases that are present despite a reduction of sarcoplasmic reticulum content. Those releases increase forward mode Na(+)/Ca(2+) exchanger type 1, thereby slowing repolarization and enabling L-type Ca(2+) current reactivation.
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Affiliation(s)
- Dmitry Terentyev
- From the Department of Medicine, Division of Cardiology, Cardiovascular Research Center, Rhode Island Hospital, Alpert Medical School of Brown University, Providence (D.T., W.L., L.L.C., H.K.J., Y.L., R.T., J.D., K.B., B.-R.C., G.K.); Physics Department, Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, MA (C.M.R., A.K.); Department of Comparative Medicine, Pennsylvania State University College of Medicine, Hershey (X.P.); and Department of Cardiology and Angiology I, Heart Center Freiburg University, Freiburg, Germany (K.E.O.).
| | - Colin M Rees
- From the Department of Medicine, Division of Cardiology, Cardiovascular Research Center, Rhode Island Hospital, Alpert Medical School of Brown University, Providence (D.T., W.L., L.L.C., H.K.J., Y.L., R.T., J.D., K.B., B.-R.C., G.K.); Physics Department, Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, MA (C.M.R., A.K.); Department of Comparative Medicine, Pennsylvania State University College of Medicine, Hershey (X.P.); and Department of Cardiology and Angiology I, Heart Center Freiburg University, Freiburg, Germany (K.E.O.)
| | - Weiyan Li
- From the Department of Medicine, Division of Cardiology, Cardiovascular Research Center, Rhode Island Hospital, Alpert Medical School of Brown University, Providence (D.T., W.L., L.L.C., H.K.J., Y.L., R.T., J.D., K.B., B.-R.C., G.K.); Physics Department, Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, MA (C.M.R., A.K.); Department of Comparative Medicine, Pennsylvania State University College of Medicine, Hershey (X.P.); and Department of Cardiology and Angiology I, Heart Center Freiburg University, Freiburg, Germany (K.E.O.)
| | - Leroy L Cooper
- From the Department of Medicine, Division of Cardiology, Cardiovascular Research Center, Rhode Island Hospital, Alpert Medical School of Brown University, Providence (D.T., W.L., L.L.C., H.K.J., Y.L., R.T., J.D., K.B., B.-R.C., G.K.); Physics Department, Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, MA (C.M.R., A.K.); Department of Comparative Medicine, Pennsylvania State University College of Medicine, Hershey (X.P.); and Department of Cardiology and Angiology I, Heart Center Freiburg University, Freiburg, Germany (K.E.O.)
| | - Hitesh K Jindal
- From the Department of Medicine, Division of Cardiology, Cardiovascular Research Center, Rhode Island Hospital, Alpert Medical School of Brown University, Providence (D.T., W.L., L.L.C., H.K.J., Y.L., R.T., J.D., K.B., B.-R.C., G.K.); Physics Department, Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, MA (C.M.R., A.K.); Department of Comparative Medicine, Pennsylvania State University College of Medicine, Hershey (X.P.); and Department of Cardiology and Angiology I, Heart Center Freiburg University, Freiburg, Germany (K.E.O.)
| | - Xuwen Peng
- From the Department of Medicine, Division of Cardiology, Cardiovascular Research Center, Rhode Island Hospital, Alpert Medical School of Brown University, Providence (D.T., W.L., L.L.C., H.K.J., Y.L., R.T., J.D., K.B., B.-R.C., G.K.); Physics Department, Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, MA (C.M.R., A.K.); Department of Comparative Medicine, Pennsylvania State University College of Medicine, Hershey (X.P.); and Department of Cardiology and Angiology I, Heart Center Freiburg University, Freiburg, Germany (K.E.O.)
| | - Yichun Lu
- From the Department of Medicine, Division of Cardiology, Cardiovascular Research Center, Rhode Island Hospital, Alpert Medical School of Brown University, Providence (D.T., W.L., L.L.C., H.K.J., Y.L., R.T., J.D., K.B., B.-R.C., G.K.); Physics Department, Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, MA (C.M.R., A.K.); Department of Comparative Medicine, Pennsylvania State University College of Medicine, Hershey (X.P.); and Department of Cardiology and Angiology I, Heart Center Freiburg University, Freiburg, Germany (K.E.O.)
| | - Radmila Terentyeva
- From the Department of Medicine, Division of Cardiology, Cardiovascular Research Center, Rhode Island Hospital, Alpert Medical School of Brown University, Providence (D.T., W.L., L.L.C., H.K.J., Y.L., R.T., J.D., K.B., B.-R.C., G.K.); Physics Department, Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, MA (C.M.R., A.K.); Department of Comparative Medicine, Pennsylvania State University College of Medicine, Hershey (X.P.); and Department of Cardiology and Angiology I, Heart Center Freiburg University, Freiburg, Germany (K.E.O.)
| | - Katja E Odening
- From the Department of Medicine, Division of Cardiology, Cardiovascular Research Center, Rhode Island Hospital, Alpert Medical School of Brown University, Providence (D.T., W.L., L.L.C., H.K.J., Y.L., R.T., J.D., K.B., B.-R.C., G.K.); Physics Department, Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, MA (C.M.R., A.K.); Department of Comparative Medicine, Pennsylvania State University College of Medicine, Hershey (X.P.); and Department of Cardiology and Angiology I, Heart Center Freiburg University, Freiburg, Germany (K.E.O.)
| | - Jean Daley
- From the Department of Medicine, Division of Cardiology, Cardiovascular Research Center, Rhode Island Hospital, Alpert Medical School of Brown University, Providence (D.T., W.L., L.L.C., H.K.J., Y.L., R.T., J.D., K.B., B.-R.C., G.K.); Physics Department, Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, MA (C.M.R., A.K.); Department of Comparative Medicine, Pennsylvania State University College of Medicine, Hershey (X.P.); and Department of Cardiology and Angiology I, Heart Center Freiburg University, Freiburg, Germany (K.E.O.)
| | - Kamana Bist
- From the Department of Medicine, Division of Cardiology, Cardiovascular Research Center, Rhode Island Hospital, Alpert Medical School of Brown University, Providence (D.T., W.L., L.L.C., H.K.J., Y.L., R.T., J.D., K.B., B.-R.C., G.K.); Physics Department, Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, MA (C.M.R., A.K.); Department of Comparative Medicine, Pennsylvania State University College of Medicine, Hershey (X.P.); and Department of Cardiology and Angiology I, Heart Center Freiburg University, Freiburg, Germany (K.E.O.)
| | - Bum-Rak Choi
- From the Department of Medicine, Division of Cardiology, Cardiovascular Research Center, Rhode Island Hospital, Alpert Medical School of Brown University, Providence (D.T., W.L., L.L.C., H.K.J., Y.L., R.T., J.D., K.B., B.-R.C., G.K.); Physics Department, Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, MA (C.M.R., A.K.); Department of Comparative Medicine, Pennsylvania State University College of Medicine, Hershey (X.P.); and Department of Cardiology and Angiology I, Heart Center Freiburg University, Freiburg, Germany (K.E.O.)
| | - Alain Karma
- From the Department of Medicine, Division of Cardiology, Cardiovascular Research Center, Rhode Island Hospital, Alpert Medical School of Brown University, Providence (D.T., W.L., L.L.C., H.K.J., Y.L., R.T., J.D., K.B., B.-R.C., G.K.); Physics Department, Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, MA (C.M.R., A.K.); Department of Comparative Medicine, Pennsylvania State University College of Medicine, Hershey (X.P.); and Department of Cardiology and Angiology I, Heart Center Freiburg University, Freiburg, Germany (K.E.O.)
| | - Gideon Koren
- From the Department of Medicine, Division of Cardiology, Cardiovascular Research Center, Rhode Island Hospital, Alpert Medical School of Brown University, Providence (D.T., W.L., L.L.C., H.K.J., Y.L., R.T., J.D., K.B., B.-R.C., G.K.); Physics Department, Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, MA (C.M.R., A.K.); Department of Comparative Medicine, Pennsylvania State University College of Medicine, Hershey (X.P.); and Department of Cardiology and Angiology I, Heart Center Freiburg University, Freiburg, Germany (K.E.O.).
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404
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Price LC, Wobeter B, Delate T, Kurz D, Shanahan R. Methadone for pain and the risk of adverse cardiac outcomes. J Pain Symptom Manage 2014; 48:333-42.e1. [PMID: 24480532 DOI: 10.1016/j.jpainsymman.2013.09.021] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Revised: 09/24/2013] [Accepted: 10/04/2013] [Indexed: 01/22/2023]
Abstract
CONTEXT There are few studies that describe cardiac adverse events in patients prescribed methadone for pain management. OBJECTIVES To describe incident cardiac adverse events and risk factors for cardiac adverse events in primary care patients prescribed methadone for pain. METHODS This was a retrospective, descriptive, cohort study in patients 18 years or older receiving methadone for pain management during 2010. Patients were followed for 12 months and were categorized as "chronic" or "non-chronic" methadone users. The primary outcomes were a cardiac event, at risk for an event, or neither. Patients were grouped on their outcome and were compared on risk factors and methadone monitoring. RESULTS A total of 1246 patients were included. Thirty (2.4%), 628 (50.4%), and 588 (47.2%) patients had a cardiac event, were at risk for an event, or had neither an event nor a risk factor, respectively. Overall, the rate of QTc prolongation was 49.4% and the rate of adherence to recommended cardiac monitoring was 39.0%. Similar percentages of chronic and non-chronic users had a cardiac event (P > 0.05). Among the patients who had a cardiac event and were at risk for an event, factors independently associated with having had an event included age (odds ratio = 1.06; 95% CI = 1.03-1.09) and a dose 100 mg/day or higher (odds ratio = 6.18; 95% CI = 1.08-35.45). CONCLUSION Few cardiac adverse events resulting from methadone use for pain were detected. However, a large proportion of patients were at risk for an adverse event, especially patients who were older and had received ≥ 100 mg/day of methadone.
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Affiliation(s)
- Lea C Price
- Kaiser Permanente-Colorado, Denver, Colorado, USA; University of Colorado Skaggs School of Pharmacy, Denver, Colorado, USA; Regis University Rueckert-Hartman College for Health Professions, School of Pharmacy, Denver, Colorado, USA.
| | - Brooke Wobeter
- Denver Health Hospital and Authority, Denver, Colorado, USA
| | - Thomas Delate
- Kaiser Permanente-Colorado, Denver, Colorado, USA; University of Colorado Skaggs School of Pharmacy, Denver, Colorado, USA
| | - Deanna Kurz
- Kaiser Permanente-Colorado, Denver, Colorado, USA
| | - Roberta Shanahan
- Kaiser Permanente-Colorado, Denver, Colorado, USA; University of Colorado Skaggs School of Pharmacy, Denver, Colorado, USA
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405
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Hidayatallah N, Silverstein LB, Stolerman M, McDonald T, Walsh CA, Paljevic E, Cohen LL, Marion RW, Wasserman D, Hreyo S, Dolan SM. Psychological stress associated with cardiogenetic conditions. Per Med 2014; 11:631-640. [PMID: 25431604 DOI: 10.2217/pme.14.50] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
AIM Genetic testing now makes it possible to identify specific mutations that may lead to life-threatening cardiac arrhythmias. This article presents data from a qualitative research study that explored the subjective experiences of individuals and families with cardiogenetic conditions. We focus on describing patients' experiences of psychological stresses associated with having a cardiogenetic condition, illustrating the importance of integrating psychological and medical care. This integration of care is particularly important as personalized genomic medicine continues to evolve and the implications of genetic testing have a profound effect on individuals and families. METHODS The researchers interviewed 50 participants from 32 families. The research team used a systematic, grounded theory procedure to code and analyze interview and focus group transcripts, incorporating multiple coders at several stages of the data analysis process. RESULTS Three major themes emerged: a bereavement trajectory associated with sudden death in the absence of prior symptoms; high anxiety about transmitting a genetic mutation; and resilience reflected in positive lifestyle changes and participation in support groups. CONCLUSION This article identifies patient perspectives on personalized genomic medicine in cardiogenetics that can improve clinical care, including: specialized bereavement counseling; improving education about cardiogenetic conditions for medical professionals; parent guidelines for discussing cardiogenetic conditions with their children; information about support groups; and the routine inclusion of clinical psychologists in interdisciplinary treatment teams. Given recent advances in technology and decreasing costs, whole-genome sequencing is likely to become common practice in the near future. Therefore, these recommendations are likely to be relevant for other genetic conditions, as well as the entire field of personalized genomic medicine.
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Affiliation(s)
- Nadia Hidayatallah
- Ferkauf Graduate School of Psychology, Yeshiva University, Bronx, New York, NY, USA ; Child & Family Institute, Department of Psychiatry, Mt. Sinai-St. Luke's, New York, NY, USA
| | - Louise B Silverstein
- Ferkauf Graduate School of Psychology, Yeshiva University, Bronx, New York, NY, USA
| | - Marina Stolerman
- Ferkauf Graduate School of Psychology, Yeshiva University, Bronx, New York, NY, USA
| | - Thomas McDonald
- Department of Medicine (Cardiology), Albert Einstein College of Medicine/Montefiore Medical Center, 1300 Morris Park Avenue, Bronx, NY 10461, USA
| | - Christine A Walsh
- Department of Pediatrics (Cardiology), Children's Hospital at Montefiore/Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
| | - Esma Paljevic
- Department of Pediatrics (Cardiology), Children's Hospital at Montefiore/Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA ; Lienhard School of Nursing, Pace University, New York, NY, USA
| | - Lilian L Cohen
- Department of Pediatrics (Genetics), Children's Hospital at Montefiore/Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA ; Department of Pediatrics, Weill Cornell Medical College/New York Presbyterian Hospital, New York, NY, USA
| | - Robert W Marion
- Department of Pediatrics (Genetics), Children's Hospital at Montefiore/Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
| | - David Wasserman
- Center for Ethics, Yeshiva University, 500 West 185th Street, New York, NY 10033, USA
| | - Sarah Hreyo
- Ferkauf Graduate School of Psychology, Yeshiva University, Bronx, New York, NY, USA
| | - Siobhan M Dolan
- Department of Obstetrics & Gynecology & Women's Health, Albert Einstein College of Medicine/Montefiore Medical Center, Block 634, 1300 Morris Park Avenue, Bronx, NY 10461, USA
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406
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Qureshi SF, Ali A, Venkateshwari A, Rao H, Jayakrishnan MP, Narasimhan C, Shenthar J, Thangaraj K, Nallari P. Atrial natriuretic peptide gene - a potential biomarker for long QT syndrome. EXCLI J 2014; 13:834-42. [PMID: 26417306 PMCID: PMC4464516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Accepted: 07/29/2014] [Indexed: 11/10/2022]
Abstract
This study highlights the possible implication of NPPA (natriuretic peptide precursor A) gene in the etiology of Long QT syndrome (LQTS) by population-based as well as familial study. Three SNPs of NPPA - C-664G, C1363A and T1766C were examined by molecular analyses in LQTS, controls and first degree relatives (FDRs). This study revealed a possible association of 1364 C>A SNP 'C' allele with LQTS (p = 0.0013). All three SNPs were in tight linkage disequilibrium. The familial study highlights the association of NPPA SNP with cLQTS and implicating it as a potential biomarker in South Indian population.
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Affiliation(s)
- Sameera Fatima Qureshi
- Department of Genetics, University College of Science, Osmania University, Hyderabad-500007, Andhra Pradesh, India
| | - Altaf Ali
- Department of Genetics, University College of Science, Osmania University, Hyderabad-500007, Andhra Pradesh, India
| | - Ananthapur Venkateshwari
- Institute of Genetics and Hospital for Genetic Diseases, Osmania University, Begumpet, Andhra Pradesh, India
| | - Hygriv Rao
- Institute of Genetics and Krishna Institute of Medical Sciences, Andhra Pradesh, India
| | - M. P. Jayakrishnan
- Institute of Maternal and Child Health, Calicut Medical College, Calicut 8, Kerala, India
| | | | | | | | - Pratibha Nallari
- Department of Genetics, University College of Science, Osmania University, Hyderabad-500007, Andhra Pradesh, India,*To whom correspondence should be addressed: Pratibha Nallari, Department of Genetics, University College of Science, Osmania University, Hyderabad-500007, Andhra Pradesh, India, E-mail:
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407
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Abstract
BACKGROUND The KCNH2 gene encodes the Kv11.1 potassium channel that conducts the rapidly activating delayed rectifier current in the heart. The relative expression of the full-length Kv11.1a isoform and the C-terminally truncated Kv11.1a-USO isoform plays an important role in regulation of channel function. The formation of C-terminal isoforms is determined by competition between the splicing and alternative polyadenylation of KCNH2 intron 9. It is not known whether changes in the relative expression of Kv11.1a and Kv11.1a-USO can cause long-QT syndrome. METHODS AND RESULTS We identified a novel KCNH2 splice site mutation in a large family. The mutation, IVS9-2delA, is a deletion of the A in the AG dinucleotide of the 3' acceptor site of intron 9. We designed an intron-containing full-length KCNH2 gene construct to study the effects of the mutation on the relative expression of Kv11.1a and Kv11.1a-USO at the mRNA, protein, and functional levels. We found that this mutation disrupted normal splicing and resulted in exclusive polyadenylation of intron 9, leading to a switch from the functional Kv11.1a to the nonfunctional Kv11.1a-USO isoform in HEK293 cells and HL-1 cardiomyocytes. We also showed that IVS9-2delA caused isoform switch in the mutant allele of mRNA isolated from patient lymphocytes. CONCLUSIONS Our findings indicate that the IVS9-2delA mutation causes a switch in the expression of the functional Kv11.1a isoform to the nonfunctional Kv11.1a-USO isoform. Kv11.1 isoform switch represents a novel mechanism in the pathogenesis of long-QT syndrome.
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Affiliation(s)
- Qiuming Gong
- From the Knight Cardiovascular Institute, Oregon Health and Science University, Portland, OR (Q.G., M.R.S., V.D., Z.Z.); and Lankenau Institute for Medical Research and Lankenau Medical Center, Jefferson Medical College, Philadelphia, PA (L.Z.)
| | - Matthew R Stump
- From the Knight Cardiovascular Institute, Oregon Health and Science University, Portland, OR (Q.G., M.R.S., V.D., Z.Z.); and Lankenau Institute for Medical Research and Lankenau Medical Center, Jefferson Medical College, Philadelphia, PA (L.Z.)
| | - Vivianne Deng
- From the Knight Cardiovascular Institute, Oregon Health and Science University, Portland, OR (Q.G., M.R.S., V.D., Z.Z.); and Lankenau Institute for Medical Research and Lankenau Medical Center, Jefferson Medical College, Philadelphia, PA (L.Z.)
| | - Li Zhang
- From the Knight Cardiovascular Institute, Oregon Health and Science University, Portland, OR (Q.G., M.R.S., V.D., Z.Z.); and Lankenau Institute for Medical Research and Lankenau Medical Center, Jefferson Medical College, Philadelphia, PA (L.Z.)
| | - Zhengfeng Zhou
- From the Knight Cardiovascular Institute, Oregon Health and Science University, Portland, OR (Q.G., M.R.S., V.D., Z.Z.); and Lankenau Institute for Medical Research and Lankenau Medical Center, Jefferson Medical College, Philadelphia, PA (L.Z.).
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408
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Makita N, Yagihara N, Crotti L, Johnson CN, Beckmann BM, Roh MS, Shigemizu D, Lichtner P, Ishikawa T, Aiba T, Homfray T, Behr ER, Klug D, Denjoy I, Mastantuono E, Theisen D, Tsunoda T, Satake W, Toda T, Nakagawa H, Tsuji Y, Tsuchiya T, Yamamoto H, Miyamoto Y, Endo N, Kimura A, Ozaki K, Motomura H, Suda K, Tanaka T, Schwartz PJ, Meitinger T, Kääb S, Guicheney P, Shimizu W, Bhuiyan ZA, Watanabe H, Chazin WJ, George AL. Novel calmodulin mutations associated with congenital arrhythmia susceptibility. ACTA ACUST UNITED AC 2014; 7:466-74. [PMID: 24917665 DOI: 10.1161/circgenetics.113.000459] [Citation(s) in RCA: 138] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
BACKGROUND Genetic predisposition to life-threatening cardiac arrhythmias such as congenital long-QT syndrome (LQTS) and catecholaminergic polymorphic ventricular tachycardia (CPVT) represent treatable causes of sudden cardiac death in young adults and children. Recently, mutations in calmodulin (CALM1, CALM2) have been associated with severe forms of LQTS and CPVT, with life-threatening arrhythmias occurring very early in life. Additional mutation-positive cases are needed to discern genotype-phenotype correlations associated with calmodulin mutations. METHODS AND RESULTS We used conventional and next-generation sequencing approaches, including exome analysis, in genotype-negative LQTS probands. We identified 5 novel de novo missense mutations in CALM2 in 3 subjects with LQTS (p.N98S, p.N98I, p.D134H) and 2 subjects with clinical features of both LQTS and CPVT (p.D132E, p.Q136P). Age of onset of major symptoms (syncope or cardiac arrest) ranged from 1 to 9 years. Three of 5 probands had cardiac arrest and 1 of these subjects did not survive. The clinical severity among subjects in this series was generally less than that originally reported for CALM1 and CALM2 associated with recurrent cardiac arrest during infancy. Four of 5 probands responded to β-blocker therapy, whereas 1 subject with mutation p.Q136P died suddenly during exertion despite this treatment. Mutations affect conserved residues located within Ca(2+)-binding loops III (p.N98S, p.N98I) or IV (p.D132E, p.D134H, p.Q136P) and caused reduced Ca(2+)-binding affinity. CONCLUSIONS CALM2 mutations can be associated with LQTS and with overlapping features of LQTS and CPVT.
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409
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Affiliation(s)
- Arthur J Moss
- Cardiology Division, Department of Medicine and Department of Pathology, University of Rochester Medical Center, Rochester, NY
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410
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Hedley PL, Carlsen AL, Christiansen KM, Kanters JK, Behr ER, Corfield VA, Christiansen M. MicroRNAs in cardiac arrhythmia: DNA sequence variation of MiR-1 and MiR-133A in long QT syndrome. Scand J Clin Lab Invest 2014; 74:485-91. [PMID: 24809446 PMCID: PMC4196592 DOI: 10.3109/00365513.2014.905696] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Long QT syndrome (LQTS) is a genetic cardiac condition associated with prolonged ventricular repolarization, primarily a result of perturbations in cardiac ion channels, which predisposes individuals to life-threatening arrhythmias. Using DNA screening and sequencing methods, over 700 different LQTS-causing mutations have been identified in 13 genes worldwide. Despite this, the genetic cause of 30-50% of LQTS is presently unknown. MicroRNAs (miRNAs) are small (∼ 22 nucleotides) noncoding RNAs which post-transcriptionally regulate gene expression by binding complementary sequences within messenger RNAs (mRNAs). The human genome encodes over 1800 miRNAs, which target about 60% of human genes. Consequently, miRNAs are likely to regulate many complex processes in the body, indeed aberrant expression of various miRNA species has been implicated in numerous disease states, including cardiovascular diseases. MiR-1 and MiR-133A are the most abundant miRNAs in the heart and have both been reported to regulate cardiac ion channels. We hypothesized that, as a consequence of their role in regulating cardiac ion channels, genetic variation in the genes which encode MiR-1 and MiR-133A might explain some cases of LQTS. Four miRNA genes (miR-1-1, miR-1-2, miR-133a-1 and miR-133a-2), which encode MiR-1 and MiR-133A, were sequenced in 125 LQTS probands. No genetic variants were identified in miR-1-1 or miR-133a-1; but in miR-1-2 we identified a single substitution (n.100A> G) and in miR-133a-2 we identified two substitutions (n.-19G> A and n.98C> T). None of the variants affect the mature miRNA products. Our findings indicate that sequence variants of miR-1-1, miR-1-2, miR-133a-1 and miR-133a-2 are not a cause of LQTS in this cohort.
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Affiliation(s)
- Paula L Hedley
- Department of Clinical Biochemistry, Immunology and Genetics, Statens Serum Institut , Copenhagen , Denmark
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411
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412
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Riuró H, Campuzano O, Arbelo E, Iglesias A, Batlle M, Pérez-Villa F, Brugada J, Pérez GJ, Scornik FS, Brugada R. A missense mutation in the sodium channel β1b subunit reveals SCN1B as a susceptibility gene underlying long QT syndrome. Heart Rhythm 2014; 11:1202-9. [PMID: 24662403 DOI: 10.1016/j.hrthm.2014.03.044] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Indexed: 01/04/2023]
Abstract
BACKGROUND Long QT syndrome (LQTS) is associated with sudden cardiac death and the prolongation of the QT interval on the electrocardiogram. A comprehensive screening of all genes previously associated with this disease leaves 30% of the patients without a genetic diagnosis. Pathogenic mutations in the sodium channel β subunits have been associated with cardiac channelopathies, including SCN4B mutations in LQTS. OBJECTIVE To evaluate the role of mutations in the sodium channel β subunits in LQTS. METHODS We screened for mutations in the genes encoding the 5 sodium β subunits (SCN1B isoforms a and b, SCN2B, SCN3B, and SCN4B) from 30 nonrelated patients who were clinically diagnosed with LQTS without mutations in common LQTS-related genes. We used the patch-clamp technique to study the properties of sodium currents and the action potential duration in human embryonic kidney and HL-1 cells, respectively, in the presence of β1b subunits. RESULTS The genetic screening revealed a novel mutation in the SCN1Bb gene (β1bP213T) in an 8-year-old boy. Our electrophysiological analysis revealed that β1bP213T increases late sodium current. In addition, β1bP213T subtly altered Nav1.5 function by shifting the window current, accelerating recovery from inactivation, and decreasing the slow inactivation rate. Moreover, experiments using HL-1 cells revealed that the action potential duration significantly increases when the mutant β1b was overexpressed compared with β1bWT. CONCLUSION These data revealed SCN1Bb as a susceptibility gene responsible for LQTS, highlighting the importance of continuing the search for new genes and mechanisms to decrease the percentage of patients with LQTS remaining without genetic diagnosis.
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Affiliation(s)
- Helena Riuró
- Centre de Genètica Cardiovascular, Institut d'Investigació Biomèdica de Girona (IdIBGI), Girona, Catalonia, Spain; Departament de Ciències Mèdiques, Universitat de Girona (UdG), Girona, Catalonia, Spain
| | - Oscar Campuzano
- Centre de Genètica Cardiovascular, Institut d'Investigació Biomèdica de Girona (IdIBGI), Girona, Catalonia, Spain; Departament de Ciències Mèdiques, Universitat de Girona (UdG), Girona, Catalonia, Spain
| | - Elena Arbelo
- Hospital Clínic de Barcelona, Universitat de Barcelona, Barcelona, Catalonia, Spain
| | - Anna Iglesias
- Centre de Genètica Cardiovascular, Institut d'Investigació Biomèdica de Girona (IdIBGI), Girona, Catalonia, Spain; Departament de Ciències Mèdiques, Universitat de Girona (UdG), Girona, Catalonia, Spain
| | - Montserrat Batlle
- Hospital Clínic de Barcelona, Universitat de Barcelona, Barcelona, Catalonia, Spain
| | - Felix Pérez-Villa
- Hospital Clínic de Barcelona, Universitat de Barcelona, Barcelona, Catalonia, Spain
| | - Josep Brugada
- Hospital Clínic de Barcelona, Universitat de Barcelona, Barcelona, Catalonia, Spain
| | - Guillermo J Pérez
- Centre de Genètica Cardiovascular, Institut d'Investigació Biomèdica de Girona (IdIBGI), Girona, Catalonia, Spain; Departament de Ciències Mèdiques, Universitat de Girona (UdG), Girona, Catalonia, Spain
| | - Fabiana S Scornik
- Centre de Genètica Cardiovascular, Institut d'Investigació Biomèdica de Girona (IdIBGI), Girona, Catalonia, Spain; Departament de Ciències Mèdiques, Universitat de Girona (UdG), Girona, Catalonia, Spain
| | - Ramon Brugada
- Centre de Genètica Cardiovascular, Institut d'Investigació Biomèdica de Girona (IdIBGI), Girona, Catalonia, Spain; Departament de Ciències Mèdiques, Universitat de Girona (UdG), Girona, Catalonia, Spain.
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413
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Abstract
We report a case of a 63-year-old woman who developed profound QT prolongation, T-wave alternans, and spontaneous ventricular fibrillation during catheter ablation of atrial fibrillation. A thorough search into the possible mechanisms identified the use of sevoflurane, an inhalational gas anesthetic as the culprit. The patient was converted to propofol anesthesia and her QT interval normalized promptly.
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Affiliation(s)
- Aditya Saini
- Heart and Vascular Institute, University of Pittsburgh Medical Center, Pittsburgh, PA
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414
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Ruan L, Quan X, Li L, Bai R, Ni M, Xu R, Zhang C. Increasing gap junction coupling suppresses ibutilide-induced torsades de pointes. Exp Ther Med 2014; 7:1279-1284. [PMID: 24940425 PMCID: PMC3991525 DOI: 10.3892/etm.2014.1601] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2013] [Accepted: 02/13/2014] [Indexed: 11/24/2022] Open
Abstract
Drug-induced torsades de pointes (TdP) is common with class III antiarrhythmic drugs. Increased transmural dispersion of repolarization (TDR) contributes significantly to the development of TdP. Gap junctions play an important role in maintaining TDR in long QT syndrome. The present study examined the effect of a gap junction enhancer, antiarrhythmic peptide 10 (AAP10), on ibutilide-induced TdP. Coronary-perfused rabbit ventricular wedge preparations were used to evaluate the effect of AAP10 on ibutilide-induced arrhythmia. Transmural electrocardiograms and action potentials were recorded simultaneously. Early afterdepolarizations (EADs), R-on-T extrasystole, TdP and changes in Tpeak-end (Tp-e) and the Tp-e/QT ratio were observed. Changes in the levels of non-phosphorylated connexin 43 (Cx43) were measured by immunoblotting. Compared with those in the control group, the QT interval, Tp-e/QT and incidence rates of EAD and TdP increased with augmented dephosphorylation in the ventricular wedge preparations perfused with ibutilide under conditions of hypokalemia and hypomagnesemia. In the presence of AAP10, the incidence rates of EAD and TdP were reduced and the Tp-e/QT ratio decreased, with a parallel reduction in the level of non-phosphorylated Cx43. The results indicate that AAP10 suppressed ibutilide-induced TdP under conditions of hypokalemia and hypomagnesemia by decreasing TDR. AAP10 reduced TDR, possibly by preventing the dephosphorylation of Cx43 and thereby increasing myocardial cell gap junction coupling.
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Affiliation(s)
- Lei Ruan
- Department of Gerontology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, P.R. China
| | - Xiaoqing Quan
- Department of Gerontology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, P.R. China
| | - Liandong Li
- Department of Gerontology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, P.R. China
| | - Rong Bai
- Department of Cardiology, Beijing Anzhen Hospital, Capital Medical University, Beijing 100029, P.R. China
| | - Mingke Ni
- Department of Gerontology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, P.R. China
| | - Rende Xu
- Department of Gerontology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, P.R. China
| | - Cuntai Zhang
- Department of Gerontology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, P.R. China
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415
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Hwang HS, Nitu FR, Yang Y, Walweel K, Pereira L, Johnson CN, Faggioni M, Chazin WJ, Laver D, George AL, Cornea RL, Bers DM, Knollmann BC. Divergent regulation of ryanodine receptor 2 calcium release channels by arrhythmogenic human calmodulin missense mutants. Circ Res 2014; 114:1114-24. [PMID: 24563457 DOI: 10.1161/circresaha.114.303391] [Citation(s) in RCA: 106] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
RATIONALE Calmodulin (CaM) mutations are associated with an autosomal dominant syndrome of ventricular arrhythmia and sudden death that can present with divergent clinical features of catecholaminergic polymorphic ventricular tachycardia (CPVT) or long QT syndrome (LQTS). CaM binds to and inhibits ryanodine receptor (RyR2) Ca release channels in the heart, but whether arrhythmogenic CaM mutants alter RyR2 function is not known. OBJECTIVE To gain mechanistic insight into how human CaM mutations affect RyR2 Ca channels. METHODS AND RESULTS We studied recombinant CaM mutants associated with CPVT (N54I and N98S) or LQTS (D96V, D130G, and F142L). As a group, all LQTS-associated CaM mutants (LQTS-CaMs) exhibited reduced Ca affinity, whereas CPVT-associated CaM mutants (CPVT-CaMs) had either normal or modestly lower Ca affinity. In permeabilized ventricular myocytes, CPVT-CaMs at a physiological intracellular concentration (100 nmol/L) promoted significantly higher spontaneous Ca wave and spark activity, a typical cellular phenotype of CPVT. Compared with wild-type CaM, CPVT-CaMs caused greater RyR2 single-channel open probability and showed enhanced binding affinity to RyR2. Even a 1:8 mixture of CPVT-CaM:wild-type-CaM activated Ca waves, demonstrating functional dominance. In contrast, LQTS-CaMs did not promote Ca waves and exhibited either normal regulation of RyR2 single channels (D96V) or lower RyR2-binding affinity (D130G and F142L). None of the CaM mutants altered Ca/CaM binding to CaM-kinase II. CONCLUSIONS A small proportion of CPVT-CaM is sufficient to evoke arrhythmogenic Ca disturbances, whereas LQTS-CaMs do not. Our findings explain the clinical presentation and autosomal dominant inheritance of CPVT-CaM mutations and suggest that RyR2 interactions are unlikely to explain arrhythmogenicity of LQTS-CaM mutations.
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Affiliation(s)
- Hyun Seok Hwang
- From the Departments of Medicine (H.S.H., M.F., A.L.G., B.C.K.), Biochemistry (C.N.J., W.J.C.), Chemistry (W.J.C.), and Pharmacology (A.L.G., B.C.K.), Vanderbilt University, Nashville, TN; Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis (F.R.N., R.L.C.); Department of Pharmacology, University of California, Davis (Y.Y., L.P., D.M.B.); and Department of School of Biomedical Sciences and Pharmacy, University of Newcastle, New South Wales, Australia (K.W., D.L.)
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416
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Rizzo S, Basso C, Troost D, Aronica E, Frigo AC, Driessen AHG, Thiene G, Wilde AAM, van der Wal AC. T-cell-mediated inflammatory activity in the stellate ganglia of patients with ion-channel disease and severe ventricular arrhythmias. Circ Arrhythm Electrophysiol 2014; 7:224-9. [PMID: 24532560 DOI: 10.1161/circep.113.001184] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Long QT syndrome (LQTS) and catecholaminergic polymorphic ventricular tachycardia (CPVT) are electric diseases characterized by catecholamine-induced ventricular arrhythmias. Unbalanced autonomic innervation of the heart may trigger arrhythmic events and stellectomy is a treatment option for patients who are resistant to pharmacological drugs. We analyzed left stellectomy specimens of LQTS and CPVT patients for signs of inflammatory activity. METHODS AND RESULTS Stellate ganglia were retrieved from 12 consecutive patients (8F; 4 mol/L; mean age, 23.4±17 years) with either LQTS (n=8) or CPVT (n=4) and serious arrhythmias. Control stellate ganglia were obtained from 10 accidently deceased patients (6F; 4 mol/L; mean age, 35±17.6 years). Sections were immunostained with antibodies against T cells (CD3, CD4, CD8, CD20, Granzyme B), CD68 (macrophages), and HLA-DR (human leukocyte antigen-DR) antigens (activation marker). Immunopositive cells were quantified as cells/mm2. Polymerase chain reaction (PCR) and reverse transcription PCR were performed to screen for herpes virus DNA. Stellate ganglia of all 12 LQTS/CPVT patients revealed mild but distinct inflammatory infiltrates composed of T lymphocytes and macrophages, which were diffusely spread, but also clustered in small foci opposed to ganglion cells, interpreted as T-cell-mediated ganglionitis. Morphometric analysis showed that CD3+ and CD8+ T cells/mm2 were significantly higher in the ganglia of LQTS/CPVT cases than in healthy controls (P=0.0018 and P=0.0009, respectively). Molecular analyses were negative for neurotropic viruses. CONCLUSIONS T-cell-mediated cytotoxicity toward ganglion cells may boost adrenergic activity as to trigger or enhance electric instability in LQTS/CPVT patients who are already genetically predisposed to arrhythmias.
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Affiliation(s)
- Stefania Rizzo
- Department of Cardiac, Thoracic, and Vascular Sciences, University of Padua, Padua, Italy
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417
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Abstract
BACKGROUND The electrophysiology of long QT syndrome (LQTS) in utero is virtually unstudied. Our goal here was to evaluate the efficacy of fetal magnetocardiography (fMCG) for diagnosis and prognosis of fetuses at risk of LQTS. METHODS AND RESULTS We reviewed the pre/postnatal medical records of 30 fetuses referred for fMCG because of a family history of LQTS (n=17); neonatal/childhood sudden cardiac death (n=3), or presentation of prenatal LQTS rhythms (n=12): 2° atrioventricular block, ventricular tachycardia, heart rate < 3(rd) percentile. We evaluated heart rate and reactivity, cardiac time intervals, T-wave characteristics, and initiation/termination of Torsade de Pointes, and compared these with neonatal ECG findings. After birth, subjects were tested for LQTS mutations. Based on accepted clinical criteria, 21 subjects (70%; 9 KCNQ1, 5 KCNH2, 2 SCN5A, 2 other, 3 untested) had LQTS. Using a threshold of corrected QT= 490 ms, fMCG accurately identified LQTS fetuses with 89% (24/27) sensitivity and 89% (8/9) specificity in 36 sessions. Four fetuses (2 KCNH2 and 2 SCN5A), all with corrected QT ≥ 620 ms, had frequent episodes of Torsade de Pointes, which were present 22-79% of the time. Although some episodes initiated with a long-short sequence, most initiations showed QRS aberrancy and a notable lack of pause dependency. T-wave alternans was strongly associated with severe LQTS phenotype. CONCLUSIONS Corrected QT prolongation (≥490 ms) assessed by fMCG accurately identified LQTS in utero; extreme corrected QT prolongation (≥620 ms) predicted Torsade de Pointes. FMCG can play a critical role in the diagnosis and management of fetuses at risk of LQTS.
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Affiliation(s)
- Bettina F Cuneo
- Department of Pediatrics, Children's Hospital of Colorado, University of Colorado School of Medicine, Denver (B.F.C.); Division of Cardiology, Department of Pediatrics, Children's Hospital of Wisconsin and Medical College of Wisconsin, Milwaukee (J.F.S.); Department of Medical Physics, University of Wisconsin-Madison, (S.Y., R.T.W.); Department of Child Health, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Japan (H.H.); Department of Biomedical Engineering, Osaka Electro-Communication University, Osaka, Japan (T.H.); and Central Research Laboratory, Hitachi, Ltd, Tokyo, Japan (A.K.)
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418
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Marquis-Nicholson R, Prosser DO, Love JM, Zhang L, Hayes I, George AM, Crawford JR, Skinner JR, Love DR. Array comparative genomic hybridization identifies a heterozygous deletion of the entire KCNJ2 gene as a cause of sudden cardiac death. ACTA ACUST UNITED AC 2014; 7:17-22. [PMID: 24395924 DOI: 10.1161/circgenetics.113.000415] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
BACKGROUND Large gene rearrangements, not detectable by standard molecular genetic sequencing techniques, are present in a minority of patients with long QT syndrome. We aimed to screen for large rearrangements in genes responsible for long QT syndrome as part of the molecular autopsy of a 36-year-old woman who died suddenly and had a negative autopsy. A retrospective analysis of an ECG identified a long QT interval, but sequencing of known LQT genes was uninformative. METHODS AND RESULTS Array comparative genomic hybridization was used to screen for deletions and duplications in 101 genes implicated in cardiac disorders and sudden death using a postmortem blood sample. A 542 kb deletion encompassing the entire KCNJ2 gene was identified in the decedent. The mother had electrocardiographic U-wave changes consistent with Andersen-Tawil syndrome and exaggerated by exercise but none of the characteristic noncardiac features. Fluorescence in situ hybridization confirmed the deletion in the decedent and established its presence in the mother. CONCLUSIONS A novel application of array comparative genomic hybridization and fluorescence in situ hybridization has identified that long QT syndrome and sudden cardiac death may occur as a result of a deletion of an entire gene. The case also supports recent research suggesting that noncardiac features of Andersen-Tawil syndrome occur only with missense or minor gene rearrangements in the KCNJ2 gene, resulting in a dominant negative effect on Kir2.x channels.
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419
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Abstract
Induced pluripotent stem cells (iPS cells or iPSCs) are typically derived by transfection of certain stem cell-associated genes into non-pluripotent cells, such as adult fibroblasts (typically adult somatic cells). Various diseases can be modeled through iPSC technology. The important implication of iPSCs to offer an unprecedented opportunity to recapitulate pathologic human tissue formation in vitro has generated great excitement and interest in the whole biomedical research community. Long QT syndrome (LQTS), an inherited heart disease, is characterized by prolonged QT interval on a surface electrocardiogram. LQTS presents with life-threatening cardiac arrhythmias, which can lead to fainting, syncope, and sudden death. The iPSC-derived cardiomyocytes from LQTS patients offer a potentially unlimited source of materials for biomedical study. They can be used to recapitulate complex physiological phenotypes, probe toxicological testing and drug screening, clarify the novel mechanistic insights and may also rectify gene defects at the cellular and molecular level. Despite the emerging challenges, iPSC technology has been increasingly recognized as a valuable and growing toolkit for modeling LQTS over other various models of human diseases.
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Affiliation(s)
- Guoliang Li
- Department of Cardiovascular Medicine, the First Affiliated Hospital of Xi'an Jiaotong University College of Medicine, Xi'an, Shaanxi 710061, P.R. China
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420
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Määttänen I, Jokela M, Pulkki-Råback L, Keltikangas-Järvinen L, Swan H, Toivonen L, Merjonen P, Hintsa T. Brief report: Emotional distress and recent stressful life events in long QT syndrome mutation carriers. J Health Psychol 2013; 20:1445-50. [PMID: 24335348 DOI: 10.1177/1359105313513049] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
To study emotional distress in symptomatic and asymptomatic long QT syndrome mutation carriers who had experienced a recent stressful life event. The participants were 209 symptomatic and 279 asymptomatic long QT syndrome mutation carriers. Emotional distress was assessed with the Cope questionnaire and stressful life events with the Social Readjustment Rating Scale. Symptomatic long QT syndrome mutation carriers with burdening recent stressful life events reported a higher emotional distress (β = 0.35, p < 0.001), while the asymptomatic did not show such difference (β = 0.13, p = 0.393). Symptomatic long QT syndrome mutation carriers who have experienced stressful life events recently report an increased emotional distress.
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421
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Kautzner J, Peichl P. Catheter Ablation of Polymorphic Ventricular Tachycardia and Ventricular Fibrillation. Arrhythm Electrophysiol Rev 2013; 2:135-40. [PMID: 27532017 DOI: 10.15420/aer.2013.2.2.135] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2013] [Accepted: 09/16/2013] [Indexed: 11/04/2022] Open
Abstract
Recently, catheter ablation (CA) has become a therapeutic option to target focal triggers of polymorphic ventricular tachycardia and ventricular fibrillation (VF) in the setting of electrical storm (ES). This strategy was first described in subjects without organic heart disease (i.e. idiopathic VF) and subsequently in other conditions, especially in patients with ischaemic heart disease. In the majority of cases, the triggering focus originates in the ventricular Purkinje system. In patients with Brugada syndrome, besides ablation of focal trigger in the right ventricular outflow tract, modification of a substrate in this region has been described to prevent recurrences of VF. In conclusion, CA appears to be a reasonable strategy for intractable cases of ES due to focally triggered polymorphic ventricular tachycardia and VF. Therefore, early transport of the patient into the experience centre for CA should be considered since the procedure could be in some cases life-saving. Therefore, the awareness of this entity and link to the nearest expert centre are important.
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Affiliation(s)
| | - Petr Peichl
- Consultant Electrophysiologist, Department of Cardiology, Institute for Clinical and Experimental Medicine, Prague, Czech Republic
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422
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Bhuiyan ZA, Al-Shahrani S, Al-Aama J, Wilde AAM, Momenah TS. Congenital Long QT Syndrome: An Update and Present Perspective in Saudi Arabia. Front Pediatr 2013; 1:39. [PMID: 24400285 PMCID: PMC3864249 DOI: 10.3389/fped.2013.00039] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Accepted: 11/05/2013] [Indexed: 12/14/2022] Open
Abstract
Primary cardiac arrhythmias are often caused by defects, predominantly in the genes responsible for generation of cardiac electrical potential, i.e., cardiac rhythm generation. Due to the variability in underlying genetic defects, type, and location of the mutations and putative modifiers, clinical phenotypes could be moderate to severe, even absent in many individuals. Clinical presentation and severity could be quite variable, syncope, or sudden cardiac death could also be the first and the only manifestation in a patient who had previously no symptoms at all. Despite usual familial occurrence of such cardiac arrhythmias, disease causal genetic defects could also be de novo in significant number of patients. Long QT syndrome (LQTS) is the most eloquently investigated primary cardiac rhythm disorder. A genetic defect can be identified in ∼70% of definitive LQTS patients, followed by Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT) and Brugada syndrome (BrS), where a genetic defect is found in <40% cases. In addition to these widely investigated hereditary arrhythmia syndromes, there remain many other relatively less common arrhythmia syndromes, where researchers also have unraveled the genetic etiology, e.g., short QT syndrome (SQTS), sick sinus syndrome (SSS), cardiac conduction defect (CCD), idiopathic ventricular fibrillation (IVF), early repolarization syndrome (ERS). There exist also various other ill-defined primary cardiac rhythm disorders with strong genetic and familial predisposition. In the present review we will focus on the genetic basis of LQTS and its clinical management. We will also discuss the presently available genetic insight in this context from Saudi Arabia.
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Affiliation(s)
- Zahurul A Bhuiyan
- Laboratoire de Génétique Moléculaire, Service de Génétique Médicale, Centre Hospitalier Universitaire Vaudois , Lausanne , Switzerland
| | - Safar Al-Shahrani
- Department of Pediatrics, Faculty of Medicine, King Khalid University , Abha , Saudi Arabia
| | - Jumana Al-Aama
- Princess Al Jawhara Albrahim Center of Excellence in Research of Hereditary Disorders , Jeddah , Saudi Arabia ; Department of Genetic Medicine, King Abdulaziz University , Jeddah , Saudi Arabia
| | - Arthur A M Wilde
- Princess Al Jawhara Albrahim Center of Excellence in Research of Hereditary Disorders , Jeddah , Saudi Arabia ; Department of Cardiology, Academic Medical Center, University of Amsterdam , Amsterdam , Netherlands
| | - Tarek S Momenah
- Department of Pediatric Cardiology, King Fahad Medical City , Riyadh , Saudi Arabia
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423
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Vittoria Matassini M, Krahn AD, Gardner M, Champagne J, Sanatani S, Birnie DH, Gollob MH, Chauhan V, Simpson CS, Hamilton RM, Talajic M, Ahmad K, Gerull B, Chakrabarti S, Healey JS. Evolution of clinical diagnosis in patients presenting with unexplained cardiac arrest or syncope due to polymorphic ventricular tachycardia. Heart Rhythm 2013; 11:274-81. [PMID: 24239842 DOI: 10.1016/j.hrthm.2013.11.008] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Indexed: 11/16/2022]
Abstract
BACKGROUND A systematic evaluation of patients with unexplained cardiac arrest (UCA) yields a diagnosis in 50% of the cases. However, evolution of clinical phenotype, identification of new disease-causing mutations, and description of new syndromes may revise the diagnosis. OBJECTIVE To assess the evolution in diagnosis among patients with initially UCA. METHODS Diagnoses were reviewed for all patients with UCA recruited from the Cardiac Arrest Survivors with Preserved Ejection Fraction Registry with at least 1 year of follow-up. RESULTS After comprehensive investigation of 68 patients (age 45.2 ± 14.9 years; 63% men), the initial diagnosis was as follows: idiopathic ventricular fibrillation (n = 34 [50%]), a primary arrhythmic disorder (n = 21 [31%]), and an occult structural cause (n = 13 [19%]). Patients were followed for 30 ± 17 months, during which time the diagnosis changed in 12 (18%) patients. A specific diagnosis emerged for 7 patients (21%) with an initial diagnosis of idiopathic ventricular fibrillation. A structural cardiomyopathy evolved in 2 patients with an initial diagnosis of primary electrical disorder, while the specific structural cardiomyopathy was revised for 1 patient. Two patients with an initial diagnosis of a primary arrhythmic disorder were subsequently considered to have a different primary arrhythmic disorder. A follow-up resting electrocardiogram was the test that most frequently changed the diagnosis (67% of the cases), followed by genetic testing (17%). CONCLUSIONS The reevaluation of patients presenting with UCA may lead to a change in diagnosis in up to 20%. This emphasizes the need to actively monitor the phenotype and also has implications for the treatment of these patients and the screening of their relatives.
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Affiliation(s)
- Maria Vittoria Matassini
- Population Health Research Institute, McMaster University, Hamilton, Canada; Polytechnic University of Marche, Ancona, Italy
| | - Andrew D Krahn
- University of British Columbia, Vancouver, British Columbia, Canada
| | | | | | - Shubhayan Sanatani
- British Columbia Children's Hospital, Vancouver, British Columbia, Canada
| | | | | | - Vijay Chauhan
- University Health Network, University of Toronto, Toronto, Ontario, Canada
| | | | | | | | - Kam Ahmad
- St. Michael's Hospital, University of Toronto, Toronto, Ontario, Canada
| | | | | | - Jeff S Healey
- Population Health Research Institute, McMaster University, Hamilton, Canada.
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424
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Abstract
Long QT syndrome (LQTS) is an inherited disorder associated with life-threatening ventricular arrhythmias. An understanding of the relationship between the genotype and phenotype characteristics of LQTS can lead to improved risk stratification and management of this hereditary arrhythmogenic disorder. Risk stratification in LQTS relies on combined assessment of clinical, electrocardiographic, and mutations-specific factors. Studies have shown that there are genotype-specific risk factors for arrhythmic events including age, gender, resting heart rate, QT corrected for heart rate, prior syncope, the postpartum period, menopause, mutation location, type of mutation, the biophysical function of the mutation, and response to beta-blockers. Importantly, genotype-specific therapeutic options have been suggested. Lifestyle changes are recommended according to the prevalent trigger for cardiac events. Beta-blockers confer greater benefit among patients with LQT1 with the greatest benefit among those with cytoplasmic loops mutations; specific beta-blocker agents may provide greater protection than other agents in specific LQTS genotypes. Potassium supplementation and sex hormone-based therapy may protect patients with LQT2. Sodium channel blockers such as mexiletine, flecainide, and ranolazine could be treatment options in LQT3.
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Affiliation(s)
- Alon Barsheshet
- Cardiology Department, Rabin Medical Center, Petah Tikva, and Sackler School of Medicine, Tel-Aviv University, Tel-Aviv, Israel; Cardiology Division, University of Rochester Medical Center, Rochester, NY
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425
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Schwartz PJ, Volders PGA. Sudden death by stress: how far under the nerves should we dig to find out why LQT1 patients die? J Am Coll Cardiol 2013; 63:828-30. [PMID: 24184246 DOI: 10.1016/j.jacc.2013.09.059] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/10/2013] [Accepted: 09/25/2013] [Indexed: 12/29/2022]
Affiliation(s)
- Peter J Schwartz
- Research Hospital Istituto Auxologico Italiano, Center for Cardiac Arrhythmias of Genetic Origin, Milan, Italy; Department of Molecular Medicine, University of Pavia, Pavia, Italy; Cardiovascular Genetics Laboratory, Hatter Institute for Cardiovascular Research in Africa, Department of Medicine, University of Cape Town, Cape Town, South Africa; Department of Medicine, University of Stellenbosch, Stellenbosch, Western Cape, South Africa; Department of Family and Community Medicine, College of Medicine, King Saud University, Riyadh, Saudi Arabia.
| | - Paul G A Volders
- Department of Cardiology, Cardiovascular Research Institute Maastricht, Maastricht University Medical Centre, Maastricht, the Netherlands
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426
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Nagels W, Brabant S, Van Aelst L, Pollet P, Anné W, Goethals M. Percutaneous left cardiac sympathetic denervation in a patient with long-QT syndrome. J Cardiothorac Vasc Anesth 2013; 28:1580-2. [PMID: 24120976 DOI: 10.1053/j.jvca.2013.06.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2013] [Indexed: 11/11/2022]
Affiliation(s)
| | | | - Lucas Van Aelst
- Department of Cardiology, Heilig-Hartziekenhuis Roeselare-Menen, Roeselare, Belgium
| | - Peter Pollet
- Department of Cardiology, Heilig-Hartziekenhuis Roeselare-Menen, Roeselare, Belgium
| | - Wim Anné
- Department of Cardiology, Heilig-Hartziekenhuis Roeselare-Menen, Roeselare, Belgium
| | - Marnix Goethals
- Department of Cardiology, Heilig-Hartziekenhuis Roeselare-Menen, Roeselare, Belgium
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427
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Calvillo L, Spazzolini C, Vullo E, Insolia R, Crotti L, Schwartz PJ. Propranolol prevents life-threatening arrhythmias in LQT3 transgenic mice: implications for the clinical management of LQT3 patients. Heart Rhythm 2013; 11:126-32. [PMID: 24135497 PMCID: PMC3882517 DOI: 10.1016/j.hrthm.2013.10.029] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Indexed: 11/26/2022]
Abstract
Background The efficacy of beta-blockers for treatment of patients with long QT syndrome type 3 (LQT3) has been repeatedly questioned, and it has been suggested that they might be detrimental for this genetic subgroup of patients with long QT syndrome (LQTS). The disquieting consequence has been that cardiologists confronted with LQT3 patients often do not even attempt pharmacologic therapy and implant cardioverter-defibrillators as first-choice treatment. However, the most recent clinical data indicate high efficacy of beta-blocker therapy in LQT3 patients. Objective The purpose of this study was to test the antiarrhythmic efficacy of beta-blockers in an established experimental model for LQT3. Methods After phenotypic validation of 65 ∆KPQ-SCN5A knock-in transgenic (TG) mice compared to 32 wild-type (WT) mice, we tested the effect of the arrhythmogenic cholinergic muscarinic agonist carbachol in 19 WT and 39 TG anesthetized mice, with and without pretreatment with propranolol given intraperitoneally. Results At the same heart rates, TG mice had a markedly longer QT interval than WT mice. Whereas carbachol had minor arrhythmic effects in the WT mice, it produced ventricular tachycardia (VT) and ventricular fibrillation (VF) in 55% of 20 TG mice. By contrast, in none of 19 TG mice pretreated with propranolol did VT/VF occur after carbachol injection. Conclusion These experimental data indicate that, contrary to previous reports, beta-blockade effectively prevents VT/VF in a validated LQT3 model. Together with the most recent clinical data, these findings indicate that there is no reason for not initiating protective therapy with beta-blockers in LQT3 patients.
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Affiliation(s)
- Laura Calvillo
- IRCCS Istituto Auxologico Italiano, Laboratory of Cardiovascular Genetics, Milan, Italy
| | - Carla Spazzolini
- Fondazione IRCCS Policlinico S. Matteo, Department of Cardiology, Pavia, Italy
| | - Eleonora Vullo
- Fondazione IRCCS Policlinico S. Matteo, Department of Cardiology, Pavia, Italy; Department of Molecular Medicine, University of Pavia, Pavia, Italy
| | - Roberto Insolia
- Department of Molecular Medicine, University of Pavia, Pavia, Italy
| | - Lia Crotti
- IRCCS Istituto Auxologico Italiano, Center for Cardiac Arrhythmias of Genetic Origin, Milan, Italy; Department of Molecular Medicine, University of Pavia, Pavia, Italy; Institute of Human Genetics, Helmholtz Zentrum München, Neuherberg, Germany
| | - Peter J Schwartz
- IRCCS Istituto Auxologico Italiano, Laboratory of Cardiovascular Genetics, Milan, Italy; Department of Molecular Medicine, University of Pavia, Pavia, Italy; IRCCS Istituto Auxologico Italiano, Center for Cardiac Arrhythmias of Genetic Origin, Milan, Italy; Cardiovascular Genetics Laboratory, Hatter Institute for Cardiovascular Research in Africa, Department of Medicine, University of Cape Town, Cape Town, South Africa; Department of Medicine, University of Stellenbosch, Stellenbosch, South Africa; Department of Family and Community Medicine, College of Medicine, King Saud University, Riyadh, Saudi Arabia.
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428
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Moreau A, Krahn AD, Gosselin-Badaroudine P, Klein GJ, Christé G, Vincent Y, Boutjdir M, Chahine M. Sodium overload due to a persistent current that attenuates the arrhythmogenic potential of a novel LQT3 mutation. Front Pharmacol 2013; 4:126. [PMID: 24098284 PMCID: PMC3787509 DOI: 10.3389/fphar.2013.00126] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Accepted: 09/11/2013] [Indexed: 12/21/2022] Open
Abstract
Long QT syndrome (LQTS) is a congenital abnormality of cardiac repolarization that manifests as a prolonged QT interval on 12-lead electrocardiograms (ECGs). The syndrome may lead to syncope and sudden death from ventricular tachyarrhythmias known as torsades de pointes. An increased persistent Na+ current is known to cause a Ca2+ overload in case of ischemia for example. Such increased Na+ persistent current is also usually associated to the LQT3 syndrome. The purpose of this study was to investigate the pathological consequences of a novel mutation in a family affected by LQTS. The impact of biophysical defects on cellular homeostasis are also investigated. Genomic DNA was extracted from blood samples, and a combination of PCR and DNA sequencing of several LQTS-linked genes was used to identify mutations. The mutation was reproduced in vitro and was characterized using the patch clamp technique and in silico quantitative analysis. A novel mutation (Q1476R) was identified on the SCN5A gene encoding the cardiac Na+ channel. Cells expressing the Q1476R mutation exhibited biophysical alterations, including a shift of SS inactivation and a significant increase in the persistent Na+ current. The in silico analysis confirmed the arrhythmogenic character of the Q1476R mutation. It further revealed that the increase in persistent Na+ current causes a frequency-dependent Na+ overload in cardiomyocytes co-expressing WT and mutant Nav1.5 channels that, in turn, exerts a moderating effect on the lengthening of the action potential (AP) duration caused by the mutation. The Q1476R mutation in SCN5A results in a three-fold increase in the window current and a persistent inward Na+ current. These biophysical defects may expose the carrier of the mutation to arrhythmias that occur preferentially in the patient at rest or during tachycardia. However, the Na+ overload counterbalances the gain-of-function of the mutation and is beneficial in that it prevents severe arrhythmias at intermediate heart rates.
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Affiliation(s)
- Adrien Moreau
- Centre de Recherche de l'Institut Universitaire en Santé Mentale de Québec, Quebec City QC, Canada
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429
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Diamant UB, Vahedi F, Winbo A, Rydberg A, Stattin EL, Jensen SM, Bergfeldt L. Electrophysiological phenotype in the LQTS mutations Y111C and R518X in the KCNQ1 gene. J Appl Physiol (1985) 2013; 115:1423-32. [PMID: 24052033 DOI: 10.1152/japplphysiol.00665.2013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Long QT syndrome is the prototypical disorder of ventricular repolarization (VR), and a genotype-phenotype relation is postulated. Furthermore, although increased VR heterogeneity (dispersion) may be important in the arrhythmogenicity in long QT syndrome, this hypothesis has not been evaluated in humans and cannot be tested by conventional electrocardiography. In contrast, vectorcardiography allows assessment of VR heterogeneity and is more sensitive to VR alterations than electrocardiography. Therefore, vectorcardiography was used to compare the electrophysiological phenotypes of two mutations in the LQT1 gene with different in vitro biophysical properties, and with LQT2 mutation carriers and healthy control subjects. We included 99 LQT1 gene mutation carriers (57 Y111C, 42 R518X) and 19 LQT2 gene mutation carriers. Potassium channel function is in vitro most severely impaired in Y111C. The control group consisted of 121 healthy subjects. QRS, QT, and T-peak to T-end (Tp-e) intervals, measures of the QRS vector and T vector and their relationship, and T-loop morphology parameters were compared at rest. Apart from a longer heart rate-corrected QT interval (QT heart rate corrected according to Bazett) in Y111C mutation carriers, there were no significant differences between the two LQT1 mutations. No signs of increased VR heterogeneity were observed among the LQT1 and LQT2 mutation carriers. QT heart rate corrected according to Bazett and Tp-e were longer, and the Tp-e-to-QT ratio greater in LQT2 than in LQT1 and the control group. In conclusion, there was a marked discrepancy between in vitro potassium channel function and in vivo electrophysiological properties in these two LQT1 mutations. Together with previous observations of the relatively low risk for clinical events in Y111C mutation carriers, our results indicate need for cautiousness in predicting in vivo electrophysiological properties and the propensity for clinical events based on in vitro assessment of ion channel function alone.
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Affiliation(s)
- Ulla-Britt Diamant
- Department of Public Health and Clinical Medicine, Heart Centre, Umeå University, Umeå, Sweden
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430
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Veerman CC, Verkerk AO, Blom MT, Klemens CA, Langendijk PNJ, van Ginneken ACG, Wilders R, Tan HL. Slow delayed rectifier potassium current blockade contributes importantly to drug-induced long QT syndrome. Circ Arrhythm Electrophysiol 2013; 6:1002-9. [PMID: 23995305 DOI: 10.1161/circep.113.000239] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
BACKGROUND Drug-induced long QT syndrome is generally ascribed to inhibition of the cardiac rapid delayed rectifier potassium current (IKr). Effects on the slow delayed rectifier potassium current (IKs) are less recognized. Triggered by a patient who carried the K422T mutation in KCNQ1 (encoding the α-subunit of the IKs channel), who presented with excessive QT prolongation and high serum levels of norfluoxetine, we investigated the effects of fluoxetine and its metabolite norfluoxetine on IKs. METHODS AND RESULTS ECG data from mutation carriers and noncarriers revealed that the K422T mutation per se had mild clinical effects. Patch clamp studies, performed on HEK293 cells, showed that heterozygously expressed K422T KCNQ1/KCNE1 channels had a positive shift in voltage dependence of activation and an increase in deactivation rate. Fluoxetine and its metabolite norfluoxetine both inhibited KCNQ1/KCNE1 current, with norfluoxetine being the most potent. Moreover, norfluoxetine increased activation and deactivation rates. Computer simulations of the effects of norfluoxetine on IKs and IKr demonstrated significant action potential prolongation, to which IKs block contributed importantly. Although the effects of the mutation per se were small, additional IKs blockade by norfluoxetine resulted in more prominent QTc prolongation in mutation carriers than in noncarriers, demonstrating synergistic effects of innate and drug-induced IKs blockade on QTc prolongation. CONCLUSIONS IKs blockade contributes importantly to drug-induced long QT syndrome, especially when repolarization reserve is reduced. Drug safety tests might have to include screening for IKs blockade.
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Affiliation(s)
- Christiaan C Veerman
- Heart Center, and Departments of Anatomy, Embryology, and Physiology, Cardiology, Hospital Pharmacy, Academic Medical Center, University of Amsterdam, the Netherlands; and Department of Hospital Pharmacy, Reinier de Graaf Group Hospitals, Delft, the Netherlands
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431
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Stump MR, Gong Q, Zhou Z. LQT2 nonsense mutations generate trafficking defective NH2-terminally truncated channels by the reinitiation of translation. Am J Physiol Heart Circ Physiol 2013; 305:H1397-404. [PMID: 23997099 DOI: 10.1152/ajpheart.00304.2013] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The human ether-a-go-go-related gene (hERG) encodes a voltage-activated K(+) channel that contributes to the repolarization of the cardiac action potential. Long QT syndrome type 2 (LQT2) is an autosomal dominant disorder caused by mutations in hERG, and patients with LQT2 are susceptible to severe ventricular arrhythmias. We have previously shown that nonsense and frameshift LQT2 mutations caused a decrease in mutant mRNA by the nonsense-mediated mRNA decay (NMD) pathway. The Q81X nonsense mutation was recently found to be resistant to NMD. Translation of Q81X is reinitiated at Met(124), resulting in the generation of NH2-terminally truncated hERG channels with altered gating properties. In the present study, we identified two additional NMD-resistant LQT2 nonsense mutations, C39X and C44X, in which translation is reinitiated at Met(60). Deletion of the first 59 residues of the channel truncated nearly one-third of the highly structured Per-Arnt-Sim domain and resulted in the generation of trafficking-defective proteins and a complete loss of hERG current. Partial deletion of the Per-Arnt-Sim domain also resulted in the accelerated degradation of the mutant channel proteins. The coexpression of mutant and wild-type channels did not significantly disrupt the function and trafficking properties of wild-type hERG. Our present findings indicate that translation reinitiation may generate trafficking-defective as well as dysfunctional channels in patients with LQT2 premature termination codon mutations that occur early in the coding sequence.
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Affiliation(s)
- Matthew R Stump
- Knight Cardiovascular Institute, Oregon Health and Science University, Portland, Oregon
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432
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Chang RY, Lee MY, Kan CB, Hsu WP, Hsiao PC. Oxaliplatin-induced acquired long QT syndrome with torsades de pointes and myocardial injury in a patient with dilated cardiomyopathy and rectal cancer. J Chin Med Assoc 2013; 76:466-9. [PMID: 23769882 DOI: 10.1016/j.jcma.2013.05.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Accepted: 03/30/2012] [Indexed: 11/16/2022] Open
Abstract
A 67-year-old woman presented with a history of dilated cardiomyopathy with congestive heart failure since 2003, who subsequently developed lower rectal cancer (adenocarcinoma) with liver, bone, and lymph node metastasis. Abdominoperineal resection and hepatectomy were performed. The patient received two rounds of intravenous chemotherapy, including 12 and six courses of FOLFOX4 (5-fluorouracil, leucovorin, and oxaliplatin; 85 mg/m(2) per cycle). She underwent a third round of intravenous FOLFOX4 because of tumor progression. During the 21(st) course of FOLFOX4 regimen, the patient developed ST segment depression in lead II and prolongation of QT interval with polymorphic ventricular tachycardia, torsades de pointes right after the start of oxaliplatin infusion. Immediate defibrillation and cardiopulmonary resuscitation were administered, and the patient regained spontaneous circulation and consciousness. Twelve-lead electrocardiogram showed ST segment elevation in III, aVF, and ST segment depression in V4-6 after resuscitation. To our knowledge, prolongation of QT interval with torsades de pointes and coronary spasm with myocardial injury that were stabilized in one patient following oxaliplatin infusion has not been reported. We present a patient with these rare complications.
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Affiliation(s)
- Rei-Yeuh Chang
- Division of Cardiology, Department of Internal Medicine, Ditmanson Medical Foundation Chia-Yi Christian Hospital, Chia-Yi, Taiwan, ROC.
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433
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Jackson HA, McIntosh S, Whittome B, Asuri S, Casey B, Kerr C, Tang A, Arbour LT. LQTS in Northern BC: homozygosity for KCNQ1 V205M presents with a more severe cardiac phenotype but with minimal impact on auditory function. Clin Genet 2013; 86:85-90. [PMID: 23844633 DOI: 10.1111/cge.12235] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Revised: 07/03/2013] [Accepted: 07/08/2013] [Indexed: 01/02/2023]
Abstract
Long QT syndrome (LQTS), a rare congenital cardiac condition associated with life-threatening ventricular arrhythmias is characterized by a prolonged QT interval on electrocardiograph corrected for heart rate [corrected QT (QTc)]. LQTS has been historically categorized into the autosomal dominant Romano-Ward syndrome (RWS) and the autosomal recessive Jervell and Lange-Nielsen syndrome (JLNS). JLNS is associated with prelingual sensorineural deafness. Both types of LQTS can be caused by mutations in channel genes (e.g. KCNQ1) responsible for potassium homeostasis in cardiac myocytes and cochlea. Autosomal dominant mutations often cause the RWS phenotype and homozygous or compound heterozygous mutations contribute to JLNS. Two First Nations communities in northern British Columbia are affected disproportionately with LQTS largely due to the V205M mutation in KCNQ1, however, the pathology and phenotypic expression for those V205M homozygous has been unknown. Here, we show that four V205M homozygous individuals have a significantly higher 'peak' QTc, and a more severe cardiac phenotype compared with 41 V205M heterozygous carriers and 57 first to third degree relatives without mutations. Given the lack of prelingual deafness the homozygous V205M LQTS patients present with a phenotype more typical of RWS than JLNS.
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Affiliation(s)
- H A Jackson
- Department of Medical Genetics and the Island Medical program, University of British Columbia, Victoria, British Columbia, Canada
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434
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Odening KE, Jung BA, Lang CN, Cabrera Lozoya R, Ziupa D, Menza M, Relan J, Franke G, Perez Feliz S, Koren G, Zehender M, Bode C, Brunner M, Sermesant M, Föll D. Spatial correlation of action potential duration and diastolic dysfunction in transgenic and drug-induced LQT2 rabbits. Heart Rhythm 2013; 10:1533-41. [PMID: 23892340 DOI: 10.1016/j.hrthm.2013.07.038] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2013] [Indexed: 11/24/2022]
Abstract
BACKGROUND Enhanced dispersion of action potential duration (APD) is a major contributor to long QT syndrome (LQTS)-related arrhythmias. OBJECTIVE To investigate spatial correlations of regional heterogeneities in cardiac repolarization and mechanical function in LQTS. METHODS Female transgenic LQTS type 2 (LQT2; n = 11) and wild-type littermate control (LMC) rabbits (n = 9 without E4031 and n = 10 with E4031) were subjected to phase contrast magnetic resonance imaging to assess regional myocardial velocities. In the same rabbits' hearts, monophasic APDs were assessed in corresponding segments. RESULTS In LQT2 and E4031-treated rabbits, APD was longer in all left ventricular segments (P < .01) and APD dispersion was greater than that in LMC rabbits (P < .01). In diastole, peak radial velocities (Vr) were reduced in LQT2 and E4031-treated compared to LMC rabbits in LV base and mid (LQT2: -3.36 ± 0.4 cm/s, P < .01; E4031-treated: -3.24 ± 0.6 cm/s, P < .0001; LMC: -4.42 ± 0.5 cm/s), indicating an impaired diastolic function. Regionally heterogeneous diastolic Vr correlated with APD (LQT2: correlation coefficient [CC] 0.38, P = .01; E4031-treated: CC 0.42, P < .05). Time-to-diastolic peak Vr were prolonged in LQT2 rabbits (LQT2: 196.8 ± 2.9 ms, P < .001; E4031-treated: 199.5 ± 2.2 ms, P < .0001, LMC 183.1 ± 1.5), indicating a prolonged contraction duration. Moreover, in transgenic LQT2 rabbits, diastolic time-to-diastolic peak Vr correlated with APD (CC 0.47, P = .001). In systole, peak Vr were reduced in LQT2 and E4031-treated rabbits (P < .01) but longitudinal velocities or ejection fraction did not differ. Finally, random forest machine learning algorithms enabled a differentiation between LQT2, E4031-treated, and LMC rabbits solely based on "mechanical" magnetic resonance imaging data. CONCLUSIONS The prolongation of APD led to impaired diastolic and systolic function in transgenic and drug-induced LQT2 rabbits. APD correlated with regional diastolic dysfunction, indicating that LQTS is not purely an electrical but an electromechanical disorder.
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Affiliation(s)
- Katja E Odening
- Department of Cardiology and Angiology I, Heart Center Freiburg University, Freiburg, Germany.
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435
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Mandyam MC, Soliman EZ, Alonso A, Dewland TA, Heckbert SR, Vittinghoff E, Cummings SR, Ellinor PT, Chaitman BR, Stocke K, Applegate WB, Arking DE, Butler J, Loehr LR, Magnani JW, Murphy RA, Satterfield S, Newman AB, Marcus GM. The QT interval and risk of incident atrial fibrillation. Heart Rhythm 2013; 10:1562-8. [PMID: 23872693 DOI: 10.1016/j.hrthm.2013.07.023] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Indexed: 10/26/2022]
Abstract
BACKGROUND Abnormal atrial repolarization is important in the development of atrial fibrillation (AF), but no direct measurement is available in clinical medicine. OBJECTIVE To determine whether the QT interval, a marker of ventricular repolarization, could be used to predict incident AF. METHODS We examined a prolonged QT interval corrected by using the Framingham formula (QT(Fram)) as a predictor of incident AF in the Atherosclerosis Risk in Communities (ARIC) study. The Cardiovascular Health Study (CHS) and Health, Aging, and Body Composition (ABC) study were used for validation. Secondary predictors included QT duration as a continuous variable, a short QT interval, and QT intervals corrected by using other formulas. RESULTS Among 14,538 ARIC study participants, a prolonged QT(Fram) predicted a roughly 2-fold increased risk of AF (hazard ratio [HR] 2.05; 95% confidence interval [CI] 1.42-2.96; P < .001). No substantive attenuation was observed after adjustment for age, race, sex, study center, body mass index, hypertension, diabetes, coronary disease, and heart failure. The findings were validated in Cardiovascular Health Study and Health, Aging, and Body Composition study and were similar across various QT correction methods. Also in the ARIC study, each 10-ms increase in QT(Fram) was associated with an increased unadjusted (HR 1.14; 95% CI 1.10-1.17; P < .001) and adjusted (HR 1.11; 95% CI 1.07-1.14; P < .001) risk of AF. Findings regarding a short QT interval were inconsistent across cohorts. CONCLUSIONS A prolonged QT interval is associated with an increased risk of incident AF.
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Affiliation(s)
- Mala C Mandyam
- Electrophysiology Section, Division of Cardiology, University of California, San Francisco, California
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436
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Wang F, Liu J, Hong L, Liang B, Graff C, Yang Y, Christiansen M, Olesen SP, Zhang L, Kanters JK. The phenotype characteristics of type 13 long QT syndrome with mutation in KCNJ5 (Kir3.4-G387R). Heart Rhythm 2013; 10:1500-6. [PMID: 23872692 DOI: 10.1016/j.hrthm.2013.07.022] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Indexed: 11/24/2022]
Abstract
BACKGROUND Long QT syndrome type 13 (LQT13) is caused by loss-of-function mutation in the KCNJ5-encoded cardiac G-protein-coupled inward rectifier potassium channel subtype 4 protein. The electrocardiographic (ECG) features of LQT13 are not described yet. OBJECTIVE To describe for the first time in detail the phenotype-genotype relationship of the ECG and clinical features in patients with LQT13. METHODS The 12-lead ECGs, 24-hour Holter recordings, and clinical information from KCNJ5-G387R mutation carriers of a fourth-generation Han Chinese family with LQT13 and a group of healthy Chinese individuals were analyzed. RESULTS Compared with the analysis of the healthy group (n = 8), age- and sex-matched pair analysis revealed that the mutation carriers (n = 8) had ventricular repolarization abnormality results in the prolongation of corrected QT and QTpeak intervals (P < .01); greater combined measure of repolarization morphology (T-wave morphology combination score) based on asymmetry, flatness, and notch (P < .01); and reduced low frequency/high frequency ratio of heart rate variability (P < .01) as a reflection of cardiac autonomic imbalance. Mean heart rate, time domain parameters of heart rate variability, time interval from T-wave peak to T-wave end, and T-wave amplitude were similar. CONCLUSIONS This study demonstrates for the first time the ECG features of patients with LQT13. Our data suggest that QTpeak intervals and T-wave morphology combination score may be the better parameters than the corrected QT interval to predict the phenotype-genotype relationship in patients with LQT13.
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437
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Smith JL, Reloj AR, Nataraj PS, Bartos DC, Schroder EA, Moss AJ, Ohno S, Horie M, Anderson CL, January CT, Delisle BP. Pharmacological correction of long QT-linked mutations in KCNH2 (hERG) increases the trafficking of Kv11.1 channels stored in the transitional endoplasmic reticulum. Am J Physiol Cell Physiol 2013; 305:C919-30. [PMID: 23864605 DOI: 10.1152/ajpcell.00406.2012] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
KCNH2 encodes Kv11.1 and underlies the rapidly activating delayed rectifier K(+) current (IKr) in the heart. Loss-of-function KCNH2 mutations cause the type 2 long QT syndrome (LQT2), and most LQT2-linked missense mutations inhibit the trafficking of Kv11.1 channels. Drugs that bind to Kv11.1 and block IKr (e.g., E-4031) can act as pharmacological chaperones to increase the trafficking and functional expression for most LQT2 channels (pharmacological correction). We previously showed that LQT2 channels are selectively stored in a microtubule-dependent compartment within the endoplasmic reticulum (ER). We tested the hypothesis that pharmacological correction promotes the trafficking of LQT2 channels stored in this compartment. Confocal analyses of cells expressing the trafficking-deficient LQT2 channel G601S showed that the microtubule-dependent ER compartment is the transitional ER. Experiments with E-4031 and the protein synthesis inhibitor cycloheximide suggested that pharmacological correction promotes the trafficking of G601S stored in this compartment. Treating cells in E-4031 or ranolazine (a drug that blocks IKr and has a short half-life) for 30 min was sufficient to cause pharmacological correction. Moreover, the increased functional expression of G601S persisted 4-5 h after drug washout. Coexpression studies with a dominant-negative form of Rab11B, a small GTPase that regulates Kv11.1 trafficking, prevented the pharmacological correction of G601S trafficking from the transitional ER. These data suggest that pharmacological correction quickly increases the trafficking of LQT2 channels stored in the transitional ER via a Rab11B-dependent pathway, and we conclude that the pharmacological chaperone activity of drugs like ranolazine might have therapeutic potential.
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Affiliation(s)
- Jennifer L Smith
- Center for Muscle Biology, Department of Physiology, University of Kentucky, Lexington, Kentucky
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438
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Ng D, Johnston JJ, Teer JK, Singh LN, Peller LC, Wynter JS, Lewis KL, Cooper DN, Stenson PD, Mullikin JC, Biesecker LG. Interpreting secondary cardiac disease variants in an exome cohort. ACTA ACUST UNITED AC 2013; 6:337-46. [PMID: 23861362 DOI: 10.1161/circgenetics.113.000039] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
BACKGROUND Massively parallel sequencing to identify rare variants is widely practiced in medical research and in the clinic. Genome and exome sequencing can identify the genetic cause of a disease (primary results), but it can also identify pathogenic variants underlying diseases that are not being sought (secondary or incidental results). A major controversy has developed surrounding the return of secondary results to research participants. We have piloted a method to analyze exomes to identify participants at risk for cardiac arrhythmias, cardiomyopathies, or sudden death. METHODS AND RESULTS Exome sequencing was performed on 870 participants not selected for arrhythmia, cardiomyopathy, or a family history of sudden death. Exome data from 22 cardiac arrhythmia- and 41 cardiomyopathy-associated genes were analyzed using an algorithm that filtered results on genotype quality, frequency, and database information. We identified 1367 variants in the cardiomyopathy genes and 360 variants in the arrhythmia genes. Six participants had pathogenic variants associated with dilated cardiomyopathy (n=1), hypertrophic cardiomyopathy (n=2), left ventricular noncompaction (n=1), or long-QT syndrome (n=2). Two of these participants had evidence of cardiomyopathy and 1 had left ventricular noncompaction on echocardiogram. Three participants with likely pathogenic variants had prolonged QTc. Family history included unexplained sudden death among relatives. CONCLUSIONS Approximately 0.5% of participants in this study had pathogenic variants in known cardiomyopathy or arrhythmia genes. This high frequency may be due to self-selection, false positives, or underestimation of the prevalence of these conditions. We conclude that clinically important cardiomyopathy and dysrhythmia secondary variants can be identified in unselected exomes.
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Affiliation(s)
- David Ng
- Genetic Disease Research Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA
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439
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Affiliation(s)
- Karine Guerrier
- Cincinnati Children's Hospital Medical Center, The Heart Institute, Burnet Avenue, Cincinnati, Ohio 45229, USA.
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440
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Chun YS, Oh HG, Park MK, Cho H, Chung S. Cholesterol regulates HERG K+ channel activation by increasing phospholipase C β1 expression. Channels (Austin) 2013; 7:275-87. [PMID: 23793622 DOI: 10.4161/chan.25122] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Human ether-a-go-go-related gene (HERG) K(+) channel underlies the rapidly activating delayed rectifier K(+) conductance (IKr) during normal cardiac repolarization. Also, it may regulate excitability in many neuronal cells. Recently, we showed that enrichment of cell membrane with cholesterol inhibits HERG channels by reducing the levels of phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] due to the activation of phospholipase C (PLC). In this study, we further explored the effect of cholesterol enrichment on HERG channel kinetics. When membrane cholesterol level was mildly increased in human embryonic kidney (HEK) 293 cells expressing HERG channel, the inactivation and deactivation kinetics of HERG current were not affected, but the activation rate was significantly decelerated at all voltages tested. The application of PtdIns(4,5)P2 or inhibitor for PLC prevented the effect of cholesterol enrichment, while the presence of antibody against PtdIns(4,5)P2 in pipette solution mimicked the effect of cholesterol enrichment. These results indicate that the effect of cholesterol enrichment on HERG channel is due to the depletion of PtdIns(4,5)P2. We also found that cholesterol enrichment significantly increases the expression of β1 and β3 isoforms of PLC (PLCβ1, PLCβ3) in the membrane. Since the effects of cholesterol enrichment on HERG channel were prevented by inhibiting transcription or by inhibiting PLCβ1 expression, we conclude that increased PLCβ1 expression leads to the deceleration of HERG channel activation rate via downregulation of PtdIns(4,5)P2. These results confirm a crosstalk between two plasma membrane-enriched lipids, cholesterol and PtdIns(4,5)P2, in the regulation of HERG channels.
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Affiliation(s)
- Yoon Sun Chun
- Department of Physiology; Samsung Biomedical Research Institute; Sungkyunkwan University School of Medicine; Suwon, South Korea
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441
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Abstract
The presence of 2 distinct populations of somatic or germline cells within a single individual harboring different genotypes is termed mosaicism. Recent reports suggest that parental mosaicism is involved in the heritability of type 1 Timothy syndrome (TS1), an extremely rare and life-threatening multisystem disorder characterized by severe QT interval prolongation, syndactyly, and several other complications. Although full TS1 is caused by a single missense mutation in the CACNA1C-encoded cardiac calcium channel, mosaic TS1 parents can display isolated syndactyly without additional phenotypic manifestations. A newborn boy presented with syndactyly at birth. The presence of syndactyly in his mother led to a diagnosis of benign familial syndactyly. However, at 9 months of age, during his first syndactyly-corrective surgery, intraoperative electrocardiograms revealed extreme QT prolongation and 2:1 atrioventricular block. A comprehensive cardiac evaluation was performed, and both mother and child were tested genetically, confirming a clinical suspicion of TS1. Only the patient tested positive for the TS1 mutation; however, more extensive molecular testing revealed a limited presence of the mutation in maternally-derived DNA. This case illustrates the potential of parental mosaicism to confound the diagnosis of potentially life-threatening genetic diseases, such as TS1. Here, a mother with a partial TS1 phenotype and genetically confirmed mosaicism transmitted the TS1-causative mutation to her son, resulting in fully expressive TS1. Thus, a shared partial phenotype should not be dismissed as a benign or insignificant finding, but should be evaluated further to rule out the possibility of parental mosaicism concealing a potentially fatal heritable disease.
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Affiliation(s)
- Keith A. Dufendach
- Departments of Medicine (Division of Cardiovascular Diseases), Pediatrics (Division of Pediatric Cardiology), and Molecular Pharmacology & Experimental Therapeutics, Windland Smith Rice Sudden Death Genomics Laboratory
| | - John R. Giudicessi
- Departments of Medicine (Division of Cardiovascular Diseases), Pediatrics (Division of Pediatric Cardiology), and Molecular Pharmacology & Experimental Therapeutics, Windland Smith Rice Sudden Death Genomics Laboratory,,Mayo Medical School, and,Mayo Graduate School, Mayo Clinic, Rochester, Minnesota
| | - Nicole J. Boczek
- Departments of Medicine (Division of Cardiovascular Diseases), Pediatrics (Division of Pediatric Cardiology), and Molecular Pharmacology & Experimental Therapeutics, Windland Smith Rice Sudden Death Genomics Laboratory,,Mayo Graduate School, Mayo Clinic, Rochester, Minnesota
| | - Michael J. Ackerman
- Departments of Medicine (Division of Cardiovascular Diseases), Pediatrics (Division of Pediatric Cardiology), and Molecular Pharmacology & Experimental Therapeutics, Windland Smith Rice Sudden Death Genomics Laboratory
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442
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Kako H, Martin DP, Cartabuke R, Beebe A, Klamar J, Tobias JD. Perioperative management of a patient with Rett syndrome. Int J Clin Exp Med 2013; 6:393-403. [PMID: 23724160 PMCID: PMC3664008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Accepted: 04/10/2013] [Indexed: 06/02/2023]
Abstract
Rett syndrome is a neurodevelopmental disorder that results from mutations in the genes encoding methyl-cytosine-guanosine binding protein 2 located on the X chromosome. Clinical features of central nervous system involvement include regression of developmental milestones in the late infant and early toddler stages, mental retardation, seizures and other electroencephalographic abnormalities. Given the invariable association of this degenerative disorder with orthopedic deformities including scoliosis, patients with Rett syndrome may present for anesthetic care during various surgical procedures. The complexity of the end-organ involvement, specifically the progressive nature of respiratory and cardiac involvement, makes the anesthetic care of such patients challenging. Specific perioperative concerns include potential difficulties with airway management, an underlying seizure disorder, an increased sensitivity to anesthetic agents, prolonged QT syndrome, and diabetes mellitus. We present an 11-year-old girl with Rett syndrome who required anesthetic care for posterior spinal fusion. Previous reports of anesthetic care for these patients are reviewed, the end-organ involvement discussed, and options for anesthetic care presented.
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Affiliation(s)
- Hiromi Kako
- Departments of Anesthesiology & Pain Medicine, Nationwide Children’s HospitalColumbus, Ohio
| | - David P Martin
- Departments of Anesthesiology & Pain Medicine, Nationwide Children’s HospitalColumbus, Ohio
- Department of Anesthesiology, The Ohio State UniversityColumbus, Ohio
| | - Richard Cartabuke
- Departments of Anesthesiology & Pain Medicine, Nationwide Children’s HospitalColumbus, Ohio
- Department of Anesthesiology, The Ohio State UniversityColumbus, Ohio
| | - Allan Beebe
- Department of Orthopedic Surgery, Nationwide Children’s HospitalColumbus, Ohio
| | - Jan Klamar
- Department of Orthopedic Surgery, Nationwide Children’s HospitalColumbus, Ohio
| | - Joseph D Tobias
- Departments of Anesthesiology & Pain Medicine, Nationwide Children’s HospitalColumbus, Ohio
- Department of Anesthesiology, The Ohio State UniversityColumbus, Ohio
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443
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Abstract
BACKGROUND Long QT syndrome (LQTS) is a disorder of ventricular repolarization usually treated with β-blockers, mostly with propanolol and nadolol. The aim of our study was to evaluate the role of bisoprolol in LQTS patients. METHODS A total of 34 patients were evaluated in an average follow-up time of 93 months: 31 months without treatment, 31 months in treatment with nadolol or propanolol and 31 months in treatment with bisoprolol. The average age of patients at diagnosis was 17.3 years. The enrolled patients were followed through a semiannual electrocardiogram and an annual 24-hour Holter monitoring. All patients underwent genotyping, routine hematologic tests, and an echocardiogram. RESULTS In 93 months there were 2 major and 12 minor cardiovascular events. Both the major events occurred in absence of β-blocking therapy. Of the 12 minor cardiovascular events 3 occurred in absence of treatment, 7 during treatment with nadolol or propranolol, and 2 during treatment with bisoprolol. The mean heart rate at 24 h Holter was 87 bpm without treatment, 71 bpm in patients treated with propanolol and nadolol, and 70 bpm in patients treated with bisoprolol. There were not statistically significant differences between the three groups in the mean QTc. CONCLUSIONS Beta-blocking therapy is the cornerstone of LQTS therapy but actually there is no clear indication about which beta-blocker should be used. In our experience bisoprolol proved to be less harmful and easier to manage than propranolol and nadolol in patients with LQTS, with the same effectiveness in preventing major cardiovascular events.
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444
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Extramiana F, Maison-Blanche P, Denjoy I, De Jode P, Messali A, Labbé JP, Leenhardt A. Gene-specific effect of beta-adrenergic blockade on corrected QT interval in the long QT syndrome. Ann Noninvasive Electrocardiol 2013; 18:399-408. [PMID: 23879280 DOI: 10.1111/anec.12048] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND In the long QT syndrome (LQTS) the effects of beta-blocker treatment on prevention of cardiac events differs according to the genotype. We aimed to assess the effect of beta-blocker treatment on QT/QTc duration in Type 1 LQTS (LQT1) and Type 2 LQTS (LQT2) patients. METHODS 24-hour digital Holter ECG were recorded before and after beta-blocking therapy initiation in LQT1 (n = 30) and LQT2 patients (n = 16). QT duration was measured on consecutive 1-minute averaged QRS-T complexes leading to up to 1440 edited QT-RR pairs for each recording. We computed subject- and treatment-specific log/log QT/RR relationships which were used to correct the QT intervals. The QT duration was also evaluated at predefined heart rates and after correction using Bazett and Fridericia coefficients. RESULTS At baseline, individual QT/RR coefficients were higher in LQT2 than in LQT1 patients (0.53 ± 0.10 vs. 0.40 ± 0.11, P < 0.001) and QT1000 was longer in LQT2 than in LQT1 patients (521 ± 38 vs. 481 ± 39 ms, P < 0.01). Beta-blockers significantly prolonged the mean RR interval (from 827 ± 161 to 939 ± 197 ms, P < 0.0001). The individual QT/RR coefficients were not significantly modified by beta-blockers. Beta-blocker treatment was associated with a prolongation of the QT1000 interval (from 481 ± 39 to 498 ± 43 ms, P < 0.01) in LQT1 patients but with a shortening in LQT2 patients (from 521 ± 38 to 503 ± 32 ms, P < 0.01). CONCLUSIONS The effect of beta-adrenergic blockade on QTc duration is different in LQT1 and LQT2 patients. Our data suggest that, in LQT1 patients, the well-known positive effect of beta-blockade might be associated with a prolongation of QTc duration. The mechanisms of beta-blockade protection may be different in LQT1 and in LQT2 patients.
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445
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Hsiao PY, Tien HC, Lo CP, Juang JMJ, Wang YH, Sung RJ. Gene mutations in cardiac arrhythmias: a review of recent evidence in ion channelopathies. Appl Clin Genet 2013; 6:1-13. [PMID: 23837003 PMCID: PMC3699290 DOI: 10.2147/tacg.s29676] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Over the past 15 years, molecular genetic studies have linked gene mutations to many inherited arrhythmogenic disorders, in particular, “ion channelopathies”, in which mutations in genes encode functional units of ion channels and/or their transporter-associated proteins in patients without primary cardiac structural abnormalities. These disorders are exemplified by congenital long QT syndrome (LQTS), short QT syndrome, Brugada syndrome (BrS) and catecholaminergic polymorphic ventricular tachycardia (CPVT). Functional and pathophysiological studies have led to better understanding of the clinical spectrum, ion channel structures and cellular electrophysiology involving dynamics of intracellular calcium cycling in many subtypes of these disorders and more importantly, development of potentially more effective pharmacological agents and even curative gene therapy. In this review, we have summarized (1) the significance of unveiling mutations in genes encoding transporter-associated proteins as the cause of congenital LQTS, (2) the technique of catheter ablation applied at the right ventricular outflow tract may be curative for severely symptomatic BrS, (3) mutations with channel function modulated by protein Kinase A-dependent phosphorylation can be the culprit of CPVT mimicry in Andersen-Tawil syndrome (LQT7), (4) ablation of the ion channel anchoring protein may prevent arrhythmogenesis in Timothy syndrome (LQT8), (5) altered intracellular Ca2+ cycling can be the basis of effective targeted pharmacotherapy in CPVT, and (6) the technology of induced pluripotent stem cells is a promising diagnostic and research tool as it has become a new paradigm for pathophysiological study of patient- and disease-specific cells aimed at screening new drugs and eventual clinical application of gene therapy. Lastly, we have discussed (7) genotype-phenotype correlation in relation to risk stratification of patients with congenital LQTS in clinical practice.
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Affiliation(s)
- Pi-Yin Hsiao
- Institute of Life Sciences, National Central University, Taoyuan, Taiwan
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446
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Erskine KE, Griffith E, Degroat N, Stolerman M, Silverstein LB, Hidayatallah N, Wasserman D, Paljevic E, Cohen L, Walsh CA, McDonald T, Marion RW, Dolan SM. An interdisciplinary approach to personalized medicine: case studies from a cardiogenetics clinic. Per Med 2013; 10:73-80. [PMID: 24496296 DOI: 10.2217/pme.12.108] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In the genomic age, the challenges presented by various inherited conditions present a compelling argument for an interdisciplinary model of care. Cardiac arrhythmias with a genetic basis, such as long QT syndrome, require clinicians with expertise in many specialties to address the complex genetic, psychological, ethical and medical issues involved in treatment. The Montefiore-Einstein Center for CardioGenetics has been established to provide personalized, interdisciplinary care for families with a history of sudden cardiac death or an acute cardiac event. Four vignettes of patient care are presented to illustrate the unique capacity of an interdisciplinary model to address genetic, psychological, ethical and medical issues. Because interdisciplinary clinics facilitate collaboration among multiple specialties, they allow for individualized, comprehensive care to be delivered to families who experience complex inherited medical conditions. As the genetic basis of many complex conditions is discovered, the advantages of an interdisciplinary approach for delivering personalized medicine will become more evident.
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Affiliation(s)
- Kathleen E Erskine
- Department of Obstetrics & Gynecology & Women's Health, Division of Reproductive Genetics, Albert Einstein College of Medicine/Montefiore Medical Center, 1695 Eastchester Road, Suite 301, Bronx, NY, USA
| | - Eleanor Griffith
- University OBGYN Associates, Ambulatory Care Center, C1673, UMDNJ, 140 Bergen Street, Newark, NJ 07103, USA
| | - Nicole Degroat
- Department of Obstetrics & Gynecology & Women's Health, Division of Reproductive Genetics, Albert Einstein College of Medicine/Montefiore Medical Center, 1300 Morris Park Avenue, Mazer 632, Bronx, NY, USA
| | - Marina Stolerman
- Private Practice, 425 E 86th Street, Suite 1A, New York, NY, USA
| | - Louise B Silverstein
- Ferkauf Graduate School of Psychology, Yeshiva University, 1300 Morris Park Avenue, Bronx, NY, USA
| | - Nadia Hidayatallah
- Ferkauf Graduate School of Psychology, Yeshiva University, 1300 Morris Park Avenue, Bronx, NY, USA
| | - David Wasserman
- Center for Ethics at Yeshiva University, 500 W 185th Street, New York, NY, USA
| | - Esma Paljevic
- Pediatric Heart Center, Children's Hospital at Montefiore, 3415 Bainbridge Avenue, Bronx, NY, USA
| | - Lilian Cohen
- Division of Medical Genetics, Weill Cornell Medical College/New York Presbyterian Hospital, 505 East 70th Street, Helmsley Tower, 3rd Floor, New York, NY, USA
| | - Christine A Walsh
- Pediatric Dysrhythmia Center, Children's Hospital at Montefiore, 3415 Bainbridge Avenue, Bronx, NY, USA
| | - Thomas McDonald
- Departments of Medicine/Cardiology & Molecular Pharmacology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Forchheimer G35, Bronx, NY, USA
| | - Robert W Marion
- Divisions of Developmental Medicine & Genetics, Children's Hospital at Montefiore, 3415 Bainbridge Avenue, Bronx, NY, USA
| | - Siobhan M Dolan
- Department of Obstetrics & Gynecology & Women's Health, Division of Reproductive Genetics, Albert Einstein College of Medicine/Montefiore Medical Center, 1300 Morris Park Avenue, Mazer 634, Bronx, NY 10461 USA
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447
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Gao Y, Li C, Liu W, Wu R, Qiu X, Liang R, Li L, Zhang L, Hu D. Genotype-phenotype analysis of three Chinese families with Jervell and Lange-Nielsen syndrome. J Cardiovasc Dis Res 2012; 3:67-75. [PMID: 22629021 PMCID: PMC3354473 DOI: 10.4103/0975-3583.95357] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
BACKGROUND Long QT syndrome (LQTS) is characterized by QT prolongation, syncope and sudden death. This study aims to explore the causes, clinical manifestations and therapeutic outcomes of Jervell and Lange-Nielsen syndrome (JLNS), a rare form of LQTS with congenital sensorineural deafness, in Chinese individuals. MATERIALS AND METHODS Three JLNS kindreds from the Chinese National LQTS Registry were investigated. Mutational screening of KCNQ1 and KCNE1 genes was performed by polymerase chain reaction and direct DNA sequence analysis. LQTS phenotype and therapeutic outcomes were evaluated for all probands and family members. RESULTS We identified 7 KCNQ1 mutations. c.1032_1117dup (p.Ser373TrpfsX10) and c.1319delT (p.Val440AlafsX26) were novel, causing JLNS in a 16-year-old boy with a QTc (QT interval corrected for heart rate) of 620 ms and recurrent syncope. c.605-2A>G and c.815G>A (p.Gly272Asp) caused JLNS in a 12-year-old girl and her 5-year-old brother, showing QTc of 590 to 600 ms and recurrent syncope. The fourth JLNS case, a 46-year-old man carrying c.1032G>A (p.Ala344Alasp) and c.569G>A (p.Arg190Gln) and with QTc of 460 ms, has been syncope-free since age 30. His 16-year-old daughter carries novel missense mutation c.574C>T (p.Arg192Cys) and c.1032G>A(p.Ala344Alasp) and displayed a severe phenotype of Romano-Ward syndrome (RWS) characterized by a QTc of 530 ms and recurrent syncope with normal hearing. Both the father and daughter also carried c.253G>A (p.Asp85Asn; rs1805128), a rare single nucleotide polymorphism (SNP) on KCNE1. Bizarre T waves were seen in 3/4 JLNS patients. Symptoms were improved and T wave abnormalities became less abnormal after appropriate treatment. CONCLUSION This study broadens the mutation and phenotype spectrums of JLNS. Compound heterozygous KCNQ1 mutations can result in both JLNS and severe forms of RWS in Chinese individuals.
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Affiliation(s)
- Yuanfeng Gao
- Heart Center, Peking University People's Hospital, Beijing - 100 044, P. R. China
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448
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Abstract
Mutations of SCN5A gene, which encodes the α-subunit of the voltage-gated Na+ channel NaV1.5, underlie hereditary cardiac arrhythmic syndromes such as the type 3 long QT syndrome, cardiac conduction diseases, the Brugada syndrome, the sick sinus syndrome, a trial standstill, and numerous overlap syndromes. Patch-clamp studies in heterologous expression systems have provided important information to understand the genotype-phenotype relationships of these diseases. However, they could not clarify how SCN5A mutations can be responsible for such a large spectrum of diseases, for the late age of onset or the progressiveness of some of these diseases and for the overlapping syndromes. Genetically modified mice rapidly appeared as promising tools for understanding the pathophysiological mechanisms of cardiac SCN5A-related arrhythmic syndromes and several mouse models have been established. This review presents the results obtained on these models that, for most of them, recapitulate the clinical phenotypes of the patients. This includes two models knocked out for Nav1.5 β1 and β3 auxiliary subunits that are also discussed. Despite their own limitations that we point out, the mouse models still appear as powerful tools to elucidate the pathophysiological mechanisms of SCN5A-related diseases and offer the opportunity to investigate the secondary cellular consequences of SCN5A mutations such as the expression remodeling of other genes. This points out the potential role of these genes in the overall human phenotype. Finally, they constitute useful tools for addressing the role of genetic and environmental modifiers on cardiac electrical activity.
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449
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Abstract
In voltage-gated cation channels, a recurrent pattern for mutations is the neutralization of positively charged residues in the voltage-sensing S4 transmembrane segments. These mutations cause dominant ion channelopathies affecting many tissues such as brain, heart, and skeletal muscle. Recent studies suggest that the pathogenesis of associated phenotypes is not limited to alterations in the gating of the ion-conducting alpha pore. Instead, aberrant so-called omega currents, facilitated by the movement of mutated S4 segments, also appear to contribute to symptoms. Surprisingly, these omega currents conduct cations with varying ion selectivity and are activated in either a hyperpolarized or depolarized voltage range. This review gives an overview of voltage sensor channelopathies in general and focuses on pathogenesis of skeletal muscle S4 disorders for which current knowledge is most advanced.
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450
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Moric-Janiszewska E, Głogowska-Ligus J, Paul-Samojedny M, Węglarz L, Markiewicz-Łoskot G, Szydłowski L. Age-and sex-dependent mRNA expression of KCNQ1 and HERG in patients with long QT syndrome type 1 and 2. Arch Med Sci 2011; 7:941-7. [PMID: 22328875 PMCID: PMC3264984 DOI: 10.5114/aoms.2011.26604] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2010] [Revised: 11/01/2010] [Accepted: 11/09/2010] [Indexed: 01/08/2023] Open
Abstract
INTRODUCTION The main goal of this study was to examine the patient age and sex dependent expression of KCNQ1 and HERG genes that encode potassium channels responsible for the occurrence of long QT syndrome (LQTS). MATERIAL AND METHODS The study enrolled 43 families whose members suffered from LQTS type 1 (LQTS1) or 2 (LQTS2) or were healthy. The study attempted to prove that β-actin is a good endogenous control when determining the expression of the studied genes. Examination of gene expression was achieved with quantitative real-time PCR (QRT-PCR). Expression of the investigated genes was inferred from the analysis of the number of mRNA copies per 1 μg total RNA isolated from whole blood. RESULTS Significantly lower KCNQ1 and KCNH2 mRNA levels in healthy females than healthy males were observed (p = 0.032; p = 0.02). In male patients both transcripts were expressed at a lower level (p = 0.0084; p = 0.035). The comparison of transcriptional activity of KCNQ1 and KCNH2 in healthy adults and children revealed higher KCNQ1 and lower KCNH2 mRNA levels in healthy adults (p = 0.033; p = 0.04), higher KCNQ1 and lower KCNH2 mRNA levels in adult patients below 55 years old than in adults over 55 years old (p=0.036; p = 0.044), and significantly higher KCNQ1 and lower KCNH2 mRNA levels in adult patients (over 55 years) than in paediatric patients (below 15 years) (p=0.047; p = 0.08). CONCLUSIONS The results support the hypothesis that KCNQ1 and HERG gene expression is influenced by age and gender in human patients with long QT syndrome and in healthy subjects.
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Affiliation(s)
| | | | | | - Ludmiła Węglarz
- Department of Biochemistry, Medical University of Silesia, Sosnowiec, Poland
| | | | - Lesław Szydłowski
- 1 Department of Paediatric Cardiology, Medical University of Silesia, Katowice-Ligota, Poland
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