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Zumhagen S, Stallmeyer B, Friedrich C, Eckardt L, Seebohm G, Schulze-Bahr E. Inherited long QT syndrome: clinical manifestation, genetic diagnostics, and therapy. Herzschrittmacherther Elektrophysiol 2012; 23:211-219. [PMID: 22996910 DOI: 10.1007/s00399-012-0232-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Accepted: 07/20/2012] [Indexed: 06/01/2023]
Abstract
Inherited long QT syndrome (LQTS) is characterized by a prolonged ventricular repolarization (QTc interval) and symptoms (syncope, sudden cardiac arrest) due to polymorphic ventricular arrhythmias. As of today, 13 different cardiac ion channel genes have been associated with congenital LQTS. The most common ones are due to KCNQ1 (LQT-1), KCNH2 (LQT-2), and SCN5A (LQT-3) gene mutations and account for up to 75 % of cases. Typical clinical findings are an increased QT interval on the surface electrocardiogram, specifically altered T wave morphologies, polymorphic ventricular arrhythmias, or an indicative family history. Recently, in the HRS/EHRA expert consensus statement, comprehensive genetic testing of major LQTS genes was recommended for index patients for whom there is a strong clinical suspicion of LQTS. Overall, antiadrenergic therapy, in particular β-receptor blockers, has been the mainstay of therapy and has significantly reduced cardiac events. For high-risk patients, an implantable cardioverter defibrillator (ICD) is recommended. Importantly, lifestyle modification and avoidance of arrhythmia triggers are additional important approaches.
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Affiliation(s)
- Sven Zumhagen
- Institute for Genetics of Heart Diseases (IfGH), Department of Cardiovascular Medicine, University Hospital Münster, Albert-Schweitzer-Campus 1, Gebäude D3, 48149, Münster, Germany.
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Vandenberg JI, Perry MD, Perrin MJ, Mann SA, Ke Y, Hill AP. hERG K+ Channels: Structure, Function, and Clinical Significance. Physiol Rev 2012; 92:1393-478. [DOI: 10.1152/physrev.00036.2011] [Citation(s) in RCA: 463] [Impact Index Per Article: 38.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The human ether-a-go-go related gene (hERG) encodes the pore-forming subunit of the rapid component of the delayed rectifier K+ channel, Kv11.1, which are expressed in the heart, various brain regions, smooth muscle cells, endocrine cells, and a wide range of tumor cell lines. However, it is the role that Kv11.1 channels play in the heart that has been best characterized, for two main reasons. First, it is the gene product involved in chromosome 7-associated long QT syndrome (LQTS), an inherited disorder associated with a markedly increased risk of ventricular arrhythmias and sudden cardiac death. Second, blockade of Kv11.1, by a wide range of prescription medications, causes drug-induced QT prolongation with an increase in risk of sudden cardiac arrest. In the first part of this review, the properties of Kv11.1 channels, including biogenesis, trafficking, gating, and pharmacology are discussed, while the second part focuses on the pathophysiology of Kv11.1 channels.
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Affiliation(s)
- Jamie I. Vandenberg
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Matthew D. Perry
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Mark J. Perrin
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Stefan A. Mann
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Ying Ke
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Adam P. Hill
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
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Perrin MJ, Gollob MH. The genetics of cardiac disease associated with sudden cardiac death: a paper from the 2011 William Beaumont Hospital Symposium on molecular pathology. J Mol Diagn 2012; 14:424-36. [PMID: 22749884 DOI: 10.1016/j.jmoldx.2012.04.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Revised: 04/03/2012] [Accepted: 04/13/2012] [Indexed: 11/17/2022] Open
Abstract
Sudden cardiac death due to ventricular arrhythmia most commonly occurs in the setting of coronary artery disease. However, a number of inherited syndromes have now been identified that carry a significant risk of sudden cardiac death and that are disproportionately represented in the young. Arrhythmia in such conditions may result from genetically mediated structural heart disease (eg, hypertrophic cardiomyopathy and arrhythmogenic right ventricular cardiomyopathy) or from altered function of cardiac ion channels in the absence of overt structural disease (eg, Brugada syndrome and long QT syndrome). The past 15 years have seen considerable progress in our understanding of the genetic underpinnings of these disorders. With the advent of clinical genetic testing as a routine part of clinical care, a new knowledge base is required of practicing cardiologists and genetic testing facilities, particularly related to the rational ordering of genetic testing and the interpretation of results. This review addresses the latest findings in regard to the genetic causes of inherited syndromes associated with sudden cardiac death and summarizes recently published guidelines for the genetic testing of affected individuals and their families.
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Affiliation(s)
- Mark J Perrin
- Division of Cardiology, Department of Medicine, University of Ottawa Heart Institute, Ottawa, Ontario, Canada
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Couderc JP, Xia X, Denjoy I, Extramiana F, Maison-Blanche P, Moss AJ, Zareba W, Lopes CM. Genotype- and Sex-Specific QT-RR Relationship in the Type-1 Long-QT Syndrome. J Am Heart Assoc 2012; 1:e000570. [PMID: 23130128 PMCID: PMC3487370 DOI: 10.1161/jaha.112.000570] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Accepted: 03/21/2012] [Indexed: 12/28/2022]
Abstract
BACKGROUND Genotype-phenotype investigations have revealed significantly larger risk for cardiac events in patients with type 1 long-QT syndrome (LQT-1), particularly in adult females, with missense mutation in the cytoplasmic loop (C-loop) regions of the α subunit of the KCNQ1 gene associated with an impaired ion channel activation by adrenergic stimulus. We hypothesize that the impaired response to increases in heart rate leads to abnormal QT-RR dynamic profiles and is responsible for the increased cardiac risk for these patients. METHODS AND RESULTS We measured the QT-RR slope in 24-hour Holter ECGs from LQT-1 patients with the mutations associated with impaired adrenergic stimulus (C-loop, n=18) and compared to LQT-1 patients with other mutations (non-C-loop, n=48), and to a healthy control group (n=195). The diurnal QT-RR slope was less steep in C-loop mutation patients (0.10±0.05) than in the ECGs from non-C-loop mutation patients (0.17±0.09, P=0.002). For female patients, slower heart rates were associated with prolonged QT and increased QT-RR slope. Male patients with C-loop mutations showed an impaired repolarization for shorter range of heart rates than in females, which is consistent with gender differences in triggers for events in this syndrome. CONCLUSIONS Our observations suggest that the C-loop LQT-1 patients have specific impaired adrenergic regulation of the ventricular repolarization. This response to heart rate increases may be useful in identification of high-risk patients with inherited prolonged QT and may help select an optimal antiarrhythmic therapeutic strategy. (J Am Heart Assoc. 2012;1:e000570 doi: 10.1161/JAHA.112.000570.).
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Affiliation(s)
- Jean-Philippe Couderc
- Center for Quantitative Electrocardiography and Cardiac Safety, Heart Research Follow-Up Program, University of Rochester Medical Center, NY (J.-P.C., X.X., A.J.M., W.Z.)
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Goldenberg I, Thottathil P, Lopes CM, Moss AJ, McNitt S, O-Uchi J, Robinson JL, Zareba W, Ackerman MJ, Kaufman ES, Towbin JA, Vincent M, Barsheshet A. Trigger-specific ion-channel mechanisms, risk factors, and response to therapy in type 1 long QT syndrome. Heart Rhythm 2011; 9:49-56. [PMID: 21871251 DOI: 10.1016/j.hrthm.2011.08.020] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Accepted: 08/20/2011] [Indexed: 11/30/2022]
Abstract
BACKGROUND Arrhythmic events in long-QT syndrome type 1 (LQT1) may be associated with exercise, acute arousal, or rest/sleep. OBJECTIVES We aimed to identify trigger-specific risk factors for cardiac events in patients with LQT1. METHODS The study population comprised 721 genetically confirmed patients with LQT1 from the US portion of the International LQTS Registry. Multivariate analysis was used to assess the independent contribution of prespecified clinical and mutation-specific factors to the development of a first reported triggered event, associated with exercise, arousal, or sleep/rest. RESULTS Cardiac events occurred in 221 study patients, of whom 121 (55%) were associated with exercise, 30 (14%) with arousal, 47 (21%) with sleep/rest, and 23 (10%) with other triggers. Multivariate analysis showed that males <13 years had a 2.8-fold (P < .001) increase in the risk for exercise-triggered events whereas females ≥13 years showed a 3.5-fold (P = .002) increase in the risk for sleep/rest nonarousal events. Cytoplasmic-loop mutations within the transmembrane region, involved in adrenergic channel regulation, were associated with the increased risk for both exercise- and arousal-triggered events (hazard ratio = 6.19 [P < .001] and 4.99 [P < .001], respectively) but were not associated with events during sleep/rest (hazard ratio = 0.72; P = .46). Beta-blocker therapy was associated with a pronounced 78% (P < .001) reduction in the risk for exercise-triggered events but did not have a significant effect on events associated with arousal or sleep/rest. CONCLUSIONS In patients with LQT1, cardiac events triggered by exercise, arousal, or rest/sleep are associated with distinctive risk factors and response to medical therapy. These findings can be used for improved recommendations for lifestyle modifications and therapeutic management in this population.
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Affiliation(s)
- Ilan Goldenberg
- Cardiology Division, University of Rochester Medical Center, Rochester, New York 14642, USA.
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The significance of protein S-100B testing in cardiac arrest patients. Clin Biochem 2011; 44:567-75. [PMID: 21458434 DOI: 10.1016/j.clinbiochem.2011.03.133] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2011] [Accepted: 03/20/2011] [Indexed: 11/24/2022]
Abstract
Cardiac arrest often represents the first expression of an underlying cardiac disease. Despite advances in neurocritical care, the neurological assessment of cardiac arrest patients relies on clinical, instrumental and biochemical parameters. The clinical significance of S-100 calcium binding protein B (S-100B) has substantially increased throughout several areas of clinical neuroscience, but reliable evidences attest it can be used as a reliable and early predictor of poor physiological and cognitive neurological outcomes after cardiac arrest.
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