1
|
Guo Y, Cheng D, Yu ZY, Schiatti T, Chan AY, Hill AP, Peyronnet R, Feneley MP, Cox CD, Martinac B. Functional coupling between Piezo1 and TRPM4 influences the electrical activity of HL-1 atrial myocytes. J Physiol 2024; 602:4363-4386. [PMID: 38098265 DOI: 10.1113/jp284474] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Accepted: 11/30/2023] [Indexed: 09/25/2024] Open
Abstract
The transient receptor potential melastatin 4 (TRPM4) channel contributes extensively to cardiac electrical activity, especially cardiomyocyte action potential formation. Mechanical stretch can induce changes in heart rate and rhythm, and the mechanosensitive channel Piezo1 is expressed in many cell types within the myocardium. Our previous study showed that TRPM4 and Piezo1 are closely co-localized in the t-tubules of ventricular cardiomyocytes and contribute to the Ca2+-dependent signalling cascade that underlies hypertrophy in response to mechanical pressure overload. However, there was no direct evidence showing that Piezo1 activation was related to TRPM4 activation in situ. In the present study, we employed the HL-1 mouse atrial myocyte-like cell line as an in vitro model to investigate whether Piezo1-TRPM4 coupling can affect action potential properties. We used the small molecule Piezo1 agonist, Yoda1, as a surrogate for mechanical stretch to activate Piezo1 and detected the action potential changes in HL-1 cells using FluoVolt, a fluorescent voltage sensitive dye. Our results demonstrate that Yoda1-induced activation of Piezo1 changes the action potential frequency in HL-1 cells. This change in action potential frequency is reduced by Piezo1 knockdown using small intefering RNA. Importantly knockdown or pharmacological inhibition of TRPM4 significantly affected the degree to which Yoda1-evoked Piezo1 activation influenced action potential frequency. Thus, the present study provides in vitro evidence of a functional coupling between Piezo1 and TRPM4 in a cardiomyocyte-like cell line. The coupling of a mechanosensitive Ca2+ permeable channel and a Ca2+-activated TRP channel probably represents a ubiquitous model for the role of TRP channels in mechanosensory transduction. KEY POINTS: The transient receptor potential melastatin 4 (TRPM4) and Piezo1 channels have been confirmed to contribute to the Ca2+-dependent signalling cascade that underlies cardiac hypertrophy in response to mechanical pressure overload. However, there was no direct evidence showing that Piezo1 activation was related to TRPM4 activation in situ. We employed the HL-1 mouse atrial myocyte-like cell line as an in vitro model to investigate the effect of Piezo1-TRPM4 coupling on cardiac electrical properties. The results show that both pharmacological and genetic inhibition of TRPM4 significantly affected the degree to which Piezo1 activation influenced action potential frequency in HL-1 cells. Our findings provide in vitro evidence of a functional coupling between Piezo1 and TRPM4 in a cardiomyocyte-like cell line. The coupling of a mechanosensitive Ca2+ permeable channel and a Ca2+-activated TRP channel probably represents a ubiquitous model for the role of TRP channels in mechanosensory transduction in various (patho)physiological processes.
Collapse
Affiliation(s)
- Yang Guo
- Victor Chang Cardiac Research Institute, Sydney, NSW, Australia
- Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia
| | - Delfine Cheng
- Victor Chang Cardiac Research Institute, Sydney, NSW, Australia
- Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia
| | - Ze-Yan Yu
- Victor Chang Cardiac Research Institute, Sydney, NSW, Australia
- Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia
| | - Teresa Schiatti
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, and Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Andrea Y Chan
- Victor Chang Cardiac Research Institute, Sydney, NSW, Australia
| | - Adam P Hill
- Victor Chang Cardiac Research Institute, Sydney, NSW, Australia
- Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia
| | - Rémi Peyronnet
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, and Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Michael P Feneley
- Victor Chang Cardiac Research Institute, Sydney, NSW, Australia
- Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia
- Department of Cardiology, St Vincent's Hospital, Sydney, NSW, Australia
| | - Charles D Cox
- Victor Chang Cardiac Research Institute, Sydney, NSW, Australia
- Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia
| | - Boris Martinac
- Victor Chang Cardiac Research Institute, Sydney, NSW, Australia
- Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia
| |
Collapse
|
2
|
Ifedili I, Maturana M, Kayali S, Levine Y, Kabra R, Jha SK. A case of short QT-interval postventricular arrhythmia arrest from Torsade De Pointes, a new phenotype, or the result of tachycardia-mediated imbalance. J Cardiovasc Electrophysiol 2024; 35:501-504. [PMID: 38174843 DOI: 10.1111/jce.16164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Revised: 12/03/2023] [Accepted: 12/15/2023] [Indexed: 01/05/2024]
Abstract
INTRODUCTION We report the case of an 18-year-old female with recurrent syncope that was discovered to have congenital long QT syndrome (LQTS) and episodes of a transiently short QT interval after spontaneous termination of polymorphic ventricular tachycardia. METHODS & RESULTS A cardiac event monitor revealed a long QT interval and initiation of polymorphic ventricular tachycardia by a premature ventricular complex on the preceding T-wave. After 1 minute of ventricular fibrillation, her arrhythmia spontaneously terminated with evidence of a short QT interval. CONCLUSIONS A transient, potentially artificial, short QT interval following Torsades de Pointes can occur in patients with LQTS.
Collapse
Affiliation(s)
- Ikechukwu Ifedili
- Department of Cardiovascular Medicine, University of Tennessee Health Science Center, Memphis, Tennessee, USA
| | - Miguel Maturana
- Department of Cardiovascular Medicine, University of Tennessee Health Science Center, Memphis, Tennessee, USA
| | - Sharif Kayali
- Department of Cardiovascular Medicine, University of Tennessee Health Science Center, Memphis, Tennessee, USA
| | - Yehoshua Levine
- Department of Cardiovascular Medicine, University of Tennessee Health Science Center, Memphis, Tennessee, USA
| | - Rajesh Kabra
- Department of Cardiovascular Medicine, University of Tennessee Health Science Center, Memphis, Tennessee, USA
- Kansas City Heart Rhythm Institute, Overland Park, Kansas, USA
| | - Sunil K Jha
- Department of Cardiovascular Medicine, University of Tennessee Health Science Center, Memphis, Tennessee, USA
| |
Collapse
|
3
|
Billur D, Olgar Y, Durak A, Yozgat AH, Unay S, Tuncay E, Turan B. An increase in intercellular crosstalk and electrotonic coupling between cardiomyocytes and nonmyocytes reshapes the electrical conduction in the metabolic heart characterized by short QT intervals in ECGs. Cell Biochem Funct 2023; 41:1526-1542. [PMID: 38014767 DOI: 10.1002/cbf.3893] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Revised: 11/07/2023] [Accepted: 11/17/2023] [Indexed: 11/29/2023]
Abstract
Cardiac conduction abnormalities are disorders in metabolic syndrome (MetS), however, their mechanisms are unknown. Although ventricular arrhythmia reflects the changes in QT-interval of electrocardiograms associated with the changes in cardiomyocyte action potential durations (APDs), recent studies emphasize role of intercellular crosstalk between cardiomyocytes and nonmyocytes via passive (electrotonic)-conduction. Therefore, considering the possible increase in intercellular interactions of nonmyocytes with cardiomyocytes, we hypothesized an early-cardiac-remodeling characterized by short QT-interval via contributions and modulations of changes by nonmyocytes to the ventricular APs in an early-stage MetS hearts. Following the feeding of 8-week-old rats with a high-sucrose diet (32%; MetS rats) and validation of insulin resistance, there was a significant increase in heart rate and changes in the electrical characteristics of the hearts, especially a shortening in action potential (AP) duration of the papillary muscles. The patch-clamp analysis of ventricular cardiomyocytes showed an increase in the Na+ -channel currents while there were decreases in l-type Ca2+ -channel (LTCC) currents with unchanged K+ -channel currents. There was an increase in the phosphorylated form of connexin 43 (pCx43), mostly with lateral localization on sarcolemma, while its unphosphorylated form (Cx43) exhibited a high degree of localization within intercalated discs. A high-level positively-stained α-SMA and CD68 cells were prominently localized and distributed in interfibrillar spaces of the heart, implying the possible contributions of myofibroblasts and macrophages to both shortened APDs and abnormal electrical conduction in MetS hearts. Our data propose a previously unrecognized pathway for SQT induction in the heart. This pathway includes not only the contribution of short ventricular-APDs via ionic mechanisms but also increasing contributions of the electrotonic-cardiomyocyte depolarization, spontaneous electrical activity-associated fast heterogeneous impulse conduction in the heart via increased interactions and relocations between cardiomyocytes and nonmyocytes, which may be an explanation for the development of an SQT in early-cardiac-remodeling.
Collapse
Affiliation(s)
- Deniz Billur
- Departments of Histology-Embryology, Faculty of Medicine, Ankara University, Ankara, Türkiye
| | - Yusuf Olgar
- Departments of Biophysics, Faculty of Medicine, Ankara University, Ankara, Türkiye
| | - Aysegul Durak
- Departments of Biophysics, Faculty of Medicine, Ankara University, Ankara, Türkiye
| | - Ayse Hande Yozgat
- Departments of Histology-Embryology, Faculty of Medicine, Ankara University, Ankara, Türkiye
| | - Simge Unay
- Departments of Biophysics, Lokman Hekim University Faculty of Medicine, Ankara, Türkiye
| | - Erkan Tuncay
- Departments of Biophysics, Faculty of Medicine, Ankara University, Ankara, Türkiye
| | - Belma Turan
- Departments of Biophysics, Lokman Hekim University Faculty of Medicine, Ankara, Türkiye
| |
Collapse
|
4
|
Yaar S, Filatova TS, England E, Kompella SN, Hancox JC, Bechtold DA, Venetucci L, Abramochkin DV, Shiels HA. Global Air Pollutant Phenanthrene and Arrhythmic Outcomes in a Mouse Model. ENVIRONMENTAL HEALTH PERSPECTIVES 2023; 131:117002. [PMID: 37909723 PMCID: PMC10619431 DOI: 10.1289/ehp12775] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Revised: 09/19/2023] [Accepted: 09/25/2023] [Indexed: 11/03/2023]
Abstract
BACKGROUND The three-ringed polycyclic aromatic hydrocarbon (PAH) phenanthrene (Phe) has been implicated in the cardiotoxicity of petroleum-based pollution in aquatic systems, where it disrupts the contractile and electrical function of the fish heart. Phe is also found adsorbed to particulate matter and in the gas phase of air pollution, but to date, no studies have investigated the impact of Phe on mammalian cardiac function. OBJECTIVES Our objectives were to determine the arrhythmogenic potential of acute Phe exposure on mammalian cardiac function and define the underlying mechanisms to provide insight into the toxicity risk to humans. METHODS Ex vivo Langendorff-perfused mouse hearts were used to test the arrhythmogenic potential of Phe on myocardial function, and voltage- and current-clamp recordings were used to define underlying cellular mechanisms in isolated cardiomyocytes. RESULTS Mouse hearts exposed to ∼ 8 μ M Phe for 15-min exhibited a significantly slower heart rate (p = 0.0006 , N = 10 hearts), a prolonged PR interval (p = 0.036 , N = 8 hearts), and a slower conduction velocity (p = 0.0143 , N = 7 hearts). Whole-cell recordings from isolated cardiomyocytes revealed action potential (AP) duration prolongation (at 80% repolarization; p = 0.0408 , n = 9 cells) and inhibition of key murine repolarizing currents-transient outward potassium current (I to ) and ultrarapid potassium current (I Kur )-following Phe exposure. A significant reduction in AP upstroke velocity (p = 0.0445 , n = 9 cells) and inhibition of the fast sodium current (I Na ; p = 0.001 , n = 8 cells) and calcium current (I Ca ; p = 0.0001 ) were also observed, explaining the slowed conduction velocity in intact hearts. Finally, acute exposure to ∼ 8 μ M Phe significantly increased susceptibility to arrhythmias (p = 0.0455 , N = 9 hearts). DISCUSSION To the best of our knowledge, this is the first evidence of direct inhibitory effects of Phe on mammalian cardiac electrical activity at both the whole-heart and cell levels. This electrical dysfunction manifested as an increase in arrhythmia susceptibility due to impairment of both conduction and repolarization. Similar effects in humans could have serious health consequences, warranting greater regulatory attention and toxicological investigation into this ubiquitous PAH pollutant generated from fossil-fuel combustion. https://doi.org/10.1289/EHP12775.
Collapse
Affiliation(s)
- Sana Yaar
- Faculty of Biology, Medicine, and Health, Division of Cardiovascular Sciences, University of Manchester, Manchester, UK
| | - Tatiana S. Filatova
- Department of Human and Animal Physiology, Lomonosov Moscow State University, Moscow, Russia
| | - Ellie England
- Faculty of Biology, Medicine, and Health, Division of Cardiovascular Sciences, University of Manchester, Manchester, UK
| | - Shiva N. Kompella
- Faculty of Biology, Medicine, and Health, Division of Cardiovascular Sciences, University of Manchester, Manchester, UK
| | - Jules C. Hancox
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, UK
| | - David A. Bechtold
- Faculty of Biology, Medicine, and Health, Division of Cardiovascular Sciences, University of Manchester, Manchester, UK
| | - Luigi Venetucci
- Faculty of Biology, Medicine, and Health, Division of Cardiovascular Sciences, University of Manchester, Manchester, UK
| | - Denis V. Abramochkin
- Department of Human and Animal Physiology, Lomonosov Moscow State University, Moscow, Russia
| | - Holly A. Shiels
- Faculty of Biology, Medicine, and Health, Division of Cardiovascular Sciences, University of Manchester, Manchester, UK
| |
Collapse
|
5
|
Dahlberg P, Axelsson K, Jensen SM, Lundahl G, Vahedi F, Perkins R, Gransberg L, Bergfeldt L. Accelerated QT adaptation following atropine-induced heart rate increase in LQT1 patients versus healthy controls: A sign of disturbed hysteresis. Physiol Rep 2022; 10:e15487. [PMID: 36324292 PMCID: PMC9630760 DOI: 10.14814/phy2.15487] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Revised: 09/08/2022] [Accepted: 09/19/2022] [Indexed: 06/16/2023] Open
Abstract
Hysteresis, a ubiquitous regulatory phenomenon, is a salient feature of the adaptation of ventricular repolarization duration to heart rate (HR) change. We therefore compared the QT interval adaptation to rapid HR increase in patients with the long QT syndrome type 1 (LQT1) versus healthy controls because LQT1 is caused by loss-of-function mutations affecting the repolarizing potassium channel current IKs , presumably an important player in QT hysteresis. The study was performed in an outpatient hospital setting. HR was increased in LQT1 patients and controls by administering an intravenous bolus of atropine (0.04 mg/kg body weight) for 30 s. RR and QT intervals were recorded by continuous Frank vectorcardiography. Atropine induced transient expected side effects but no adverse arrhythmias. There was no difference in HR response (RR intervals) to atropine between the groups. Although atropine-induced ΔQT was 48% greater in 18 LQT1 patients than in 28 controls (p < 0.001), QT adaptation was on average 25% faster in LQT1 patients (measured as the time constant τ for the mono-exponential function and the time for 90% of ΔQT; p < 0.01); however, there was some overlap between the groups, possibly a beta-blocker effect. The shorter QT adaptation time to atropine-induced HR increase in LQT1 patients on the group level corroborates the importance of IKs in QT adaptation hysteresis in humans and shows that LQT1 patients have a disturbed ultra-rapid cardiac memory. On the individual level, the QT adaptation time possibly reflects the effect-size of the loss-of-function mutation, but its clinical implications need to be shown.
Collapse
Affiliation(s)
- Pia Dahlberg
- Department of Molecular and Clinical MedicineInstitute of Medicine, Sahlgrenska Academy, University of GothenburgGothenburgSweden
- Region Västra Götaland, Department of CardiologySahlgrenska University HospitalGothenburgSweden
| | - Karl‐Jonas Axelsson
- Department of Molecular and Clinical MedicineInstitute of Medicine, Sahlgrenska Academy, University of GothenburgGothenburgSweden
- Region Västra Götaland, Department of CardiologySahlgrenska University HospitalGothenburgSweden
| | - Steen M. Jensen
- Department of Public Health and Clinical Medicine, and Heart CentreUmeå UniversityUmeåSweden
| | - Gunilla Lundahl
- Department of Molecular and Clinical MedicineInstitute of Medicine, Sahlgrenska Academy, University of GothenburgGothenburgSweden
| | - Farzad Vahedi
- Department of Molecular and Clinical MedicineInstitute of Medicine, Sahlgrenska Academy, University of GothenburgGothenburgSweden
- Region Västra Götaland, Department of CardiologySahlgrenska University HospitalGothenburgSweden
| | - Rosie Perkins
- Department of Molecular and Clinical MedicineInstitute of Medicine, Sahlgrenska Academy, University of GothenburgGothenburgSweden
| | - Lennart Gransberg
- Department of Molecular and Clinical MedicineInstitute of Medicine, Sahlgrenska Academy, University of GothenburgGothenburgSweden
| | - Lennart Bergfeldt
- Department of Molecular and Clinical MedicineInstitute of Medicine, Sahlgrenska Academy, University of GothenburgGothenburgSweden
- Region Västra Götaland, Department of CardiologySahlgrenska University HospitalGothenburgSweden
| |
Collapse
|
6
|
Yang HQ, Echeverry FA, ElSheikh A, Gando I, Anez Arredondo S, Samper N, Cardozo T, Delmar M, Shyng SL, Coetzee WA. Subcellular trafficking and endocytic recycling of K ATP channels. Am J Physiol Cell Physiol 2022; 322:C1230-C1247. [PMID: 35508187 PMCID: PMC9169827 DOI: 10.1152/ajpcell.00099.2022] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 04/27/2022] [Accepted: 04/30/2022] [Indexed: 11/22/2022]
Abstract
Sarcolemmal/plasmalemmal ATP-sensitive K+ (KATP) channels have key roles in many cell types and tissues. Hundreds of studies have described how the KATP channel activity and ATP sensitivity can be regulated by changes in the cellular metabolic state, by receptor signaling pathways and by pharmacological interventions. These alterations in channel activity directly translate to alterations in cell or tissue function, that can range from modulating secretory responses, such as insulin release from pancreatic β-cells or neurotransmitters from neurons, to modulating contractile behavior of smooth muscle or cardiac cells to elicit alterations in blood flow or cardiac contractility. It is increasingly becoming apparent, however, that KATP channels are regulated beyond changes in their activity. Recent studies have highlighted that KATP channel surface expression is a tightly regulated process with similar implications in health and disease. The surface expression of KATP channels is finely balanced by several trafficking steps including synthesis, assembly, anterograde trafficking, membrane anchoring, endocytosis, endocytic recycling, and degradation. This review aims to summarize the physiological and pathophysiological implications of KATP channel trafficking and mechanisms that regulate KATP channel trafficking. A better understanding of this topic has potential to identify new approaches to develop therapeutically useful drugs to treat KATP channel-related diseases.
Collapse
Affiliation(s)
- Hua-Qian Yang
- Cyrus Tang Hematology Center, Soochow University, Suzhou, People's Republic of China
| | | | - Assmaa ElSheikh
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, Oregon
- Department of Medical Biochemistry, Tanta University, Tanta, Egypt
| | - Ivan Gando
- Department of Pathology, NYU School of Medicine, New York, New York
| | | | - Natalie Samper
- Department of Pathology, NYU School of Medicine, New York, New York
| | - Timothy Cardozo
- Department of Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, New York
| | - Mario Delmar
- Department of Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, New York
- Department of Medicine, NYU School of Medicine, New York, New York
| | - Show-Ling Shyng
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, Oregon
| | - William A Coetzee
- Department of Pathology, NYU School of Medicine, New York, New York
- Department of Neuroscience & Physiology, NYU School of Medicine, New York, New York
- Department of Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, New York
| |
Collapse
|
7
|
Osadchii OE. Electrocardiographic marker of the cardiac action potential triangulation induced by antiarrhythmic drugs in perfused guinea-pig heart. Exp Physiol 2022; 107:864-878. [PMID: 35561081 DOI: 10.1113/ep090349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Accepted: 05/09/2022] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? Can triangular appearance of ventricular action potential, indicating proarrhythmic profile of antiarrhythmic agent, be approximated by specific changes on ECG? What is the main finding and its importance? The triangulation of the ventricular action potential seen when antiarrhythmic drugs induce a greater lengthening of the late repolarization compared to the initial repolarization in epicardium, is closely approximated by a greater prolongation of the T wave upslope relative to the interval between the J point and the start of the T wave (the JTstart interval) on ECG. These findings may improve the power of ECG assessments in predicting the drug-induced arrhythmia resulting from slowed phase 3 repolarization. ABSTRACT Antiarrhythmic drugs prescribed to treat atrial fibrillation can occasionally precipitate ventricular tachyarrhythmia through a prominent slowing of the phase 3 repolarization. The latter results in the triangular shape of ventricular action potential, indicating high arrhythmic risks. However, clinically, the utilility of triangulation assessments for predicting arrhythmia is limited owing to the invasive nature of the ventricular action potential recordings. This study examined whether the triangulation effect can be detected indirectly from ECG analysis. Epicardial monophasic action potentials and ECG were simultaneously recorded in perfused guinea-pig hearts. With antiarrhythmics (dofetilide, quinidine, procainamide and flecainide), a prolongation of the initial repolarization seen in the action potential recordings was closely approximated by lengthening of the interval bewteen the J point and the start of the T wave (the JTstart interval) on ECG, whereas a prolongation of the late repolarization was paralleled by widening of the T wave upslope. Dofetilide, quinidine and procainamide induced a prominent slowing of the phase 3 repolarization in epicardium, leading to triangulation of the action potential. These effects were accompanied by a greater prolongation of the T wave upslope compared to the JTstart interval. Flecainide elicited a proportional prolongation of the initial and the late ventricular repolarization, and therefore failed to induce triangulation, based on analysis of both epicardial action potential and ECG profiles. Collectively, these findings suggest that the ratio between the durations of the T wave upslope and the JTstart interval may represent ECG metric of the ventricular action potential triangulation induced by antiarrhythmic drugs. This article is protected by copyright. All rights reserved.
Collapse
Affiliation(s)
- Oleg E Osadchii
- Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3, 2200, Copenhagen N, Denmark.,Department of Pharmacology, Kuban State Medical University, Sedin Street 4, Krasnodar, 350063, Russia
| |
Collapse
|
8
|
Axelsson KJ, Gransberg L, Lundahl G, Vahedi F, Bergfeldt L. Adaptation of ventricular repolarization time following abrupt changes in heart rate: comparisons and reproducibility of repeated atrial and ventricular pacing. Am J Physiol Heart Circ Physiol 2020; 320:H381-H392. [PMID: 33164576 DOI: 10.1152/ajpheart.00542.2020] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Adequate adaptation of ventricular repolarization (VR) duration to changes in heart rate (HR) is important for cardiac electromechanical function and electrical stability. We studied the QT and QTpeak adaptation in response to abrupt start and stop of atrial and ventricular pacing on two occasions with an interval of at least 1 mo in 25 study subjects with permanent pacemakers. Frank vectorcardiography was used for data collection. Atrial or ventricular pacing was performed for 8 min aiming at a cycle length (CL) of 500 ms. We measured the immediate response (IR), the time constant (τ) of the exponential phase, and T90 End, the time to reach 90% change of QT and QTpeak from baseline to steady state during and after pacing. During atrial pacing, the CL decreased on average 45% from mean (SD) 944 (120) to 518 (46) ms and QT decreased on average 18% from 388 (20) to 318 (17) ms. For QT, T90 End was 103 (24) s and 126 (15) s after start versus stop of atrial pacing; a difference of 24 (27) s (P = 0.006). The response pattern was similar for τ but IR did not differ significantly between pacing start and stop. The response pattern was similar for QTpeak and also for QT and QTpeak following ventricular pacing start and stop. The coefficients of variation for repeated measures were 7%-21% for T90 End and τ. In conclusion, the adaptation of VR duration was significantly more rapid following increasing than decreasing HR and intraindividually a relatively reproducible process.NEW & NOTEWORTHY We studied the duration of ventricular repolarization (VR) adaptation and its hysteresis, following increasing and decreasing heart rate by abrupt start and stop of 8-min atrial or ventricular pacing in study subjects with permanent pacemakers and repeated the protocol with ≥1 mo interval, a novel approach. VR adaptation was significantly longer following decreasing than increasing heart rate corroborating previous observations. Furthermore, VR adaptation was intraindividually a reproducible and, hence, robust phenomenon, a novel finding.
Collapse
Affiliation(s)
- Karl-Jonas Axelsson
- Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.,Department of Cardiology, Region Västra Götaland, Sahlgrenska University Hospital, Gothenburg Sweden
| | - Lennart Gransberg
- Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Gunilla Lundahl
- Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Farzad Vahedi
- Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.,Department of Cardiology, Region Västra Götaland, Sahlgrenska University Hospital, Gothenburg Sweden
| | - Lennart Bergfeldt
- Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.,Department of Cardiology, Region Västra Götaland, Sahlgrenska University Hospital, Gothenburg Sweden
| |
Collapse
|
9
|
Wang X, Fitts RH. Cardiomyocyte slowly activating delayed rectifier potassium channel: regulation by exercise and β-adrenergic signaling. J Appl Physiol (1985) 2020; 128:1177-1185. [DOI: 10.1152/japplphysiol.00802.2019] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Results demonstrate that exercise training (TRN) downregulates ventricular IKs channel current and the channel’s responsiveness to β-agonist factors mediated by TRN-induced decline in channel subunits KCNQ1 and KCNE1 and the A-kinase anchoring protein yotiao. The reduced IKs current helps explain the TRN-induced prolongation of the action potential in basal conditions and, coupled with previously reported upregulation of the KATP channel, results in a more efficient heart that is better able to respond to beat-by-beat changes in metabolism.
Collapse
Affiliation(s)
- Xinrui Wang
- Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin
| | - Robert H. Fitts
- Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin
| |
Collapse
|
10
|
Osadchii OE. Antiarrhythmic drug effects on premature beats are partly determined by prior cardiac activation frequency in perfused guinea-pig heart. Exp Physiol 2020; 105:819-830. [PMID: 32175633 DOI: 10.1113/ep088165] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Accepted: 03/13/2020] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? Can antiarrhythmic drug effects on repolarization, conduction time and excitation wavelength in premature beats be determined by prior cardiac activation frequency? What is the main finding and its importance? In premature beats induced after a series of cardiac activations at a slow rate, antiarrhythmics prolong repolarization but evoke little or no conduction delay, thus increasing the excitation wavelength, which indicates an antiarrhythmic effect. Fast prior activation rate attenuates prolongation of repolarization, while amplifying the conduction delay induced by drugs, which translates into the reduced excitation wavelength, indicating proarrhythmia. These findings suggest that a sudden increase in heart rate can shape adverse pharmacological profiles in patients with ventricular ectopy. ABSTRACT Antiarrhythmic drugs used to treat atrial fibrillation can occasionally induce ventricular tachyarrhythmia, which is typically precipitated by a premature ectopic beat through a mechanism related, in part, to the shortening of the excitation wavelength (EW). The arrhythmia is likely to occur when a drug induces a reduction, rather than an increase, in the EW of ectopic beats. In this study, I examined whether the arrhythmic drug profile is shaped by the increased cardiac activation rate before ectopic excitation. Ventricular monophasic action potential durations, conduction times and EW values were assessed during programmed stimulations applied at long (S1 -S1 [basic drive cycle length] = 550 ms) and short (S1 -S1 = 200 ms) cycle lengths in perfused guinea-pig hearts. The premature activations were induced with extrastimulus application immediately upon termination of the refractory period. With dofetilide, a class III antiarrhythmic agent, a prolongation in action potential duration and the resulting increase in the EW obtained at S1 -S1 = 550 ms were significantly attenuated at S1 -S1 = 200 ms, in both the regular (S1 ) and the premature (S2 ) beats. With class I antiarrhythmic agents (quinidine, procainamide and flecainide), fast S1 -S1 pacing was found to attenuate the drug-induced increase in action potential duration, while amplifying drug-induced conduction slowing, in both S1 and S2 beats. As a result, although the EW was increased (quinidine and procainamide) or not changed (flecainide) at the long S1 -S1 intervals, it was invariably reduced by these agents at the short S1 -S1 intervals. These findings indicate that the increased heart rate before ectopic activation shapes the arrhythmic profiles by facilitating drug-induced EW reduction.
Collapse
Affiliation(s)
- Oleg E Osadchii
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen N, Denmark.,Department of Health Science and Technology, University of Aalborg, Aalborg, Denmark
| |
Collapse
|
11
|
Abstract
Changes of intracellular Ca2+ concentration regulate many aspects of cardiac myocyte function. About 99% of the cytoplasmic calcium in cardiac myocytes is bound to buffers, and their properties will therefore have a major influence on Ca2+ signaling. This article considers the fundamental properties and identities of the buffers and how to measure them. It reviews the effects of buffering on the systolic Ca2+ transient and how this may change physiologically, and in heart failure and both atrial and ventricular arrhythmias, as well. It is concluded that the consequences of this strong buffering may be more significant than currently appreciated, and a fuller understanding is needed for proper understanding of cardiac calcium cycling and contractility.
Collapse
Affiliation(s)
- Godfrey L Smith
- Institute of Cardiovascular and Medical Sciences, College of Medical, Veterinary, and Life Sciences, University of Glasgow, UK (G.L.S.)
| | - David A Eisner
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, University of Manchester, UK (D.A.E.)
| |
Collapse
|
12
|
Statins with different lipophilic indices exert distinct effects on skeletal, cardiac and vascular smooth muscle. Life Sci 2019; 242:117225. [PMID: 31881229 DOI: 10.1016/j.lfs.2019.117225] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Revised: 10/20/2019] [Accepted: 12/23/2019] [Indexed: 01/14/2023]
Abstract
AIMS Data concerning the influence of statin lipophilicity on the myotoxic and pleiotropic effects of statins is conflicting, and mechanistic head-to-head comparison studies evaluating this parameter are limited. In order to address the disparity, this mechanistic investigation aimed to assess the effects of two short-acting statins with different lipophilic indices on skeletal, cardiac and vascular smooth muscle physiology. MATERIALS AND METHODS Young female Wistar rats were randomised to simvastatin (80 mg kg-1 day-1), pravastatin (160 mg kg-1 day-1) or control treatment groups. Changes in functional muscle performance were assessed, as well as mRNA levels of genes relating to atrophy, hypertrophy, mitochondrial function and/or oxidative stress. KEY FINDINGS There were no significant differences in the mRNA profiles of isolated skeletal muscles amongst the treatment groups. In terms of skeleletal muscle performance, simvastatin reduced functionality but treatment with pravastatin significantly improved force production. Rodents given simvastatin demonstrated comparable myocardial integrity to the control group. Conversely, pravastatin reduced left ventricular action potential duration, diastolic stiffness and Mhc-β expression. Pravastatin improved endothelium-dependent relaxation, particularly in muscular arteries, but this effect was absent in the simvastatin-treated rats. The responsiveness of isolated blood vessels to noradrenaline also differed between the statin groups. The findings of this study support that the effects of statins on skeletal, cardiac and vascular smooth muscle vary with their lipophilic indices. SIGNIFICANCE The results of this work have important implications for elucidating the mechanisms responsible for the myotoxic and pleiotropic effects of statins.
Collapse
|
13
|
Axelsson KJ, Brännlund A, Gransberg L, Lundahl G, Vahedi F, Bergfeldt L. Adaptation of ventricular repolarization duration and dispersion during changes in heart rate induced by atrial stimulation. Ann Noninvasive Electrocardiol 2019; 25:e12713. [PMID: 31707762 PMCID: PMC7358894 DOI: 10.1111/anec.12713] [Citation(s) in RCA: 5] [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: 07/11/2019] [Revised: 09/03/2019] [Accepted: 09/11/2019] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND The duration of ventricular repolarization (VR) and its spatial and temporal heterogeneity are central elements in arrhythmogenesis. We studied the adaptation of VR duration and dispersion and their relationship in healthy human subjects during atrial pacing. METHODS Patients 20-50 years of age who were scheduled for ablation of supraventricular tachycardia without preexcitation but otherwise healthy were eligible. Vectorcardiography recordings with Frank leads were used for data collection. Incremental atrial pacing from a coronary sinus electrode was performed by decrements of 10ms/cycle from just above sinus rate, and then kept at a fixed heart rate (HR) just below the Wenckebach rate for ≥5min and then stopped. VR duration was measured as QT and VR dispersion as T area, T amplitude and ventricular gradient. The primary measure (T90 End) was the time to reach 90% change from baseline to the steady state value during and after pacing. RESULTS A complete study protocol was accomplished in 9 individuals (6 women). VR duration displayed a monophasic adaptation during HR acceleration lasting on average 20s. The median (Q1-Q3) T90 End for QT was 85s (51-104), a delay by a factor >4. All dispersion measures displayed a tri-phasic response pattern during HR acceleration and T90 End was 3-5 times shorter than for VR duration. CONCLUSIONS Even during close to "physiological" conditions, complex and differing response patterns in VR duration and dispersion measures followed changes in HR. Extended knowledge about these responses in disease conditions might assist in risk evaluation and finding therapeutic alternatives.
Collapse
Affiliation(s)
- Karl-Jonas Axelsson
- Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.,Department of Cardiology, Region Västra Götaland, Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Adam Brännlund
- Department of Anesthesiology and Intensive Care Medicine, Region Västra Götaland, Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Lennart Gransberg
- Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Gunilla Lundahl
- Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Farzad Vahedi
- Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.,Department of Cardiology, Region Västra Götaland, Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Lennart Bergfeldt
- Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.,Department of Cardiology, Region Västra Götaland, Sahlgrenska University Hospital, Gothenburg, Sweden
| |
Collapse
|
14
|
Bernardo BC, Ooi JYY, Weeks KL, Patterson NL, McMullen JR. Understanding Key Mechanisms of Exercise-Induced Cardiac Protection to Mitigate Disease: Current Knowledge and Emerging Concepts. Physiol Rev 2018; 98:419-475. [PMID: 29351515 DOI: 10.1152/physrev.00043.2016] [Citation(s) in RCA: 99] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The benefits of exercise on the heart are well recognized, and clinical studies have demonstrated that exercise is an intervention that can improve cardiac function in heart failure patients. This has led to significant research into understanding the key mechanisms responsible for exercise-induced cardiac protection. Here, we summarize molecular mechanisms that regulate exercise-induced cardiac myocyte growth and proliferation. We discuss in detail the effects of exercise on other cardiac cells, organelles, and systems that have received less or little attention and require further investigation. This includes cardiac excitation and contraction, mitochondrial adaptations, cellular stress responses to promote survival (heat shock response, ubiquitin-proteasome system, autophagy-lysosomal system, endoplasmic reticulum unfolded protein response, DNA damage response), extracellular matrix, inflammatory response, and organ-to-organ crosstalk. We summarize therapeutic strategies targeting known regulators of exercise-induced protection and the challenges translating findings from bench to bedside. We conclude that technological advancements that allow for in-depth profiling of the genome, transcriptome, proteome and metabolome, combined with animal and human studies, provide new opportunities for comprehensively defining the signaling and regulatory aspects of cell/organelle functions that underpin the protective properties of exercise. This is likely to lead to the identification of novel biomarkers and therapeutic targets for heart disease.
Collapse
Affiliation(s)
- Bianca C Bernardo
- Baker Heart and Diabetes Institute , Melbourne , Australia ; Department of Paediatrics, University of Melbourne , Victoria , Australia ; Department of Diabetes, Central Clinical School, Monash University , Victoria , Australia ; Department of Medicine, Central Clinical School, Monash University , Victoria , Australia ; and Department of Physiology, School of Biomedical Sciences , Victoria , Australia
| | - Jenny Y Y Ooi
- Baker Heart and Diabetes Institute , Melbourne , Australia ; Department of Paediatrics, University of Melbourne , Victoria , Australia ; Department of Diabetes, Central Clinical School, Monash University , Victoria , Australia ; Department of Medicine, Central Clinical School, Monash University , Victoria , Australia ; and Department of Physiology, School of Biomedical Sciences , Victoria , Australia
| | - Kate L Weeks
- Baker Heart and Diabetes Institute , Melbourne , Australia ; Department of Paediatrics, University of Melbourne , Victoria , Australia ; Department of Diabetes, Central Clinical School, Monash University , Victoria , Australia ; Department of Medicine, Central Clinical School, Monash University , Victoria , Australia ; and Department of Physiology, School of Biomedical Sciences , Victoria , Australia
| | - Natalie L Patterson
- Baker Heart and Diabetes Institute , Melbourne , Australia ; Department of Paediatrics, University of Melbourne , Victoria , Australia ; Department of Diabetes, Central Clinical School, Monash University , Victoria , Australia ; Department of Medicine, Central Clinical School, Monash University , Victoria , Australia ; and Department of Physiology, School of Biomedical Sciences , Victoria , Australia
| | - Julie R McMullen
- Baker Heart and Diabetes Institute , Melbourne , Australia ; Department of Paediatrics, University of Melbourne , Victoria , Australia ; Department of Diabetes, Central Clinical School, Monash University , Victoria , Australia ; Department of Medicine, Central Clinical School, Monash University , Victoria , Australia ; and Department of Physiology, School of Biomedical Sciences , Victoria , Australia
| |
Collapse
|
15
|
Durães Campos I, Pinto V, Sousa N, Pereira VH. A brain within the heart: A review on the intracardiac nervous system. J Mol Cell Cardiol 2018; 119:1-9. [PMID: 29653111 DOI: 10.1016/j.yjmcc.2018.04.005] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/27/2017] [Revised: 03/30/2018] [Accepted: 04/08/2018] [Indexed: 12/11/2022]
Abstract
Cardiac function is under the control of the autonomic nervous system, composed by the parasympathetic and sympathetic divisions, which are finely tuned at different hierarchical levels. While a complex regulation occurs in the central nervous system involving the insular cortex, the amygdala and the hypothalamus, a local cardiac regulation also takes place within the heart, driven by an intracardiac nervous system. This complex system consists of a network of ganglionic plexuses and interconnecting ganglions and axons. Each ganglionic plexus contains numerous intracardiac ganglia that operate as local integration centres, modulating the intricate autonomic interactions between the extrinsic and intracardiac nervous systems. Herein, we summarize the current understanding on the intracardiac nervous system, and acknowledge its role in the pathophysiology of cardiovascular diseases.
Collapse
Affiliation(s)
- Isabel Durães Campos
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal; ICVS/3B's - PT Government Associate Laboratory, Braga, Guimarães, Portugal; Cardiology Department, Hospital of Braga, Braga, Portugal
| | - Vitor Pinto
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal; ICVS/3B's - PT Government Associate Laboratory, Braga, Guimarães, Portugal
| | - Nuno Sousa
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal; ICVS/3B's - PT Government Associate Laboratory, Braga, Guimarães, Portugal
| | - Vitor H Pereira
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal; ICVS/3B's - PT Government Associate Laboratory, Braga, Guimarães, Portugal.
| |
Collapse
|
16
|
Arrhythmogenic drugs can amplify spatial heterogeneities in the electrical restitution in perfused guinea-pig heart: An evidence from assessments of monophasic action potential durations and JT intervals. PLoS One 2018; 13:e0191514. [PMID: 29352276 PMCID: PMC5774816 DOI: 10.1371/journal.pone.0191514] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Accepted: 01/06/2018] [Indexed: 01/01/2023] Open
Abstract
Non-uniform shortening of the action potential duration (APD90) in different myocardial regions upon heart rate acceleration can set abnormal repolarization gradients and promote arrhythmia. This study examined whether spatial heterogeneities in APD90 restitution can be amplified by drugs with clinically proved proarrhythmic potential (dofetilide, quinidine, procainamide, and flecainide) and, if so, whether these effects can translate to the appropriate changes of the ECG metrics of ventricular repolarization, such as JT intervals. In isolated, perfused guinea-pig heart preparations, monophasic action potentials and volume-conducted ECG were recorded at progressively increased pacing rates. The APD90 measured at distinct ventricular sites, as well as the JTpeak and JTend values were plotted as a function of preceding diastolic interval, and the maximum slopes of the restitution curves were determined at baseline and upon drug administration. Dofetilide, quinidine, and procainamide reverse rate-dependently prolonged APD90 and steepened the restitution curve, with effects being greater at the endocardium than epicardium, and in the right ventricular (RV) vs. the left ventricular (LV) chamber. The restitution slope was increased to a greater extent for the JTend vs. the JTpeak interval. In contrast, flecainide reduced the APD90 restitution slope at LV epicardium without producing effect at LV endocardium and RV epicardium, and reduced the JTpeak restitution slope without changing the JTend restitution. Nevertheless, with all agents, these effects translated to the amplified epicardial-to-endocardial and the LV-to-RV non-uniformities in APD90 restitution, paralleled by the increased JTend vs. JTpeak difference in the restitution slope. In summary, these findings suggest that arrhythmic drug profiles are partly attributable to the accentuated regional heterogeneities in APD90 restitution, which can be indirectly determined through ECG assessments of the JTend vs. JTpeak dynamics at variable pacing rates.
Collapse
|
17
|
Osadchii OE. Role of abnormal repolarization in the mechanism of cardiac arrhythmia. Acta Physiol (Oxf) 2017; 220 Suppl 712:1-71. [PMID: 28707396 DOI: 10.1111/apha.12902] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
In cardiac patients, life-threatening tachyarrhythmia is often precipitated by abnormal changes in ventricular repolarization and refractoriness. Repolarization abnormalities typically evolve as a consequence of impaired function of outward K+ currents in cardiac myocytes, which may be caused by genetic defects or result from various acquired pathophysiological conditions, including electrical remodelling in cardiac disease, ion channel modulation by clinically used pharmacological agents, and systemic electrolyte disorders seen in heart failure, such as hypokalaemia. Cardiac electrical instability attributed to abnormal repolarization relies on the complex interplay between a provocative arrhythmic trigger and vulnerable arrhythmic substrate, with a central role played by the excessive prolongation of ventricular action potential duration, impaired intracellular Ca2+ handling, and slowed impulse conduction. This review outlines the electrical activity of ventricular myocytes in normal conditions and cardiac disease, describes classical electrophysiological mechanisms of cardiac arrhythmia, and provides an update on repolarization-related surrogates currently used to assess arrhythmic propensity, including spatial dispersion of repolarization, activation-repolarization coupling, electrical restitution, TRIaD (triangulation, reverse use dependence, instability, and dispersion), and the electromechanical window. This is followed by a discussion of the mechanisms that account for the dependence of arrhythmic vulnerability on the location of the ventricular pacing site. Finally, the review clarifies the electrophysiological basis for cardiac arrhythmia produced by hypokalaemia, and gives insight into the clinical importance and pathophysiology of drug-induced arrhythmia, with particular focus on class Ia (quinidine, procainamide) and Ic (flecainide) Na+ channel blockers, and class III antiarrhythmic agents that block the delayed rectifier K+ channel (dofetilide).
Collapse
Affiliation(s)
- O. E. Osadchii
- Department of Health Science and Technology; University of Aalborg; Aalborg Denmark
| |
Collapse
|
18
|
Abstract
Sachse et al. highlight work that reveals a Na+-dependent inactivation mechanism in the Na+/K+ pump.
Collapse
Affiliation(s)
- Frank B Sachse
- Department of Bioengineering and Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT
| | - Robert Clark
- Faculties of Kinesiology and Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Wayne R Giles
- Faculties of Kinesiology and Medicine, University of Calgary, Calgary, Alberta, Canada
| |
Collapse
|
19
|
Osadchii OE. Assessments of the QT/QRS restitution in perfused guinea-pig heart can discriminate safe and arrhythmogenic drugs. J Pharmacol Toxicol Methods 2017; 87:27-37. [PMID: 28552278 DOI: 10.1016/j.vascn.2017.04.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Accepted: 04/25/2017] [Indexed: 10/19/2022]
Abstract
INTRODUCTION Drug-induced arrhythmia remains a matter of serious clinical concern, partly due to low prognostic value of currently available arrhythmic biomarkers. METHODS This study examined whether arrhythmogenic risks can be predicted through assessments of the rate adaptation of QT interval, ventricular effective refractory period (ERP), or the QT/QRS ratio, in perfused guinea-pig hearts. RESULTS When the maximum restitution slope was taken as a metric of proarrhythmia, neither QT interval nor ERP measurements at progressively increased pacing rates were found to fully discriminate arrhythmogenic drugs (dofetilide, quinidine, flecainide, and procainamide) from those recognized as safe antiarrhythmics (lidocaine and mexiletine). For example, the slope of QT restitution was increased by dofetilide and quinidine, but remained unchanged by flecainide, procainamide, lidocaine, and mexiletine. With ERP rate adaptation, even though the restitution slope was increased by dofetilide, all class I agents reduced the slope value independently of their safety profile. The QRS measurements revealed variable drug effects, ranging from significant use-dependent conduction slowing (flecainide, quinidine, and procainamide) to only modest increase in QRS (lidocaine and mexiletine), or no change at all (dofetilide). However, with the QT/QRS rate adaptation, the restitution slope was significantly increased by all agents which have been reported to produce proarrhythmic effects (dofetilide, quinidine, flecainide, and procainamide), but not changed by lidocaine and mexiletine. DISCUSSION These findings suggest that the slope of the QT/QRS rate adaptation can be considered as a novel electrophysiological biomarker in predicting potential arrhythmic risks associated with pharmacotherapy in cardiac patients.
Collapse
Affiliation(s)
- Oleg E Osadchii
- Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3, 2200 Copenhagen N, Denmark; Department of Health Science and Technology, University of Aalborg, Fredrik Bajers Vej 7E, 9220 Aalborg, Denmark.
| |
Collapse
|
20
|
Riad FS, Razak E, Saba S, Shalaby A, Nemec J. Recent heart rate history affects QT interval duration in atrial fibrillation. PLoS One 2017; 12:e0172962. [PMID: 28273109 PMCID: PMC5342318 DOI: 10.1371/journal.pone.0172962] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Accepted: 02/13/2017] [Indexed: 11/18/2022] Open
Abstract
QT interval prolongation is associated with a risk of polymorphic ventricular tachycardia. QT interval shortens with increasing heart rate and correction for this effect is necessary for meaningful QT interval assessment. We aim to improve current methods of correcting the QT interval during atrial fibrillation (AF). Digitized Holter recordings were analyzed from patients with AF. Models of QT interval dependence on RR intervals were tested by sorting the beats into 20 bins based on corrected RR interval and assessing ST-T variability within the bins. Signal-averaging within bins was performed to determine QT/RR dependence. Data from 30 patients (29 men, 69.3±7.3 years) were evaluated. QT behavior in AF is well described by a linear function (slope ~0.19) of steady-state corrected RR interval. Corrected RR is calculated as a combination of an exponential weight function with time-constant of 2 minutes and a smaller “immediate response” component (weight ~ 0.18). This model performs significantly (p<0.0001) better than models based on instantaneous RR interval only including Bazett and Fridericia. It also outperforms models based on shorter time-constants and other previously proposed models. This model may improve detection of repolarization delay in AF. QT response to heart rate changes in AF is similar to previously published QT dynamics during atrial pacing and in sinus rhythm.
Collapse
Affiliation(s)
- Fady S. Riad
- Department of Internal Medicine, The University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, United States of America
| | - Eathar Razak
- Department of Cardiology, VA Pittsburgh Healthcare System, Pittsburgh, Pennsylvania, United States of America
| | - Samir Saba
- Heart and Vascular Institute, The University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, United States of America
| | - Alaa Shalaby
- Department of Cardiology, VA Pittsburgh Healthcare System, Pittsburgh, Pennsylvania, United States of America
| | - Jan Nemec
- Heart and Vascular Institute, The University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, United States of America
- * E-mail:
| |
Collapse
|
21
|
Cardona K, Trenor B, Giles WR. Changes in Intracellular Na+ following Enhancement of Late Na+ Current in Virtual Human Ventricular Myocytes. PLoS One 2016; 11:e0167060. [PMID: 27875582 PMCID: PMC5119830 DOI: 10.1371/journal.pone.0167060] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Accepted: 11/08/2016] [Indexed: 12/19/2022] Open
Abstract
The slowly inactivating or late Na+ current, INa-L, can contribute to the initiation of both atrial and ventricular rhythm disturbances in the human heart. However, the cellular and molecular mechanisms that underlie these pro-arrhythmic influences are not fully understood. At present, the major working hypothesis is that the Na+ influx corresponding to INa-L significantly increases intracellular Na+, [Na+]i; and the resulting reduction in the electrochemical driving force for Na+ reduces and (may reverse) Na+/Ca2+ exchange. These changes increase intracellular Ca2+, [Ca2+]i; which may further enhance INa-L due to calmodulin-dependent phosphorylation of the Na+ channels. This paper is based on mathematical simulations using the O'Hara et al (2011) model of baseline or healthy human ventricular action potential waveforms(s) and its [Ca2+]i homeostasis mechanisms. Somewhat surprisingly, our results reveal only very small changes (≤ 1.5 mM) in [Na+]i even when INa-L is increased 5-fold and steady-state stimulation rate is approximately 2 times the normal human heart rate (i.e. 2 Hz). Previous work done using well-established models of the rabbit and human ventricular action potential in heart failure settings also reported little or no change in [Na+]i when INa-L was increased. Based on our simulations, the major short-term effect of markedly augmenting INa-L is a significant prolongation of the action potential and an associated increase in the likelihood of reactivation of the L-type Ca2+ current, ICa-L. Furthermore, this action potential prolongation does not contribute to [Na+]i increase.
Collapse
Affiliation(s)
- Karen Cardona
- Centro de Investigación e Innovación en Bioingeniería, Universitat Politècnica de València, Valencia, Spain
| | - Beatriz Trenor
- Centro de Investigación e Innovación en Bioingeniería, Universitat Politècnica de València, Valencia, Spain
- * E-mail:
| | - Wayne R. Giles
- Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
| |
Collapse
|
22
|
Gao Z, Sierra A, Zhu Z, Koganti SRK, Subbotina E, Maheshwari A, Anderson ME, Zingman LV, Hodgson-Zingman DM. Loss of ATP-Sensitive Potassium Channel Surface Expression in Heart Failure Underlies Dysregulation of Action Potential Duration and Myocardial Vulnerability to Injury. PLoS One 2016; 11:e0151337. [PMID: 26964104 PMCID: PMC4786327 DOI: 10.1371/journal.pone.0151337] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2015] [Accepted: 02/26/2016] [Indexed: 11/18/2022] Open
Abstract
The search for new approaches to treatment and prevention of heart failure is a major challenge in medicine. The adenosine triphosphate-sensitive potassium (KATP) channel has been long associated with the ability to preserve myocardial function and viability under stress. High surface expression of membrane KATP channels ensures a rapid energy-sparing reduction in action potential duration (APD) in response to metabolic challenges, while cellular signaling that reduces surface KATP channel expression blunts APD shortening, thus sacrificing energetic efficiency in exchange for greater cellular calcium entry and increased contractile force. In healthy hearts, calcium/calmodulin-dependent protein kinase II (CaMKII) phosphorylates the Kir6.2 KATP channel subunit initiating a cascade responsible for KATP channel endocytosis. Here, activation of CaMKII in a transaortic banding (TAB) model of heart failure is coupled with a 35–40% reduction in surface expression of KATP channels compared to hearts from sham-operated mice. Linkage between KATP channel expression and CaMKII is verified in isolated cardiomyocytes in which activation of CaMKII results in downregulation of KATP channel current. Accordingly, shortening of monophasic APD is slowed in response to hypoxia or heart rate acceleration in failing compared to non-failing hearts, a phenomenon previously shown to result in significant increases in oxygen consumption. Even in the absence of coronary artery disease, failing myocardium can be further injured by ischemia due to a mismatch between metabolic supply and demand. Ischemia-reperfusion injury, following ischemic preconditioning, is diminished in hearts with CaMKII inhibition compared to wild-type hearts and this advantage is largely eliminated when myocardial KATP channel expression is absent, supporting that the myocardial protective benefit of CaMKII inhibition in heart failure may be substantially mediated by KATP channels. Recognition of CaMKII-dependent downregulation of KATP channel expression as a mechanism for vulnerability to injury in failing hearts points to strategies targeting this interaction for potential preventives or treatments.
Collapse
Affiliation(s)
- Zhan Gao
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Ana Sierra
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Zhiyong Zhu
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Siva Rama Krishna Koganti
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Ekaterina Subbotina
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Ankit Maheshwari
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Mark E. Anderson
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
- François Abboud Cardiovascular Research Center, University of Iowa, Iowa City, Iowa, United States of America
| | - Leonid V. Zingman
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
- François Abboud Cardiovascular Research Center, University of Iowa, Iowa City, Iowa, United States of America
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa, United States of America
- Veterans Affairs Medical Center, Iowa City, Iowa, United States of America
| | - Denice M. Hodgson-Zingman
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
- François Abboud Cardiovascular Research Center, University of Iowa, Iowa City, Iowa, United States of America
- * E-mail:
| |
Collapse
|
23
|
Caru M, Lalonde F, Gravel H, Daigle C, Tournoux F, Jacquemet V, Curnier D. Remote ischaemic preconditioning shortens QT intervals during exercise in healthy subjects. Eur J Sport Sci 2016; 16:1005-13. [DOI: 10.1080/17461391.2016.1156161] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
|
24
|
Abstract
KATP channels are integral to the functions of many cells and tissues. The use of electrophysiological methods has allowed for a detailed characterization of KATP channels in terms of their biophysical properties, nucleotide sensitivities, and modification by pharmacological compounds. However, even though they were first described almost 25 years ago (Noma 1983, Trube and Hescheler 1984), the physiological and pathophysiological roles of these channels, and their regulation by complex biological systems, are only now emerging for many tissues. Even in tissues where their roles have been best defined, there are still many unanswered questions. This review aims to summarize the properties, molecular composition, and pharmacology of KATP channels in various cardiovascular components (atria, specialized conduction system, ventricles, smooth muscle, endothelium, and mitochondria). We will summarize the lessons learned from available genetic mouse models and address the known roles of KATP channels in cardiovascular pathologies and how genetic variation in KATP channel genes contribute to human disease.
Collapse
Affiliation(s)
- Monique N Foster
- Departments of Pediatrics, Physiology & Neuroscience, and Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, New York
| | - William A Coetzee
- Departments of Pediatrics, Physiology & Neuroscience, and Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, New York
| |
Collapse
|
25
|
Seethala S, Singh P, Shusterman V, Ribe M, Haugaa KH, Němec J. QT Adaptation and Intrinsic QT Variability in Congenital Long QT Syndrome. J Am Heart Assoc 2015; 4:e002395. [PMID: 26675252 PMCID: PMC4845278 DOI: 10.1161/jaha.115.002395] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Accepted: 11/03/2015] [Indexed: 01/08/2023]
Abstract
BACKGROUND Increased variability of QT interval (QTV) has been linked to arrhythmias in animal experiments and multiple clinical situations. Congenital long QT syndrome (LQTS), a pure repolarization disease, may provide important information on the relationship between delayed repolarization and QTV. METHODS AND RESULTS Twenty-four-hour Holter monitor tracings from 78 genotyped congenital LQTS patients (52 females; 51 LQT1, 23 LQT2, 2 LQT5, 2 JLN, 27 symptomatic; age, 35.2±12.3 years) were evaluated with computer-assisted annotation of RR and QT intervals. Several models of RR-QT relationship were tested in all patients. A model assuming exponential decrease of past RR interval contributions to QT duration with 60-second time constant provided the best data fit. This model was used to calculate QTc and residual "intrinsic" QTV, which cannot be explained by heart rate change. The intrinsic QTV was higher in patients with long QTc (r=0.68; P<10(-4)), and in LQT2 than in LQT1/5 patients (5.65±1.28 vs 4.46±0.82; P<0.0002). Both QTc and intrinsic QTV were similar in symptomatic and asymptomatic patients (467±52 vs 459±53 ms and 5.10±1.19 vs 4.74±1.09, respectively). CONCLUSIONS In LQTS patients, QT interval adaptation to heart rate changes occurs with time constant ≈60 seconds, similar to results reported in control subjects. Intrinsic QTV correlates with the degree of repolarization delay and might reflect action potential instability observed in animal models of LQTS.
Collapse
Affiliation(s)
- Srikanth Seethala
- Scripps ClinicSan DiegoCA
- Present address: University of TennesseeCollege of MedicineChattanoogaTN
| | | | | | - Margareth Ribe
- Department of CardiologyCenter for Cardiological Innovation and Institute for Surgical ResearchOslo University Hospital, RikshospitaletOsloNorway
| | - Kristina H. Haugaa
- Department of CardiologyCenter for Cardiological Innovation and Institute for Surgical ResearchOslo University Hospital, RikshospitaletOsloNorway
- University of OsloNorway
| | | |
Collapse
|
26
|
Zhao Y, Huang H, Du Y, Li X, Lv T, Zhang S, Wei H, Shang J, Liu P, Liu H. β1-Adrenoceptor autoantibodies affect action potential duration and delayed rectifier potassium currents in guinea pigs. Cardiovasc Toxicol 2015; 15:1-9. [PMID: 24894912 DOI: 10.1007/s12012-014-9261-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
β1-Adrenoceptor autoantibodies (β1-AAs) affect the action potential duration (APD) in cardiomyocytes and are related to ventricular arrhythmias. The delayed rectifier potassium current (I K) plays a crucial role in APD, but the effects of β1-AAs on I K have not been completely illuminated. This work aimed to observe the effects of β1-AAs on I K and APD and further explore the mechanisms of β1-AA-mediated ventricular arrhythmias. β1-AAs were obtained from sera of patients with coronary heart disease (CHD) and nonsustained ventricular tachycardia. With whole-cell patch clamp technique, action potentials and I K were recorded. The results illustrated 0.1 μmol/L β1-AAs shortened APD at 50 % (APD50) and 90 % (APD90) of the repolarization. However, at 0.01 μmol/L, β1-AAs had no effects on either APD90 or APD50 (P > 0.05). At 0.001 μmol/L, β1-AAs significantly prolonged APD90 and APD50. Moreover, β1-AAs (0.001, 0.01, 0.1 μmol/L) dose-dependently increased the rapidly activating delayed rectifier potassium current (I Kr), but similarly decreased the slowly activating delayed rectifier potassium current (I Ks) and increased L-type calcium currents at the different concentrations. Taken together, the IKr increase induced by high β1-AA concentrations is responsible for a significant APD reduction which would contribute to repolarization changes and trigger the malignant ventricular arrhythmias in CHD patients.
Collapse
Affiliation(s)
- Yuhui Zhao
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, 100069, China
| | | | | | | | | | | | | | | | | | | |
Collapse
|
27
|
Cardiac memory: The slippery slope twixt normalcy and pathology. Trends Cardiovasc Med 2015; 25:687-96. [DOI: 10.1016/j.tcm.2015.02.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Revised: 02/17/2015] [Accepted: 02/18/2015] [Indexed: 12/19/2022]
|
28
|
Krul SPJ, Berger WR, Veldkamp MW, Driessen AHG, Wilde AAM, Deneke T, de Bakker JMT, Coronel R, de Groot JR. Treatment of Atrial and Ventricular Arrhythmias Through Autonomic Modulation. JACC Clin Electrophysiol 2015; 1:496-508. [PMID: 29759403 DOI: 10.1016/j.jacep.2015.09.013] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Revised: 08/19/2015] [Accepted: 09/24/2015] [Indexed: 11/26/2022]
Abstract
This paper reviews the contribution of autonomic nervous system (ANS) modulation in the treatment of arrhythmias. Both the atria and ventricles are innervated by an extensive network of nerve fibers of parasympathetic and sympathetic origin. Both the parasympathetic and sympathetic nervous system exert arrhythmogenic electrophysiological effects on atrial and pulmonary vein myocardium, while in the ventricle the sympathetic nervous system plays a more dominant role in arrhythmogenesis. Identification of ANS activity is possible with nuclear imaging. This technique may provide further insight in mechanisms and treatment targets. Additionally, the myocardial effects of the intrinsic ANS can be identified through stimulation of the ganglionic plexuses. These can be ablated for the treatment of atrial fibrillation. New (non-) invasive treatment options targeting the extrinsic cardiac ANS, such as low-level tragus stimulation and renal denervation, provide interesting future treatment possibilities both for atrial fibrillation and ventricular arrhythmias. However, the first randomized trials have yet to be performed. Future clinical studies on modifying the ANS may not only improve the outcome of ablation therapy but may also advance our understanding of the manner in which the ANS interacts with the myocardium to modify arrhythmogenic triggers and substrate.
Collapse
Affiliation(s)
- Sébastien P J Krul
- Heart Center, Department of Clinical and Experimental Cardiology, Academic Medical Center, Amsterdam, the Netherlands
| | - Wouter R Berger
- Heart Center, Department of Clinical and Experimental Cardiology, Academic Medical Center, Amsterdam, the Netherlands
| | - Marieke W Veldkamp
- Heart Center, Department of Clinical and Experimental Cardiology, Academic Medical Center, Amsterdam, the Netherlands
| | - Antoine H G Driessen
- Heart Center, Department of Clinical and Experimental Cardiology, Academic Medical Center, Amsterdam, the Netherlands
| | - Arthur A M Wilde
- Heart Center, Department of Clinical and Experimental Cardiology, Academic Medical Center, Amsterdam, the Netherlands; Princess Al-Jawhara Al-Brahim Centre of Excellence in Research of Hereditary Disorders, Jeddah, Kingdom of Saudi Arabia
| | - Thomas Deneke
- Heart Center Bad Neustadt, Bad Neustadt a.d. Saale, Germany
| | - Jacques M T de Bakker
- Heart Center, Department of Clinical and Experimental Cardiology, Academic Medical Center, Amsterdam, the Netherlands; Interuniversity Cardiology Institute of the Netherlands, Utrecht, the Netherlands
| | - Ruben Coronel
- Heart Center, Department of Clinical and Experimental Cardiology, Academic Medical Center, Amsterdam, the Netherlands; L'Institut de RYthmologie et de modélisation Cardiaque (LIRYC), Université Bordeaux Segalen, Bordeaux, France
| | - Joris R de Groot
- Heart Center, Department of Clinical and Experimental Cardiology, Academic Medical Center, Amsterdam, the Netherlands.
| |
Collapse
|
29
|
Osadchii OE. Flecainide attenuates rate adaptation of ventricular repolarization in guinea-pig heart. SCAND CARDIOVASC J 2015; 50:28-35. [DOI: 10.3109/14017431.2015.1099721] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- Oleg E. Osadchii
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen N, Denmark
- Department of Health Science and Technology, University of Aalborg, Aalborg, Denmark
| |
Collapse
|
30
|
Winter J, Lee AW, Niederer S, Shattock MJ. Vagal modulation of dispersion of repolarisation in the rabbit heart. J Mol Cell Cardiol 2015; 85:89-101. [DOI: 10.1016/j.yjmcc.2015.05.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Revised: 05/08/2015] [Accepted: 05/13/2015] [Indexed: 10/23/2022]
|
31
|
Qiu H, Li N, Liu JY, Harris TR, Hammock BD, Chiamvimonvat N. Soluble epoxide hydrolase inhibitors and heart failure. Cardiovasc Ther 2015; 29:99-111. [PMID: 20433684 DOI: 10.1111/j.1755-5922.2010.00150.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Cardiovascular disease remains one of the leading causes of death in the Western societies. Heart failure (HF) is due primarily to progressive myocardial dysfunction accompanied by myocardial remodeling. Once HF develops, the condition is, in most cases, irreversible and is associated with a very high mortality rate. Soluble epoxide hydrolase (sEH) is an enzyme that catalyzes the hydrolysis of epoxyeicosatrienoic acids (EETs), which are lipid mediators derived from arachidonic acid through the cytochrome P450 epoxygenase pathway. EETs have been shown to have vasodilatory, antiinflammatory, and cardioprotective effects. When EETs are hydrolyzed by sEH to corresponding dihydroxyeicosatrienoic acids, their cardioprotective activities become less pronounced. In line with the recent genetic study that has identified sEH as a susceptibility gene for HF, the sEH enzyme has received considerable attention as an attractive therapeutic target for cardiovascular diseases. Indeed, sEH inhibition has been demonstrated to have antihypertensive and antiinflammatory actions, presumably due to the increased bioavailability of endogenous EETs and other epoxylipids, and several potent sEH inhibitors have been developed and tested in animal models of cardiovascular disease including hypertension, cardiac hypertrophy, and ischemia/reperfusion injury. sEH inhibitor treatment has been shown to effectively prevent pressure overload- and angiotensin II-induced cardiac hypertrophy and reverse the pre-established cardiac hypertrophy caused by chronic pressure overload. Application of sEH inhibitors in several cardiac ischemia/reperfusion injury models reduced infarct size and prevented the progressive cardiac remodeling. Moreover, the use of sEH inhibitors prevented the development of electrical remodeling and ventricular arrhythmias associated with cardiac hypertrophy and ischemia/reperfusion injury. The data published to date support the notion that sEH inhibitors may represent a promising therapeutic approach for combating detrimental cardiac remodeling and HF.
Collapse
Affiliation(s)
- Hong Qiu
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of California, Davis, CA, USA Department of Veterans Affairs, Northern California Health Care System Mather, CA, USA Department of Entomology and UC Davis Cancer Center, University of California, Davis, CA, USA
| | | | | | | | | | | |
Collapse
|
32
|
Osadchii OE. Reduced intrinsic heart rate is associated with reduced arrhythmic susceptibility in guinea-pig heart. SCAND CARDIOVASC J 2014; 48:357-67. [PMID: 25334079 DOI: 10.3109/14017431.2014.976256] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVES In the clinical setting, patients with slower resting heart rate are less prone to cardiovascular death compared with those with elevated heart rate. However, electrophysiological adaptations associated with reduced cardiac rhythm have not been thoroughly explored. In this study, relationships between intrinsic heart rate and arrhythmic susceptibility were examined by assessments of action potential duration (APD) rate adaptation and inducibility of repolarization alternans in sinoatrial node (SAN)-driven and atrioventricular (AV)-blocked guinea-pig hearts perfused with Langendorff apparatus. DESIGN Electrocardiograms, epicardial monophasic action potentials, and effective refractory periods (ERP) were assessed in normokalemic and hypokalemic conditions. RESULTS Slower basal heart rate in AV-blocked hearts was associated with prolonged ventricular repolarization during spontaneous beating, and with attenuated APD shortening at increased cardiac activation rates during dynamic pacing, when compared with SAN-driven hearts. During hypokalemic perfusion, the inducibility of repolarization alternans and tachyarrhythmia by rapid pacing was found to be lower in AV-blocked hearts. This difference was ascribed to prolonged ERP in the setting of reduced basal heart rate, which prevented ventricular capture at critically short pacing intervals required to induce arrhythmia. CONCLUSIONS Reduced basal heart rate is associated with electrophysiological changes that prevent electrical instability upon an abrupt cardiac acceleration.
Collapse
Affiliation(s)
- Oleg E Osadchii
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen N, Denmark and Department of Health Science and Technology, University of Aalborg , Aalborg , Denmark
| |
Collapse
|
33
|
Poulikakos D, Banerjee D, Malik M. T wave morphology changes during hemodialysis. J Electrocardiol 2013; 46:492-6. [DOI: 10.1016/j.jelectrocard.2013.07.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Indexed: 10/26/2022]
|
34
|
Chen WT, Chen YC, Lu YY, Kao YH, Huang JH, Lin YK, Chen SA, Chen YJ. Apamin modulates electrophysiological characteristics of the pulmonary vein and the Sinoatrial Node. Eur J Clin Invest 2013; 43:957-63. [PMID: 23834267 DOI: 10.1111/eci.12125] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Accepted: 06/07/2013] [Indexed: 12/23/2022]
Abstract
BACKGROUND Small-conductance calcium-activated potassium (SK) channels play an important role in atrial electrophysiology. Blocking SK channels prolongs action potential (AP) duration and attenuate electrical remodelling. The effects of SK blocking on the pulmonary vein (PV) and the sinoatrial node (SAN) remain unclear. MATERIALS AND METHODS Conventional microelectrodes were used to record the AP in SANs and in isolated rabbit PVs with and without denudation before and after treatment with apamin (1, 10 nM). Using the whole-cell patch-clamp technique, the SK current was investigated in isolated single PV and SAN myocytes. RESULTS In nondenudated PVs (n = 6), apamin (1 and 10 nM) increased PV spontaneous activity (from 1.8 ± 0.2 Hz to 2.4 ± 0.2 Hz and 2.3 ± 0.2 Hz, P < 0.05) and increased the PV tension by 42 ± 14% and 37 ± 11%. Conversely, in denudated PVs (n = 6), apamin (1 and 10 nM) decreased spontaneous activity (from 2.2 ± 0.3 Hz to 1.9 ± 0.2 Hz and 1.8 ± 0.2 Hz, P < 0.05) and prolonged AP duration without changing PV tensions. Additionally, apamin (1 and 10 nM) decreased spontaneous activity (from 2.8 ± 0.1 Hz to 2.4 ± 0.1 Hz, and 2.4 ± 0.1 Hz, P < 0.05) and prolonged AP duration in SAN (n = 6). SAN myocytes had larger SK currents than did PV cardiomyocytes. Treatment with apamin (10 nM) resulted in a greater decrease (25 ± 8 vs. 20 ± 13%, P < 0.05) in spontaneous activity in isolated single SAN (n = 17) vs. PV cardiomyocytes (n = 16). CONCLUSION Small-conductance calcium-activated potassium channels play a key role in SAN and PV spontaneous activity and AP morphology. Apamin may modulate PV electrical activity with and without endothelium dependence.
Collapse
Affiliation(s)
- Wei-Ta Chen
- Division of Cardiovascular Medicine, Department of Internal Medicine, Wan Fang Hospital, Taipei Medical University, Taiwan
| | | | | | | | | | | | | | | |
Collapse
|
35
|
Kim JJ, Němec J, Papp R, Strongin R, Abramson JJ, Salama G. Bradycardia alters Ca(2+) dynamics enhancing dispersion of repolarization and arrhythmia risk. Am J Physiol Heart Circ Physiol 2013; 304:H848-60. [PMID: 23316064 DOI: 10.1152/ajpheart.00787.2012] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Bradycardia prolongs action potential (AP) durations (APD adaptation), enhances dispersion of repolarization (DOR), and promotes tachyarrhythmias. Yet, the mechanisms responsible for enhanced DOR and tachyarrhythmias remain largely unexplored. Ca(2+) transients and APs were measured optically from Langendorff rabbit hearts at high (150 × 150 μm(2)) or low (1.5 × 1.5 cm(2)) magnification while pacing at a physiological (120 beats/min) or a slow heart rate (SHR = 50 beats/min). Western blots and pharmacological interventions were used to elucidate the regional effects of bradycardia. As a result, bradycardia (SHR 50 beats/min) increased APDs gradually (time constant τf→s = 48 ± 9.2 s) and caused a secondary Ca(2+) release (SCR) from the sarcoplasmic reticulum during AP plateaus, occurring at the base on average of 184.4 ± 9.7 ms after the Ca(2+) transient upstroke. In subcellular imaging, SCRs were temporally synchronous and spatially homogeneous within myocytes. In diastole, SHR elicited variable asynchronous sarcoplasmic reticulum Ca(2+) release events leading to subcellular Ca(2+) waves, detectable only at high magnification. SCR was regionally heterogeneous, correlated with APD prolongation (P < 0.01, n = 5), enhanced DOR (r = 0.9277 ± 0.03, n = 7), and was gradually reversed by pacing at 120 beats/min along with APD shortening (P < 0.05, n = 5). A stabilizer of leaky ryanodine receptors (RyR2), 3-(4-benzylcyclohexyl)-1-(7-methoxy-2,3-dihydrobenzo[f][1,4]thiazepin-4(5H)-yl)propan-1-one (K201; 1 μM), suppressed SCR and reduced APD at the base, thereby reducing DOR (P < 0.02, n = 5). Ventricular ectopy induced by bradycardia (n = 5/15) was suppressed by K201. Western blot analysis revealed spatial differences of voltage-gated L-type Ca(2+) channel protein (Cav1.2α), Na(+)-Ca(2+) exchange (NCX1), voltage-gated Na(+) channel (Nav1.5), and rabbit ether-a-go-go-related (rERG) protein [but not RyR2 or sarcoplasmic reticulum Ca(2+) ATPase 2a] that correlate with the SCR distribution and explain the molecular basis for SCR heterogeneities. In conclusion, acute bradycardia elicits synchronized subcellular SCRs of sufficient magnitude to overcome the source-sink mismatch and to promote afterdepolarizations.
Collapse
Affiliation(s)
- Jong J Kim
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | | | | | | | | | | |
Collapse
|
36
|
Shattock MJ, Tipton MJ. 'Autonomic conflict': a different way to die during cold water immersion? J Physiol 2012; 590:3219-30. [PMID: 22547634 DOI: 10.1113/jphysiol.2012.229864] [Citation(s) in RCA: 137] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Cold water submersion can induce a high incidence of cardiac arrhythmias in healthy volunteers. Submersion and the release of breath holding can activate two powerful and antagonistic responses: the 'cold shock response' and the 'diving response'. The former involves the activation of a sympathetically driven tachycardia while the latter promotes a parasympathetically mediated bradycardia. We propose that the strong and simultaneous activation of the two limbs of the autonomic nervous system ('autonomic conflict') may account for these arrhythmias and may, in some vulnerable individuals, be responsible for deaths that have previously wrongly been ascribed to drowning or hypothermia. In this review, we consider the evidence supporting this claim and also hypothesise that other environmental triggers may induce autonomic conflict and this may be more widely responsible for sudden death in individuals with other predisposing conditions.
Collapse
Affiliation(s)
- Michael J Shattock
- Cardiovascular Division, King's College London, The Rayne Institute, Lambeth Wing, St Thomas' Hospital, London SE1 7EH, UK.
| | | |
Collapse
|
37
|
Osadchii OE. Effects of ventricular pacing protocol on electrical restitution assessments in guinea-pig heart. Exp Physiol 2012; 97:807-21. [DOI: 10.1113/expphysiol.2012.065219] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
38
|
Trenor B, Cardona K, Gomez JF, Rajamani S, Ferrero JM, Belardinelli L, Saiz J. Simulation and mechanistic investigation of the arrhythmogenic role of the late sodium current in human heart failure. PLoS One 2012; 7:e32659. [PMID: 22427860 PMCID: PMC3299678 DOI: 10.1371/journal.pone.0032659] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Accepted: 02/02/2012] [Indexed: 11/18/2022] Open
Abstract
Heart failure constitutes a major public health problem worldwide. The electrophysiological remodeling of failing hearts sets the stage for malignant arrhythmias, in which the role of the late Na+ current (INaL) is relevant and is currently under investigation. In this study we examined the role of INaL in the electrophysiological phenotype of ventricular myocytes, and its proarrhythmic effects in the failing heart. A model for cellular heart failure was proposed using a modified version of Grandi et al. model for human ventricular action potential that incorporates the formulation of INaL. A sensitivity analysis of the model was performed and simulations of the pathological electrical activity of the cell were conducted. The proposed model for the human INaL and the electrophysiological remodeling of myocytes from failing hearts accurately reproduce experimental observations. The sensitivity analysis of the modulation of electrophysiological parameters of myocytes from failing hearts due to ion channels remodeling, revealed a role for INaL in the prolongation of action potential duration (APD), triangulation of the shape of the AP, and changes in Ca2+ transient. A mechanistic investigation of intracellular Na+ accumulation and APD shortening with increasing frequency of stimulation of failing myocytes revealed a role for the Na+/K+ pump, the Na+/Ca2+ exchanger and INaL. The results of the simulations also showed that in failing myocytes, the enhancement of INaL increased the reverse rate-dependent APD prolongation and the probability of initiating early afterdepolarizations. The electrophysiological remodeling of failing hearts and especially the enhancement of the INaL prolong APD and alter Ca2+ transient facilitating the development of early afterdepolarizations. An enhanced INaL appears to be an important contributor to the electrophysiological phenotype and to the dysregulation of [Ca2+]i homeostasis of failing myocytes.
Collapse
Affiliation(s)
- Beatriz Trenor
- Instituto de Investigación Interuniversitario en Bioingeniería y Tecnología Orientada al Ser Humano, Universitat Politècnica de València, Valencia, Spain.
| | | | | | | | | | | | | |
Collapse
|
39
|
Zhao TT, Wasti B, Xu DY, Shen L, Du JQ, Zhao SP. Soluble epoxide hydrolase and ischemic cardiomyopathy. Int J Cardiol 2011; 155:181-7. [PMID: 21704394 DOI: 10.1016/j.ijcard.2011.05.067] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/26/2010] [Revised: 03/08/2011] [Accepted: 05/13/2011] [Indexed: 02/01/2023]
Abstract
BACKGROUND The development of cardiovascular disease has been linked to lowered levels of epoxyeicosatrienoic acids (EETs) in the cardiovascular system. Ischemic cardiomyopathy is caused by atherosclerotic lesions in multi-coronary arteries especially diffusive lesions, which can lead to severe myocardial dysfunction, heart enlargement, heart failure, or arrhythmia, and so on. The EETs are metabolized by the soluble epoxide hydrolase (sEH) encoded by the EPHX2 gene that has several known polymorphisms. CONTENT The EPHX2 gene polymorphism is associated with sEH catalytic activity and various cardiovascular diseases. sEH is distributed in a variety of organs and tissues and regulated by multiple factors. Research in the area has led to the presence of multiple powerful soluble epoxide hydrolase inhibitors (sEHIs), whose molecular structure and function has been optimized gradually. sEHIs increase EETs' concentration by inhibiting hydration of EETs into their corresponding vicinal diols. EETs are important signaling molecules and known as endothelium-derived hyperpolarizing factors (EDHF). sEHIs have been developed for their ability to prevent atherosclerosis, dilate the coronary artery, promote angiogenesis, ameliorate postischemic recovery of heart contractile function, decrease ischemia/reperfusion injury, modulate postischemic arrhythmia, and prevent heart failure. SUMMARY sEH is one of the etiological factors of cardiovascular diseases, and plays an important role in the progression of myocardium ischemia. This indicates that sEHIs provide a new method for the prevention and treatment of ischemic cardiomyopathy.
Collapse
Affiliation(s)
- Ting-Ting Zhao
- Department of Cardiovascular Internal Medicine, Second Xiangya Hospital, Central South University Changsha, 410011, PR China
| | | | | | | | | | | |
Collapse
|
40
|
Zingman LV, Zhu Z, Sierra A, Stepniak E, Burnett CML, Maksymov G, Anderson ME, Coetzee WA, Hodgson-Zingman DM. Exercise-induced expression of cardiac ATP-sensitive potassium channels promotes action potential shortening and energy conservation. J Mol Cell Cardiol 2011; 51:72-81. [PMID: 21439969 DOI: 10.1016/j.yjmcc.2011.03.010] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Revised: 02/19/2011] [Accepted: 03/14/2011] [Indexed: 12/25/2022]
Abstract
Physical activity is one of the most important determinants of cardiac function. The ability of the heart to increase delivery of oxygen and metabolic fuels relies on an array of adaptive responses necessary to match bodily demand while avoiding exhaustion of cardiac resources. The ATP-sensitive potassium (K(ATP)) channel has the unique ability to adjust cardiac membrane excitability in accordance with ATP and ADP levels, and up-regulation of its expression that occurs in response to exercise could represent a critical element of this adaption. However, the mechanism by which K(ATP) channel expression changes result in a beneficial effect on cardiac excitability and function remains to be established. Here, we demonstrate that an exercise-induced rise in K(ATP) channel expression enhanced the rate and magnitude of action potential shortening in response to heart rate acceleration. This adaptation in membrane excitability promoted significant reduction in cardiac energy consumption under escalating workloads. Genetic disruption of normal K(ATP) channel pore function abolished the exercise-related changes in action potential duration adjustment and caused increased cardiac energy consumption. Thus, an expression-driven enhancement in the K(ATP) channel-dependent membrane response to alterations in cardiac workload represents a previously unrecognized mechanism for adaptation to physical activity and a potential target for cardioprotection.
Collapse
Affiliation(s)
- Leonid V Zingman
- Department of Internal Medicine, University of Iowa, Carver College of Medicine, Iowa City, IA 52242, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|
41
|
Seethala S, Shusterman V, Saba S, Mularski S, Němec J. Effect of β-adrenergic stimulation on QT interval accommodation. Heart Rhythm 2011; 8:263-70. [DOI: 10.1016/j.hrthm.2010.10.012] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/07/2010] [Accepted: 10/08/2010] [Indexed: 01/10/2023]
|
42
|
Hund TJ, Koval OM, Li J, Wright PJ, Qian L, Snyder JS, Gudmundsson H, Kline CF, Davidson NP, Cardona N, Rasband MN, Anderson ME, Mohler PJ. A β(IV)-spectrin/CaMKII signaling complex is essential for membrane excitability in mice. J Clin Invest 2010; 120:3508-19. [PMID: 20877009 DOI: 10.1172/jci43621] [Citation(s) in RCA: 210] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2010] [Accepted: 07/28/2010] [Indexed: 02/04/2023] Open
Abstract
Ion channel function is fundamental to the existence of life. In metazoans, the coordinate activities of voltage-gated Na(+) channels underlie cellular excitability and control neuronal communication, cardiac excitation-contraction coupling, and skeletal muscle function. However, despite decades of research and linkage of Na(+) channel dysfunction with arrhythmia, epilepsy, and myotonia, little progress has been made toward understanding the fundamental processes that regulate this family of proteins. Here, we have identified β(IV)-spectrin as a multifunctional regulatory platform for Na(+) channels in mice. We found that β(IV)-spectrin targeted critical structural and regulatory proteins to excitable membranes in the heart and brain. Animal models harboring mutant β(IV)-spectrin alleles displayed aberrant cellular excitability and whole animal physiology. Moreover, we identified a regulatory mechanism for Na(+) channels, via direct phosphorylation by β(IV)-spectrin-targeted calcium/calmodulin-dependent kinase II (CaMKII). Collectively, our data define an unexpected but indispensable molecular platform that determines membrane excitability in the mouse heart and brain.
Collapse
Affiliation(s)
- Thomas J Hund
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242, USA.
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
43
|
Pueyo E, Husti Z, Hornyik T, Baczkó I, Laguna P, Varró A, Rodríguez B. Mechanisms of ventricular rate adaptation as a predictor of arrhythmic risk. Am J Physiol Heart Circ Physiol 2010; 298:H1577-87. [DOI: 10.1152/ajpheart.00936.2009] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Protracted QT interval (QTI) adaptation to abrupt heart rate (HR) changes has been identified as a clinical arrhythmic risk marker. This study investigates the ionic mechanisms of QTI rate adaptation and its relationship to arrhythmic risk. Computer simulations and experimental recordings in human and canine ventricular tissue were used to investigate the ionic basis of QTI and action potential duration (APD) to abrupt changes in HR with a protocol commonly used in clinical studies. The time for 90% QTI adaptation is 3.5 min in simulations, in agreement with experimental and clinical data in humans. APD adaptation follows similar dynamics, being faster in midmyocardial cells (2.5 min) than in endocardial and epicardial cells (3.5 min). Both QTI and APD adapt in two phases following an abrupt HR change: a fast initial phase with time constant < 30 s, mainly related to L-type calcium and slow-delayed rectifier potassium current, and a second slow phase of >2 min driven by intracellular sodium concentration ([Na+]i) dynamics. Alterations in [Na+]i dynamics due to Na+/K+ pump current inhibition result in protracted rate adaptation and are associated with increased proarrhythmic risk, as indicated by action potential triangulation and faster L-type calcium current recovery from inactivation, leading to the formation of early afterdepolarizations. In conclusion, this study suggests that protracted QTI adaptation could be an indicator of altered [Na+]i dynamics following Na+/K+ pump inhibition as it occurs in patients with ischemia or heart failure. An increased risk of cardiac arrhythmias in patients with protracted rate adaptation may be due to an increased risk of early afterdepolarization formation.
Collapse
Affiliation(s)
- Esther Pueyo
- Oxford University Computing Laboratory, University of Oxford, Oxford, United Kingdom
- Instituto de Investigación en Ingeniería de Aragón, Universidad de Zaragoza, Zaragoza, Spain
- Centro de Investigación Biomédica En Red de Bioingeniería, Biomateriales y Nanomedicina, Zaragoza, Spain; and
| | - Zoltán Husti
- Department of Pharmacology and Pharmacotherapy, University of Szeged, and
| | - Tibor Hornyik
- Department of Pharmacology and Pharmacotherapy, University of Szeged, and
- Research Unit for Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary
| | - István Baczkó
- Department of Pharmacology and Pharmacotherapy, University of Szeged, and
| | - Pablo Laguna
- Instituto de Investigación en Ingeniería de Aragón, Universidad de Zaragoza, Zaragoza, Spain
- Centro de Investigación Biomédica En Red de Bioingeniería, Biomateriales y Nanomedicina, Zaragoza, Spain; and
| | - András Varró
- Department of Pharmacology and Pharmacotherapy, University of Szeged, and
- Research Unit for Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary
| | - Blanca Rodríguez
- Oxford University Computing Laboratory, University of Oxford, Oxford, United Kingdom
| |
Collapse
|
44
|
Sheridan PJ, Marques JL, Newman CM, Heller SR, Clayton RH. Rate-dependent measures of repolarization predict inducibility of ventricular arrhythmias. ACTA ACUST UNITED AC 2010; 12:553-60. [DOI: 10.1093/europace/euq024] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
|
45
|
Smith NP, Hunter PJ, Paterson DJ. The Cardiac Physiome: at the heart of coupling models to measurement. Exp Physiol 2009; 94:469-71. [PMID: 19359341 DOI: 10.1113/expphysiol.2008.044040] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Nicolas P Smith
- 1University Computing Laboratory, University of Oxford, Oxford, UK.
| | | | | |
Collapse
|