Modulation of Cardiac Alternans by Altered Sarcoplasmic Reticulum Calcium Release: A Simulation Study

被引:15
|
作者
Tomek, Jakub [1 ]
Tomkova, Marketa [2 ]
Zhou, Xin [1 ]
Bub, Gil [3 ]
Rodriguez, Blanca [1 ]
机构
[1] Univ Oxford, Dept Comp Sci, British Heart Fdn Ctr Res Excellence, Oxford, England
[2] Univ Oxford, Nuffield Dept Med, Oxford, England
[3] McGill Univ, Dept Physiol, Montreal, PQ, Canada
来源
FRONTIERS IN PHYSIOLOGY | 2018年 / 9卷
基金
英国惠康基金; 英国工程与自然科学研究理事会; 英国国家替代、减少和改良动物研究中心;
关键词
alternans; calcium handling; calcium release; calcium release dynamics; sarcoplasmic reticulum cycling; computer modeling; HEART-FAILURE; CA2+ RELEASE; ELECTRICAL ALTERNANS; VENTRICULAR MYOCYTES; RYANODINE RECEPTOR; REPOLARIZATION ALTERNANS; MYOCARDIAL-INFARCTION; MECHANISMS; MUSCLE; CARDIOMYOCYTES;
D O I
10.3389/fphys.2018.01306
中图分类号
Q4 [生理学];
学科分类号
071003 ;
摘要
Background: Cardiac alternans is an important precursor to arrhythmia, facilitating formation of conduction block, and re-entry. Diseased hearts were observed to be particularly vulnerable to alternans, mainly in heart failure or after myocardial infarction. Alternans is typically linked to oscillation of calcium cycling, particularly in the sarcoplasmic reticulum (SR). While the role of SR calcium reuptake in alternans is well established, the role of altered calcium release by ryanodine receptors has not yet been studied extensively. At the same time, there is strong evidence that calcium release is abnormal in heart failure and other heart diseases, suggesting that these changes might play a pro-alternans role. Aims: To demonstrate how changes to intracellular calcium release dynamics and magnitude affect alternans vulnerability. Methods: We used the state-of-the-art Heijman-Rudy and O'Hara-Rudy computer models of ventricular myocyte, given their detailed representation of calcium handling and their previous utility in alternans research. We modified the models to obtain precise control over SR release dynamics and magnitude, allowing for the evaluation of these properties in alternans formation and suppression. Results: Shorter time to peak SR release and shorter release duration decrease alternans vulnerability by improved refilling of releasable calcium within junctional SR; conversely, slow release promotes alternans. Modulating the total amount of calcium released, we show that sufficiently increased calcium release may surprisingly prevent alternans via a mechanism linked to the functional depletion of junctional SR during release. We show that this mechanism underlies differences between "eye-type" and "fork-type" alternans, which were observed in human in vivo and in silico. We also provide a detailed explanation of alternans formation in the given computer models, termed "sarcoplasmic reticulum calcium cycling refractoriness." The mechanism relies on the steep SR load-release relationship, combined with relatively limited rate of junctional SR refilling. Conclusion: Both altered dynamics and magnitude of SR calcium release modulate alternans vulnerability. In particular, slow dynamics of SR release, such as those observed in heart failure, promote alternans. Therefore, acceleration of intracellular calcium release, e.g., via synchronization of calcium sparks, may inhibit alternans in failing hearts and reduce arrhythmia occurrence.
引用
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页数:15
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