期刊
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY
卷 296, 期 4, 页码 H1017-H1026出版社
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajpheart.01216.2008
关键词
arrhythmia; cardiac electrophysiology; mathematical modeling; ion channels
资金
- National Heart, Lung, and Blood Institute Merit Award [R37-HL-33343, RO1-HL-49054]
- Fondation Leducq Award
Decker KF, Heijman J, Silva JR, Hund TJ, Rudy Y. Properties and ionic mechanisms of action potential adaptation, restitution, and accommodation in canine epicardium. Am J Physiol Heart Circ Physiol 296: H1017-H1026, 2009. First published January 23, 2009; doi:10.1152/ajpheart.01216.2008.-Computational models of cardiac myocytes are important tools for understanding ionic mechanisms of arrhythmia. This work presents a new model of the canine epicardial myocyte that reproduces a wide range of experimentally observed rate-dependent behaviors in cardiac cell and tissue, including action potential (AP) duration (APD) adaptation, restitution, and accommodation. Model behavior depends on updated formulations for the 4-aminopyridine-sensitive transient outward current (I-to1), the slow component of the delayed rectifier K+ current (I-Ks), the L-type Ca2+ channel current (I-Ca,I-L), and the Na+-K+ pump current (I-NaK) fit to data from canine ventricular myocytes. We found that I-to1 plays a limited role in potentiating peak I-Ca,I-L and sarcoplasmic reticulum Ca2+ release for propagated APs but modulates the time course of APD restitution. IKs plays an important role in APD shortening at short diastolic intervals, despite a limited role in AP repolarization at longer cycle lengths. In addition, we found that I-Ca,I-L plays a critical role in APD accommodation and rate dependence of APD restitution. Ca2+ entry via I-Ca,I-L at fast rate drives increased Na+-Ca2+ exchanger Ca2+ extrusion and Na+ entry, which in turn increases Na+ extrusion via outward I-NaK. APD accommodation results from this increased outward I-NaK. Our simulation results provide valuable insight into the mechanistic basis of rate-dependent phenomena important for determining the heart's response to rapid and irregular pacing rates (e.g., arrhythmia). Accurate simulation of rate-dependent phenomena and increased understanding of their mechanistic basis will lead to more realistic multicellular simulations of arrhythmia and identification of molecular therapeutic targets.
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