Title :
Mechanism of Abnormal Sarcoplasmic Reticulum Calcium Release in Canine Left-Ventricular Myocytes Results in Cellular Alternans
Author :
Armoundas, Antonis A.
Author_Institution :
Harvard Med. Sch., Charlestown, MA
Abstract :
Electrocardiographic alternans are known to predispose to increased susceptibility to life threatening arrhythmias and sudden cardiac death. While deficiencies in Ca2+ transport processes have been implicated in the genesis of cellular alternans, the underlying mechanisms have been elusive, and are the goal of this study. A novel reverse engineering approach that applies a simultaneous action potential (AP) and [Ca2+ ]i clamp of experimentally obtained data, to a previously described left-ventricular canine myocyte model, is employed to isolate the molecular and cellular mechanisms underlying cardiac alternans. The model-derived sarcoplasmic reticulum (SR) Ca2+ in control beats (102.1 plusmn 12.9 nM, n = 639 ), although larger, is not statistically significantly different as compared to beats corresponding to small [Ca2+ ]i (99.3 plusmn 35.4 nM, n = 310, p = NS), but is significantly smaller as compared to beats corresponding to large [Ca2+ ]i (122.6 plusmn 31.0 nM, n = 311, p<0.000001) during alternans. The model indicates that the increased SR Ca2+ in these beats triggers multiple ryanodine receptor (RyR) channel openings and delayed Ca2+ release that subsequently triggers an inward depolarizing current, a subthreshold early after depolarization, and AP prolongation. In conclusion, the results presented in this study support the idea that aberrant RyR openings on alternate beats are responsible for the [Ca2+ ]i alternans-type oscillations, which, in turn, give rise to AP alternans.
Keywords :
cellular biophysics; electrocardiography; molecular biophysics; Ca2 + transport processes; abnormal sarcoplasmic reticulum calcium release; alternans-type oscillations; arrhythmias; canine left-ventricular myocytes; cardiac death; cellular alternans; depolarization; depolarizing current; electrocardiographic alternans; molecular mechanisms; ryanodine receptor channel opening; sarcoplasmic reticulum; Calcium; Cardiology; Clamps; Delay; Heart; Hospitals; Morphology; Myocardium; Reverse engineering; Stability; Stress; Strontium; Cellular alternans; model; myocyte; ryanodine receptor (RyR); sarcoplasmic reticulum (SR); Action Potentials; Animals; Arrhythmias, Cardiac; Calcium; Cells, Cultured; Data Interpretation, Statistical; Death, Sudden, Cardiac; Dogs; Electrocardiography; Heart; Heart Rate; Heart Ventricles; Male; Models, Cardiovascular; Myocytes, Cardiac; Ryanodine Receptor Calcium Release Channel; Sarcoplasmic Reticulum; Signal Processing, Computer-Assisted;
Journal_Title :
Biomedical Engineering, IEEE Transactions on
DOI :
10.1109/TBME.2008.2003283