Abstract 18082: Differences in Ca2+ Cycling in Atrial Myocytes Isolated From Ventricular-Tachypaced Hearts vs. Atrial Tachypaced Hearts: Implication That Aberrant Ca2+ Cycling Contributes More AF Initiation Than to AF Maintenance

Background: We have recently paid much attention to Ca2+ waves in canine and human atrial myocytes that occur only upon rapid pacing, which we have termed “triggered Ca2+ waves”. The temporal character of triggered Ca2+ waves suggests that they are likely to affect action potential duration beat-to-beat, and so could prompt dispersion of repolarization predisposing to reentrant arrhythmias. We therefore asked whether Ca2+ waves are prevalent in atrial myocytes isolated from failing hearts (proarrhythmic substrate) and/or hearts in atrial fibrillation (AF). Methods: Atrial myocytes were isolated from normal hearts (canine & human), failing hearts (4-6 weeks ventricular tachypaced; canine only) and hearts in atrial fibrillation (canine_5 weeks atrial tachypaced canine hearts; human_in AF), and examined (@ 37°C) for the incidences triggered Ca2+ waves and Ca2+ alternans during pacing at 1000-200ms cyclelengths (CLs) using Ca2+ fluorescent confocal microscopy. Results: Triggered Ca2+ waves were much more prev...