Correlation between Alternans of Early and Late Phases of Ventricular Action Potential

OF THESIS CORRELATION BETWEEN ALTERNANS OF EARLY AND LATE PHASES OF VENTRICULAR ACTION POTENTIAL Several studies suggest that action potential duration (APD) alternans play an important role in initiation of arrhythmias, while less is known about the alternans of early phases of action potential (AP) and phase relation between the two. Transmembrane potentials recorded from swine and canine ventricles were analyzed to determine the correlation and phase relation between alternans of early and late phases of an AP. In both species, for activation intervals ≤ 400 ms, action potential amplitude (APA) alternans occurred≥ 50% of times when APD alternans occurred and vice versa, both were mostly in phase. Also, alternans of APA and APD were mostly in phase with alternans of maximal rate of depolarization. The correlation between alternans in early and later parts of AP, however, was variable between species; APD10 and APD90 alternans were out of phase 81 % versus 34 % in canines and swines. These observations suggest that ionic mechanisms underlying alternans of depolarization and early repolarization phases may be distinct from those underlying later phases of repolarization. Simulations conducted to see the spatiotemporal effect of phase behavior between these alternans show that out of phase behavior suppresses oscillations in wavelength and minimizes the chances of spatial discordance.