Abstract
Background: Alternans of early phase and of duration of action potential (AP) critically affect dispersion of refractoriness through their influence on conduction and repolarization. We investigated the phase relationship between the two alternans and its effect on conduction. Methods and Results: Transmembrane potentials recorded from ventricles of eight swine and three canines during paced activation intervals of ≤300 ms were used to quantify alternans of maximum rate of depolarization (|dv/dt|max) and of action potential duration (APD). Incidence of APD alternans was 62 and 76% in swine and canines. Alternans of APD was frequently accompanied with alternans of |dv/dt|max. Of these, 4 and 26% were out of phase in swine and canines, i.e., low |dv/dt|max preceded long APD. Computer simulations show that out of phase alternans attenuate variation of wavelength and thus minimize formation of spatially discordant alternans. Conclusion: The spontaneous switching of phase relationship between alternans of depolarization and repolarization suggests that mechanisms underlying these alternans may operate independent of each other. The phase between these alternans can critically impact spatial dispersion of refractoriness and thus stability of conduction, with the in phase relation promoting transition from concord to discord while out of phase preventing formation of discord.
Highlights
Beat-to-beat variation in action potential (AP) morphology is termed as alternans
These results suggest that the phase relationship between alternans of early phase of AP and of action potential duration (APD) plays an important role in stability of activation
ALTERNANS OF |dv /dt |MAX AND APD IN CANINES In 56 trials (n = 3), all with cycle length (CL) ≤300 ms, incidence of APD alternans was 76% and they were always accompanied with alternans of |dv/dt |max
Summary
Beat-to-beat variation in action potential (AP) morphology is termed as alternans. Several studies suggest that alternans of repolarization, i.e., of action potential duration (APD), play an important role in mechanisms of ventricular fibrillation (VF; Koller et al, 1998; Fox et al, 2002; Banville et al, 2004). Simulations show a mechanism by which the phase relationship between the two affects generation of spatial discord in repolarization These results suggest that the phase relationship between alternans of early phase of AP and of APD plays an important role in stability of activation. Conclusion:The spontaneous switching of phase relationship between alternans of depolarization and repolarization suggests that mechanisms underlying these alternans may operate independent of each other. The phase between these alternans can critically impact spatial dispersion of refractoriness and stability of conduction, with the in phase relation promoting transition from concord to discord while out of phase preventing formation of discord
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have