Kr. Laurita et Ds. Rosenbaum, IMPLICATIONS OF ION-CHANNEL DIVERSITY TO VENTRICULAR REPOLARIZATION AND ARRHYTHMOGENESIS - INSIGHTS FROM HIGH-RESOLUTION OPTICAL MAPPING, Canadian journal of cardiology, 13(11), 1997, pp. 1069-1076
Recent evidence from experiments in isolated cells suggests that subst
antial ion channel diversity exists throughout the heart. However, due
to limitations of conventional electrophysiological recording techniq
ues, the influence of ion channel diversity on ventricular repolarizat
ion and arrhythmia vulnerability at the level of the intact heart are
poorly understood. High resolution optical mapping with voltage-sensit
ive dye was used to measure significant heterogeneity in the kinetics
of cellular repolarization between cells across the epicardial surface
(1x1 cm) of the intact guinea-pig heart. Such diversity of repolariza
tion kinetics modulates dispersion of repolarization in a biphasic fas
hion as premature coupling interval is shortened. Moreover, evidence i
s provided that modulation of repolarization by a premature stimulus i
n a coupling interval-dependent manner also modulates arrhythmia vulne
rability in parallel, ie, 'modulated dispersion' hypothesis. Therefore
, due to diversity of repolarization kinetics between epicardial cells
, a premature stimulus serves not only as a 'trigger' of arrhythmias,
but also importantly modulates spatial dispersion of repolarization an
d the arrhythmogenic substrate for reentry.