AJP - Heart and Circulatory Physiology, Vol 254, Issue 1 1-10, Copyright © 1988 by American Physiological Society
Phase-locked rhythms in periodically stimulated heart cell aggregates
M. R. Guevara, A. Shrier and L. Glass
Department of Physiology, McGill University, Montreal, Quebec, Canada.
We have studied the effect of injecting a periodic train of current pulses
into spontaneously beating aggregates of embryonic chick ventricular heart
cells. Over a range of stimulation frequencies around the intrinsic
frequency of an aggregate we find one action potential for each stimulus
with a fixed latency from each stimulus to the subsequent action potential.
For a stimulation frequency higher (lower) than the intrinsic frequency,
this corresponds to overdrive (underdrive). At high frequencies of
stimulation dropped beats occur leading to complex rhythms analogous to
various Wenckebach rhythms observed clinically. At higher stimulation
frequencies one can obtain a complete suppression of action potential
generation. At low frequencies of stimulation, there are rhythms containing
escape beats. Almost every rhythm seen bears a striking resemblance to some
cardiac arrhythmia. We present a simple classification scheme that predicts
the order of appearance of all the classes of rhythms experimentally
observed as one changes the stimulation frequency. We propose that this
scheme can be used generally to describe the behavior of other biological
oscillators.
