AJP - Heart and Circulatory Physiology, Vol 257, Issue 4 1263-H1274, Copyright © 1989 by American Physiological Society
Mechanism of Wenckebach periods: hypothesis based on computer modeling experiments
M. Malik and A. J. Camm
Department of Cardiological Sciences, St. George's Hospital Medical School, London, United Kingdom.
Wenckebach periodicity is characterized by progressive lengthening of
conduction intervals and by progressive shortening of the intervals between
conducted excitations. Although different hypotheses have been suggested to
explain the mechanisms of Wenckebach periods, no serious proposition
explaining both components of the phenomenon has yet been reported. A
computer model simulating detailed mechanisms of excitation transmission
and electrotonic interactions between neighboring cardiac cells has been
employed to investigate the conduction properties of a one-dimensional
cable composed of simulated cells. When introducing gradual prolongation of
the recovery phase for the elements in the center of the cable and when
incorporating physiologically realistic shapes of premature action
potential curves into the simulation experiments, the model was able to
reproduce all aspects of Wenckebach periodicity. Systematic evaluation with
simulation experiments showed that a shorter duration of premature action
potentials (i.e., of action potentials resulting from excitation of a cell
before it has been fully repolarized) produced shortening of intervals
between conducted excitations during a Wenckebach period.
