Mechanism of Wenckebach periods: hypothesis based on computer modeling experiments.

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.