Ephaptic impulse transmission between ventricular myocardial cells in vitro

Abstract

Impulse transmission between closely appositioned cylindrical ferret myocardial preparations was studied in vitro. One preparation was driven and when the longitudinal extracellular potential difference between electrodes 800 .mu.m apart was made larger than 30-60 mV by increasing the resistance of the extracellular space, ephaptic (i.e., non synaptic) impulse transmission from one preparation to another occurred. In 2 of 8 pairs of preparations examined, the impulse transmission was bidirectional. The latency of the transmission varied from 9 to 369 ms. Various rate dependent blocks (sometimes associated with a Wenckebach phenomenon) were observed at stimulation frequencies above 1 Hz. The experimental situation has pathophysiological properties relevant to the analysis of the genesis of arrhythmias. Ephaptic interaction may be involved in the shaping of the wavefront of excitation under both normal and pathological conditions.