Ephaptic impulse transmission between ventricular myocardial cells in vitro.

Impulse transmission between closely appositioned cylindrical myocardial preparations , from the ferret, was studied in vitro. One preparation was driven, and when the longitudinal extracellular potential difference between electrodes 80 micrometers 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 out 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.