In isolated rabbit myocyte pairs, conduction block occurred at lower junctional resistance during Purkinje-to-ventricular conduction (85 +/- 39 M omega) than ventricular-to-Purkinje conduction.
Intrinsic differences in phase 1 repolarization, such as transient outward current and calcium current, contribute to unidirectional block at the Purkinje-ventricular junction.
Conduction at the Purkinje-ventricular junction (PVJ) demonstrates unidirectional block under both physiological and pathophysiological conditions. Although this block is typically attributed to multidimensional electrotonic interactions, we examined possible membrane-level contributions using single, isolated rabbit Purkinje (P) and ventricular (V) myocytes coupled by an electronic circuit. When we varied the junctional resistance (Rj) between paired V myocytes, conduction block occurred at lower Rj values during conduction from the smaller to larger myocyte (115 +/- 59 M omega) than from the larger to smaller myocyte (201 +/- 51 M omega). In Purkinje-ventricular myocyte pairs, however, block occurred at lower Rj values during P-to-V conduction (85 +/- 39 M omega) than during V-to-P conduction (912 +/- 175 M omega), although there was little difference in the mean cell size. Companion computer simulations, performed to examine how the early platea currents affected conduction, showed that P-to-V block occurred at lower Rj values when the transient outward current was increased or the calcium current was decreased in the model P cell. These results suggest that intrinsic differences in phase 1 repolarization can contribute to unidirectional block at the PVJ.
Huelsing et al. (Wed,) conducted a other in Conduction block at the Purkinje-ventricular junction. Varying junctional resistance vs. Ventricular-to-Purkinje conduction was evaluated on Junctional resistance at which conduction block occurred. In isolated rabbit myocyte pairs, conduction block occurred at lower junctional resistance during Purkinje-to-ventricular conduction (85 +/- 39 M omega) than ventricular-to-Purkinje conduction.