Variations in the functional electrical coupling between the subendocardial Purkinje and ventricular layers of the canine left ventricle.

Action potential propagation from the subendocardial Purkinje network into the ventricular muscle is an essential link in cardiac activation. Studies of papillary muscles have indicated that ventricular muscle activation by the Purkinje network occurs only at discrete, localized regions near the papillary muscle base. Over the rest of the endocardial surface, however, the spatial distribution of these subendocardial Purkinje to ventricular muscle connections has been less well defined. We therefore studied in vitro 12 canine left ventricular preparations (eight from the septum, four from the lateral wall), using a high-density (1-mm spacings), high-resolution extracellular mapping technique to determine the subendocardial Purkinje and ventricular muscle activation sequences. These studies show that the distribution of subendocardial Purkinje to ventricular muscle electrical coupling is spatially inhomogeneous, and that the junctional regions themselves have variable degrees of electrical coupling. We also...