Wenckebach Phenomenon of Entrance Block in Intermittent Ventricular Parasystole

¹ Second Department of Medicine, Hokkaido University School of Medicine, Sapporo, Japan

This report indicates the presence of an intermittent ventricular parasystole with the Wenckebach phenomenon of entrance block. Such incomplete ventricular-ectopic (V-E) block of the second degree, although hitherto unrecognized, does not seem to be an extremely rare phenomenon. The features of ordinary continuous ventricular parasystole might be explained by such incomplete V-E block, rather than by unidirectional block. It is emphasized that unidirectional block in continuous parasystole, ie, continuous entrance block without exit block, might appear to be continuous but, in fact, is not continuous due to second degree V-E block.