Acute hypertensive effect of digitalis glycosides.

reentrant tachycardia. Micro-reentry within the peripheral ramifications of the Purkinje system, and at Purkinje fiber-ventricular muscle junctions has been demonstrated in a variety of experimental preparations.13-l5 In each case the essential requirement has been the establishment of inhomogeneous conduction and unidirectional block. The arrhythmias generated in these laboratory models have a striking resemblance to those encountered clinically: extrasystoles with fixed coupling, idioventricular rhythm, ventricular tachycardia, and ventricular fibrillation. It is probable that reentry is a common cardiac event. The conditions necessary for its initiation are encountered in many areas of the heart, especially the diseased heart. The varied electrocardiographic manifestations of reentry reflect the site and size of the circuit, and the speed with which impulses traverse it. Increased understanding of this fundamental electrophysiologic phenomenon should yield more effective therapeutic tools for the management of clinical arrhythmias. Kenneth S . Gimbel, M.D.* Cincinnati