Supraventricular tachycardia initiated by sinus beats.

In the present report, A-V dissociation with concealed retrograde conduction into the A-V node, caused SINUS beats to exhibit antegrade A-V nodal conduction delay sufficient to result in episodes of supraventricular tachycardia (SVT). In this patient, atrial ectopic premature depolarizations were never observed. The primary role of A-V nodal conduction delay in the genesis of paroxysmal SVT is substantiated by this unusual electrophysiological observation.