The Mechanism of Synchronization in Isorhythmic A-V Dissociation

Abstract

We studied 11 patients with spontaneous isorhythmic atrioventricular (A-V) dissociation occurring during cardiac surgery. The period of synchronization or accrochage was shown to result from retrograde capture of the atria by an A-V junctional rhythm. The P wave in leads II, III, and aV F was biphasic (–, +) during the period of synchronization, with the initial negative portion of the P wave or the entire P wave often buried within the QRS complex. It was concluded that isorhythmic A-V dissociation occurs only during the period when the rhythm alternates between an atrial rhythm and an A-V junctional rhythm and results when either the dominant pacemaker slows or the latent pacemaker accelerates.