Atrioventricular dissociation between two atrioventricular nodal rhythms.

A case presenting with AV nodal escape rhythms after obvious sinus depression is described. The escape rhythms arise from two dissociated AV nodal pacemakers with differential physiological properties. Variation in the rate of the upper AV nodal pacemaker results in a form of escape-capture bigeminy. Temporary acceleration of the sinus rhythm results in dissociation between sinus and lower AV nodal pacemakers, or conducted sinus rhythm. AV dissociation usually occurs between sinus or, less commonly, an ectopic atrial rhythm, and an AV nodal or a ventricular rhythm. Dissociation between two AV nodal pacemakers is exceptionally rare; only a few cases have been described (Luten and Jensen, I932; Schott, I937; Miller and Sharrett, I957; Castellanos, Azan, and Calvinio, I958; Sanghvi, I96I; Chung, Walsh, and Massie, I964). The following is another example of this unusual arrhythmia.