A curious alliance: Sinus nodal dysfunction precipitating atrioventricular block

An elderly woman presented with recurrent syncope. Sinus bradycardia and sinoatrial block were seen on the electrocardiogram; however, PR interval prolongation after sinus pauses suggested atrioventricular conduction system disease. The occurrence of complete atrioventricular block after a pause during the electrophysiological study confirmed a diagnosis of paroxysmal atrioventricular block precipitated by sinus pauses secondary to sinus nodal disease.