Alternation of partial and total atrial standstill.

A forty-five year old man with longstanding rheumatic heart disease whose surface electrocardiogram (ECG) showed absent P waves and two alternating QRS complex rhythms, one regular and the other irregular, was submitted to electrophysiological studies. For regular QRS complex rhythm these studies revealed (1) presence of total and bilateral atrial standstill and (2) regular ventricular rhythm originating in the A-V junction; while for irregular QRS complex rhythm the studies showed (1) presence of atrial standstill in the area of the upper right atrium, and (2) a +/- 150/min atrial activity rate in the intracavitary and esophageal electrogram and a +/- 300/min rate in the epicardial mapping. The spread of conduction of this atrial activity indicates that it originated within an atrial area near the tricuspid valve. The presence of an alternating partial and total atrial standstill is a unique feature which to data has not been reported in the literature.