Partial atrial electrical standstill: report of three cases and review of clinical and electrophysiological features

Three patients with partial atrial electrical standstill aredescribed. Serial electrocardiograms and electrophysiologicalstudies were performed after a clinical follow-up ranging fromfour to ten years. Two patients had valvular heart disease andone patient had a sick sinus syndrome. Case I presented, onthe admission electrocardiogram, an atrioventricular (AV) junctionalrhythm whereas paroxysmal atrial fibrillation had been previouslydocumented. Case 2, who had had long-standing atrial fibrillationpresented on admission absence of fibrillation waves and simulatedAV junctional rhythm. In case 3 with known sino-atrial block,electrocardiographic monitoring showed sinus rhythm with episodesof slow AV junctional rhythm. Atrial endocardial mapping showedan electrically silent area ranging from a small region nearthe sinus node (case 1) to the entire right atrium except fora discrete area near the tricuspid valve (case 2). AV dissociationbetween the electrical activity recorded in the remaining atriumand the junctional escape rhythm was present in every patient. The clinical and electrophysiological features of this entityare reviewed. This study emphasizes the limitations of the electrocardiogramin making the diagnosis of atrial standstill. However, partialatrial electrical standstill should be suspected in patientswith AV junctional rhythm or atrial fibrillation with fine waves.This diagnosis may have important therapeutic implications.