Persistent atrial standstill due to atrial inexcitability. An electrophysiological and histological study.

Electrophysiological and histopathological examinations were carried out in 2 patients with persistent atrial standstill. Intracardiac studies revealed that atrial standstill was due to atrial inexcitability. It was demonstrated in both patients that prolongation of the H-V interval and the duration of H deflection was associated with complete right bundle branch block and that the escape rhythm was an A-V junctional origin. Histologically, marked fibrosis of the right atrium and fibrous strands in the right ventricle were demonstrated in a 69-year-old man with idiopathic cardiomyopathy. In another female patient with peripartum heart disease aged 40 years, there was moderate degeneration of the myocardium in the right ventricle. The results of electron microscopic observations are also presented. The importance of the examination of His bundle electrography in persistent atrial standstill and the diagnostic criteria and treatment of this lesion are discussed.