Escape capture bigeminy: a manifestation of sinoatrial conduction block.

Sinoatrial block (SAB) is often difficult to identify in the presence of bradycardic rhythms. This study demonstrates several manifestations of so-called escape capture bigeminy in 14 patients. Although periods of 1:1 sinoatrial conduction can aid in the analysis of SAB, the electrocardiographic pattern of bigeminal rhythm may be the only electrocardiographic clue of SAB. In one case, both sinoatrial entrance and exit block were identified. In eight instances, digitalis or digitalis plus a beta or calcium blocking agent could be partially implicated as the cause of SAB. In 6 of 14 patients, a permanent pacemaker was required to correct the bradycardia, in spite of discontinuation of aggravating antiarrhythmic agents or electrolyte derangement.