Intermittent Intra-atrial Block: Its Diagnosis, Incidence and Implications

Abstract

Fifty-six cases of intermittent intra-atrial block (IIAB), were found among 4,500 consecutive routine electrocardiograms (1.2 percent). Intermittently, abnormally wide P waves occurring either every other sinus beat or slightly more irregularly during sinus rhythm were ascribed to intermittent functional block in the anterior internodal tract. Other forms of intra-atrial block (IAB) are discussed. The course and possible prognostic significance of IIAB are presented.