First-Degree Atrioventricular Block Not as Benign as Previously Thought

First-degree atrioventricular (AV) block (i.e., PR interval >200 milliseconds) generally is thought to be benign, but that reassurance comes from studies in healthy young men. In this community-based cohort study, based on Framingham Heart Study data, 124 (1.6%) of 7575 adults (mean age, 47) had first-degree AV block on baseline electrocardiograms. During roughly 36 years of follow-up, 481 subjects developed atrial fibrillation (AF), 124 underwent pacemaker implantation, and 1739 died.

The multivariate-adjusted hazard ratios among subjects with and without first-degree AV block were 2.06 for AF, 2.89 for pacemaker placement, and 1.44 for all-cause mortality; all these risks were significant.