Context Prolongation of the electrocardiographic PR interval, known as first-degree
atrioventricular block when the PR interval exceeds 200 milliseconds, is frequently
encountered in clinical practice. Objective To determine the clinical significance of PR
prolongation in ambulatory individuals. Design, Setting, and Participants Prospective,
community-based cohort including 7575 individuals from the Framingham Heart Study
(mean age, 47 years; 54% women) who underwent routine 12-lead electrocardiography …