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In relatively small retrospective studies, prolongation of the PR interval on an otherwise normal electrocardiogram has not proven to be prognostically important. Indeed, PR prolongation can result from increased vagal tone, which is common in athletes and healthy individuals. However, PR prolongation can also result from intrinsic cardiovascular disease. These investigators used prospective, community-based data from the Framingham Heart Study to evaluate the long-term prognostic implications of PR prolongation.
Of 7575 adults (mean age at entry, 47) followed for up to 40 years, 481 developed atrial fibrillation, 124 underwent pacemaker implantation, and 1739 died. Per 1-standard-deviation increase in PR interval, the adjusted hazard ratios…