TUESDAY, June 23 (HealthDay News) -- Patients with first-degree atrioventricular block may have an increased risk of atrial fibrillation, pacemaker implantation, and all-cause mortality, according to a study published in the June 24 issue of the Journal of the American Medical Association.

Susan Cheng, M.D., of the Framingham Heart Study in Massachusetts, and colleagues studied 7,575 subjects who underwent baseline examinations in 1968 to 1974. During follow-up through 2007, they observed 481 cases of atrial fibrillation, 124 cases requiring pacemaker implantation, and 1,739 deaths.

The researchers' multivariable analyses showed that each 20-millisecond increment in PR was associated with an increased risk of atrial fibrillation, pacemaker implantation, and death (hazard ratios, 1.11, 1.22, and 1.08, respectively). Overall, they found that patients with first-degree atrioventricular block had a two-fold adjusted risk of atrial fibrillation, a three-fold adjusted risk of pacemaker implantation, and a 1.4-fold adjusted risk of all-cause mortality.

"These results suggest that the natural history of first-degree atrioventricular block is not as benign as previously believed," the authors conclude. "Additional studies are needed to determine appropriate follow-up for individuals found to have prolongation of the PR interval on a routine electrocardiogram."

Abstract
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