A common abnormality detected in electrocardiograms that has been thought to be inconsequential is associated with a substantially increased risk of erratic heartbeats, the need for a pacemaker and a modestly increased risk of death, researchers reported today.
Although there is no known way to forestall such events, the presence of the abnormality should lead to increased monitoring of patients to detect problems early, while they are more treatable, the team reported in the Journal of the American Medical Association.
The abnormality, called an increased PR interval, “is fairly common in healthy people. We see it often in clinical practice and typically assume that it is a benign finding,” said Dr. Thomas J. Wang of Massachusetts General Hospital in Boston, lead author of the report.
But increased PR intervals also are seen in people with congenital heart disease and other problems, “so we know that it is not always so benign,” he said.
The PR interval is the time it takes for an electrical signal emitted by the heart’s natural pacemaker, the sinus node, to spread from the upper chambers of the heart to the lower chambers. A PR interval of less than 200 microseconds is considered normal. A longer interval is called a first-degree atrioventricular block. Previous short-term studies in military men and athletes suggested the condition caused no problems.
To assess the condition, Wang and his colleagues studied 7,575 individuals enrolled in the Framingham Heart Study, the multi-decade study of residents of a Massachusetts town.
Those with a PR interval longer than 200 microseconds at the beginning of the study had about twice the risk of developing atrial fibrillation (erratic heartbeats), about three times the risk of needing a pacemaker and about a 40 percent increased risk of death.
