The criteria for normal-length PR, QRS, and QT intervals in electrocardiograms should be reconsidered for patients more than 80 years old, according to an article published in the March-April issue of the American Journal of Geriatric Cardiology.

Researchers at the Mayo Clinic analyzed readings from 702 patients 80 years of age or older who had electrocardiography done as part of an annual examination. Of the total, 331 patients (46 percent) were men. Just under 18 percent of participants had a history of cardiac disease.

The researchers found that the average cutoff points for measuring all three electrocardiographic intervals -- PR, QRS and QT -- were greater than the current established norms. Basing their reference ranges on a healthy subgroup of 578 patients who either had no history of heart disease or who were taking heart medication, the researchers established averages for each of the three prolonged intervals in men and women. In all cases, the average interval cutoffs for women were higher than the standards set out in the current medical literature. For men, the cutoffs were considerably higher -- in some cases more than twice as high.

Based on the findings, the authors suggest that electrocardiographic standards be reexamined for both sexes of the older population.

"What is normal for a population of middle-aged individuals may not be the same for the steadily increasing elderly population in this country," said Latha Stead, MD, lead author of the study and chair of the Division of Emergency Medicine Research at Mayo Clinic.