Blunted Blood Pressure Response to Exercise May Predict Impending Heart Failure

ORLANDO -- Results of an exercise stress test may help identify recovering heart-attack patients who could be at increased risk of heart failure and premature death, but the predictor in this case turns out to be lowered blood pressure, a factor usually considered an asset.

A University at Buffalo study has shown that heart-attack patients whose systolic blood pressure did not rise above 140 mm Hg while they were exercising had a significantly increased risk of dying as early as three years after the baseline test, compared to patients whose peak exercise systolic blood pressure went higher.

Results were presented here today (June 6, 1998) at the annual meeting of the American College of Sports Medicine.

"As exercise increases, heart rate and systolic blood pressure should increase," said Joan Dorn, Ph.D., UB assistant professor of social and preventive medicine and lead author on the study. "If you do more work without getting a rise in blood pressure, something is wrong."

A systolic pressure of 140 mm Hg is only slightly higher than the resting high-normal blood pressure for men.

"The men with lower peak systolic blood pressure did not exhibit any major problems during the stress test, and they were capable of doing a significant amount of work," Dorn said. "Based on those results, they would not have been considered at increased risk of premature death. Yet over time, more of them died, predominately from heart ailments."

Careful blood-pressure measurements during routine stress tests of heart-attack patients could be a simple, inexpensive, non-invasive way of identifying those at risk of early death so that further tests could be done and lives saved, Dorn said.

The 651 men in the study were participants in the National Exercise and Heart Disease Project (NEHDP), a clinical trial assessing the effect of exercise on men recovering from a myocardial infarction, conducted at several centers in the U.S. from 1976-79. John P. Naughton, UB professor of medicine, was principal investigator on the trial.

All patients were between the ages of 30 and 64 at the study's inception. They completed a multistage treadmill exercise test as part of the original project, with blood-pressure measurements taken at rest and at each exercise stage. Participants were followed until their death or until Dec. 31, 1994, the end of the current follow-up period. At that time, researchers were able to confirm the status of 90 percent of the men, nearly half of whom had died. They compared peak blood pressure with deaths, beginning at three years post-test.

"More of the men who couldn't get their peak blood pressure above 140 died than those who could, and the effect was still strong at the 18-year follow-up," Dorn said. "Surprisingly, they weren't able to overcome this risk at all by exercise."

Dorn said the researchers have not yet pinpointed the mechanism or mechanisms that prevented blood pressure from rising in response to exercise in these patients, but suspect they were very close to left-ventricle failure at the time, a condition the heart compensated for temporarily by beating faster, masking the true problem.

"Peak systolic blood pressure under 140 mm Hg during an exercise stress test should send up a red flag," she said. "Persons at risk then could be treated for the underlying problem."

Additional researchers on the study were Naughton, Enrique Schisterman and Maurizio Trevisan, M.D., all of UB, on behalf of the NEHDP. The current research was supported by a grant from the National Institutes of Health. The National Institute for Developmental Disabilities and Rehabilitation Research funded the initial clinical trial.