News Release

Abnormal heart rate recovery during treadmill exercise testing predicts subsequent mortality

Peer-Reviewed Publication

Center for Advancing Health

Study suggests incorporating heart rate recovery score into exercise test interpretation

CHICAGO - Among patients referred for exercise electrocardiography, heart rate recovery is a strong, independent predictor of mortality, and provides additional prognostic information over and above conventional treadmill test scores, according to an article in the September 20 issue of The Journal of the American Medical Association.

Erna Obenza Nishime, MD, and colleagues with the Cleveland Clinic Foundation, followed 9,454 patients who underwent symptom-limited electrocardiographic (ECG) testing (treadmill "stress" tests) between September 1990 and December 1997. The researchers wanted to find out if heart rate recovery (how quickly the heart rate decreases after peak exercise) adds to or interacts with the treadmill test score as a predictor of all-cause mortality. Patients were excluded from the study if they were younger than 30 years of age, had a history of heart failure or valvular disease, pacemaker implantation, or uninterpretable electrocardiograms.

According to background information cited in the study, both attenuated heart rate recovery following exercise and the Duke treadmill exercise score have been demonstrated to be independent predictors of mortality, but their prognostic value relative to each other has not been studied. The Duke treadmill exercise score is a composite of measures of functional capacity (including duration of exercise) and stress-induced ischemia (or evidence of insufficient blood supply to the heart muscle during exercise testing).

The researchers followed patients for a median of 5.2 years after testing. There were 312 deaths during the follow-up period. "The presence of abnormal heart rate recovery was strongly associated with death (8 percent vs. 2 percent in patients with normal heart rate recovery)," the authors write.

The researchers defined abnormal heart rate recovery as failure of the heart rate to decrease by more than 12 beats per minute during the first minute after peak exercise. Among the patients in the study, 1,852, or 20 percent, experienced abnormal heart rate recovery, and 1,996, or 21 percent, had an intermediate- to high-risk treadmill exercise score.

After adjusting for age, sex, standard cardiovascular risk factors, medication use, and other factors, abnormal heart rate recovery remained predictive of death among all patients except those taking beta-blockers.

The researchers found that abnormal heart rate recovery provided additional prognostic information to the treadmill exercise score, with no interaction noted. "Our study suggests that by using heart rate response and treadmill exercise score, exercise tests can be used as a powerful marker of risk even in healthy patients," they write.

"Patients with intermediate- to high-risk treadmill exercise scores were found to have even higher mortality if abnormal heart rate recovery was also present. Patients with both low-risk treadmill exercise scores and normal heart rate recovery had very low risk of death," they continue. The authors assert that together, heart rate recovery and treadmill exercise scores appear to be complementary, strengthening the predictive value of exercise stress testing.

"Heart rate recovery provides additional prognostic information to the established treadmill exercise score and should be considered for routine incorporation into exercise test interpretation," they conclude.

###

(The Journal of the American Medical Association. 2000; 284:1392-1398)

Editor's Note: Co-author Michael S. Lauer, MD, is the recipient of an Established Investigator Grant from the American Heart Association.

For more information about The Journal of the American Medical Association or to obtain a copy of the study, please contact the American Medical Association's Science News Department at (312) 464-5374.

Posted by the Center for the Advancement of Health <http://www.cfah.org>. For information about the Center, call Petrina Chong, <pchong@cfah.org> (202) 387-2829.



Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.