Changes in Heart Rate during and after Exercise Treadmill Test as Prognostic Factor in Cardiovascular Disease

BACKGROUND AND OBJECTIVES: Many studies have established risk factors for cardiovascular diseases. The Duke treadmill score has gained widespread acceptance for prognosis and diagnosis in cardiac diseases. Recently, changes in heart rate during and after exercise have also been studied to predict the prognosis of cardiac diseases. We examined the relationship between the incidence of cardiovascular events and exercise capacity, achievement of 85% maximal predicted heart rate (MPHR) or heart rate recovery (HRR) after a routine exercise treadmill test.

SUBJECTS AND METHODS: We studied 88 patients with chest pain who were over the age of 30. They were referred for exercise treadmill test for assessment of chest pain and underwent symptom-limited, exercise test with a cool down period of 30 seconds. HRR was defined as the difference in heart rate between peak exercise and 1 minute after exercise. Delta heart rate (DHR) was defined as the difference in heart rate between resting and peak exercise. Other parameters in the exercise test were also measured.

RESULTS: Cardiovascular events were found in 13 of the 88 patients. In the events group, age, peak heart rate in exercise, ST depression, maximal exercise capacity, HRR, DHR and achievement of 85% MPHR were all significant variables. There was a favorable prognosis in the patients with a value of HRR >22 beats/minute and a value of DHR >83 beats/minute. Even after adjusting for age, sex, ST depression and left ventricular hypertrophy, the parameters of maximal exercise capacity, HRR, DHR, and achievement of 85% MPHR remained predictive prognostic factors in cardiovascular events.

CONCLUSION: Parameters in exercise treadmill test, such as maximal exercise capacity, HRR, DHR and achievement of 85% MPHR, appear to provide additional information and are important variables associated with the prediction of risk in cardiac events.