PREDICTION OF PERFORMANCE TIME ON A TREADMILL STRESS TEST FOLLOWING A BRUCE PROTOCOL

Abstract

Graded exercise stress testing is a widely used procedure for the diagnosis of coronary artery disease. To reduce variability in test results, American Heart Association guidelines state that an optimum treadmill test time should be six to twelve minutes following an acceptable protocol. Thus, we asked if screening tools could be developed to determine if a patient would reach the six minute threshold. PURPOSE: To determine if treadmill performance time following a Bruce protocol could be predicted from a self-reporting questionnaire and resting physiological variables. METHODS: Prior to undergoing a treadmill stress test using the Bruce protocol, 108 patients (64 males, 57 ± 12 yr and 44 females, 57 ± 13 yr) completed a physical work capacity questionnaire, and had heart rate, blood pressure, grip strength, heart rate after 5 sec hand-grip, and time for heart rate to return to baseline after 5 sec hand-grip measured. A stepwise regression analysis was used to develop prediction equations for treadmill time. RESULTS: Separate prediction equations were developed for males and females. For males, predicted time (sec) = 640.842–6.945(age) + 32.473(highest self-reported MET level). For females, predicted time (sec) = 275.474 + 33.451 (highest self-reported MET level)–4.934(SBP) + 7.164(DBP). Of the 108 patients, 52 males and 33 females had actual treadmill test times of six min or more. The prediction equations predicted that 59 males and 35 females would exceed the six min threshold. Thus, the accuracy rate of prediction was 88% for males and 94% for females. CONCLUSION: These results suggest that a self-reporting questionnaire and resting physiological data can be used as screening tools to identify with reasonable accuracy those patients who can meet or exceed a six min stress test performance time.