Rate pressure product, age predicted maximum heart rate or heart rate reserve. Which one better predicts cardiovascular events following exercise stress echocardiography?

BACKGROUND Age-predicted maximum heart rate (APMHR) has been demonstrated to be a poor predictor of future cardiovascular (CV) events and is yet to be validated as a termination point during exercise testing. In contrast, maximum rate pressure product (MRPP) is recognized as a strong predictor of CV outcome with superior CV event prediction over APMHR. Heart rate reserve (HRR) has been shown to be a powerful predictor of CV mortality during exercise testing, however thus far, this is not confirmed for non-fatal CV events. The aim of this study was to compare APMHR, MRPP and HRR as predictors of CV events following otherwise negative exercise treadmill testing. METHODS After exclusions, 1080 patients being investigated for coronary artery disease performed an exercise stress echocardiogram (ESE) to volitional fatigue on a motorised treadmill. Blood pressure was measured manually, and ultrasound images performed as per current American Society of Echocardiography guidelines. Rate pressure product and HRR were calculated throughout the test and maximum values were identified. Patients were followed for 5.3±2.6 mean years. RESULTS From receiver operating characteristic analysis, cut points were established for APMHR (94.6%) (AUC 0.687), MRPP (25085) (AUC 0.729) and HRR% (95.9) (AUC 0.688). MRPP outperformed both APMHR and HRR% for the prediction of future CV events. Furthermore, on Cox proportional hazard analysis MRPP was the strongest uni- and multivariate predictor (p<0.0001) with APMHR and HRR% failing to reach any statistical significance. CONCLUSIONS The current study demonstrates the substantial prognostic power of MRPP over both APMHR and HRR% to predict CV events following an otherwise negative ESE for myocardial ischemia.