Among Patients Taking Beta-Adrenergic Blockade Therapy, Use Measured (Not Predicted) Maximal Heart Rate to Calculate a Target Heart Rate for Cardiac Rehabilitation

Abstract

Purpose: Among patients in cardiac rehabilitation (CR) on beta-adrenergic blockade (βB) therapy, this study describes the frequency for which target heart rate (THR) values computed using a predicted maximal heart rate (HRmax), correspond to a THR computed using a measured HRmax in the guideline-based heart rate reserve (HRreserve) method. Methods: Before CR, patients completed a cardiopulmonary exercise test to measure HRmax, with the data used to determine THR via the HRreserve method. Additionally, predicted HRmax was computed for all patients using the 220 − age equation and two disease-specific equations, with the predicted values used to calculate THR via the straight percent and HRreserve methods. The THR was also computed using resting heart rate (HR) +20 and +30 bpm. Results: Mean predicted HRmax using the 220 − age equation (161 ± 11 bpm) and the disease-specific equations (123 ± 9 bpm) differed (P < .001) from measured HRmax (133 ± 21 bpm). Also, THR computed using predicted HRmax resulted in values that were infrequently within the guideline-based HRreserve range calculated using measured HRmax. Specifically, 0 to ≤61% of patients would have had an exercise training HR that fell within the guideline-based range of 50-80% of measured HRreserve. Use of standing resting HR +20 or +30 bpm would have resulted in 100% and 48%, respectively, of patients exercising below 50% of HRreserve. Conclusions: A THR computed using either predicted HRmax or resting HR +20 or +30 bpm seldom results in a prescribed exercise intensity that is consistent with guideline recommendations for patients in CR.