Predicting maximal HR in heart failure patients on β-blockade therapy

PURPOSE: Standards for estimating maximal HR are important when interpreting the adequacy of physiologic stress during exercise testing, assessing chronotropic response, and prescribing an exercise training regimen. The equation 220 - age is used to estimate maximum HR; however, it overestimates measured maximal HR in patients taking β-adrenergic blockade (βB) therapy. This study developed and validated a practical equation to predict maximal HR in patients with heart failure (HF) taking βB therapy. METHODS: Data from symptom-limited exercise tests completed on patients with systolic HF participating in the Heart Failure: A Controlled Trial Investigating Outcomes of Exercise Training trial and taking a βB agent were used to develop a simplified equation, which was validated using bootstrapping. RESULTS: The simplified derived equation was 119 + 0.5 (resting HR) - 0.5 (age) - (0, if test was completed using a treadmill; 5, if using a stationary bike). The R ² and SEE were 0.28 and 18 beats•min, respectively. Validation of this equation yielded a mean R ² and SEE of 0.28 and 18 beats•min, respectively. For the equation 220 - age, the R ² was -2.93, and the SEE was 43 beats•min. CONCLUSIONS: We report a valid and simple population-specific equation for estimating peak HR in patients with HF taking βB therapy. This equation should be helpful when evaluating chronotropic response or assessing if a maximum effort was provided during exercise testing. We caution, however, that the magnitude of the variation (SEE = 18 beats•min ^-1) associated with this prediction equation may make it impractical when prescribing exercise intensity.