A cutoff point for peak VO2 with beta-blocker therapy in heart failure patients

Abstract

Introduction: An attenuated heart rate recovery (HRR) following exercise test (ET) portends a higher mortality risk in asymptomatic subjects as in patients (pts) with coronary heart disease. Its prognostic value in heart failure pts has yet to be confirmed. The aim of this study was to determine the prognostic implications of attenuated HRR relative to well established prognostic factors peak oxygen uptake (pVO2) and VE/VCO2 slope in heart failure. Methods: We evaluated 171 pts (age 55±10 years, 45 female) with an ejection fraction <40% who underwent a treadmill-based cardiopulmonary exercise test (CPET) for risk stratification. The difference between maximal heart frequency and the frequency at the end of the first minute of recovery was defined as HRR. ROC curve analyses were used to identify the HRR value that more accurately predicted death. Results: Therapy at the time of CPET included a beta-blocker in 149 pts (77%) and an ACE inhibitor or ARB in 177 pts (91%). During follow-up (920±449 days) 12 pts died. HRRwas significantly lower in pts who died (7.7±6.0 bpm vs 15.8±13.7 bpm; P= 0.042). HRR ≤10 bpm (present in 70 pts) was associated with higher mortality, even after adjustment for the effects of age, gender, body mass index, coronary heart disease aetiology, diabetes, smoking, left bundle branch block, mean blood pressure, heart rate, pVO2, and VE/VCO2 slope (adjusted HR= 5.2, 95% CI, 1.0-26.1). In this multivariable analysis, VE/CO2 slope remained an independent prognostic factor (HR=1.04 per unit increase, 95% CI, 1.0-1.1), but not pVO2. Conclusions: In pts with left ventricular systolic dysfunction, a HRR ≤10 bpm at the first minute after a cardiopulmonary exercise test is an independent predictor of mortality, and adds prognostic information to the VE/VCO2 slope. HRR should be considered when estimating the outcome of heart failure pts with low ejection fraction.