Predictors of impaired heart rate recovery: a myocardial perfusion SPECT study

Background Heart rate recovery (HRR) is an established prognostic predictor. However, a number of methodological issues have not been fully explored, including differences in HRR 1 versus 2 min after exercise termination, absolute versus relative HRR, and the impact of beta-blockers. Design Cross-sectional study. Methods Predictors of impaired absolute and relative HRR 1 (HRR-1, HRR-1%) and 2 min after exercise termination (HRR-2, HRR-2%), defined as their lowest quartiles, were assessed in 1667 patients undergoing cycle exercise myocardial perfusion single photon emission computed tomography, and measures of HRR were compared between patients undergoing myocardial perfusion single photon emission computed tomography with continued, discontinued, and without beta-blockers. Results Higher resting heart rate was an independent predictor of all measures of impaired HRR (P < 0.001 for all). Lower peak heart rate was independently associated with impaired HRR-1, HRR-2, and HRR-2% (P < 0.001 for all) but not HRR-1%. Higher summed rest score as a marker of scar and in part left ventricular dysfunction was an independent predictor of impaired HRR-1 (P = 0.010) and HRR-1% (P = 0.025) but not HRR-2 and HRR-2%, whereas lower stroke volume index was an independent predictor of slow HRR-2 (P = 0.004) and HRR-2% (P = 0.02) but not HRR-1 and HRR-1%. HRR-1 (P = 0.98) and HRR-2 (P = 0.86) were similar in patients with continued, discontinued, and without beta-blocker therapy. In contrast, HRR-1% (P = 0.01) and HRR-2% (P = 0.001) were faster in patients on beta-blockers than in the other groups. Conclusion HRR-1 and HRR-2 as well as HRR-1% and HRR-2% reflect different pathophysiological processes. Relative but not absolute measures of HRR seem to be enhanced under beta-blockers. Eur J Cardiovasc Prev Rehabil 17:303-308 (C) 2010 The European Society of Cardiology