title: Predictors of impaired heart rate recovery: a myocardial perfusion SPECT study.
abstract: 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.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  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.
authors: Department of Cardiology, University Hospital, Basel, Switzerland.
authors: Micha T
authors: MT
authors: Maeder
authors: Cornelia
authors: C
authors: Duerring
authors: Reto P
authors: RP
authors: Engel
authors: Claudia
authors: C
authors: Boesch
authors: Matthias E
authors: ME
authors: Pfisterer
authors: Jonathan
authors: J
authors: Myers
authors: Jan
authors: J
authors: Müller-Brand
authors: Michael J
authors: MJ
authors: Zellweger
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use; D000368:Aged; D016009:Chi-Square Distribution; D003326:Coronary Circulation / Q000187:drug effects; D003430:Cross-Sectional Studies; D015444:Exercise; D005080:Exercise Test; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging* / Q000187:drug effects / Q000503:physiopathology; D006331:Heart Diseases / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000503:physiopathology; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D055414:Myocardial Perfusion Imaging / Q000379:methods*; D016017:Odds Ratio; D011237:Predictive Value of Tests; D020127:Recovery of Function; D012189:Retrospective Studies; D013557:Switzerland; D013997:Time Factors; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D000319:Adrenergic beta-Antagonists