title: Is there a better way to predict death using heart rate recovery?
abstract: BACKGROUND
  Heart rate recovery (HRR) during exercise testing is an independent predictor of prognosis. The relative predictive power of computational analysis of HRR as a function of resting and maximum heart rate (HR) compared with direct measurement of the drop in HR has not been determined.
  
  
  OBJECTIVE
  We aimed to improve on the prognostic value of HRR by the use of mathematical representations of HRR kinetics.
  
  
  METHODS
  In all, 2,193 patients who underwent exercise testing, coronary angiography, and clinical evaluation were followed up for 10.2 +/- 3.6 years. Mathematical functions were used to model HRR as a function of resting (HR(Rest)), maximum HR (HR(Peak)) and time (t): (a) HRR= HR(Rest) + (HR(peak) - HR(Rest)) X e(-kt) and (b) HRR= HR(Rest) + (HR(peak) - HR(Rest)) e(-kt2)
  
  
  RESULTS
  Equation (b) provided the best fit of the recovery HR curve. An abnormal HRR at 2 min was a better predictor of mortality than HRR at 1, 3, or 5 min. At 2 min, HRR also predicted mortality better than computational models of HRR, relating HRR as a function of maximum and resting HRs. After adjusting for univariately significant predictors of mortality, HRR, age, exercise capacity, and maximum HR were chosen in order as the best predictors of mortality.
  
  
  CONCLUSIONS
  Even though the computational models of HRR and the determination of HRR at different time intervals were significant predictors of mortality, the simple discrete measure of HRR at 2 min was the best predictor of mortality. At 2 min, HRR outperformed age, METs, and maximum exercise HR in predicting all-cause mortality.
authors.affiliation: Stanford University VA Palo Alto Health Care System, Palo Alto, California 94304, USA. dmitrygorelik@yahoo.com
authors.forename: Dmitry David
authors.initials: DD
authors.lastname: Gorelik
authors.forename: David
authors.initials: D
authors.lastname: Hadley
authors.forename: Jonathan
authors.initials: J
authors.lastname: Myers
authors.forename: Victor
authors.initials: V
authors.lastname: Froelicher
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D017023:Coronary Angiography; D003324:Coronary Artery Disease / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000401:mortality* / Q000503:physiopathology*; D005080:Exercise Test; D017079:Exercise Tolerance; D005500:Follow-Up Studies; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011379:Prognosis; D016016:Proportional Hazards Models; D020127:Recovery of Function; D016019:Survival Analysis; D013997:Time Factors; D014481:United States / Q000453:epidemiology