title: Prognostic value of heart rate increase at onset of exercise testing.
abstract: BACKGROUND
  The initial response of heart rate to dynamic exercise has been proposed as having prognostic value in limited studies that have used modalities other than the treadmill. Our aim was to evaluate the prognostic value of early heart rate parameters in patients referred for routine clinical treadmill testing.
  
  
  RESULTS
  The heart rate rise at the onset of exercise was measured in 1959 patients referred for clinical treadmill testing at the Palo Alto (Calif) Veterans Affairs Medical Center from 1997 to 2004. Multivariable Cox survival analysis was performed for 197 all-cause and 74 cardiovascular deaths that accrued during a mean follow-up of 5.4+/-2.1 years. Decreased heart rate changes at all initial relative exercise workloads were associated with significantly increased all-cause mortality. The heart rate rise at one-third total exercise capacity, however, was the only early heart rate variable that significantly predicted both all-cause and cardiovascular risk after adjustment for confounders. Failing to reach 1 SD in the heart rate rise at one-third total exercise capacity was associated with a 28% increased all-cause mortality rate (hazard ratio, 0.72; 95% CI, 0.61 to 0.85; P<0.001) and a 35% cardiovascular mortality rate (hazard ratio, 0.65; 95% CI, 0.49 to 0.86; P=0.003). Of all heart rate measurements considered (initial and recovery), the heart rate increase at peak exercise was the most powerful predictor of cardiovascular prognosis after adjustment for potential confounders. The Duke treadmill score, however, was superior to all heart rate measurements in the prediction of cardiovascular mortality.
  
  
  CONCLUSIONS
  In the present study population, a rapid initial heart rate rise was associated with improved survival, but the heart rate increase at peak exercise and other conventional measurements such as exercise capacity and the Duke treadmill score were more powerful predictors of prognosis.
authors.affiliation: Stanford University Medical Center, Stanford University Medical School, Calif, USA. nleeper@cvmed.stanford.edu
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Leeper
authors.forename: Frederick E
authors.initials: FE
authors.lastname: Dewey
authors.forename: Euan A
authors.initials: EA
authors.lastname: Ashley
authors.forename: Marcus
authors.initials: M
authors.lastname: Sandri
authors.forename: Swee Yaw
authors.initials: SY
authors.lastname: Tan
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; D000787:Angina Pectoris / Q000175:diagnosis / Q000401:mortality / Q000503:physiopathology; D002637:Chest Pain / Q000175:diagnosis / Q000401:mortality / Q000503:physiopathology; D003324:Coronary Artery Disease / Q000175:diagnosis* / Q000401:mortality* / Q000503:physiopathology; D005080:Exercise Test; D005260:Female; D005500:Follow-Up Studies; D006333:Heart Failure / Q000175:diagnosis / Q000401:mortality / Q000503:physiopathology; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000175:diagnosis / Q000401:mortality / Q000503:physiopathology; D011237:Predictive Value of Tests; D011379:Prognosis; D016016:Proportional Hazards Models; D012307:Risk Factors; D016019:Survival Analysis