title: 85% of maximal age-predicted heart rate is not a valid endpoint for exercise treadmill testing.
abstract: BACKGROUND
  Exercise testing should be symptom-limited. Nevertheless, 40% of clinical laboratories applying for ICANL accreditation use 85% of maximal age-predicted heart rate (MPHR) as the primary exercise endpoint. We hypothesized that this approach importantly may underestimate exercise capacity and inducible ischemia.
  
  
  METHODS
  Two patient cohorts were studied. 1. A prospective registry of patients referred for exercise testing. 2. A retrospective cohort of patients with positive exercise ECG.
  
  
  RESULTS
  Of 306 registry patients, 211 (69%) continued exercising after reaching 85% MPHR to maximal HR of 101% ± 7% of MPHR. Forty-two patients (14%) stopped <1 minute after achieving 85% MPHR; 53 (17%) did not achieve 85% MPHR. More women (75%) than men (64%) achieved >85% MPHR (P = .02). Of 300 patients with positive ECG, 232 patients (77%) exercised to >85% MPHR. At 85% MPHR 144 patients (62%) had positive ECG (1.2 ± .7 mm ST depression) compared to 232 patients (100%) at peak exercise (2.3 ± .9 mm ST depression, P < .001). Mean workload at 85% MPHR was 7.3 ± 2.4 METs compared to 10.6 ± 2.8 METs at peak exercise (P < .001).
  
  
  CONCLUSIONS
  Achievement of 85% MPHR is not a valid diagnostic or functional exercise endpoint because it significantly underestimates exercise capacity and inducible ischemia.
authors.affiliation: The Section of Cardiovascular Medicine, Department of Internal Medicine and the Cardiovascular Nuclear Imaging and Stress Laboratories, Yale University School of Medicine, New Haven, CT 06510, USA.
authors.forename: Mohit
authors.initials: M
authors.lastname: Jain
authors.forename: Chileshe
authors.initials: C
authors.lastname: Nkonde
authors.forename: Ben A
authors.initials: BA
authors.lastname: Lin
authors.forename: Alerice
authors.initials: A
authors.lastname: Walker
authors.forename: Frans J Th
authors.initials: FJ
authors.lastname: Wackers
mesh_terms: D000375:Aging; D000465:Algorithms; D003237:Connecticut / Q000453:epidemiology; D004562:Electrocardiography / Q000379:methods* / Q000706:statistics & numerical data*; D023381:Endpoint Determination / Q000379:methods*; D005080:Exercise Test / Q000379:methods*; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000175:diagnosis* / Q000453:epidemiology*; D015995:Prevalence; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity