title: Different thresholds of myocardial ischemia in ramp and standard bruce protocol exercise tests in patients with positive exercise stress tests and angiographically demonstrated coronary arterial narrowing.
abstract: Gradual instead of abrupt increases in workload favor a more physiologic response in terms of hemodynamic and gas exchange parameters. Therefore, we investigated whether myocardial ischemia is attenuated with a ramp compared with a standard Bruce exercise protocol in patients with coronary artery disease. We compared electrocardiographic ischemic parameters on the standard Bruce protocol treadmill and the individualized ergocycle ramp protocol in 18 men with coronary artery disease and a reproducible ischemic electrocardiographic exercise test. Oxygen consumption (VO2), ischemic threshold (rate-pressure product [RPP]=systolic blood pressure x heart rate at 1-mm ST-segment depression), and maximum ST-segment depression corresponding to the highest RPP common to the 2 tests were determined. Ischemic threshold was higher with the ramp than with the Bruce protocol (23,420+/-5,732 vs 20,018+/-3,542 beats.min/mm Hg, p=0.007). Peak RPP was higher during the ramp than during the Bruce protocol (28,492+/-6,450 vs 25,519+/-6,067 beats.min/mm Hg, respectively, p=0.02) despite similar peak VO2 (25.59+/-5.05 vs 26.39+/-4.65 mlO2.kg-1.min-1, respectively, p=0.6). Maximum ST-segment depression corresponding to the highest RPP common to the 2 tests was less with the ramp than with the Bruce protocol (-1.2+/-0.9 vs -1.9+/-0.7 mm, p=0.003). In conclusion, exercise-induced myocardial ischemia is markedly attenuated on the more gradually increasing workload of the individualized ramp ergocycle compared with the standard Bruce treadmill protocol. This effect is unexplained by energy expenditure (VO2) or myocardial work (RPP) and is consistent with a "warm-up" ischemic mechanism.
authors.affiliation: Quebéc Heart Institute/Laval Hospital, Laval Sainte University Foy, Quebéc, Canada.
authors.forename: Martin
authors.initials: M
authors.lastname: Noël
authors.forename: Jean
authors.initials: J
authors.lastname: Jobin
authors.forename: Paul
authors.initials: P
authors.lastname: Poirier
authors.forename: Gilles R
authors.initials: GR
authors.lastname: Dagenais
authors.forename: Peter
authors.initials: P
authors.lastname: Bogaty
mesh_terms: D000368:Aged; D001794:Blood Pressure; D017023:Coronary Angiography; D023921:Coronary Stenosis / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D015716:Electrocardiography, Ambulatory; D004734:Energy Metabolism; D005080:Exercise Test / Q000379:methods; D017079:Exercise Tolerance; D006329:Heart Conduction System / Q000503:physiopathology; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000000981:diagnostic imaging / Q000503:physiopathology; D010101:Oxygen Consumption; D011659:Pulmonary Gas Exchange; D015203:Reproducibility of Results