We previously observed an attenuation of exercise-induced myocardial ischemia on the ergocycle during a ramp protocol compared to the standard Bruce protocol treadmill test in patients with coronary heart disease. However, it was uncertain whether decreased ischemia on the ergocycle resulted from the warm-up effect of the more gradual ramp protocol or from the mode of exercise itself (cycling vs running). Sixteen stable patients, aged 64 +/- 5 years, with documented coronary heart disease (> or =70% coronary artery stenosis and/or reversible myocardial perfusion defects) performed 3 symptom-limited exercise tests: the standard Bruce protocol treadmill test and 2 individualized ramp protocols (treadmill and ergocycle). We measured the ischemic threshold (heart rate x systolic blood pressure product at 1-mm ST-segment depression) and oxygen consumption (VO(2)). The ischemic threshold was higher during cycling (ergocycle ramp, 24,009 +/- 5,769 beats/min x mm Hg) compared to running (Bruce treadmill, 20,429 +/- 3,508 beats/min x mm Hg; and ramp treadmill, 19,451 +/- 3,392 beats/min x mm Hg; p <0.001), independently of exercise intensity (VO(2)). The peak VO(2) did not significantly differ among all tests (p = 0.25) despite a greater peak rate-pressure product achieved with the ergocycle (29,378 +/- 6,291 beats/min x mm Hg) compared to either treadmill protocol (Bruce, 26,202 +/- 5,831 beats/min x mm Hg; ramp, 25,654 +/- 6,492 beats/min x mm Hg; p <0.001). In conclusion, the mode of exercise (ergocycle vs treadmill), rather than the type of protocol (ramp vs Bruce), is associated with an attenuation of electrocardiographic parameters of myocardial ischemia, independently of exercise intensity (VO(2)) and myocardial demand (rate-pressure product).
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