THE PATIENT WITH CORONARY HEART-DISEASE AT ALTITUDE - OBSERVATIONS DURING ACUTE EXPOSURE TO 3100 METERS

Nine men with documented coronary artery disease who had exercise-induced angina and/or ST segment depression were studied by treadmill testing at 1600 m and during acute exposure to 3100 m altitude. Mean maximal oxygen uptake was reduced at altitude by 11% (range, 5-26%). Ventilation, heart rate, and systolic pressure at submaximal workloads were increased at 3100 m, but maximal values were unchanged. Oxygen saturation was reduced at rest, and during submaximal and maximal exercise (88.3 +/- 14 vs 93.4 +/- 0.7%). Angina and/or ST segment depression occurred at the same heart rate systolic pressure product, but at lower workloads. Systolic time intervals were unchanged at altitude. A target heart rate range of 70-85% of the ischemic end-point rate at lower altitude predicted an appropriate level of tolerable exercise at high altitude. We conclude that activity prescription for coronary patients with angina on arrival at high altitude should be based on heart rate rather than workload.