Asymptomatic and electrically silent myocardial ischemia during upright leg cycle ergometry and treadmill exercise (clandestine myocardial ischemia).

The frequency of "clandestine" (electrically silent and asymptomatic, but scintigraphically evident) myocardial ischemia during treadmill and upright leg cycle ergometric studies was compared in 38 patients with coronary artery disease and reversible ischemia on both thallium-201 scintigraphy and exercise radionuclide angiography. A similar peak double product was attained in both studies. Angina pectoris was significantly more frequent with treadmill exercise than with leg cycling (29 vs 5%, p = 0.0079). An interpretable and positive exercise electrocardiogram occurred in 53% of treadmill tests, but in only 19% of leg cycle tests (p = 0.0025); in a group of 22 patients without scintigraphic ischemia, leg cycle testing had greater specificity (95 vs 64%, p = 0.0248). Ischemia was manifest by symptoms or an abnormal electrocardiogram in 59% of treadmill tests, but in only 18% of leg cycle tests (p = 0.0003). There were no differences between the exercise variables or the degree of scintigraphic abnormalities of the 22 patients with manifest ischemia and the 16 with clandestine ischemia. However, patients with previous coronary artery bypass surgery experienced clandestine ischemia more frequently than did those without bypass surgery (80 vs 33%, p = 0.0103). Thus, clandestine ischemia occurs more frequently during symptom-limited upright leg cycle ergometry (82%) than during treadmill exercise (42%). The symptomatic and electrical manifestations of exercise-induced ischemia have a critical dependence on the type of exercise used.