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 w ith coronary artery disease and reversible ischemia on both thallium-2 01 scintigraphy and exercise radionuclide angiography. A similar peak double product was attained in both studies. Angina pectoris was signi ficantly more frequent with treadmill exercise than with leg cycling ( 29 vs 5%, p = 0.0079). An interpretable and positive exercise electroc ardiogram occurred in 53% of treadmill tests, but in only 19% of leg c ycle tests (p = 0.0025); in a group of 22 patients without scintigraph ic ischemia, leg cycle testing had greater specificity (95 vs 64%, p = 0.0248). There mia was manifest by symptoms or an abnormal electrocar diogram 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, patie nts with previous coronary artery bypass surgery experienced clandesti ne 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 manifestation s of exercise-induced ischemia have a critical dependence on the type of exercise used.