Effects of treadmill exercise on total and myocardial creatine phosphokinase.

The percentage of increase in total and MB creatine phosphokinase (CPK) after treadmill exercise was determined in 29 patients--ten patients with ST segment depression greater than 1 mm (group 1) and 19 patients with no ST segment depression (group 2). Values were determined pretest and 6, 12, and 24 hours after exercise. The mean exercise duration was 8 min, 18 sec. Total CPK increased within the normal range 12 hours after exercise in group 1 patients exercising less than 8 min, 18 sec, and in all patients exercising longer. The MB CPK remained unchanged after exercise in all patients. These data suggest that while normal range variation of total CPK occurs after treadmill exercise testing, the myocardium does not release MB CPK, regardless of the level of treadmill exercise our patients performed or the development of presumed ischemic ST segment responses. Abnormal elevation of MB CPK suggests myocardial damage.