Abstract
To detect whether creatine kinase is released by the myocardium during cardiac catheterization or exercise stress testing, the sera of 100 patients who underwent cardiac catheterization and of 51 patients and 11 normal subjects who performed exercise stress tests were analyzed for the activity of isoenzymes of creatine kinase. The analysis of creatine kinase was done by a very sensitive and precise method using ion-exchange column chromatography. There was little change in the activity of the myocardial form of creatine kinase (MB form) following uncomplicated coronary arteriographic studies or cardiac catheterizations, but there was a 55 percent increase in the activity of the MM form of creatine kinase (P < 0.001). Six patients had clinically important increases in the activity of the MB form; these included three otherwise uncomplicated cases and one patient each with an intramyocardial injection, an endomyocardial biopsy, and an arrhythmia requiring therapy with electrical countershock. The activity of the MB form of creatine kinase remained normal in all patients who exercised to a symptom-tolerated maximum, regardless of ST-segment depression. Patients included 15 who continued exercising with greater than 3 mm of ST-segment depression until experiencing pain in the chest and 16 who exercised for longer than three minutes following ST-segment depression. These results suggest that there is no significant increase in the activity of the MM form of creatine kinase due to exercise-induced myocardial hypoxia or following uncomplicated cardiac catheterizations. Therefore, an increase in the activity of the MB form following these procedures suggests myocardial damage.
