Plasma MB creatine kinase activity and other conventional enzymes. Comparison in patients with chest pain and tachyarrhythmias.

We studied 67 patients with tachycardia and chest pain admitted with suspected myocardial infarction; 29 had myocardial infarction (20 transmural, nine subendocardial) with elevated MB creatine kinase (CK) activity, as well as elevated total CK and lactate dehydrogenase (LDH) levels. However, hydroxybutyric dehydrogenase and SGOT activity remained normal in three and four patients, respectively. Despite abnormal ECGs in 84% and typical chest pain in 54%, 38 patients had normal MB CK activity. However, 15 of them had elevated MM CK levels, presumably due to release from skeletal muscle. In total, 29 patients had elevated activity of MM, CK, LDH, or SGOT, but 72% of these patients had cardiac failure, hypotension, or skeletal muscle trauma due to cardioversion. Eleven patients with normal MB CK had elevated hydroxybutyric dehydrogenase activity. Despite elevated activity of other enzymes, MB CK remained normal. Thus, elevated plasma MB CK activity appears to remain a good diagnostic marker of myocardial necrosis in patients with tachyarrhythmias.