MB isoenzyme of creatine kinase was measured every 3 hours during the first 24 hours of admission to C.C.U. and successively every 4-6 hours in the next 24-48 hours in 42 patients with acute transmural myocardial infarction. The pain-C.C.U. admission time interval was less than 6 hours in all cases. 22 patients were treated by propranolol (2 mg bolus followed by 0.1 mg/Kg/die for the next 48 hours in continuous i.v. infusion), 20 patients served as a control. Cumulated activity, peak plasma value, rate of release and total duration of release of MB-CK did not differ significantly between the two groups. In patients treated within 3 hours from pain onset (n = 12) cumulated activity, peak plasma value and rate of release of MB-CK were significantly inferior than control group. In patients treated between the 3rd and 6th hour from pain onset (n = 10) the total duration of release of isoenzyme was significantly prolonged. No treated patients developed clinical or radiologic signs of cardiac insufficiency. The incidence of ventricular arrhythmias was 17% in the treated group vs. 62% in the control group (P0.05). The data show that propranolol, if started early in the course of acute myocardial infarction, reduces significantly infarct size and slows down the evolution of necrotic process.
