186 out of 391 patients with acute myocardial infarction were treated with C-3 and 205 with placebo in a multicenter, double-blind clinical trial. Ensuing complications were treated in the same way in both groups. C-3 was injected i.v. slowly at the dose of 2 g statim plus 6 g by continuous drip infusion over 24 hrs for 5 days. During
treatment, clinical progress was influenced only in regard to cardiac failure since in the C-3 group the improvement was more significant than in the placebo one (P less than 0.0025). Mortality rates were 8.1% and 11.2% for the C-3 and placebo groups, respectively. The difference in mortality was significant (P less than 0.05) for patients treated with C-3 for more than 24 hours. Mortality in male patients treated with C-3 for more than 12 hours was significantly lower (P less than 0.025). In patients less than 60 years old mortality rate was significantly lower (P less than 0.05) and was more so in patients receiving C-3 for more than 12 hours (P less than 0.025). Mortality due to complications was lower in the C-3 group, with arrhythmias (9.8% vs 14.2%), cardiogenic shock (69.2% vs 75%), and cardiac failure (9% vs 19.4%). Results agree with the hypothesis that C-3 may be effective in acute myocardial infarction by improving the action of traditional antiarrhythmic drugs, and augmenting myocardial contraction energy.