Effects of captopril in heart failure complicating acute myocardial infarction and persistence of acute haemodynamic effects in chronic heart failure after 3 years of treatment.

A study was made of ten subjects with post myocardial left ventricular failure. All patients were treated with captopril with successive doses of 12.5 mg, 25 mg, 50 mg. Heart rate and mean blood pressure remained unchanged. Cardiac output increased from 4.30 +/- 0.56 to 4.6 +/- 0.57 litres/min in response to the 12.5 mg dose (P less than 0.05), from 4.30 +/- 0.56 to 4.77 +/- 0.59 litres/min on administration of the 25 mg dose (P less than 0.01) and from 4.34 +/- 0.56 to 4.86 +/- 0.66 litres/min after the 50 mg dose (P less than 0.01). Total systemic resistance fell from a baseline mean of 1847 +/- 338 to 1697 +/- 35 dyne/s/cm-5 with the 12.5 mg dose, to 1547 +/- 329 with the 25 mg dose and to 1489 +/- 308 with the 50 mg dose. All the reductions were statistically significant. Right atrial pressure, pulmonary blood pressure, wedge pressure, total pulmonary resistance and pre-capillary resistance decreased statistically significantly. In a separate study on the possibility that captopril long term therapy may induce tachyphylaxis we studied the acute haemodynamic effects of a dose of 25 mg of captopril after 17 to 36 months (mean 29.5 +/- 5.3) treatment with it for chronic congestive heart failure. Cardiac index increased from 2.02 +/- 0.25 to 2.59 +/- 0.62 (P less than 0.01) total systemic resistance, mean pulmonary pressure and wedge pressure decreased statistically significantly.