THE EFFECT OF EARLY CONVERTING-ENZYME INHIBITION ON NEUROHUMORAL ACTIVATION IN ACUTE MYOCARDIAL-INFARCTION

The effect of early converting enzyme inhibition with enalapril on the extent of neurohumoral activation in acute myocardial infarction was evaluated in a randomized, placebo-controlled double blind fashion. Pl asma levels of atrial natriuretic factor and noradrenaline on day 1, i .e. prior to randomization (n = 99), and on days 3 (n = 145) and 30 (n = 69) following myocardial infarction were determined. Enalapril did not significantly affect neurohumoral activation on day 3 (enalapril v s. placebo (mean (S.E.M.); atrial natriuretic factor: 35.3 (3.0) vs. 3 7.2 (2.9) pmol/l; noradrenaline: 2.82 (0.20) vs. 3.70 (1.02) nmol/l) o r at 1 month (atrial natriuretic factor: 33.1 (3.0) vs. 32.4 (3.9) pmo l/l; noradrenaline: 2.77 (0.25) vs. 2.82 (0.28) nmol/l). However, in m yocardial infarction patients developing heart failure, a significant attenuation of the day 3 atrial natriuretic factor, but not of the nor adrenaline response, was seen (atrial natriuretic factor: 47.0 (7.7) v s. 59.0 (6.4) pmol/l, P < 0.05; noradrenaline: 3.37 (0.42) vs. 6.59 (3 .26) nmol/l, P = ns). In conclusion, enalapril did not significantly r educe neurohumoral activation in acute myocardial infarction, possibly because the activation in most patients is modest and confined to the early convalescent phase. However, in patients with myocardial infarc tion and heart failure enalapril therapy was associated with a reducti on in early plasma atrial natriuretic factor levels, compatible with d ecreased cardiac filling pressures.