Activation of neurohumoral systems in postinfarction left ventricular dysfunction

Objectives. This study was conducted to evaluate the degree of neurohumoral activation around the time of hospital discharge after myocardial infarction. Background. Because pharmacologic interventions that block the effects of neurohumoral activation improve the prognosis after infarction, we hypothesized that widespread neurohumoral activation persists in some patients until at least the time of hospital discharge and that the determinants of activation vary from one system to another. Methods. Five hundred nineteen patients in the Survival and Ventricular Enlargement Study (SAVE) had plasma neurohormones measured before randomization at a mean of 12 days after infarction. All patients had left ventricular dysfunction (left ventricular ejection fraction ≤40%) but no overt heart failure. Results. Although all neurohormones except epinephrine were increased compared with values in age-matched control subjects, plasma norepinephrine (301 ± 193 vs. 222 ± 87 pg/ml, p < 0.001), renin activity (3.0 ± 3.7 vs. 1.2 ± 1.2 ng/ml per h, p < 0.001), arginine vasopressin (1.9 ± 6.9 vs. 0.7 ± 0.3 pg/ml, p < 0.001) and atrial natriuretic peptide (75 ± 75 vs. 21 ± 9 pg/ml, p < 0.001) values ranged from normal to very high, indicating a wide spectrum of neurohumoral activation. Activation of one system did not correlate with activation of another. The clinical and laboratory variables most closely associated with neurohumoral activation were Killip class, left ventricular ejection fraction, age and use of diuretic drugs. The association between neurohumoral activation and clinical and laboratory variables varied from one neurohormone to another. Conclusions. Neurohumoral activation occurs in a significant proportion of patients at the time of hospital discharge after infarction. Which neurohormone is activated and which clinical and laboratory variables determine this activation vary from one neurohormone to another.