Selective activation of atrial natriuretic peptide in patients with myocardial infarction and mild left ventricular dysfunction.

The purpose of this study was to investigate whether neurohumoral activation occurs in asymptomatic patients with acute myocardial infarction (AMI) and without clinical signs of heart failure. During the early phase of AMI (mean 8 days), the neurohumoral profiles of 60 patients (mean age 59 range 37 to 70) were examined. Blood levels of the following humoral parameters were measured: atrial natriuretic peptide (ANP), plasma renin activity, aldosterone and vasopressin. All patients underwent cardiac catheterization during hospitalization. Baseline hemodynamic characteristics identified left ventricular dysfunction (ejection fraction < or = 45% and/or left ventricular end-diastolic pressure > or = 15 mmHg) in 32 patients; the remaining 28 patients had normal hemodynamic parameters. In patients with AMI, plasma ANP levels differed significantly from control subjects (111 +/- 74 pg/ml vs. 53 +/- 18 pg/ml; P < 0.001). In patients with AMI and mild left ventricular dysfunction ANP levels were significantly increased when compared to patients with AMI and normal left ventricular function (129 +/- 73 pg/ml vs. 82 +/- 69 pg/ml; P < 0.001). The hemodynamic data showed a significant correlation with ANP only in patients with AMI and left ventricular dysfunction (EF% r = 0.42; LVEDP r = 0.44; P < 0.001). These data show that in patients with myocardial infarction and without heart failure, the atrial natriuretic peptide is the only neurohumoral system activated out of all neurohumoral systems tested in this population and its circulating levels are strictly related to the degree of left ventricular dysfunction.