Increased plasma atrial natriuretic peptide levels after heart transplant: relation to ventricular expression and severity of rejection.

To determine whether elevated plasma atrial natriuretic peptide (ANP) levels observed after cardiac transplant are related to ventricular ANP expression and/or the severity of rejection, 59 ambulatory patients with cardiac transplant underwent hemodynamic evaluation, endomyocardial biopsy, and plasma ANP sampling. Forty-two of the 59 patients had right ventricular (RV) biopsy specimens immunohistochemically stained for the presence of ANP. Plasma ANP levels were elevated (p < 0.0001) in transplant patients (172 +/- 12 pg/ml) compared to normal subjects (36 +/- 4 pg/ml). Sixty-four percent of transplant patients showed stainable RV ANP on endomyocardial biopsy. There was no significant difference in plasma ANP levels between patients with or without RV ANP. The degree of RV staining did not correlate with plasma ANP levels, degree of rejection, mean atrial or systemic pressures, or specific immunosuppressive regimen. Plasma ANP levels were higher in patients with moderate or severe rejection (237 +/- 17 pg/ml) compared to patients with mild or no rejection (163 +/- 12 pg/ml; p 0.03), but there was significant overlap of values. These data suggest that ventricular ANP secretion may account for some of the increase in plasma ANP levels in cardiac transplant patients. However, increased plasma ANP levels in some transplant patients who have no RV ANP and the lack of correlation between the amount of stainable RV ANP and plasma ANP levels suggest that other mechanisms are also likely responsible for plasma ANP elevations in this setting.