The effect of aortic valve replacement on N-terminal natriuretic propeptides in patients with aortic stenosis.

BACKGROUND: Increased plasma concentrations of natriuretic peptides have been demonstrated to be associated with increased intracardiac pressure and left ventricular (LV) hypertrophy. After aortic valve replacement (AVR) in aortic stenosis patients, there is a relief of the left outflow obstruction with a substantial hemodynamic improvement. This is followed by a gradual regression of the LV hypertrophy.

HYPOTHESIS: After AVR, reduction in LV filling pressure is expected to occur rapidly, while regression of LV hypertrophy will take place over a longer time period. On this basis we hypothesized that the plasma levels of N-terminal proatrial natriuretic peptide (NT-proANP) would be reduced early in the postoperative period, while N-terminal probrain natriuretic peptide (NT-proBNP), through its closer reflection of LV hypertrophy, would be sustained for a longer period.

METHODS: Two groups of patients with aortic stenosis undergoing AVR were followed for 4 and 12 months, respectively. Plasma concentrations of NT-proANP and NT-proBNP were measured before and after AVR and related to preoperative findings and changes in the aortic valve area index.

RESULTS: Before AVR, the patients had significantly increased plasma levels of NT-proANP and NT-proBNP. After AVR, NT- proANP was decreased at 4 and 12 months but remained elevated compared with controls. N-terminal-proBNP tended to decrease, but did not change significantly. When the patients were followed for 12 months, only those with elevated preoperative pulmonary capillary wedge pressure had decreased peptide levels (NT-proANP: p = 0.017, NT-proBNP: p = 0.058). There was no regression of LV hypertrophy. The patients with the largest postoperative valve area index [1.27 (1.10-1.55) cm2/m2] had the largest reduction of NT-proBNP (47%). Those with the smallest valve area index [0.67 (0.54-0.73) cm2/m2] had no decrease in NT-proBNP.

CONCLUSIONS: Our study suggests that a reduction in left atrial pressure is the main factor causing the change of NT-proANP level after AVR. A small prosthetic valve orifice area with a high aortic valve gradient might prevent regression of LV hypertrophy, thus representing a stimulus for increased cardiac secretion of NT-proBNP.