Relationship between prosthesis-patient mismatch and pro-brain natriuretic peptides after aortic valve replacement

It has been shown previously that elevated plasma levels of B-type natriuretic peptide (BNP) and its N-terminal fragment (NT-pro-BNP) are related to the degree and progression of native aortic valve disease. In addition, NT-pro-BNP levels have been shown to decrease after successful aortic valve replacement (AVR). The presence of a valve prosthesis-patient mismatch (PPM) may affect the beneficial effects of AVR, however. The study aim was to investigate the relationship between PPM and NT-pro-BNP plasma levels late after AVR.

A series of consecutive patients (42 males, 31 females; mean age 66 +/- 13 years) who had undergone isolated AVR between May 2004 and July 2007 was enrolled into the study. Patients with preoperative moderate to severe mitral regurgitation, coronary artery disease, left ventricular (LV) dysfunction (ejection fraction <45%) and serum creatinine >150 mmol/l were excluded. PPM was defined severe as an indexed effective orifice area (EOAi) < or = 0.65 cm2/m2, or moderate when the EOAi was 0.66-0.85 cm2/m2. Plasma NT-pro-BNP levels and echocardiographic assessments were performed in all patients during routine follow up after surgery.

The patients received either a biological (n = 42) or mechanical (n = 31) prosthesis. Among the patients, 21 had no PPM, 27 moderate PPM, and 25 severe PPM. At a median follow up of 18 months, the mean NT-pro-BNP plasma level was 532 pg/ml (95% CI: 393.1-671.6), and the mean LV mass index (LVMI) 120 +/- 4 g/m2, the LVEF 60 +/- 1%, the peak aortic prosthesis gradient 28 +/- 2 mmHg, and the EOAi 0.74 +/- 0.02 cm2/m2. Multivariate statistical analysis showed that NT-pro-BNP level correlated with age (beta = 0.57, p<0.0001), LVMI (beta = 0.32, p = 0.02), NYHA class (beta = 0.50, p = 0.003) and EOAi (beta = -0.38, p = 0.02).

The study results showed that NT-pro-BNP levels were independently related to PPM late after isolated AVR in patients with preserved LV function. However, further investigations are required to confirm these findings and to identify their clinical implications.