Prognostic Utility of Brain Natriuretic Peptide in Asymptomatic Patients With Significant Mitral Regurgitation and Preserved Left Ventricular Ejection Fraction

We sought to study the prognostic utility of serum brain natriuretic peptide (BNP) in patients with significant primary mitral regurgitation (MR) and preserved left ventricular (LV) ejection fraction (EF). Consecutive 548 asymptomatic patients (age 62 ± 13 years and 66% men) with ≥3 + primary MR and preserved LVEF on echo at rest, evaluated at our center from 2005 to 2008 were studied. Baseline clinical and echo data were recorded and the Society of Thoracic Surgeons (STS) score was calculated. Mean STS score was 4 ± 1%. Mean LVEF, mitral effective regurgitant orifice, indexed LV end-systolic diameter, and right ventricular systolic pressure (RVSP) were 62 ± 4%, 0.55 ± 0.3 cm2, 1.6 ± 0.3 cm/m2, and 38 ± 15 mm Hg; 43% had flail. Median log-transformed brain natriuretic peptide (lnBNP) was 4.1 (interquartile range 3.30 to 5.0), corresponding to an absolute BNP value of 60 pg/ml (only 13% had an absolute BNP value >250 pg/ml). At 7.4 ± 2 years, 493 patients (90%) had mitral surgery (92% repair) and nonmalignancy death occurred in 53 patients (10%). On multivariate Cox analysis, higher STS score (hazard ratio [HR] 1.50, 95% CI 1.20 to 1.88), higher baseline RVSP (HR 1.17, 95% CI 1.02 to 1.35), and higher ln BNP (HR 2.51, 95% CI 1.86 to 3.39) predicted death, whereas mitral surgery (HR 0.17, 95% CI 0.09 to 0.30) was associated with improved survival (all p <0.01). Eighty-nine percent of deaths occurred in patients with lnBNP >4.1. Addition of lnBNP to a model of STS score, baseline RVSP, and mitral surgery provided incremental prognostic utility (chi-square for mortality increased from 137 to 162, p <0.001). In conclusion, in asymptomatic patients with ≥3 + primary MR and preserved LVEF, the addition of BNP improved risk stratification and higher BNP independently predicted reduced survival.