B-type natriuretic peptide in organic mitral regurgitation: determinants and impact on outcome

B-type natriuretic peptide (BNP) activation observed in cardiac diseases is a predictor of poor outcome; however, in organic mitral regurgitation (MR), BNP determinants and prognostic value are unknown.

We prospectively enrolled 124 patients with chronic organic MR (aged 63+/-15 years, 60% males) in whom we measured BNP level and simultaneously quantified MR degree, left ventricular (LV) remodeling, and left atrial (LA) volumes and analyzed long-term outcome. Baseline BNP level (54+/-67 pg/mL, median 31 pg/mL) was associated univariately with multiple clinical and echocardiographic characteristics, but in multivariate analysis, independent determinants of BNP, beyond age and sex (both P< or =0.01), were LV end-systolic volume index, LA volume, atrial fibrillation, and symptoms (all P<0.02). Conversely, MR degree was not independently associated with BNP. During follow-up, patients with high versus low BNP (> or =31 versus <31 pg/mL) displayed lower survival rates (at 5 years, 72+/-10% versus 95+/-5%, P=0.03) and higher rates of the combined end point of death and heart failure (at 5 years, 42+/-10% versus 16+/-7%, P=0.03). In multivariate analysis, with adjustment for age, sex, functional class, MR severity, and ejection fraction, BNP was independently predictive of mortality (hazard ratio per 10 pg/mL, 1.23 [95% CI 1.07 to 1.48], P=0.004) and of death or heart failure (hazard ratio per 10 pg/mL, 1.09 [95% CI 1.001 to 1.19], P=0.04).

BNP activation in organic MR reflects primarily ventricular and atrial consequences rather than degree of MR. Higher BNP level in patients with organic MR independently predicts adverse events under conservative management. Therefore, BNP activation in organic MR is an emerging biomarker of severity of MR consequences and of poor clinical outcome, and its assessment should be considered in the clinical evaluation and risk stratification of patients with MR.