Functional mitral regurgitation (MR) is a factor affecting prognosis of patients with chronic left ventricular (LV) dysfunction. The aim of the study was to investigate whether the evaluation of plasma N-terminal protype-B natriuretic peptide (NT-proBNP) concentrations is useful for prognostic assessment of patients with functional MR due to either ischemic or nonischemic chronic LV dysfunction.

Echocardiograms were obtained in 207 patients with chronic LV dysfunction (ejection fraction ≤45%) and secondary MR at color flow imaging. The NT-proBNP was measured at the time of the index echocardiogram. The MR was graded as mild when a small central jet <4 cm² or <20% of left atrial area or a vena contracta width <0.3 cm was present. It was considered moderate in the presence of signs of more-than-mild MR without criteria for severe MR. A vena contracta width ≥0.7 cm raised MR grade to severe. Median follow-up duration was 29 months.

The NT-proBNP levels increased significantly with MR severity. At multivariate analysis, NT-proBNP was an independent predictor of cardiac death (hazard ratio 2.17, CI 1.10-4.30, P = .026) and the most powerful predictor of cardiac death or heart failure–related hospitalization (hazard ratio 3.19, CI 1.89-5.37, P < .0001). A progressively worse outcome was apparent when patients were stratified by a graded increase in MR severity and by quartiles of NT-proBNP levels. Increased NT-proBNP concentrations and more-than-mild MR identified patients with the highest risk of cardiac mortality.

Assessment of plasma NT-proBNP allows for stratifying patients with functional MR regardless of their degree of valvular incompetence. Even in case of only mild or moderate MR, but increased NT-proBNP, patients have to face poor outcome.