Irrelevant B-Type Natriuretic Peptide Levels in Patients With Mechanical Prostheses in the Mitral Position Presenting With Congestive Heart Failure

Background: Plasma B-type natriuretic peptide (BNP) level is reported to be a strong marker of congestive heart failure (CHF). Heterogeneity of the BNP levels among individuals with CHF, however, can cause confusion in interpreting the results. The influence of mitral mechanical prostheses on BNP levels in patients presenting with CHF is not well known. Methods and Results: In the present study 214 consecutive patients with CHF diagnosed using the Framingham criteria were enrolled and divided into 2 groups with and without mitral mechanical prostheses (prosthesis group, n=31; native group, n=183). The plasma BNP levels were measured, and clinical examinations including echo-cardiography were performed at the same time to assess cardiac performance. There was no difference in the left ventricular ejection fractions between the 2 groups. Despite having a lower body mass index, larger prevalence ratio of atrial fibrillation and larger size of the left atrium, the prosthesis group had a significantly lower logBNP level than the native group (prosthesis group vs native group: 5.12 +/- 1.01 vs 6.21 +/- 0.92, P<0.001; BNP level: 167 +/- 324 pg/ml vs 498 +/- 380 pg/ml). On multivariate analysis the presence of a mitral mechanical prosthesis was extracted as an independent predictor for decreased BNP level in patients with CHF. Conclusions: Plasma BNP level cannot correctly reflect the severity of CHF in patients with mechanical prostheses in the mitral position. (Circ J 2010; 74: 1584-1590)