170 Left Ventricular Longitudinal Function is a Determinant of Plasma Brain Natriuretic Peptide in Degenerative Mitral Regurgitation

Abstract

In organic mitral regurgitation (OMR), brain natriuretic peptide (BNP) may be used as a surrogate marker of MR consequences on LV. The use of tissue Doppler imaging (TDI) and 2-D speckle-tracking (2DSt) to assess longitudinal strain improve the detection of subclinical LV dysfunction. However, whether decreased longaxis function is a determinant of BNP has never been examined. Transthoracic echocardiography including Doppler, TDI and 2DSt quantification were performed in 56 consecutive patients (61±15 years, 54% of male) with moderate to severe OMR. Peak annulus velocity and time-to-peak velocity (TP) were measured using TDI for Ea-, Aa- and Sa-wave. 2DSt was used to evaluate global longitudinal strain (GLS). Simultaneously to echocardiography, blood sample was drawn and plasma BNP level was measured. Patients were separated into 2 groups according to the median of BNP level (≥26pg/ml). Patients with BNP ≥26pg/ml were significantly older (65±13 vs. 56±16 yrs, p=0.03) and had higher LV systolic diameter (37±5 vs. 33±7mm, p=0.03), lower GLS (19±4 vs. 22±3%, p=0.0016) and slower TP-Ea (480±49 vs. 456±45ms, p=0.03). By contrast, there was no significant difference between the 2 groups with regard to LV volume and ejection fraction and MR severity. Plasma BNP was correlated with age (r=0.29, p=0.04), LV systolic diameter (r=0.29, p=0.04), TP-Ea (r=0.37, p=0.004) and GLS (r=-0.57, p<0.0001). On multivariate analysis, after adjustment for age, sex and LV systolic diameter, only TP-Ea (r 2 =0.10, p=0.004) and GLS (r 2 =0.32, p<0.0001) were independently associated with BNP. Interestingly, for 1% decrease in GLS, BNP raise of 2.6pg/ml. In addition, GLS was an independent predictor of BNP ≥26pg/l (odds-ratio=1.3, 95%CI: 1.05-1.56, p=0.005). In OMR, BNP release is rather related to LV longitudinal and filling function than severity of MR. Consequently, BNP may be used to unmask subclinical LV dysfunction and to improve the clinical management of patients with OMR.