Prognostic Importance of Brain Natriuretic Peptide and Left Ventricular Longitudinal Function in Asymptomatic Degenerative Mitral Regurgitation
What are the determinants and the impact on outcome of B-type natriuretic peptide (BNP) in asymptomatic patients with degenerative mitral regurgitation (MR)?
Comprehensive transthoracic echocardiography including two-dimensional speckle tracking quantification was performed in 135 consecutive asymptomatic patients (60 ± 14 years, 56% men) with moderate to severe degenerative MR and preserved left ventricular (LV) function. Blood samples were collected at the time of the echocardiography, and plasma BNP levels were measured. The main outcome measures were BNP level and cardiac events. Cox proportional hazards models were used both in individual and multivariable analyses to identify the independent predictors of cardiac event-free survival.
BNP was correlated with age, indexed LV end-systolic diameter, indexed left atrium (LA) volume, estimated LV filling pressure with E/Ea ratio, systolic pulmonary arterial pressure, and global longitudinal strain (GLS). In multiple regression analysis, indexed LA volume (p = 0.008), mitral deceleration time (p = 0.003), and GLS (p < 0.0001) were independently associated with BNP. During follow-up (mean 23 ± 19 months), 54 events occurred resulting in 4-year event-free survival of 50 ± 6%. There was a graded relationship between the increase in BNP (i.e., according to quartile) and reduced event-free survival (p < 0.0001). In Cox multivariable analysis, indexed LA volume (hazard ratio [HR], 1.04; p = 0.003), GLS (HR, 1.14; p = 0.007), and 3rd and 4th quartiles of BNP (HR, 8.5; p = 0.002 and HR, 8.8; p = 0.002) were independent determinants of event-free survival.
The authors concluded that in asymptomatic degenerative MR, LV longitudinal function and LA volume are the main determinants of BNP release.
This study reports that BNP level may vary considerably in asymptomatic patients with moderate to severe degenerative MR and preserved LV function. The main independent predictors of BNP level are mitral deceleration time, LA volume, and LV longitudinal myocardial deformation. A high BNP level is independently associated with reduced cardiac-related event-free survival. It appears that BNP level is a low-cost, simple, and easily and rapidly measurable biomarker that may provide important incremental prognostic value and help better define the optimal timing of surgery in asymptomatic patients with degenerative MR. Further studies in larger cohorts are needed to validate these findings.
Keywords: Multivariate Analysis, Proportional Hazards Models, Biological Markers, Ventricular Function, Left, Arterial Pressure, Regression Analysis, Echocardiography, Natriuretic Peptide, Brain
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