Ventricular Irregularity, But Not Ventricular Rate, Is Important for Determination of NT-ProBNP Levels in Chronic Atrial Fibrillation: Evidence for Lenient Rate Control in Atrial Fibrillation

Abstract

Background: Role of ventricular rate (VR) and its irregularity in AF have not been well studied with respect to the elevation of NT-proBNP. Methods and Results: In 66 patients with AF (71±9 years, 32 men), NT-proBNP, indices of VR irregularity (mean VR, standard deviation (SD) of VR, SD of successive differences and SD of 5-minute averages (SDAVR)) derived from 24-hour Holter and transthoracic echocardiographic parameters (early mitral inflow velocity (e)/mitral annular velocity (e′), left atrial volume index and left ventricular ejection fraction (LVEF)) were measured. Mean VR, LVEF, e/e′, SDVR and SDAVR were significant univariate predictors of NT-proBNP. e/e′ and SDAVR remained as significant predictors after multivariate adjustment (standardized β=0.306, P=0.007, and β=−0.362, P=0.002, respectively), but mean VR did not. By partial correlation, e/e′ was found to be independently correlated with NT-proBNP (r=0.283, P=0.031), but mean VR was not (r=0.032, P=0.811). When the patients were stratified with the 33rd and 67th percentile values of e/e′ (11.8 and 15.4, respectively), a significant positive correlation between mean VR and NT-proBNP was present only in patients with the upper tertile value. Conclusions: VR is not as important as LV diastolic function and VR irregularity in the elevation of NT-proBNP in AF. VR control may be needed in patients with severe LV diastolic dysfunction. Our results support the findings of RACE II trial.