Left bundle branch block and reduction in QT interval dispersion are independent prognostic predictors in patients with chronic heart failure treated with carvedilol

Abstract

Introduction: The role of QT interval dispersion (QTD) in heart failure (HF) remains poorly defined and controversial. Hypothesis: Evaluate the impact of QTD in the clinical evolution of chronic HF patients compensated due to the use of carvedilol (CVD). Methods: A total of 108 patients (22-82 years), 65.7% male, 72.2% caucasians, with stable chronic HF and NYHA functional class (FC) II, III and IV on optimized treatment, with an left ventricle ejection fraction (EF) of<0.40 were selected for therapy with CVD. All patients had complete history performed, laboratorial evaluation, ECG (mainly for QTD measurement), ECHO (mainly for EF evaluation) and followed-up for an average period of 38.2 months. All used CVD at the maximum tolerated dose. The evaluated parameters were: general characteristics, etiology of the HF, concomitant medications used, NYHA FC, maximum CVD dose, EF and QTD before and 6 months after CVD, presence of left bundle branch blockade (LBBB), cardiovascular admissions, complications and deaths. Results: A QTD reduction and an increase in the EF were found after 6 months of therapy with CVD (p<0.001). The general characteristics (p>0.05), concomitant medications (p>0.05), CVD dose (p=0.80), cardiomyopathy etiology (p=0.959), presence of complications (p=0.851) and of LBBB (p=0.161) did not influence in the QTD reduction. This reduction was related to the patients with worse FC pre-CVD (p=0.007), with FC improvement (p=0.028) and with fewer admissions per year of follow-up (p=0.047). A pre-CVD QTD of ≤90ms was predictive of admissions (AUC=0.636; sens.=43.1%; spec.=82%; positive likelihood ratio [LR]=2.39; negative LR=0.69). The presence of LBBB (p=0.002; OR=4.606) and post-CVD QTD>90ms were mortality predictors (p=0.034; OR=3.912) (AUC=0.061; sens.=29.2%; spec.=90.5%; positive LR=3.06; negative LR=0.78). The independent predictors of survival found were LBBB (p=0.007; OR=0.293), the presence of complications during follow-up (p=0.006; OR=0.133) and the QTD reduction (p=0.004; OR=5.48).Conclusions: CVD use reduced the QTD and increased the EF in patients with chronic HF. The QTD reduction was positively related to the HF improvement and less hospitalizations. The independent survival predictors were the presence of LBBB and the occurrence of complications, determining a reduced survival and the QTD reduction related to an increased survival.