Background and Objective: One-third of heart failure cases also represent conduction disorders, such as Left Bundle Branch Block (LBBB), which leads to mechanical defects and ventricular dyssynchrony. This study aims to investigate the correlation between the degree of LBBB and other electrocardiographic parameters, along with the severity of ventricular dysfunction and Mitral Regurgitation (MR).
Methods: In this cross-sectional study, multiple electrocardiographic (including, QRS duration, R voltage in limb leads, S voltage in precordial leads, Cornell index, Sokolow-Lyon index, QRS axis deviation, and notched QRS in lateral leads), echocardiographic (i.e., LVEF and degree of functional MR), and Tissue Doppler variables were examined in selected patients. Moreover, the correlation between the degree of dyssynchrony and the studied variables was evaluated.
Findings: Forty patients (20 women and 20 men) with LBBB manifestations on ECG were selected. The average age of the patients was 64±13.5 years. 77.5% had LVEF less than 35%, 57.5% had intraventricular dyssynchrony >60, and 60% had interventricular dyssynchrony >40. There was a statistically significant correlation between the amount of LVEF (r=-0.464; p=0.003) and MR severity (r=0.332; p=0.037) with the severity of intraventricular dyssynchrony. In addition, the amount of septal to lateral wall delay in patients with LVEF less than 35% was significantly correlated with the degree of intraventricular dyssynchrony (r=0.6712; p=0.000). Among the ECG parameters in patients with LVEF less than 35%, there was only a significant relationship between the maximum R amplitude and the degree of interventricular dyssynchrony (r=0.438; p=0.014).
Conclusion: Our results indicated that LVEF and MR were correlated with the degree of ventricular dyssynchrony and they could be considered as valuable markers for LBBB. The septum to lateral delay, and septum to posterior, were also correlated.