Assessment and Comparison of Electrocardiographic Characteristics of Left Bundle Branch Block between Patients with and without Severe Left Ventricular Dysfunction

Objective: There is a greater risk of mortality and morbidity for patients with left bundle branch block (LBBB). In most cases, LBBB is accompanied by left ventricular dysfunction. We investigated the electrocardiographic characteristics of LBBB patients with and without congestive heart failure to determine parameters for the follow-up of this group of patients. Method: In this cross-sectional study, all patients who referred to our tertiary center with LBBB (with preserved left ventricular function) candidated for cardiac resynchronization therapy were included between January 2007 and January 2008. Electrocardiographic characteristics such as QRS notching, intrinsicoid deflection, and QRS duration were compared between two groups. Result: Seventy-five patients were enrolled (mean age = 60.20±12.55 years, range=18-77). There was a statistically significant relationship between QRS notching in the precordial leads and severe left ventricular dysfunction (72.7% of patients with severe left ventricular dysfunction vs. 27.8% of patients with preserved left ventricular function; p value=0.04). The relationship between QRS notching in the limb leads and severe left ventricular dysfunction was not statistically significant (70.7% in patients with severe left ventricular dysfunction vs. 29.3% in patients with preserved left ventricular function; p value > 0.05). Our study showed a significant relationship between QRS wave duration in the precordial and limb leads and severe left ventricular dysfunction (p value < 0.05), but there was no significant relation between intrinsicoid deflection and severe left ventricular dysfunction (p value > 0.05). Conclusion: QRS wave fragmentation (presence of a notch in R or S) may be associated with inactivation and dyssynchronization, both of which can reflect ischemic condition. There are reports of a correlation between this disorder and dyssynchronization; this can be one of the causes of the pathophysiology of congestive heart failure. Increase in QRS duration in the ECG was strongly associated with some changes in left ventricular function and structure, which can be allied to congestive heart failure. Also, dyssynchronization due to LBBB can increase the risk of congestive heart failure.