Left bundle branch block in coronary artery disease: toward novel electrocardiographic markers

BACKGROUND: Complete left bundle branch block is a classic example of an electrocardiogram that is non-informative when assessed using conventional criteria for myocardial ischemia. QRS duration is an established electrocardiographic marker of ventricular dyssynchrony and is used to predict the clinical course of chronic heart failure. Fragmented QRS, a less studied electrocardiographic parameter that reflects myocardial scarring, has emerged as a negative prognostic marker in coronary artery disease, being associated with recurrent cardiovascular events, hospitalizations, and mortality in patients with narrow QRS complexes. However, data on the value of fragmented QRS in the setting of wide QRS complexes remain limited.

AIM: To conduct a comparative analysis of the clinical, instrumental, and epidemiologic characteristics of patients with coronary artery disease and complete left bundle branch block, with consideration of the fragmented QRS presence.

MATERIALS AND METHODS: The study included 45 hospitalized patients with coronary artery disease (mean age 76±8 years). The main group consisted of 10 patients with fragmented QRS, and the control group included 35 patients without fragmented QRS. At the first stage (2018–2019), clinical history, electrocardiographic parameters, and echocardiographic characteristics (global and regional left ventricular contractility) were assessed. At the second stage (2024), medical records were analyzed using the Unified Medical Information and Analytical System.

RESULTS: Patients in the main group had longer QTc intervals (463 vs 433 ms in the control group; p=0.028), wider QRS complexes (160 vs 120 ms; p=0.009), and slightly lower left ventricular ejection fraction (34.2±14.4% vs 42.8±13.9%; p=0.063). The groups differed significantly in the severity of chronic heart failure (p=0.043), with stage 2B CHF (CHF was assessed using the Strazhesko classification which is commonly applied in clinical practice in Eastern Europe and Russia) observed in 80% of the main group vs 49% of the control group. The median number of fragmented leads was 4.5. Cardiovascular-related hospitalizations were slightly more frequent in the main group (p=0.061). A total of 27 deaths were recorded, most due to noncardiac causes. Death due to progression of chronic heart failure occurred in 30% of the main group and 17.1% of the control group. There were no significant differences in the mortality structure between groups.

CONCLUSION: The presence of fragmented QRS complexes on electrocardiogram in patients with complete left bundle branch block is associated with further QRS widening and QTc prolongation, a trend toward reduced left ventricular ejection fraction, increased frequency of cardiovascular-related hospitalizations, and progression of heart failure severity. These findings may be considered in the development of prognostic models for patients with coronary artery disease and initially abnormal QRS complexes.