Left ventricular conduction delays and relation to QRS configuration in patients with left ventricular dysfunction

Area of Science:

• Cardiology
• Electrophysiology
• Heart Failure Management

Background:

• Left ventricular activation delay (LVAT) >100 ms is a potential predictor of cardiac resynchronization therapy (CRT) response.
• The prevalence of significant LVAT and its relationship with different QRS complex morphologies in heart failure (HF) patients remain incompletely understood.

Purpose of the Study:

• To investigate the prevalence of LVAT >100 ms across various QRS configurations in patients with heart failure.
• To examine the correlation between QRS duration, QRS configuration, and LVAT in HF patients compared to controls.

Main Methods:

• Retrospective analysis comparing QRS duration and LVAT in control subjects (n=30) with HF patients (n=120).
• HF patients were categorized into narrow QRS (NQRS(HF), n=35), left bundle branch block (LBBB(HF), n=54), and right bundle branch block (RBBB(HF), n=31) groups.
• LVAT was measured as the interval from QRS onset to basal inferolateral LV depolarization.

Main Results:

• LVAT exceeded 100 ms in 23% of NQRS(HF) patients, 87% of LBBB(HF) patients, and 45% of RBBB(HF) patients.
• LVAT was significantly prolonged in all HF groups compared to controls (p <0.001).
• Correlation between QRS duration and LVAT varied significantly across groups (p=0.004 in controls, p<0.001 in LBBB(HF)).

Conclusions:

• Left ventricular conduction delays in HF patients are dependent on QRS configuration and duration.
• A substantial proportion of HF patients, particularly those with LBBB, exhibit LVAT >100 ms, suggesting potential for CRT.
• Fewer than 25% of RBBB(HF) patients showed delays comparable to LBBB(HF) patients, indicating heterogeneity in conduction abnormalities within this group.