PR Prolongation predicts inadequate resynchronization with biventricular pacing in left bundle branch block

Area of Science:

• Cardiology
• Electrophysiology
• Medical Devices

Background:

• Prolonged PR interval is linked to poorer outcomes in cardiac resynchronization therapy (CRT) for patients with left bundle branch block (LBBB).
• Mechanisms underlying this association remain unclear.
• This study explores clinical, electrocardiogram (ECG), and echocardiogram changes post-CRT based on PR interval duration.

Purpose of the Study:

• To investigate the impact of baseline PR interval on clinical outcomes after CRT in LBBB patients.
• To identify potential mechanisms, including ECG and echocardiogram changes, that explain outcome differences.
• To stratify CRT recipients by PR interval quartiles to analyze treatment response.

Main Methods:

• Retrospective analysis of 291 CRT recipients with ejection fraction ≤35% and LBBB.
• Patients categorized into baseline PR interval quartiles.
• Primary endpoint: time to heart transplantation, LVAD implantation, or death. Secondary analysis of ECG and echocardiogram variables.

Main Results:

• Patients with PR interval >200 ms (quartile 4) had higher rates of prior atrial fibrillation, CABG, ICD, and amiodarone use.
• A PR interval >200 ms was associated with a 1.7-fold increased adjusted hazard ratio for the primary endpoint.
• Patients with PR >200 ms showed less QRS duration/area reduction and greater QT/QTc interval increase post-CRT; echocardiographic changes were similar across PR quartiles.

Conclusions:

• PR interval prolongation is a predictor of reduced event-free survival in LBBB patients undergoing CRT.
• Inadequate ventricular resynchronization may underlie the poorer outcomes associated with prolonged PR intervals.
• Further research into the electrophysiological mechanisms is warranted.