The effect of left ventricular electrical delay on AV optimization for cardiac resynchronization therapy

Area of Science:

• Cardiology
• Electrophysiology
• Medical Devices

Background:

• The effectiveness of atrioventricular optimization (AVO) in cardiac resynchronization therapy (CRT) remains debated.
• Identifying patient subgroups that benefit from AVO is crucial for improving CRT outcomes.
• Pacing at sites of late electrical activation, measured by the QLV interval, has shown potential to improve CRT-induced remodeling.

Purpose of the Study:

• To investigate if pacing at sites with prolonged left ventricular (LV) electrical delay enhances the efficacy of AVO.
• To determine the relationship between QLV interval duration and CRT response.

Main Methods:

• A substudy of the SMART-AV trial randomized 280 subjects to electrogram-based AVO (SmartDelay) or a nominal atrioventricular delay (120 ms).
• The QLV interval was measured from QRS onset to the LV electrogram peak.
• CRT response was defined as a >15% reduction in LV end-systolic volume at 6 months.

Main Results:

• Longer QLV intervals were significantly associated with a positive CRT response (P < .01).
• The benefit of AVO increased proportionally with QLV interval duration.
• Patients in the longest QLV quartile showed a more than 6-fold increase in remodeling response compared to nominal delays.

Conclusions:

• Baseline electrical dyssynchrony, indicated by the QLV interval, predicts CRT response.
• AVO significantly increases the likelihood of structural response in patients with long QLV intervals.
• Combining AVO with QLV-optimized LV lead placement may synergistically maximize CRT response.