Effect of Interventricular Electrical Delay on Atrioventricular Optimization for Cardiac Resynchronization Therapy.

Area of Science:

• Cardiology
• Electrophysiology
• Medical Devices

Background:

• Routine atrioventricular optimization (AVO) has not consistently improved outcomes in cardiac resynchronization therapy (CRT).
• Recent subgroup analyses suggest specific electrocardiographic or lead positions may benefit from AVO.
• Interventricular electrical delay is a potential factor influencing AVO efficacy.

Purpose of the Study:

• To evaluate if interventricular electrical delay modifies the impact of AVO on reverse remodeling in CRT patients.
• To determine the relationship between baseline interventricular delay and CRT response.
• To investigate the synergistic effect of AVO and LV lead optimization on CRT response.

Main Methods:

• A substudy of the SMART-AV trial randomized 275 subjects to electrogram-based AVO (SmartDelay) or nominal atrioventricular delay (120 ms).
• Interventricular delay was measured as the time between right ventricular (RV) and left ventricular (LV) electrogram peaks (RV-LV duration).
• CRT response was defined as a >15% reduction in LV end-systolic volume at 6 months.

Main Results:

• Longer RV-LV durations were significantly associated with CRT response (P<0.01).
• The benefit of AVO increased with prolonged RV-LV duration.
• At the longest quartile of RV-LV duration, odds of remodeling response were 4.26 times greater with AVO compared to nominal delays (P=0.010).

Conclusions:

• Baseline interventricular delay is a predictor of CRT response.
• AVO enhances the likelihood of reverse remodeling in CRT patients with long RV-LV durations.
• Optimizing AVO and LV lead placement to maximize interventricular delay may synergistically improve CRT response.