Rate-adaptive AV delay and exercise performance following cardiac resynchronization therapy.

Area of Science:

• Cardiology
• Biomedical Engineering
• Exercise Physiology

Background:

• Physiological shortening of the atrioventricular (AV) interval with increasing heart rate is normal.
• This phenomenon is utilized in dual-chamber pacing for bradycardia.
• Optimal AV delay management is crucial for patients with heart failure receiving cardiac resynchronization therapy (CRT).

Purpose of the Study:

• To evaluate the effect of exercise on optimal AV delay in CRT patients.
• To determine the impact of patient-specific rate-adaptive AV delay (RAAVD) on exercise capacity.
• To assess if RAAVD can mimic physiological AV shortening during exercise.

Main Methods:

• Phase 1: Iterative AV delay optimization was performed at rest and during exercise in 52 CRT patients.
• Phase 2: Cardiopulmonary exercise testing was conducted in 20 patients with RAAVD programmed ON versus OFF.
• Measurements included exercise time and maximal oxygen consumption (Vo(2)max).

Main Results:

• A significant reduction (mean 50%) in optimal AV delay was observed during exercise in 94% of patients (P < .001).
• Exercise capacity was significantly improved with RAAVD ON (8.7 min) compared to RAAVD OFF (7.9 min) (P = .003).
• Vo(2)max was also significantly higher with RAAVD ON (16.1 mL/(kg·min)) versus RAAVD OFF (14.9 mL/(kg·min)) (P = .024).

Conclusions:

• Optimal AV delay significantly shortens during physiological exercise in CRT patients with heart failure.
• Programmable RAAVD effectively replicates this physiological response.
• RAAVD programming leads to a substantial improvement in exercise capacity for CRT patients.