[Chronic frequency-adaptive pacemaker therapy in patients with heart failure]

Area of Science:

• Cardiology
• Biomedical Engineering
• Exercise Physiology

Background:

• Patients with bradyarrhythmias often require pacemakers for rate control.
• Rate-adaptive pacemakers aim to optimize cardiac output during varying physical demands.
• The optimal programming of upper rate limits in rate-adaptive ventricular pacing remains an area of investigation, especially for patients with heart failure.

Purpose of the Study:

• To evaluate the impact of different rate-adaptive pacemaker settings on exercise capacity in patients with complete atrioventricular block or sick sinus syndrome.
• To compare the efficacy of VVI (fixed rate) pacing versus VVIR (rate-adaptive) pacing with low (VVIR1) and high (VVIR2) upper rate limits.
• To identify patient subgroups that benefit most from specific rate-adaptive pacing strategies.

Main Methods:

• Twenty patients with pacemakers underwent randomized ergospirometry assessments after 4 weeks of VVI, VVIR1 (70-110 bpm), and VVIR2 (70-130 bpm) pacing.
• Measurements included oxygen uptake (VO2) and work load (W) at peak exercise and anaerobic threshold (AT).
• Patients were stratified based on exercise capacity using the Weber classification (C and D).

Main Results:

• Rate-adaptive pacing (VVIR1 and VVIR2) significantly increased peak oxygen uptake (VO2-max) compared to VVI pacing in the overall population.
• Only the VVIR1 mode (low upper rate) significantly improved VO2 at the anaerobic threshold (AT).
• Patients with severely reduced exercise capacity (Weber class D) showed significant benefits in VO2-max and VO2-AT with VVIR1 pacing, unlike those with moderately limited capacity (Weber class C).

Conclusions:

• Rate-adaptive ventricular pacing, particularly with a lower upper rate limit (110 bpm), enhances exercise capacity and workload at the anaerobic threshold.
• Patients with heart failure and severe exercise intolerance (Weber D) experience significant benefits from this pacing strategy.
• Programming the upper rate in a lower range is recommended for rate-adaptive ventricular pacemaker systems in patients with heart failure.