Spontaneous daily variability of atrial sensitivity. A study with an implanted DDD pacemaker

Area of Science:

• Cardiology
• Biomedical Engineering
• Electrophysiology

Background:

• Spontaneous variations in chronic stimulation thresholds are well-studied, but dynamic variability in atrial sensitivity is less understood.
• Existing literature presents conflicting data on the extent of atrial sensitivity variations.
• A 2:1 safety margin is commonly recommended, yet some studies suggest it's insufficient for accurate sensing.

Purpose of the Study:

• To evaluate the daily variability of atrial sensitivity (AS) in patients with Cosmos 3 DDD pacemakers.
• To assess AS using an algorithm that continuously measures minimum-maximum sensitivity over 12-hour periods.

Main Methods:

• 34 patients (20 male, 14 female, mean age 72±5) with Cosmos 3 DDD pacemakers were studied.
• Indications for pacing included sick sinus syndrome (21 patients) and high-degree AV block (13 patients).
• Atrial bipolar leads were used, and AS minimum-maximum values were analyzed at 1, 2, 3, and 6 months post-implant.

Main Results:

• Mean atrial sensitivity varied more than threefold daily, with minimums around 0.68 mV and maximums around 2.19 mV across follow-ups.
• No significant differences in variability were observed between the four follow-up time points.
• Seven patients exhibited fourfold variations, and five patients showed fivefold variations in AS.

Conclusions:

• Atrial sensitivity demonstrates significant daily variability, necessitating adjustments to current programming recommendations.
• A 3:1 safety margin is recommended over the traditional 2:1 ratio to ensure reliable sensing.
• Optimizing atrial signal amplitude at implant and using bipolar leads are crucial to prevent oversensing.