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Physical determinants of the endocardial P wave
A H Shandling1, J Florio, M J Castellanet
1Memorial Heart Institute, Long Beach, California 90801-1428.
Pacing and Clinical Electrophysiology : PACE
|December 1, 1990
Summary
Pacemaker P wave sensing is affected by body position and respiration. P wave amplitude increases with respiration extremes and standing, but exercise does not significantly alter it, suggesting standard supine testing is adequate.
Area of Science:
- Cardiology
- Biomedical Engineering
- Electrophysiology
Background:
- Reliable atrial sensing of intrinsic P wave activity is crucial for optimal pacemaker function.
- Physical factors like posture, respiration, and exercise can influence P wave characteristics, potentially impairing pacemaker sensing.
- Understanding these influences is key to ensuring accurate pacemaker performance.
Purpose of the Study:
- To investigate the impact of body position, respiration, and exercise on P wave amplitude (PWA) and slew rates in patients with pacemakers.
- To determine if standard supine testing is sufficient for setting atrial sensitivity across various physiological conditions.
Main Methods:
- Measurements of P wave amplitude (PWA) and slew rates were performed on 32 patients using Pacesetter pacemakers.
- Data was acquired from telemetered printouts under various conditions: different body positions (supine, erect), stages of respiration (inspiration, expiration, quiet), and during upright exercise.
Main Results:
- Mean PWA significantly increased in the supine position during full inspiration and expiration compared to quiet respiration.
- Mean PWA also significantly increased upon assuming the erect position.
- Upright exercise did not result in a significant change in erect PWA compared to pre-exercise values.
- Slew rates showed no significant difference between lying and standing positions.
Conclusions:
- Mean PWA is significantly affected by the extremes of respiration and by assuming an erect body position.
- Upright exercise does not appreciably alter the erect PWA.
- Current atrial sensitivity settings based on standard supine testing are likely adequate for all body positions, ensuring reliable pacemaker function.