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Rate-dependent threshold changes during atrial pacing: clinical and experimental studies.
K Katsumoto1, T Niibori, Y Watanabe
1Department of Cardiovascular Surgery, National Saitama Hospital, Wako, Japan.
Pacing and Clinical Electrophysiology : PACE
|August 1, 1990
Summary
Right atrial pacing shows rate-dependent stimulation thresholds in patients with sick sinus syndrome. Lower thresholds at higher pacing rates improve capture, suggesting electrode contact fluctuations are key.
Area of Science:
- Cardiology
- Electrophysiology
- Medical Devices
Background:
- Permanent right atrial pacing is used for sick sinus syndrome and atrioventricular block.
- Understanding stimulation thresholds is crucial for effective pacing.
Purpose of the Study:
- To investigate rate-dependent changes in stimulation thresholds after atrial lead implantation.
- To explore the relationship between pacing rate, atrial dimensions, and capture efficacy.
Main Methods:
- Studied 36 patients with permanent right atrial pacing, measuring thresholds at various rates (60-120 bpm).
- Conducted echocardiography in 8 patients to assess left atrial diameter changes with pacing rate.
- Performed experiments in dogs involving blood withdrawal to simulate changes in atrial dimension.
Main Results:
- 80% of patients exhibited rate-dependent thresholds, with significantly lower thresholds at higher pacing rates.
- Increased pacing rates (100-120 bpm) led to a decrease in left atrial end-diastolic diameter.
- Atrial dimension changes correlated with increased electrogram amplitude and improved capture efficacy.
Conclusions:
- Rate-dependent stimulation thresholds are common in the early phase of atrial pacing.
- Fluctuations in electrode-endocardial contact are likely responsible for these observed threshold variations.