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Effect of stimulus intensity on atrial refractoriness and sinus node recovery
F A Ehlert1, R S Damle, J J Goldberger
1Department of Medicine, Northwestern University School of Medicine, Chicago, Illinois.
Journal of Cardiovascular Electrophysiology
|June 1, 1994
Summary
Pacing stimulus intensity affects atrial effective refractory period and sinus node recovery time. This suggests autonomic system interactions are crucial for interpreting electrophysiologic effects during cardiac pacing.
Area of Science:
- Cardiology
- Electrophysiology
- Cardiac Pacing
Background:
- Previous studies lacked data on overdrive pacing stimulus intensity's effect on sinus node response.
- Ventricular refractoriness is known to be affected by pacing, but atrial effects were unstudied.
Purpose of the Study:
- To evaluate the impact of drive train stimulus intensity on human atrial effective refractory period and sinus node recovery time.
Main Methods:
- Studied 42 patients undergoing clinical electrophysiologic tests.
- Assessed atrial effective refractory period and sinus node recovery time at varying stimulus intensities (1.5x LDT, 5 mA, 10 mA).
- Evaluated effects under baseline, beta-adrenergic blockade, parasympathetic blockade (atropine), and combined blockade.
Main Results:
- Atrial effective refractory period was significantly shorter at higher stimulus intensities (5 mA, 10 mA) compared to 1.5x LDT.
- Sinus node recovery time showed no consistent effect across conditions, except a shortening after isolated parasympathetic blockade with atropine at 10 mA.
- Variability in sinus node recovery time decreased after parasympathetic blockade.
Conclusions:
- Drive train stimulus intensity influences atrial and sinus node electrophysiologic properties.
- Effects appear mediated by local catecholamine and acetylcholine release.
- Cardiac autonomic system interactions with pacing stimuli require consideration in electrophysiologic evaluations.