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Neurocardiogenic syncope in chronic atrioventricular block
Celso Mendoza-González1, Manlio F Márquez, Antonio G Hermosillo
1Department of Electrocardiology, Instituto Nacional de Cardiología Ignacio Chávez, Mexico City, Mexico.
Journal of Electrocardiology
|October 12, 2005
Summary
This study found that syncope in a patient with atrioventricular (AV) block can be neurally mediated, with AV block appearing only at the moment of syncope during a vasovagal reaction.
Area of Science:
- Cardiology
- Electrophysiology
- Autonomic Nervous System
Background:
- A 37-year-old male presented with syncope and was diagnosed with type I second-degree atrioventricular (AV) block.
- The patient was referred for pacemaker implantation due to recurrent syncope.
Observation:
- Electrophysiological testing confirmed Wenckebach's cycles with block within the AV node.
- Head-up tilt testing with sublingual isosorbide dinitrate was positive, indicating a neurally mediated cause for syncope.
- During the vasovagal reaction, a decrease in atrial rate did not immediately cause depressed AV node conduction.
Findings:
- Syncope was determined to be neurally mediated, specifically a vasovagal response.
- Incomplete AV block manifested only at the precise moment of syncope.
- The sinus node and AV node exhibited differential time-course responses to autonomic stimulation.
Implications:
- This case highlights a neurally mediated origin of syncope in individuals with pre-existing atrioventricular block.
- Understanding the distinct autonomic responses of the sinus and AV nodes is crucial for diagnosing and managing syncope in this patient population.