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An abnormal neural reflex plays a role in causing syncope in sinus bradycardia
P Alboni1, C Menozzi, M Brignole
1Division of Cardiology, Ospedale Civile, Cento (Fe), Italy.
Journal of the American College of Cardiology
|October 1, 1993
Summary
An abnormal neural reflex, not sinus node dysfunction severity, causes syncope in patients with sinus bradycardia. This finding impacts understanding and managing syncope in this patient population.
Area of Science:
- Cardiology
- Neuroscience
- Autonomic Function
Background:
- Syncope is often associated with sinus bradycardia, but its occurrence is unpredictable.
- Prognosis for sinus bradycardia patients with or without syncope is similar, suggesting other factors contribute to syncope.
Purpose of the Study:
- To investigate the role of abnormal neural reflexes in syncope among patients with sinus bradycardia.
- To differentiate the mechanisms of syncope in patients with sinus bradycardia.
Main Methods:
- Compared 25 patients with sinus bradycardia and syncope to 25 without syncope.
- Utilized head-up tilt testing, carotid sinus massage, 24-h Holter ECG, and electrophysiologic studies.
- Assessed autonomic blockade effects on heart rate and syncope induction.
Main Results:
- Head-up tilt testing and carotid sinus massage were significantly more positive in patients with syncope.
- Abnormal intrinsic heart rate was more prevalent in the syncope group (66% vs. 26%).
- Positive test results were independent of intrinsic sinus node dysfunction severity.
Conclusions:
- Abnormal neural reflexes contribute to syncope in sinus bradycardia patients.
- The underlying mechanism is distinct from the severity of sinus node dysfunction.
- This highlights a specific reflex pathway involved in syncope.