Vagal cardiovascular reflexes in young persons with syncope

Area of Science:

• Neurocardiology
• Autonomic Nervous System Physiology
• Clinical Neurophysiology

Background:

• Syncope, or fainting, in young individuals can be triggered by emotional stress.
• Understanding the underlying neurocardiologic mechanisms is crucial for effective management.

Purpose of the Study:

• To investigate neurocardiologic reflexes in adolescents experiencing syncope due to emotional stress.
• To compare autonomic function between young individuals with syncope and healthy controls.

Main Methods:

• A case-control study involving 60 adolescents (15-17 years) with emotional syncope and 40 age-matched healthy controls.
• Measurements included resting ECG, heart rate variability during deep breathing, Valsalva maneuver response, and orthostatic blood pressure.
• Neurocardiologic reflexes were assessed in a clinical neurophysiology laboratory setting.

Main Results:

• Adolescents with syncope exhibited higher vagal autonomic tone compared to controls.
• Key indicators of elevated vagal tone included slower resting heart rate, greater heart rate variability with breathing, and a higher Valsalva ratio.
• No significant differences were observed in ECG intervals (PR, QTc) or orthostatic blood pressure response.

Conclusions:

• Elevated vagal tone predisposes young individuals to the cardioinhibitory component of emotional syncope.
• Physiological age-related decreases in vagal cardiac responses may contribute to the lower incidence of this syncope type in older populations.