Sympathetic and parasympathetic baroreflex dysfunction in familial dysautonomia

Area of Science:

• Cardiovascular Physiology
• Autonomic Nervous System Function
• Human Physiology

Background:

• Familial dysautonomia (FD) is a genetic disorder affecting the autonomic nervous system.
• Cardiovascular symptoms are common in FD, but their underlying mechanisms require further elucidation.
• Baroreflex dysfunction is suspected to play a role in FD's cardiovascular manifestations.

Purpose of the Study:

• To investigate baroreflex modulation of heart rate and arterial vasculature in FD patients.
• To determine the contribution of baroreflex abnormalities to cardiovascular symptoms in familial dysautonomia.
• To assess efferent sympathetic and parasympathetic pathways in FD.

Main Methods:

• Twenty-one FD patients and 22 controls underwent head-up tilt (HUT) and sinusoidal neck suction (NS) for baroreceptor stimulation.
• Respiration was controlled at 15 breaths/minute during NS.
• Blood pressure (BP), RR-intervals (RRI), and respiration were monitored; spectral analysis assessed NS-induced changes.

Main Results:

• FD patients displayed orthostatic hypotension without compensatory tachycardia during HUT.
• Low-frequency neck suction (LF-NS) increased LF power of RRI and BP in controls, but not in FD patients.
• High-frequency neck suction (HF-NS) increased HF power of RRI in controls, but not in FD patients.

Conclusions:

• Familial dysautonomia patients present with generalized baroreflex abnormalities.
• These abnormalities involve efferent sympathetic control of resistance vessels and both sympathetic and parasympathetic control of the heart.
• Baroreflex dysfunction is strongly implicated in the blood pressure and heart rate dysregulation observed in FD.