Standardized Autonomic Testing in Patients With Probable Radiation-Induced Afferent Baroreflex Failure

Area of Science:

• Neurology
• Cardiology
• Autonomic Neuroscience

Background:

• Radiation-induced afferent baroreflex failure (R-ABF) presents diagnostic challenges.
• Understanding the autonomic dysfunction patterns in R-ABF is crucial for patient management.

Purpose of the Study:

• To investigate the autonomic dysfunction patterns in patients with probable R-ABF using standardized autonomic testing.
• To characterize cardiovascular, cardiovagal, and sudomotor function in R-ABF.

Main Methods:

• Retrospective analysis of autonomic reflex screens, ambulatory blood pressure monitoring, plasma norepinephrine levels, and thermoregulatory sweat tests.
• Reviewed data from 90 patients with probable R-ABF at Mayo Clinic (2000-2020).

Main Results:

• Significant cardiovascular adrenergic impairment (94.4%) with orthostatic hypotension (75.6%) and delayed BP recovery post-Valsalva (78.9%).
• Common cardiovagal impairment (e.g., abnormal Valsalva ratio in 87.2%).
• Elevated plasma norepinephrine, hypertension, BP lability, and focal neck anhidrosis (78.9%) were observed.

Conclusions:

• Standardized autonomic testing in R-ABF reveals prominent cardiovascular adrenergic and cardiovagal impairment.
• Autonomic dysfunction includes orthostatic hypotension, BP lability, and elevated norepinephrine.
• Sudomotor deficits are typically localized to direct radiation effects.