ABF is rare, and accurate identification relies on precise history taking and specific autonomic findings. Detailed analysis of objective autonomic data in patients with ABF allows for better understanding of its pathophysiology.

To describe the autonomic testing profile in afferent baroreflex failure (ABF)

We performed a retrospective chart review of all autonomic reflex screens (ARS) performed at Mayo Clinic in Rochester, MN, between 2000 and 2020 in patients with ABF. Composite autonomic severity score (CASS) was calculated on all patients. Additional tests included 24-hour blood pressure (BP) monitoring, fractioned plasma catecholamines, and thermoregulatory sweat tests (TST).

We identified 104 patients with ABF. Etiologies included head and neck radiation (86.5%), neck surgery (5.8%), and other (7.7%). The median total CASS was 7. Median CASS sudomotor, cardiovagal, and adrenergic scores were 0, 2, and 4, respectively. Orthostatic hypotension (OH) [drop in systolic BP>30mmHg during tilt (ΔSBP)] was seen in 88 patients (77.9%). Cardiovagal impairment was demonstrated by abnormal heart rate responses to deep breathing (77%) and Valsalva ratio (82%) while baroreflex cardiovagal sensitivity was uniformly low (median 0.92mmHg.msec-1) and below the 5th percentile in 44% of patients. Adrenergic impairment was demonstrated by increased BP recovery time (median 16sec) and OH (median ΔSBP -58mmHg at 3min, -34mmHg at 5min). 24-hour BP monitoring revealed hypertension (85.6%), postural hypotension (65.2%), hypertensive surges (60.2%), and loss of nocturnal fall in BP (51.7%). Mean supine and standing plasma norepinephrine was elevated (703pg/mL and 1247pg/mL, respectively). The most frequent abnormality on TST was focal head and neck anhidrosis (64.3%).

Autonomic testing is helpful for the diagnosis of ABF. Most prominently involved is adrenergic, followed by cardiovagal function, while sudomotor deficits are largely limited to direct radiation effects. A chaotic BP profile is common, and plasma norepinephrine is high and surges further with standing.