Quantitative indices of baroreflex-sympathoneural function: application to patients with chronic autonomic failure.
OBJECTIVE
Chronic autonomic failure syndromes such as Parkinson disease with orthostatic hypotension (PD + OH), multiple system atrophy (MSA), and pure autonomic failure (PAF) typically feature arterial baroreflex failure. Identifying baroreflex-sympathoneural failure from hemodynamic responses to the maneuver usually has been qualitative. We report quantitative methods for evaluating baroreflex-sympathoneural function, based on beat-to-beat systolic blood pressure (BPs) responses to the Valsalva maneuver.


METHODS
Using the trapezoid rule, we calculated the area under the curve (baroreflex area, BRA) between baseline systolic blood pressure (BPs) and the BPs for each beat in Phase II (BRA-II) and Phase IV (BRA-IV) in 136 autonomic failure patients and 171 controls. The sum of the areas was defined as total BRA (BRA-T). We compared individual values by the BRA approach with those by other measures.


RESULTS
Mean values for log BRA-II, BRA-IV, and BRA-T were higher in PD + OH, PAF, and MSA than in controls (p < 0.001 each). The log of BRA-T correlated negatively with the fractional orthostatic change in total peripheral resistance (r = -0.41, p < 0.001), fractional orthostatic change in plasma norepinephrine (r = -0.27, p < 0.001), orthostatic change in BPs (r = -0.62, p < 0.001), fall in BPs in Phase II of the Valsalva (r = 0.58, p < 0.001), and log of baroreflex-cardiovagal slope (r = -0.40, p < 0.001). Areas under receiver operating characteristic curves were 0.85 for BRA-T and 0.89 for BRA-IV (p < 0.001).


CONCLUSIONS
The BRA approach provides quantitative measures of baroreflex-sympathoneural function. Chronic autonomic failure syndromes entail deficiencies of both the cardiovagal and sympathoneural limbs of the arterial baroreflex.
Clinical Neurocardiology Section, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), 10 Center Drive MSC-1620, Building 10 Room 5N220, Bethesda, MD, 20892-1620, USA.
Faisal
F
Rahman
David S
DS
Goldstein
D000368:Aged; D001342:Autonomic Nervous System Diseases / Q000175:diagnosis* / Q000503:physiopathology; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009474:Neurons / Q000502:physiology*; D009638:Norepinephrine / Q000097:blood; D015203:Reproducibility of Results; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D014636:Valsalva Maneuver; D014655:Vascular Resistance / Q000502:physiology
D009638:Norepinephrine