Diurnal blood pressure variation in progressive autonomic failure

To investigate the role of the autonomic nervous system (ANS) in the genera tion of the circadian blood pressure (BP) variation, the degree of impairme nt of the ANS was related to the results of ambulatory BP recordings in 212 patients with progressive autonomic failure due to familial amyloid polyne uropathy. On the basis of BP and/or heart rate (HR) responses to the Valsal va maneuver, 60 degrees head-up tilting, deep-breathing tests, and plasma n orepinephrine levels, 4 groups of patients were distinguished. In all patie nts and in 38 age-matched control subjects, ambulatory BP was monitored. Pa tients of group I (n=40, aged 32 +/- 3 y), with no evidence yet of impairme nt of their ANS, had circadian BP and HR variations indistinguishable from controls, Patients of group II (n=41, aged 34 +/- 5 y) had a variable degre e of impairment of their parasympathetic ANS, but their sympathetic ANS was still intact. Twenty-four-hour HR was higher in these patients than in con trols (88 +/- 11 versus 78 +/- 7 bpm, P<0.01). Their circadian HR variation was maintained, but their circadian BP variation was diminished (10 +/- 6/ 11 +/- 4 versus 17 +/- 6/16 +/- 4 mm Hg in controls, P<0.01) because of an attenuation of the nocturnal BP decline. Patients of group III (n=69, aged 36 +/- 6 y), with parasympathetic failure and intermediate sympathetic dysf unction, had a blunted diurnal BP variation, whereas patients of group IV ( n=62, aged 38 +/- 6 y), with parasympathetic failure and severe sympathetic dysfunction, had an absent diurnal BP variation. In patients of groups III and IV, a decrease in daytime BP accounted for the blunted circadian BP va riation. This extensive study in progressive autonomic failure confirms the important role of the ANS in the generation of circadian BP variation. For the maintenance of a normal circadian BP pattern, not only an intact sympa thetic but also an intact afferent parasympathetic ANS is a prerequisite.