Diurnal blood pressure variation in progressive autonomic failure

To investigate the role of the autonomic nervous system (ANS) in the generation of the circadian blood pressure (BP) variation, the degree of impairment of the ANS was related to the results of ambulatory BP recordings in 212 patients with progressive autonomic failure due to familial amyloid polyneuropathy. On the basis of BP and/or heart rate (HR) responses to the Valsalva maneuver, 60 degrees head-up tilting, deep-breathing tests, and plasma norepinephrine levels, 4 groups of patients were distinguished. In all patients and in 38 age-matched control subjects, ambulatory BP was monitored. Patients of group I (n=40, aged 32+/-3 y), with no evidence yet of impairment 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 degree of impairment of their parasympathetic ANS, but their sympathetic ANS was still intact. Twenty-four-hour HR was higher in these patients than in controls (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 dysfunction, 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 variation. 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 sympathetic but also an intact afferent parasympathetic ANS is a prerequisite.