Baroreflex sensitivity in patients with Takayasu's aortitis.

Takayasu's aortitis is an arterial inflammatory disease of arteries of unknown etiology. Fainting is a common symptom and has been attributed to ypersensitivity of the baroreflex. We studied baroreflex sensitivity in 11 patients with Takayasu's aortitis and compared it with that of eight control subjects of comparable age. Baroreflex sensitivity was assessed by determining the slope of a regression line relating the rise of systolic arterial pressure to the prolongation of the R-R interval of the electrocardiogram during a transient rise of arterial pressure induced by an intravenous injection of phenylephrine. The average baroreflex slope of patients with Takayasu's arteritis (4.0 +/- 0.8 msec/mm Hg) was significantly less than that of control subjects (10.7 +/- 0.8 msec/mm Hg, P less than 0.001). Reduced baroreflex sensitivity in patients with Takayasu's aortitis may be due to the hardening of the arteries where baroreceptors lie, or to hypertension and/or cardiac disease which was present in most of the patients included in this study. Patients with Takayasu's aortitis who complained of fainting also showed the reduced baroreflex sensitivity. This indicates that fainting in this disease is not likely to be caused by the hyperreactivity of the baroreceptors as is commonly postulated.