Primary dysfunction of the afferent limb of the arterial baroreceptor reflex system in a patient with severe supine hypertension and orthostatic hypotension.

A 33 year old man with a history of recurrent episodes of orthostatic dizziness since adolescence was noted to have a supine blood pressure of 200/120 mm Hg and a standing blood pressure of 90/60 mm Hg. Results of extensive laboratory studies for secondary hypertension were negative. Studies of the autonomic nervous system function revealed normal plasma catecholamines, cold pressor test and response to 4 minute 30% of maximal static handgrip contraction and an appropriate increase in heart rate on intravenous injection of atropine. In contrast, the heart rate response to phenylephrine and sodium nitroprusside infusion, carotid massage and graded neck suction with an airtight chamber was very abnormal, indicating marked dysfunction of the afferent limb of the arterial baroreceptor reflex system. Methyldopa decreased the supine hypertension and increased the standing blood pressure.