BLOOD-PRESSURE RESPONSE TO THE VALSALVA MANEUVER IN PHEOCHROMOCYTOMA AND PSEUDOPHEOCHROMOCYTOMA

To elucidate whether a difference in blood pressure reactivity exists between patients with pheochromocytoma (n=8) and pseudopheochromocytom a (n=22), we evaluated blood pressure changes during a Valsalva maneuv er and baroreceptor reflex sensitivity. We also examined the effects O f propranolol and prazosin on blood pressure reactivity during a Valsa lva maneuver in patients with pseudopheochromocytoma. Pseudopheochromo cytoma was defined as a paroxysmal rise in blood pressure accompanying pheochromocytoma-like symptoms and normal catecholamine values. The d ifference in systolic blood pressure between phase IV of the Valsalva maneuver and baseline (Delta SBP) was markedly smaller in the pheochro mocytoma patients (8.4+/-18.4 mm Hg) than in the essential hypertensio n patients (n=30, 30.9+/-19.4 mm Hg) and normotensive control subjects (n=10, 31.3+/-11.4 mm Hg), whereas Delta SBP in the pseudopheochromoc ytoma patients (77.8+/-11.2 mm Hg) was markedly greater than in the ot her three groups. Delta SBP was markedly suppressed by the administrat ion of both propranolol and prazosin. Baroreceptor reflex sensitivity index was lower in the pheochromocytoma group than in the other three groups. In conclusion, blood pressure reactivity responses to a Valsal va maneuver are disparate between pheochromocytoma and pseudopheochrom ocytoma. The high blood pressure reactivity to a Valsalva maneuver in pseudopheochromocytoma is due to hyperactivity in both beta- and alpha (1)-adrenergic receptor functions, and the low blood pressure reactivi ty to a Valsalva maneuver in pheochromocytoma seems to be mainly due t o the desensitization of both adrenergic systems associated with chron ic catecholamine excess. In addition, the impaired baroreceptor functi on in pheochromocytoma is partially responsible for it.