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 pseudopheochromocytoma (n=22), we evaluated blood pressure changes during a Valsalva maneuver and baroreceptor reflex sensitivity. We also examined the effects Of propranolol and prazosin on blood pressure reactivity during a Valsalva maneuver in patients with pseudopheochromocytoma. Pseudopheochromocytoma was defined as a paroxysmal rise in blood pressure accompanying pheochromocytoma-like symptoms and normal catecholamine values. The difference in systolic blood pressure between phase IV of the Valsalva maneuver and baseline (Delta SBP) was markedly smaller in the pheochromocytoma patients (8.4+/-18.4 mm Hg) than in the essential hypertension 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 pseudopheochromocytoma patients (77.8+/-11.2 mm Hg) was markedly greater than in the other three groups. Delta SBP was markedly suppressed by the administration 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 Valsalva maneuver are disparate between pheochromocytoma and pseudopheochromocytoma. 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 reactivity to a Valsalva maneuver in pheochromocytoma seems to be mainly due to the desensitization of both adrenergic systems associated with chronic catecholamine excess. In addition, the impaired baroreceptor function in pheochromocytoma is partially responsible for it.