The reversibility of cardiac neuronal function after removal of a pheochromocytoma: an I-123 MIBG Scintigraphic Study.

Purpose: Twelve patients with proved pheochromocytoma evaluated in our institution between 1991 and 1997 are described. Methods: The patients' urinary excretion rates and their metabolites (vanylmandelic acid and metanephrines) were significantly greater than normal before surgery. Echocardiography showed normal left ventricular ejection fractions (72% ± 8%). All of the patients underwent planar 1-123 metaiodobenzylguanidine (MIBG) scintigraphy to assess cardiac neuronal uptake 4 hours after and locate a pheochromocytoma 24 hours after intravenous injection of 185 MBq (3 mCi) 1-231 MIBG. Ten patients with pheochromocytoma had positive tumoral findings with 1-123 MIBG scintigraphyh. Twelve patients had significant impairment of cardiac neuronal uptake of MIBG, with a heart:mediastinum ratio averaging 142% ± 18% (normal value, 230% ± 30%, P < 0.05). Postoperative cardiac MIBG imaging was performed in all patients (at 6 ± 3 months). Results: After surgical removal of the pheochromocytoma, cardiac MIBG uptake and the heart:mediastinum uptake ratios improved significantly (197% ± 20%, P < 0.05) in all the patients. Urinary excretion rates and metabolites returned to the normal range. However, no significant correlation was found between cardiac MIBG uptake and urinary excretion rates and metabolites after the tumors were removed. Conclusion: Removing a pheochromocytoma reversed cardiac neuronal function as assessed by MIBG scintigraphy.