Assessment of sympathetic innervation of the heart in diabetes mellitus using 123I-MIBG

Radio-labeled metaiodobenzylguanidine (MIBG) is considered an established s ympathetic neuron imaging agent capable of scintigraphically visualizing th e organs richly innervated by the sympathetic nervous system. Its clinical applications now include cardiac and pulmonary adrenergic imaging. The quan titative determination of global and/or regional abnormalities of MIBG hear t uptake has been demonstrated to be very useful in several clinical settin gs representing one of the major determinants of adverse prognosis. The pre sence and the severity of autonomic neuropathy are known as important progn ostic factors in patients with diabetes. MIBG scintigraphy is able to non-i nvasively assess and characterize the adrenergic abnormalities of the cardi ac innervation also in these patients. In order to evaluate whether 123I-MI BG is able to reveal abnormalities of myocardial adrenergic function in dif ferent groups of diabetic patients, we performed 123I-MIBG scintigraphy in control subjects and in normotensive Type 1 diabetic patients with and with out autonomic neuropathy (N+ and N- patients), selected according to result s of cardiovascular reflex tests, Regional abnormalities of adrenergic inne rvation were revealed in 10% of control subjects, in 70% of N- patients and in 100% of N+ patients. The finding of a higher than expected prevalence o f MIBG regional abnormalities in patients without signs or symptoms of auto nomic neuropathy allows to hypothesize that cardiac autonomic nervous damag e occurs earlier than previously known in diabetic patients whose cardiovas cular tests are still completely normal. (C) 2000, Editrice Kurtis.