REDUCED MYOCARDIAL I-123 METAIODOBENZYLGUANIDINE UPTAKE IN NEWLY-DIAGNOSED IDDM PATIENTS

I-123-labeled metaiodobenzylguanidine (I-123-MIBG) scintigraphy is a n ovel technique for the assessment of cardiac sympathetic dysinnervatio n. To evaluate defects of the cardiac autonomic nervous system at the onset of IDDM, this technique together with conventional electrocardio gram (ECG)-based cardiac reflex tests and measurement of the QT interv al was applied to 22 newly diagnosed metabolically stabilized IDDM pat ients without myocardial perfusion abnormalities (Tc-99m-labeled metho xyisobutylisonitrile scintigraphy) and 9 matched control subjects, Sev enteen diabetic patients (77%), but none of the control subjects, were observed to have a reduced global myocardial uptake of I-123-MIBG. In contrast, only two diabetic patients (9%) demonstrated an EGG-based c ardiac autonomic neuropathy (two or more of five age-related cardiac r eflex tests abnormal) (P < 0.001), In newly diagnosed IDDM patients, t he uptake of I-123-MIBG was reduced more in the posterior myocardial r egion compared with the lateral and apical region (P < 0.01, P = 0.03) , The septal myocardial region exhibited a smaller uptake than the lat eral myocardial region (P = 0.02), The maximum/minimum 30:15 ratio cor related with the global, anterior, lateral, and septal myocardial upta ke of I-123-MIBG (P < 0.05, P < 0.05, P < 0.01, P < 0.05). A correlati on between global and regional myocardial I-123-MIBG uptake and HbA(1c ) or QT interval was not observed. Newly diagnosed metabolically stabi lized IDDM patients without myocardial perfusion defects show evidence of cardiac sympathetic dysinnervation, as indicated by a reduction of I-123-MIBG uptake, at a significant higher proportion than EGG-based cardiac autonomic neuropathy, Furthermore they present with regional d ifferences of myocardial I-123-MIBG uptake.