OBJECTIVE Global myocardial uptake of ¹²³I-metaiodobenzylguanidine (MIBG) has been shown to be decreased in diabetic patients with autonomic neuropathy, indicating cardiac sympathetic dysfunction. However, possible differences in myocardial MIBG distribution between NIDDM and IDDM diabetic patients are not known.

RESEARCH DESIGN AND METHODS Regional myocardial distribution of ¹²³I-MIBG was studied in seven male IDDM patients (age 45 ± 2 years, duration of diabetes 30 ± 3 years, means ± SE) and 13 NIDDM patients (8 men, 5 women, age 59 ± 2 years, duration of diabetes 10 ± 1 years). A dual-tracer single-photon emission tomography was carried out with ¹²³I-MIBG and ^99mTc-methoxyisobutylisonitrrile to asses simultaneously myocardial sympathetic innervation and perfusion at rest. Conventional autonomic nervous function tests, power spectral analysis of heart rate variability, and echocardiography were performed for assessments of autonomic function and cardiac dimensions and function.

RESULTS Autonomic nervous function tests and echocardiography showed similar results in IDDM and NIDDM patients. Despite this, global myocardial MIBG uptake (0.43 ± 0.04 vs. 0.59 ± 0.06, P = 0.03) and MIBG heart-to-liver ratio (0.59 ± 0.03 vs. 0.68 = 0.03, P = 0.05) were lower in NIDDM compared with IDDM patients. Regional distribution of MIBG uptake and regional MIBG/perfusion ratio revealed significantly reduced uptake in NIDDM patients especially in the inferoposterior segments of the left ventricle compared with IDDM patients. Difference in age between NIDDM and IDDM patients did not explain the results.

CONCLUSIONS Reduced myocardial MIBG uptake was found in NIDDM patients compared withthe uptake in IDDM patients, particularly involving inferoposterior segments.Regional sympathetic damage not detectable with conventional autonomic function tests is relatively common in NIDDM.