Cardiac autonomic neuropathy in the diabetic patient: does 123I-MIBG imaging have a role to play in early diagnosis?

OBJECTIVES In diabetes, extended adrenergic receptor stimulation with hyperglycemia and insulin deficiency is associated with cardiac autonomic dysfunction. Clinically evident diabetic cardiac autonomic neuropathy (CAN) is associated with a poor prognosis. Research studies indicate that autonomic function tests, which are traditionally used to diagnose diabetic CAN, are less sensitive than (123)I-metaiodobenzylguanidine (MIBG) imaging, particularly in the early stages of the disease. This established imaging technique makes use of the noradrenaline analog MIBG, which is radiolabeled with (123)I to assess the noradrenaline uptake-1 mechanism of the sympathetic nervous system. Although scintigraphic studies indicate that long-standing cardiac autonomic dysfunction is permanent, some authors have shown partial reversibility with early metabolic intervention. (123)I-MIBG imaging could therefore have an important clinical role to play in the early diagnosis and treatment monitoring of diabetic CAN. METHODS A PubMed/MEDLINE Internet search was performed using MIBG, diabetes, and cardiac autonomic neuropathy as key words. CONCLUSION The general expense of (123)I-MIBG imaging, together with the lack of commercial availability of this radiopharmaceutical in the United States, has limited the clinical use of this technique. As such, the clinical role of (123)I-MIBG imaging in the early diagnosis of diabetic CAN has yet to be validated and defined in most regions of the world, and further study is required.