[Evaluation of cardiac sympathetic innervation with 123I-metaiodobenzylguanidine in patients with diabetes mellitus].

OBJECTIVES: To evaluate the usefulness of iodine-123 metaiodobencylguanidine (123I-MIBG) in the study of the cardiac autonomic neuropathy in insulin-dependent diabetic patients, by means of: a) analysis of heart to mediastinic ratio and tomographic images with 123I-MIBG; b) comparison with conventional non-invasive cardiac reflex test, and c) analysis of left ventricle ejection fraction. POPULATION AND METHODS: Ten patients submitted for cardiac evaluation with 123I-MIBG were compared with a control group of 11 patients. In both groups we excluded the presence of coronary pathology by means of an exercise test. We carried out planar and SPECT studies, using 123I-MIBG, and the calculation of the ejection fraction by equilibrium ventriculography. RESULTS: The uptake of 123I-MIBG in diabetic patients was significantly smaller than the control group in the calculated index (heart to mediastinic ratio: 1.64 +/- 0.20 vs 2.00 +/- 0.26; p < 0.001; SPECT index: 44.87 +/- 8.37 vs 55.54 +/- 3.96; p < 0.001). In polar images we noted a more reduced uptake in the diabetic group in the inferior wall (p = 0.020). Patients with cardiac sympa-thetic dysinnervation demonstrated less uptake in both indexes (p < 0.05 and 0.005, respectively), essentially in the inferior wall and in basal and medium territories (p < 0.05). No differences in respect to the ejection fraction parameter were found. CONCLUSIONS: Despite the small sample population, insuli-dependent diabetic patients in show a significant reduction of the uptake of 23I-MIBG, more accentuated in the base. Scintigraphy using 123I-MIBG can be an approach to investigate the pattern and the natural history of the sympathetic innervation in these patients.