SENSITIVITY OF HEART SCINTIGRAPHIC IMAGING USING (123-I) MIBG COMPARED TO EWING TESTS IN CARDIAC AUTONOMIC NEUROPATHY IN DIABETES

Cardiac autonomic neuropathy is a frequent complication of diabetes le ading to resting tachycardia, postural hypotension, painless myocardia l ischaemia, rhythm disturbances and sudden cardiac death. The aim of the study was to evaluate in a diabetic population the sensitivity of two exploration modes of autonomic neuropathy in diabetics : the Ewing tests which are, at present time, the reference method and the (123-I ) meta-iodo-benzyl-guanidine (MIBG) single photon emission computed to mography (SPECT) which evaluates the cardiac sympathetic innervation. Patients and methods: 9 male insulin-dependent diabetes mellitus patie nts were studied. Mean age was 40.7 +/- 15 years and diabetes duration was 10.8 +/- 6 years. None had hypertension or macroangiography as de monstrated by patient's history, clinical examination, rest and exerci se electrocardiography and ambulatory blood pressure monitoring. The c omplications observed were background retinopathy in 2 patients, incip ient nephropathy in 3 and a peripheral neuropathy in 1 patient. Ewing tests, i.e. Valsalva maneuver, beat to beat heart rate variation durin g deep breathing and standing, blood pressure response to standing and to sustained handgrip, were performed. The results were considered as pathologic when the score was over 2. After injection of 10 mCi (123- I) MIBG, planar imagies were realized at times 1, 2 and 4 hours and SP ECT imagies after 2 hours. The heart/mediastinum uptake ratio was calc ulated. Results : We noted abnormalities of planar imagies in 3 patien ts, SPECT imagies in 1, and both in 1 patient. None was positive for E wing tests. Conclusion : Although MIBG SPECT will explore only the sym pathetic innervation, these preliminary findings suggest that this tec hnique could be more sensitive for the evaluation of cardiac autonomic neuropathy. Nevertheless cost and lack of disponibility of this techn ique should limit its use.