EFFECT OF GLYCEMIC CONTROL ON MYOCARDIAL SYMPATHETIC INNERVATION ASSESSED BY [I-123] METAIODOBENZYLGUANIDINE SCINTIGRAPHY - A 4-YEAR PROSPECTIVE-STUDY IN IDDM PATIENTS

Diabetic cardiovascular autonomic neuropathy (CAN) has been directly c haracterized by reduced or absent myocardial [I-123]metaiodobenzylguan idine (MIBG) uptake, but there is no information available on the rela tionship between the myocardial adrenergic innervation defects and lon g-term glycaemic control. In a prospective study over a mean of 3 year s we examined myocardial sympathetic innervation in 12 Type 1 (insulin -dependent) diabetic patients using MIBG scintigraphy (absolute and re lative global MIBG uptake at 2 h p.i.) in conjunction with cardiovascu lar autonomic function tests, QTc interval, and QT dispersion. Six hea lthy non-diabetic subjects served as controls for the MIBG scintigraph y at baseline. HbA(1c) was measured twice a year. One patient, in whom MIBG accumulation was reduced maximally, died during follow up. Among the remaining patients 5 had good or borderline glycaemic control (me an HbA(1c) < 7.6 %; Group 1), whereas 6 patients were poorly controlle d (mean HbA(1c) greater than or equal to 7.6 %; Group 2). Absolute glo bal MIBG uptake increased from baseline to follow-up by 260 (-190-540) [median (range)] cpm/g in Group 1 and decreased by -150 (-450-224) cp m/g in Group 2 (p < 0.05 vs Group 1). Relative global MIBG uptake decr eased by -1.7 (-3.4-9.4)% in Group 1 and by -4.7 (-17.4-1.3) % in Grou p 2 (p < 0.05 vs Group 1). No differences between the groups were note d for the changes in the automatic function tests, QTc interval, and Q T dispersion. In conclusion, long-term poor glycaemic control constitu tes an essential determinant in the progression of left ventricular ad renergic dysinnervation which may be prevented by near-normoglycaemia. Evaluation of susceptibility to metabolic intervention may be superio r when CAN is characterized directly by MIBG scintigraphy rather than by indirect autonomic function testing.