Diabetic cardiac autonomic dysfunction: parasympathetic versus sympathetic

Diabetic cardiac autonomic dysfunction often causes lethal arrhythmia and s udden cardiac death. I-123-Metaiodobenzylguanidine (MIBG) can evaluate card iac sympathetic dysfunction, and analysis of heart rate variability (HRV) c an reflect cardiac parasympathetic activity. We examined whether cardiac pa rasympathetic dysfunction assessed by HRV may correlate with sympathetic dy sfunction assessed by MIBG in diabetic patients. Methods and Results: In 24-hour electrocardiography, we analyzed 4 HRV para meters: high-frequency power (HF), HF in the early morning (EMHF), rMSSD an d pNN50. MIBG planar images and SPECT were obtained 15 minutes (early) and 150 minutes (late) after injection and the heart washout rate was calculate d. The defect score in 9 left ventricular regions was scored on a 4 point s cale (0 = normal similar to 3 = severe defect). In 20 selected diabetic pat ients without congestive heart failure, coronary artery disease and renal f ailure, parasympathetic HRV parameters had a negative correlation with the sum of defect scores (DS) in the late images (R = -0.47 similar to -0.59, p < 0.05) and some parameters had a negative correlation with the washout ra te (R = -0.50 similar to -0.55, p < 0.05). In a total of 64 diabetic patien ts also, these parameters had a negative correlation with late DS (R = -0.2 8 similar to -0.35, p < 0.05) and early DS (R = -0.27 similar to -0.32, p < 0.05). Conclusions: The progress of diabetic cardiac parasympathetic dysfunction m ay parallel the sympathetic one.