QTc interval and scintigraphically assessed myocardial perfusion in newly diagnosed and long-term type 1 diabetes mellitus

In diabetes mellitus, heart rate corrected QT interval (QTc) has been suggested to be related to ischemic heart disease and increased risk of sudden cardiac death. The aim of the study was to analyze the length of QTc interval with regard to global and regional myocardial perfusion in type 1 diabetic patients. Myocardial perfusion was investigated in 20 newly diagnosed and 40 long-term type 1 diabetic patients without clinical evidence for coronary artery disease by means of Tc-99-methoxyisobutylisonitrile (Tc-99m-MIBI)-scintigraphy (myocardial uptake (MU) score: 1-6). Five consecutive RR and QT intervals of resting electrocardiogram (ECG) tracing were measured and corrected for the previous cycle length. ECG-based cardiac autonomic neuropathy (CAN) was assessed with five cardiac reflex tests. Length of QTc interval was 423+/-29 ms in newly diagnosed and 433+/-26 ms in long-term type 1 diabetic patients. Nine (45%) newly diagnosed and 18 (45%) long-term diabetic patients demonstrated a prolonged QTc interval (>440 ms). Both newly diagnosed and long-term diabetic patients did not display significant global or regional myocardial perfusion defects (mean MU scores<3). In newly diagnosed diabetic patients, the length of QTc interval was related to global, posterior and septal Tc-99m-MIBI uptake (p<0.05, respectively). In long-term diabetic patients, the length of QTc interval was associated with apical Tc-99m-MIBI uptake (p<0.05). Two (10%) newly diagnosed and 19 (48%) long-term type 1 diabetic patients demonstrated ECG-based CAN. In long-term type 1 diabetic patients, global myocardial Tc-99m-MIBI uptake did not differ significantly between patients with and without CAN. QTc interval was not significantly different between diabetic patients with and without ECG-based CAN (433+/-19 ms vs. 428+/-17 ms). Long-term diabetic patients, of whom 10 (25%) patients had microalbuminuria and seven (18%) patients had macroalbuminuria, demonstrated an association between QTc interval and albuminuria (p<0.05). The results somewhat suggest an association between QTc interval and vascular factors in type 1 diabetes mellitus. Future investigations are required to analyze the role of QTc interval in the pathogenesis of abnormalities of myocardial perfusion.