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 sugge sted to be related to ischemic heart disease and increased risk of sudden c ardiac death. The aim of the study was to analyze the length of QTc interva l with regard to global and regional myocardial perfusion in type 1 diabeti c patients. Myocardial perfusion was investigated in 20 newly diagnosed and 40 long-term type 1 diabetic patients without clinical evidence for corona ry 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 c orrected for the previous cycle length. EGG-based cardiac autonomic neuropa thy (CAN) was assessed with five cardiac reflex tests. Length of QTc interv al 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 dia betic patients demonstrated a prolonged QTc interval (>440 ms). Both newly diagnosed and longterm diabetic patients did not display significant global or regional myocardial perfusion defects (mean MU scores <3). In newly dia gnosed 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 epic al Tc-99m-MTBI uptake (p < 0.05). Two (10%) newly diagnosed and 19 (48%) lo ng-term type 1 diabetic patients demonstrated EGG-based CAN. In long-term t ype 1 diabetic patients, global myocardial Tc-99m-MIBI uptake did not diffe r significantly between patients with and without CAN. QTc interval was not significantly different between diabetic patients with and without EGG-bas ed CAN (433 +/- 19 ms vs. 428 +/- 17 ms). Long-term diabetic patients, of w hom 10 (25%) patients had microalbuminuria and seven (18%) patients had mac roalbuminuria. demonstrated an association between QTc interval and albumin uria (p < 0.05). The results somewhat suggest an association between QTc in terval and vascular factors in type 1 diabetes mellitus. Future investigati ons are required to analyze the role of QTc interval in the pathogenesis of abnormalities of myocardial perfusion. (C) 2000 Elsevier Science Inc. All rights reserved.