QT dispersion: comparison between diabetic and non-diabetic individuals and correlation with cardiac autonomic neuropathy.

Introduction: The QT interval on the resting electrocardiogram (ECG) expresses the myocardial depolarisation and repolarisation time. Elevated values of QT dispersion (QTd) are associated with cardiovascular mortality in diabetics. Cardiac autonomic neuropathy (CAN) is a common complication of diabetes that is also associated with increased morbidity and mortality. However, there are no data in the literature concerning the relation between CAN and QTd in diabetics. The aim of this study was to investigate: 1) the differences in QTd between diabetics and non-diabetics; 2) the differences in QTd between those with type 1 and type 2 diabetes; 3) the relation between QTd and CAN.
Methods: The study population included 184 diabetics (63 type 1, group D1; 121 type 2, group D2) and 100 healthy controls who had similar age and sex distribution to D1 (n=44) and D2 (n=56) subjects. CAN assessment was made using the standard Ewing and Clarke tests. The QT interval was measured on the 12-lead resting ECG. QTd was calculated automatically using special software.
Results: QTd values did not differ significantly between controls and D1 (p=0.15) or D2 (p=0.27). QTd was significantly greater in D2 than in D1 (p=0.02). There was no significant difference in QTd between those with and without CAN in either group of diabetics.
Conclusions: QTd values do not differ between individuals with and without diabetes. Type 2 diabetes is associated with higher QTd values than is type 1 diabetes. CAN does not affect QTd in diabetics.