QT-interval dispersion in type 2 diabetic and non-diabetic patients with post-myocardial infarction

QT-interval dispersion (QTD), which reflects spatial ventricular repolarization inhomogeneity, has been reported to increase and to have a prognostic value in patients with either myocardial infarction or diabetes. Our aim was to compare increases in QTD in type 2 diabetic and non-diabetic patients following post-myocardial infarction (post-MI). We also compared QTD in type 2 diabetic patients with post-MI treated with insulin, sulfonylurea, or diet alone.

We determined the rate corrected QT-interval (QTc) dispersion (QTcD) in 178 consecutive post-MI patients, including 48 type 2 diabetic and 130 non-diabetic patients. The QTcD, measured with software (QTD-1), was defined as the difference in the minimum and maximum QTc in any of the 12 standard electrocardiographic leads. There were no significant differences in age, gender, left ventricular end-diastolic diameter, ejection fraction, or minimum QTc between type 2 diabetic and non-diabetic patients with post-MI. Compared with post-MI patients without diabetes, those with type 2 diabetes had higher maximum QTc (481+/-37 vs. 459+/-43ms, P<0.05) and QTcD (67+/-18 vs. 58+/-16ms, P<0.05). Among type 2 diabetic patients with post-MI treated with insulin, sulfonylurea, or diet alone, the QTcD (81+/-18 vs. 64+/-16 vs. 62+/-17ms, P<0.05, respectively) was significantly greater and the R-R interval was shorter in the insulin therapy group.

Type 2 diabetes is associated with an additional increase in the QTD in post-MI patients. This additional increase in spatial repolarization inhomogeneity might be implicated in the increased mortality risk in post-MI patients with type 2 diabetes. These findings were thought to be more striking in the insulin therapy group.