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

Abstract 

Background and aims

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.

Methods and results

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.

Conclusions

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.

Keywords: QT-interval dispersion, Myocardial infarction, Type 2 diabetes, Insulin therapy, Repolarization inhomogeneity