The clinical utility of QT interval assessment in diabetes

A prolonged (QT) interval is considered an indicator of an increased risk of malignant ventricular arrhythmias and/or sudden death. It has been proposed that autonomic neuropathy in diabetes is related to QT interval prolongation and higher mortality rates. More recently, the interlead difference in QT interval duration has been referred to as QT interval dispersion, which has proven to be predictive of ventricular arrhythmias and mortality in different groups of patients. QT interval duration and dispersion are significantly related, but are not concordant in a substantial number of cases in identifying patients at risk. The prevalence of QT prolongation in Type 1 and Type 2 diabetic (T1 and T2DM) patients is higher than 20%. Several studies in T1 and T2DM patients have confirmed the independent relation between prolonged QT interval duration and increased QT interval dispersion and chronic ischemic heart disease. It has been consistently shown that autonomic neuropathy is related to QT interval duration, while more controversies exist on the association with QT interval dispersion. In recent years 5 studies have been published which confirm the value of QT interval as a predictor of total mortality in diabetic as well as in non-diabetic subjects. Surprisingly, no data exist on the relation between the risk of sudden death and QT interval prolongation in diabetic patients. As corrected QT interval is significantly related to mortality, it could be used to stratify the death risk in diabetic patients, particularly those who are candidates for surgery or kidney and/or pancreas transplantation. We still do not know why QT interval is prolonged and how this abnormality leads to death: however, a simple, low-cost measurement, which is easily obtainable without the need of the patient's compliance, could help select patients who need second level diagnostic procedures and strict observation.