QT interval abnormalities are often present at diagnosis in diabetes and are better predictors of cardiac death than ankle brachial pressure index and autonomic function tests

Objectives: To study serial measures of maximum QT interval corrected for heart rate (QTc) and QT
dispersion (QTD) and their association with cardiac mortality patients with non-insulin dependent diabetes
and to compare QT abnormalities with other mortality predictors (ankle brachial pressure index (ABPI) and
autonomic function tests) in their ability to predict cardiac death.
Setting: Teaching hospital.
Methods and patients: QT interval analysis, heart rate (RR) variation in response to deep breathing and
standing, and ABPI were analysed in 192 patients with non-insulin dependent diabetes. Cardiac death
was the primary end point.
Results: Mean (SD) follow up was 12.7 (3.2) years (range 1.2–17.1 years). There were 48 deaths, of
which 26 were cardiac. QTc and QTD were individually significant predictors of cardiac mortality
throughout the follow up period (p , 0.001). The predictability of QT parameters was superior to the
predictability of ABPI and RR interval analysis. Temporal changes in QT parameters showed that the mean
absolute QT parameter was a significant predictor of cardiac death (p , 0.001), whereas an
intraindividual change in QT parameter over time was not predictive.
Conclusion: QT abnormalities seem to exist at the point of diagnosis of diabetes and do not appear to
change between then and the subsequent cardiac death. Furthermore, the analysis of QT interval is
superior to ABPI and the RR interval in identifying diabetic patients at high risk of cardiac death.