CARDIOVASCULAR MEDICINE

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

B S Rana¹, P O Lim¹, A A O Naas¹, S A Ogston², R W Newton³, R T Jung³, A D Morris³, A D Struthers¹

¹ Department of Clinical Pharmacology and Therapeutics, University of Dundee, Ninewells Hospital, Dundee, UK
² Statistics Department, University of Dundee
³ Department of Clinical Medicine, University of Dundee

Correspondence to:
Correspondence to:
Dr Bushra Rana
Department of Clinical Pharmacology and Therapeutics, University of Dundee, Ninewells Hospital, Dundee DD1 9SY, UK; bushrasrana{at}yahoo.co.uk

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.

Abbreviations: ABPI, ankle brachial pressure index; QTc, QT interval corrected for heart rate; QTD, maximum heart rate corrected QT interval; QTD, QT dispersion; ROC, receiver operating characteristic; UKPDS, United Kingdom prospective diabetes study

Keywords: diabetes; QT interval; ankle brachial pressure index; autonomic function

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