Relation of QT interval dispersion to the number of different cardiac abnormalities in diabetes mellitus.
Three studies have clearly shown that a prolonged QT dispersion (QTD) is the best predictor of cardiac death in patients with type 2 diabetes mellitus (DM). This was originally believed to be because QTD identified electrical inhomogeneity, but recent data suggests that this is unlikely. The alternative possibility is that QTD is a convenient identifier of hidden but lethal cardiac abnormalities. We explored whether the latter possibility is true by examining exactly what spectrum of cardiac abnormalities, if any, are over-represented in diabetics with a prolonged QTD. Two hundred nineteen patients with type 2 DM who had been first diagnosed with DM 3 to 6 years previously underwent intensive cardiac examinations. Patients with prolonged QTD had a significantly increased incidence of myocardial ischemia and left ventricular (LV) hypertrophy, and to a lesser extent, autonomic dysfunction. The main independent determinant of a prolonged QTD was ischemia, as seen on both ambulatory ST-segment monitoring (p <0.001) and Duke score on treadmill testing (p <0.001). It was also observed that QTD increased progressively as the number of different cardiac abnormalities increased (p <0.001). These studies suggest that QTD is a useful, general prescreening test to select diabetics for more detailed cardiac examinations (especially for ischemia and LV hypertrophy), and that if cardiac examinations were targeted by way of QTD screening, then a high incidence of hidden but treatable cardiac abnormalities could be found.
Department of Clinical Pharmacology and Therapeutics, Ninewells Hospital, Dundee, United Kingdom.
Bushra S
BS
Rana
Margaret M
MM
Band
Simon
S
Ogston
Andrew D
AD
Morris
Stuart D
SD
Pringle
Allan D
AD
Struthers
D000368:Aged; D003924:Diabetes Mellitus, Type 2 / Q000150:complications*; D004562:Electrocardiography; D005260:Female; D006330:Heart Defects, Congenital / Q000150:complications* / Q000175:diagnosis*; D006801:Humans; D017379:Hypertrophy, Left Ventricular / Q000150:complications; D008133:Long QT Syndrome / Q000150:complications*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011237:Predictive Value of Tests; D012372:ROC Curve; D012307:Risk Factors; D012680:Sensitivity and Specificity; D016037:Single-Blind Method; D013223:Statistics as Topic; D006113:United Kingdom