[Increase of the QT interval dispersion in diabetes mellitus]

The QT dispersion, measured as the interlead variability of QT interval (QTd = QTmax-QTmin), reflects the spatial inhomogeneity of ventricular repolarization times. The authors studied QTd and heart rate-corrected QTd (QTc-d) in 81 patients with diabetes mellitus (IDDM: 39, NIDDM: 42) using Bazett's formula; 20 non-diabetic subjects acted as controls (means +/- SD). QTd (43 +/- 17 ms) and QT c-d (52 +/- 20 ms) were increased (p < 0.05) as compared to the control values (QTd = 32 +/- 17 and, QTc-d = 35 +/- 17 ms, respectively). A significant difference was also observed in QTc-d if the two diabetic groups were compared to the control separately (p < 0.05). Moreover, comparison of the diabetic groups (IDDM vs NIDDM) revealed that type I diabetes mellitus is accompanied by a more pronounced spatial dispersion of ventricular reporlarization (QTd = 49 +/- 16, and QTc-d = 59 +/- 19 ms) as compared to NIDDM (QTd = 38 +/- 16, QTc-d = 46 +/- 20 ms [p < 0.01]). The hypothesis that increased QTd/QTc-d is truly a predictive marker of sudden arrhythmic cardiac death in patients with diabetes mellitus needs further clinical investigation.