QT INTERVAL PROLONGATION IN TYPE-2 (NON-INSULIN-DEPENDENT) DIABETIC-PATIENTS WITH CARDIAC AUTONOMIC NEUROPATHY

QT interval alterations were measured in 41 non-insulin-dependent (type 2) diabetic patients and 14 age- and sex-matched control subjects. Cardiac autonomic neuropathy (CAN) was assessed by noninvasive tests (deep breathing, Valsalva maneuver and lying-to-standing) and diabetics were divided into three groups according to the results of these tests: diabetics with definitive (n = 14), early (n = 13) and without (n = 14) CAN. The corrected values of QT intervals (QT(c)) at rest were significantly longer in diabetics with definitive (447 +/- 5 ms; p < 0.001), early (426 +/- 5 ms; p < 0.05) and without (424 +/- 5 ms; p < 0.05) CAN than in controls (407 +/- 5 ms). Moreover, QT(c) intervals at rest were significantly (p < 0.01) longer in diabetics with definitive CAN than in diabetics with early and without CAN. QT(c) intervals at maximum tachycardia, induced by Valsalva maneuver, were considerably longer in diabetics with definitive CAN (451 +/- 6 ms) than in controls (407 +/- 6 ms; p < 0.001) and in diabetics with early (434 +/- 6 ms; p < 0.05) or without (422 +/- 6 ms; p < 0.01) CAN. Furthermore, QT(c) intervals at maximum tachycardia were significantly (p < 0.01) longer in diabetics with early CAN than in controls. QT(c) intervals at maximum bradycardia after Valsalva maneuver were significantly longer in diabetics with definitive (446 +/- 5 ms; p < 0.001), early (434 +/- 5 ms; p < 0.001) and without (424 +/- 5 ms; p < 0.01) CAN than in controls (403 +/- 5 ms). Moreover, QT(c) intervals at maximum bradycardia were considerably (p < 0.01) longer in diabetics with definitive than without CAN. At least one abnormal (> 440 ms) QT(c) period was found in 19 out of 27 patients with early or definitive CAN, but 4 of 14 diabetics without any signs of CAN and non of the controls exibited adnormal QT(c) period. It was concluded that QT(c) interval prolongation due to imbalance of autonomic nervous tone could be observed in type 2 diabetic patients with CAN, suggesting a possible role in sudden cardiac death.