CARDIAC AUTONOMIC NEUROPATHY AND QT INTERVAL LENGTH - A FOLLOW-UP-STUDY IN DIABETIC-PATIENTS

For evaluating the clinical significance of QT interval prolongation in diabetics with cardiac autonomic neuropathy (CAN), 53 diabetic patients were followed-up for 5 years or to death and the results of cardiovascular function tests as well as the values of QT intervals were repeatedly determined. At baseline investigation, the QT(c) intervals were significantly longer in diabetics with definitive (456 +/- 5 ms, xBAR +/- SEM, n = 17) than those with early (435 +/- 5 ms, n = 13, p < 0.01) and without (413 +/- 4 ms, n = 23, p < 0.001) signs of CAN or in controls (414 +/- 5 ms, n = 15, p < 0.001). Thirteen patients died during the follow-up period (1 without, 2 with early and 10 with definitive signs of CAN) but QT(c) intervals did not differ significantly between patients with cardiac (456 +/- 9 ms, n = 8) and non-cardiac (459 +/- 15 ms, n = 5) causes of death. At reinvestigation of 40 patients, the severity of CAN worsened in 22 patients, remained unchanged in 15 patients and improved in 3 patients. Accordingly, the mean values of autonomic function tests decreased (beat-to-beat variation from 15 +/- 2 to 9 +/- 1 beats/min, p < 0.01; 30:15 ratio from 1.19 +/- 0.03 to 1.09 +/- 0.02, p < 0.01) while QT(c) interval increased (from 424 +/- 3 to 431 +/- 4 ms, p < 0.01). It was concluded that CAN carries a poor prognosis in diabetic patients. Nevertheless, QT(c) interval prolongation could be evaluated as rather an additional sign of CAN than the only explanation for mechanism in the pathogenesis of sudden cardiac death in diabetic patients.