VALUE OF RATE-CORRECTED QT INTERVAL FOR T HE DIAGNOSIS OF CARDIAC AUTONOMIC NEUROPATHY IN LONG-STANDING TYPE-1 DIABETES-MELLITUS

Objective: To assess the relationship between rate-corrected QT interv al (QTc interval) and cardiac reflex tests in order to determine the v alue of QTc interval measurements in the diagnosis of diabetic cardiac autonomic neuropathy. Investigations: The QTc interval was measured i n the resting ECG of 97 type 1 diabetics (58 women, 39 men; mean age 3 5 +/- 12 years; duration of diabetes 18 +/- 10 years; HbA(1c) 7.8 +/- 1.8%). Age-related results were compared with five cardiac function te sts (heart rate variation at rest and on forced breathing; 30/15 ratio of heart rate; Valsalva manoeuvre; orthostasis). Results: The QTc int erval was not prolonged (less than or equal to 440 ms) in 68 patients (70%), while in 29 (30%) it was prolonged (>440 ms). No significant di fferences regarding QTc interval were found between patients with auto nomic cardiac neuropathy (greater than or equal to 2 abnormal function tests) and those without (<2 abnormal function tests) (QTc interval 4 36 +/- 25 vs 426 +/- 19 ms). QTc intervals correlated with the coeffic ients of variation for heart rate variation at rest and on forced brea thing and the 30/15 ratio of heart rate (P = 0.001; P = 0.001; P = 0.0 3), but not with the results of the Valsalva manoeuvre and the orthost asis test. Conclusion: Prolongation of the QTc interval in longstandin g type 1 diabetes does not provide a reliable indication of cardiac au tonomic neuropathy and this measure cannot replace conventional reflex tests for its diagnosis.