IS THE CORRECTED QT INTERVAL A RELIABLE INDICATOR OF THE SEVERITY OF DIABETIC AUTONOMIC NEUROPATHY

OBJECTIVE - We investigated whether the corrected QT interval correlat ed with two other tests for diagnosing autonomic dysfunction in 60 typ e I diabetic patients with proven peripheral neuropathy. The mean age +/- SD was 48.3 +/- 11.2 yr, the mean duration of diabetes was 24.9 +/ - 11.4 yr, and the mean HbA1 was 9.3 +/- 2.4%. RESEARCH DESIGN AND MET HODS - All patients underwent three autonomic function tests: 1) the s tandard five cardiovascular Ewing tests, each scored 0 (normal), 0.5 ( borderline), or 1.0 (abnormal). We used the sum of the abnormal findin gs for the analysis, the cardiovascular autonomic score; 2) measuremen t of the corrected QT interval taken from a routine electrocardiogram recording; and 3) static and dynamic pupillometry: measurement of dark adapted pupil diameter as percentage of total iris diameter and of pu pil constriction latency using an infrared light reflex technique. RES ULTS - No significant correlation was found between age, duration of d iabetes, or HbA1 and any of the autonomic function tests, except for o ne between age and cardiovascular autonomic score (r = 0.3202, P = 0.0 126). Corrected QT interval did not correlate with cardiovascular auto nomic score, pupil diameter, or constriction latency. A significant in verse correlation was found between cardiovascular autonomic score and pupil diameter (r = - 0.4861, P < 0.001) and constriction latency (r = 0.3783, P < 0.001). Pupil diameter and constriction latency correlat ed well (r = -0.4276, P < 0.001). CONCLUSIONS - The corrected QT inter val did not correlate with cardiovascular autonomic tests nor pupillom etry results. The corrected QT interval therefore should not be used f or the diagnosis of the severity of diabetic autonomic neuropathy.