Is There A Relationship Between Baroreflex Sensitivity, Cardiac Autonomic Function And Cardiac Repolarisation In Type 1 Patients?

Abstract

Established diabetic autonomic neuropathy (DAN) carries a poor prognosis, with an increased risk of sudden death. Recently, baroreflex sensitivity (BRS) has been proposed as a sensitive marker of autonomic function in diabetes (DM). An association between DAN and abnormal cardiac repolarisation, manifest by increases in QT interval and/or QT dispersion on the ECG, has also been described. The aim of this study was to investigate the relationship between BRS and QT parameters. We have studied 28 Type 1 DM subjects (age 39 ± 10yrs (mean ± SD), DM duration 14 ± 11yrs, HbA1c 8.5 ± 1.3%) with normal cardiac autonomic function tests (DAN–) and 8 subjects (age 49 ± 13yrs, duration 22 ± 9yrs, HbA1c 9.5 ± 1.1%) with abnormal tests using standard criteria (DAN+). We measured supine BRS using sequence analysis of systolic blood pressure and pulse interval. Rate‐corrected QT (QTc) interval was measured using a high‐resolution ECG system, and QT dispersion from a 12‐lead ECG recorded at 50mm/s. Results are summarised below.Regression analysis revealed no correlation between BRS and QTc interval or QT. In summary, DAN+ patients had significantly lower BRS (p < 0.001) and increased QT dispersion (p < 0.01) compared to DAN− subjects, but no difference in QTc. In contrast to BRS, changes in QTc and QT dispersion may occur relatively late in the disease. BRS ms/mmHg QTc interval QT dispersion DAN− 12.7 ± 6.6 (n=28) 411 ± 22 ms (n=28) 38 ± 12 ms (n=28) DAN+ 3.9 ± 1.9 (n=8) 409 ± 22 ms (n=8) 54 ± 12 ms (n=6)