[Circadian rhythm of QT- and QTc-intervals in diabetics and hypertensives].

UNLABELLED

Few studies have been done on the circadian rhythm of QT- und corrected QT-interval in diabetics.

METHOD

13 type II diabetics (mean duration 10.08 yrs +/- 1.95 (SEM), 12 insulin-dependent) and 13 hypertensives, mean age 58.2 +/- 197 (SEM) and 57.3 +/- 1.4 yrs (p = n.s.), respectively, without cardiovascular events within the last 6 months before rehabilitation underwent Holter monitoring. We investigated mean and maximum QT-interval, QTc-interval (Bazett-formula), RR-interval as well as spectral parameters LF, HF, and LF/HF ratio.

RESULTS

Both groups showed significant circadian variations of mean and maximum QT-intervals. No group differences were found. There was no significant circadian rhythm of mean or maximum QTc-interval. Diabetics had significantly prolonged maximum QTc-intervals during the day-time. Mean and maximum RR-intervals in diabetics were significantly shorter. Both groups showed a significant circadian rhythm. LF and HF were significantly shorter in diabetics. Only in diabetics could significant circadian rhythm of LF and HF be demonstrated. The LF/HF ratio was significantly shorter in diabetics. The hypertensive group showed a decreasing circadian trend whereas diabetics showed increasing LF/HF ratio trend.

CONCLUSION

Mean and maximum QT-intervals are significantly shorter in diabetics than in hypertensives. Maximum QTc-interval prolongation is highly significant (p < 0.01) in diabetics. Spectral parameters LF and HF are reduced in comparison with hypertensives. The prolongation of the maximum QTc-interval could be expression of an increased arrythmogenic and cardiovascular risk in diabetics.