Effect of Valsalva Maneuver on QT Dispersion in Hemodialysis Patients.

Increased QT dispersion seems to be related to an increased risk of arrhythmia and sudden death, a common cause of mortality in hemodialysis (HD) patients. Increase in sympathetic tone has been documented in HD patients. In this study, we aimed to investigate the effect of changes in the autonomic tone on QT dispersion (QTd) in HD patients. Twenty HD patients (M/F 13/7; age, mean ±SD, 28 ± 10 years) and 22 age- and sex-matched healthy controls (M/F 12/10; age, 30 ± 10 years) were included. The patients were dialyzed three-times weekly; time on dialysis was 17 ± 8 months. The QT durations were measured from 12 lead surface EKGs and were corrected for RR intervals. Corrected maximum (QTc max) and minimum (QTc min) QT intervals and their difference (QT c d) were recorded. The effect of the Valsalva maneuver in the release phase on QT c intervals and dispersion was assessed. The HD patients had prolonged values compared to controls: QT c d, 59 ± 17 ms versus 35 ± 7 ms, p < 0.001; QT c max, 458 ± 41 ms versus 397 ± 21 ms, p < 0.001; and QT c min, 398 ± 36 ms versus 362 ± 25 ms, p < 0.001. After the Valsalva maneuver no changes were observed in controls: QT c max, 397 ± 21 ms versus 396 ± 22 ms, p = 0.9; QT c min, 362 ± 24 ms versus 358 ± 19 ms, p = 0.5; and QT c d, 35 ± 7 ms versus 38 ± 10 ms, p = 0.15. Whereas, in HD patients all values were significantly shortened: QTc max, 458 ± 41 ms versus 427 ± 35 ms, p = 0.003; QTc min, 398 ± 36 ms versus 379 ± 34 ms, p = 0.04; and QTc d, 59 ± 17 ms versus 48 ± 15 ms, p = 0.01. The decrease in QTmax was more prominent than the decrease in QTmin, hence QT dispersion was significantly decreased after the Valsalva maneuver, but differences from controls were still significant. In conclusion, increased sympathetic activity may have a role in the prolonged QT duration and increased QT dispersion in HD patients.