Impact of thoracic epidural sympathetic block on cardiac repolarization

The interval from the peak to the end of the T wave (Tp-Te) on electrocardiography is considered a marker of ventricular arrhythmias. A previous study suggested that right stellate ganglion block prolonged QT and QT dispersion (QTD). We investigated the effect of thoracic epidural sympathetic block with 1% mepivacaine on QT, QTD, Tp-Te, and Tp-Te/QT by using computerized measurement.

After obtaining the approval of the ethics committee of Dokkyo Medical University Hospital, 23 patients with American Society of Anesthesiologists physical status I or II who were scheduled to undergo thoracic surgery were enrolled. An epidural catheter was inserted at the Th4-5 or 5-6 level and then used for injection of 7 mL of 1% mepivacaine. Changes in RR interval, QT, corrected QT (QTc), QTD, QTc dispersion (QTcD), Tp-Te, Tp-Te/QT, and Tp-Te/QTc before and after epidural injection were assessed by computerized measurement. Statistical analysis was performed by one-way ANOVA.

Systolic blood pressure was consistently suppressed 10-15 minutes after injection (baseline: 136±10 mmHg, 11 minutes: 113±12 mmHg, 12 minutes: 112±13 mmHg, 13 minutes: 112±12 mmHg, 14 minutes: 108±17 mmHg, 15 minutes: 111±14 mmHg; P<0.05). However, RR interval, QT, QTc, QTD, QTcD, Tp-Te, Tp-Te/QT, and Tp-Te/QTc were not changed after epidural block.

Thoracic epidural injection of 1% mepivacaine did not alter QT, QTc, QTD, QTcD, Tp-Te, Tp-Te/QT, or Tp-Te/QTc. These results emphasize the safety of thoracic epidural sympathetic block with 1% mepivacaine for patients compared with right stellate ganglion block, in terms of cardiac repolarization.