Effect of anthracyclines and isoflurane on QTc interval

BackgroundAnaesthetics and anthracyclines can affect the QT interval of the electrocardiogram (ECG). This study investigated whether the use of isoflurane in anthracyclines pretreated patients may induce or augment the QT prolongation to an arrhythmogenic level.Materials and methodsFifty-four female patients with breast cancer scheduled for mastectomy were included in the study, 27 received anthracyclines based chemotherapy before surgery, whereas 27 did not. All patients received a standardized balanced anaesthetic in which 0.5% end tidal concentration of isoflurane was used. The QT and corrected QT intervals (QTc) were measured before anaesthesia, after 1, 5, 15, 30, 60 min, respectively, following intubation and during recovery from anaesthesia.ResultsStatistically significant QTc prolongation was observed in patients who received anthracycline chemotherapy even prior to the administration of anaesthesia. The comparison of QTc interval at different intervals of isoflurane anaesthesia also showed a statistically significant difference between the two groups namely anthracycline treated group (study group) versus control group.A sample size of 27 in each group was calculated in order to achieve a study power of 80% with type 1 error rate of 5%. For the purpose of calculation, values of QT and QTc interval (range, mean, standard deviation) from the study of Owczuk et al. were used. t-test and analysis of variance were employed using SPSS version 10. P < 0.05 was considered as statistically significant.ConclusionsAnthracycline chemotherapy can produce significant prolongation of QTc interval. In addition, use of 0.5% end tidal concentration of isoflurane can further augment the QTc interval significantly.