Evaluation of cardiac arrhythmia incidence with holter monitoring in patients treated with oral moxifloxacin

The effect of moxifloxacin on QT interval is reversible and dose-related; mainly provided by weakly but rapidly activated rectifying potassium channel blockade, IKr or HERG (human ether-a-go-go-related gene) potassium channels. Retrospective data suggest an increase in cardiac event rates with moxifloxacin use. Some side effects of the oral moxifloxacin are well known. Nevertheless, except for case reports and experimental trials about QT/QTc, there is insufficient data in the literature on the incidence of cardiac arrhythmias detected by electrocardiography (ECG) and Holter monitoring. In this trial, we sought to determine the effects of newly administrated oral moxifloxacin (with the indications of upper airway infections, community-acquired pneumonia and acute exaggerated bronchitis) on the incidence of cardiac arrhythmias. All patients were screened for cardiac arrhythmia before therapy (0th day - BT), on the 3th day (during therapy - DT) and on the 10th day (after therapy - AT) with ECG and on the 3th day (during therapy - DT) and on the 10th day (after therapy - AT) with Holter monitorization. Before starting of the therapy, structural heart diseases were excluded using transthroracic echocardiography, other exclusion criteria were based on the laboratory tests. The mean heart rate assessed by Holter monitoring was not significantly different during and after antibiotic therapy, although the mean heart rate measured from surface ECG was significantly reduced during and after antibiotic therapy compared to baseline (BT: 80.3±13.9 BPM vs DT: 76.3±11.3 BPM vs AT: 75.9±106 BPM, p=0.007). Mean QT interval value was increased on the 3th day when compared to 0th day and was similar with the value on the 10th day (BT: 353.1±246 msn vs DT: 363.3±23.7 msn vs AT: 361.8±20.8 msn; p=0.034). Mean QTc interval was significantly increased on the 3th day, however was decreased to the baseline value (BT: 396.4±20.2 msn vs DT: 404.4±19.3 msn vs AT: 397.5±21.0 msn; p=0.011). This result was thought to be due to decrease of the mean heart rate during and after therapy. In our study, ECG and Holter monitoring were utilized together and we did not find any differences in life- threatening and other arrhythmias with 400 mg oral moxifloxacin therapy. When the Holter monitoring findings of our study were analysed in term of gender interaction, minimal and maximal HR, QT dispersion parameters as well as the frequencies of ventricular and supraventricular extrasystoles were not different between male and female subgroups. As a result, 400 mg of oral moxifloxacin started on an outpatient basis with the indications of upper and/or lower airway infections results in an increase in QT interval during therapy. However, it does not affect QTc, and is not related with serious cardiac arrhythmias during Holter monitoring. Key Words: Arrhytmia, Electrocardiography, Holter Monitoring, Moxifloxacin, QT/QTc intervals, QT dispersion