Statistical analysis
ATRIAL ARRHYTHMIA, EVENTS, EVENT, RECRUITMENT
In this time-to-event study of hospital episodes, the sample size was estimated using the log-rank test under the Freedman method based on the occurrence of first event during the 12-month follow-up period. The null hypothesis was that there was no difference in the distributions. An initial two-sided alpha of 0.05 was chosen, and given the need to allow for the inherent multiple testing between the three arms of the study, the conservative Bonferroni correction was applied and the alpha value used in the power calculations was reduced to 0.025.Estimating the proportion experiencing a hospital episode in the follow-up period in the anti-arrhythmic arm as 0.63 and the corresponding proportion in the AVATAR ablation arm as 0.40, assuming the occurrence of 103 events, with 100 evaluable patients in each of the two treatment arms yields a power of 0.80. A similar power is obtained for the comparison of the AVATAR ablation arm (0.40) and the conventional AF ablation arm (0.20). These estimates were based on published data for ‘freedom from 30 s of AF’. Using a loss to follow-up of 7%, a recruitment target of 321 patients was set.Treatment was considered failed when a patient experienced any hospital episode related to treatment for atrial arrhythmia. Time to failure was the time from first intervention to time of event. The ‘decision not to discharge’ was used as the endpoint for analysis in those patients who were not discharged after the 12-week treatment period.Data were analysed using intention-to-treat principle, and a 