ABC | Volume 114, Nº5, May 2020

Original Article Bianco et al. Ablation of atrial flutter and fibrillation Arq Bras Cardiol. 2020; 114(5):775-782 on electrocardiogram before ablation. Therefore, patients with electrocardiographic documentation of AF before ablation of CTI-dependent atrial flutter were excluded. The flowchart of patients’ inclusion and exclusion is illustrated in Figure 1. This study was approved by the Ethics Committee of Universidade do Sul de Santa Catarina (Unisul) (approval number 79539517.1.0000.5369). All procedures involved in this study was conducted according the Helsinki Declaration, 1975, updated in 2013, and the 466 resolution of the Brazilian National Health Council (December 2012). Data collection The patients included in the study, with diagnosis of CTI-dependent atrial flutter, undergoing catheter ablation, were followed for the occurrence of AF after the index procedure. Recurrence of CTI-dependent atrial flutter and occurrence of AF were confirmed by data collected from medical records – electrocardiogram, 24-hour Holter monitoring, routine consultations, emergency services and ablation procedures. Protocol of CTI-dependent atrial flutter ablation Ablation of CTI-dependent atrial flutter was performed under general anesthesia. Two punctures were made in the right femoral vein, with placement of a decapolar deflectable 8mm ablation catheter. Ablation was then performed (60W at 60oC for up to 2 minutes), started near the tricuspid valve towards the inferior vena cava at six o’clock in a left-anterior oblique position, until interruption of the atrial flutter. When arrythmia was interrupted, double atrial potentials were observed on the ablation line, with periods of at least 100 milliseconds during continuous pacemaking of coronary sinus and lateral atrial wall for confirmation of bidirectional block and conclusion of the procedure. Patients were kept in observation for 24 hours after the procedure and instructed to consult their assistant physicians after hospital discharge. Statistical analysis Clinical data and procedures were compared between the groups of patients with and without atrial flutter after the ablation procedure. A convenience (non-probabilistic) sample was used, according to inclusion and exclusion criteria, and time of follow-up. Continuous variables were described as mean and standard deviation and compared using the unpaired, two-tailed Student’s t-test, according to normality of data distribution, assessed by the Shapiro-Wilk test. Categorical variables were described as absolute numbers and percentages and compared using the chi-square test of the Fisher’s exact test. Significance level was set at 5%. The Kaplan-Meier curve was used for analysis of recurrence rate during the follow- up period (truncation at 24 months). Predictive factors were assessed by logistic regression, with occurrence and non- occurrence of AF following atrial flutter ablation as outcomes. All variables associated with a p<0.20 in the univariate logistic regression analysis were included in the multivariate model for final adjustment. No selection was applied in the multivariate models. Statistical analysis was performed using the IBM SPSS Statistics software, version 22.0. Results Patients Atrial flutter ablation was performed in 227 patients between 2017 and 2018 at two centers in Santa Catarina, Brazil. Of these, 110 patients had a history of AF and 33 patients did not have enough clinical data. Therefore, 84 patients without history of AF before CTI-dependent atrial flutter ablation were enrolled in the study. During a mean follow-up of 26±18 months, 45 (53.6%) had AF after ablation. Table 1 summarizes clinical characteristics of patients with and without AF after ablation of CTI-dependent atrial flutter ablation. Figure 1 – Flowchart of inclusion and exclusion of patients undergoing ablation of cavotricuspid isthmus-dependent atrial flutter categorized by occurrence of atrial fibrillation after the procedure. 776