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 (Table 3). Figure 3 shows the distribution of the HATCH and CHA 2 DS 2 -VASC scores according to the occurrence or not of AF after CTI-dependent atrial flutter ablation. No difference was found between the two groups. Distribution of the HATCH score values by occurrence or not of AF after ablation was 1 (1-3) in the group with AF and 1 (0-3) in the group without AF. Distribution of the CHA 2 DS 2 -VASC score values was 3 (2- 4) and 3 (1-4) in patients with and without AF, respectively. Discussion The main findings of the present study were (1) ablation of CTI-dependent atrial flutter is an effective and safe procedure, with low complication rates (1.2%); (2) AF is a frequently occurring complication (53.6%) in patients without history of AF; and (3) no criterion or predictive score for AF after ablation of CTI-dependent atrial flutter was identified. Ablation of CTI-dependent atrial flutter by radiofrequency Ablation of arrhythmogenic circuits of CTI-dependent atrial flutter using radiofrequency is associated with high success rates, superior to the exclusive use of antiarrhythmic drugs. 9,12 Among the known side effects, in case of recurrence of CTI- dependent atrial flutter, the use of antiarrhythmic drugs like propafenone may facilitate the atrioventricular conduction and increase ventricular response, with possible hemodynamic instability. Besides, the quality of life of patients treated with antiarrhythmic drugs is not improved, and 63% of patients require readmission. 13 Therefore, radiofrequency ablation is recommended as the treatment of choice for CTI-dependent atrial flutter. In a recent meta-analysis, Pérez et al. 1 reported a recurrence rate of CTI-dependent atrial flutter of 10.6%, similar to that found in the present study, and complication rates of up to 2.6%. 1,3 Patients with CTI-dependent atrial flutter undergoing successful ablation showed lower mortality and lower risk of stroke and thromboembolic events, compared with patients treated only with drug therapy. 3 In the present study, we found recurrence rate of CTI- dependent atrial flutter of 11.5% and complication rate of 1.2%. No patient had embolic event or pericardial effusion, and no patient died despite the long period of follow-up of the study sample. Occurrence of AF after ablation of CTI-dependent atrial flutter In our study, recurrence rate of AF after ablation of CTI-dependent atrial flutter was 53.6%. This is of clinical significance, due to the high risk of thromboembolic events associated with this arrhythmia, particularly stroke. The presence of AF is associated with 4-5 times greater risk of developing ischemic stroke. Stroke caused by AF has been associated with higher mortality and more severe functional deficits. 14,15 Thus, patients with AF are not only at greater risk of developing stroke, but also of having more severe disease, with more debilitating complications. In a study on patients undergoing ablation of CTI-dependent atrial flutter, the incidence of stroke during a mean follow-up of 40 months after the procedure was four times greater than the general population, and the only risk factor identified was occurrence of AF after ablation of CTI-dependent atrial flutter. 16 For this reason, considering the high incidence of AF in this population, discontinuation of oral anticoagulation may expose them to the risk of thromboembolic events and hence should be considered individually, considering the CHA2DS2-VASC score of the patient with atrial flutter, just as with patients with AF. 17 Therefore, a significant number of patients remains symptomatic due to the development of AF after CTI- dependent atrial flutter ablation. A second ablation procedure may be then necessary for the control of AF. Although isolation of pulmonary veins by radiofrequency ablation (required in the treatment of AF) is a more complex procedure, with higher costs and risks compared with CTI-dependent atrial flutter ablation, an alternative may be to treat both arrhythmias using a combined procedure, thus avoiding a second intervention. 9,11 Is it worth to perform isolation of the pulmonary veins simultaneously with ablation of CTI-dependent atrial flutter in patients with history of AF? In the ablation of CTI-dependent atrial flutter procedure, the electrophysiologist makes an ablation line in the cavo- tricuspid isthmus area, to prevent or block the macroreentrant circuit in the right atrium. In this case, the access of the ablation catheters to the right atrium occurs exclusively by puncture of the femoral veins. Ablation of AF ablation, in turn, is a more complex and time-taking procedure that requires the access to the left atrium by transseptal puncture (passage of the catheters from the right to the left atrium by puncture of the interatrial septum) for electrical isolation of the pulmonary veins, generally responsible for the triggering of AF. The REDUCE AF study, involving 216 patients, showed that combined ablation of CTI-dependent atrial flutter plus AF resulted in a longer arrhythmia- free interval compared with the CTI-dependent atrial flutter ablation alone, especially in >55 age patients. In this subgroup of patients, the number needed to treat (NNT) was seven, with an absolute risk reduction in AF occurrence of 14%. 11 Using a cost-effectiveness analysis, a Canadian study proposed that the combined ablation (CTI-dependent atrial flutter plus AF) does not provide financial and risk benefit. With an incidence rate of AF of up to 33%, the mean cost of performing the procedures separately was lower than the combined strategy. In addition, when performed alone, the mean risk of ablation of CTI-dependent atrial flutter is lower, since the risk of AF ablation exceeds the risk of CTI-dependent atrial flutter ablation by 25% or more. One should consider, however, that risk, cost and complication rates vary regionally, like the incidence of AF after ablation of CTI-dependent atrial flutter, which was twice greater than that predicted in cost-effectiveness studies. Also, cost-effectiveness analysis usually does not consider the negative long-term impact of embolic events in patients with new onset AF. In the state of Santa Catarina, the mean cost of hospitalization due to cardioembolic stroke with AF reaches BRL 40,539 per patient. 18 Thus, the risks and costs involved in the combined ablation procedure (CTI-dependent atrial flutter and AF) would not be justifiable in short term; instead, long-term studies 780