ABC | Volume 110, Nº4, April 2018

Original Article Muñoz et al Atrial fibrillation ablation in valve disease Arq Bras Cardiol. 2018; 110(4):312-320 We speculate that the lack of association of LA strain and strainR parameters with AF postoperative recurrence may be explained by severe atrial dilation with extensive areas of fibrosis before surgery in both responders and non-responders to AF ablative techniques. Very large areas of atrial fibrosis may result in an important decrease in atrial mechanics, as shown by deformation parameters of patients included in this study in comparison with healthy individuals. Comparisons between responders and non-responders to AF are limited by the very low parameters of atrial deformation in all patients, which affects the sensitivity of deformation parameters to predict AF recurrences. However, the more fibrosis, the less likely it is to maintain SR. For illustrating this hypothesis, in Figure 5, we compare the anatomopathological characteristics of a patient with more extensive fibrosis and AF recurrence (Figure 5A) with another in SR during follow-up (Figure 5B). Larger studies and inclusion of LA tissue sampling should be necessary to demonstrate this hypothesis. In accordance with prior reports, 20 in the current study, larger LA was associated with AF recurrence, suggesting that patients who could benefit more from this technique are those with LA volume < 64 ml/m 2 . Another novel contribution of the series presented here, is that despite the fact that LA diameter has been traditionally considered one of the major inclusion criteria for candidate selection, only LA volume appears as a predictor of AF recurrence. To the best of our knowledge, the prognostic value of LA biplane volume to predict recurrences after AF cryoablation in VHD patients has not been previously reported and may contribute to better selection of candidates with VHD. The suppression of AF was most successful in patients undergoing mitral valve surgery, patients in whom cryoablation was systematically used. Patients who underwent aortic valve surgery and AF ablation withHIFU-Epicor had significantly lower rate of SR maintenance. In prior publications, the success rate of Epicor system was also lower. 21 Endocardial approach (used in cryoablation) has shown higher success rates in comparison with the more superficial epicardial approach (HIFU-Epicor). However, according to other authors, this difference may not be due uniquely to the lower efficiency of the ablation system employed, and they speculate whether the underlying heart disease may also influence outcome, because it is well known, that isolated mitral valve surgery (without additional AF ablation) has a significant beneficial effect on spontaneous conversion to SR. 5,21 Antiarrhythmic management is important in patients with recurrent AF in the post-operative period in improving results of SA. 4 However, in our study, no association was found between antiarrhythmic treatment and SR maintenance. We could not infer from our data whether this finding was due to the small number of patients was discharged with amiodarone, or if amiodarone is not effective for SR maintenance in these patients. In the univariate analyses, age was associated with the recurrence of AF, however, this relationship was not observed after multivariate testing. It appears, therefore, that age is a confounding variable, since patients undergoing both mitral valve intervention and cryoablation are significantly younger. It is well known that AF is associated with LA myocardial remodeling and ultra-structural changes, including fibrosis and accumulation of extracellular matrix – effects that may predispose to the formation of zones of slow conduction, which promote re-entry. 22 ACE-inhibitors are thought to reduce atrial dilatation, dysfunction, and fibrosis, which may reduce the propensity for developing AF. 23 In some studies, after catheter ablation, there is a trend towards fewer AF recurrences in patients treated with ACE‑inhibitors, however, the efficacy of this treatment in routine clinical practice remains unknown. 24 In the present study, ACE-inhibitors were used in a substantial proportion of patients (48%), but they were not found to be effective enough for preventing AF recurrence. As it has been demonstrated in previous studies, 25 AF surgical ablation is a safe procedure without increasing total surgical time, in comparison with the traditional Cox-Maze procedure, which has an elevated success rate but significantly increases intraoperative time. In our series we have not found major complications related to this technique. Limitations of the study Despite the systematic use of 24 hour Holter monitoring in the present series, silent AF remains an important issue in the post-operative follow-up of this type of patients. A major limitation of studies about AF treatment is that the burden of arrhythmia cannot be a reliable determinant unless an implantable device is used. It is also difficult to make a proper comparison with other studies in the absence of universal criteria for defining AF recurrences. Results on the antiarrhythmic treatment should be interpreted with caution, since treatment with amiodarone (which was not uniformly employed across patients) could affect the success of the AF ablation technique. When antiarrhythmic drugs were forced into the multivariate model, recurrence predictors remained unchanged. This study was carried out for a limited time period, with a relatively small sample size and in a single tertiary center. Multicenter studies and larger number of patients will be needed in the future to obtain more evidences about efficacy and safety of this technique in VHD patients. Conclusions Left atrial volume was larger in patients with AF recurrence, and emerges as the main predictor of recurrences improving candidate selection for this therapy; however, no differences were found regarding myocardial deformation parameters. Despite electrical maintenance of SR, left atriummechanics did not recover after AF ablation performed during VHD surgery. Author contributions Conception and design of the research, Analysis and interpretation of the data, Statistical analysis and Critical revision of the manuscript for intellectual content: Lorenzo N, Aguilar R; Acquisition of data: Lorenzo N, Mendez I, Taibo M, 318