Page 84 - ADD-ON ABLATION SURGERY IN PATIENTS WITH ATRIAL FIBRILLATION

Chapter 9
Hereafter,these anatomic and electrophysiological features may be the basis for the inconsistent results reported for left atrial isolation and Cox-Maze operations76 and it may suggest that a right-side ablation should always be performed to interrupt the interatrial connections and to improve clinical results. However, the importance of the right atrial lesions included in the add-on procedure is difficult to define, as biatrial versus left atrial surgical ablation has never been compared in a randomised clinical trial and it is, therefore, still matter of debate. Indeed, whereas some studies found no significant difference between left-side and biatrial ablation77or achieved comparable results to those of Maze III with the simple isolation of pulmonary veins78, other studies confirmed the superiority of the biatrial approach compared to isolated left atrial ablation79.
We found that a higher number of patients undergoing the biatrial approach were in NSR off-ADD (p<0.001) with a lower 10-year cumulative incidence of AF recurrence compared to patients undergoing LA ablation (p<0.001). Onorati et al80 postulated that whereas left side procedures can succeed in patients with normal atria due to the shorter refractory periods of LA, patients with enlarged atria may require additional right ablation lines.This conclusion did not come out from our results: indeed, at competing risk regression, corrected by preoperative LA diameter and area, the absence of right atrial ablation (SHR 2.7, p=0.011) was an independent predictor of AF recurrence. In other words, from our data, the performance of additional right ablation lines seems to be indicated even in patients with normal atria. A strength of our findings is that all patients having a biatrial ablation underwent the same right lesion set including intercaval ablation, cavo- tricuspid isthmus line and isolation of right atrial appendage and terminal crest. Another important finding of our study is that among LA lines, only the MI ablation was not a significant predictor of AF recurrence at multivariate analysis which is in contrast with previous reports that have shown the significance of the left atrial isthmus lesion in patients with permanent AF81, 82.
The mitral isthmus refers to the atrial myocardium between the MV annulus and the left-sided PVs83. Anatomically, since this isthmus extends into the left inferior pulmonary vein, the width of the isthmus will depend on the extent of the myocardial sleeves associated with this vein.The wall of the isthmus ranges from 2-8 mm in myocardial thickness84 and its endocardial surface may contain pits and troughs where the atrial wall becomes exceptionally thin85. Finally, the presence of crevices in the isthmus area which may hinder safe and efficient radiofrequency energy delivery, the continuation of atrial myocardium onto the
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