Page 78 - ADD-ON ABLATION SURGERY IN PATIENTS WITH ATRIAL FIBRILLATION

Chapter 9
to establish the cost-effectiveness of add-on surgery also employing different energy sources.
Add-on surgery: Effectiveness of electrical cardioversion after unsuccessful surgery
We reported early and mid-term outcomes in patients who underwent cardioversion for persistent AF occurring after RF ablation associated with mitral valve surgery and we compared these outcomes to patients undergoing ECV after mitral surgery without concomitant AF ablation (Chapter 5).
After successful ECV, more than 78% of patients in the ablation group were in stable SR off- antiarrhythmic drugs at follow-up whereas only 21.4% of patients in the no-ablation group did not show recurrent AF (p<0.001). In addition, omission of the ablation procedure (p<0.001) was the strongest predictor of AF recurrence after ECV.
We can postulate that some kind of substrate modification occurred after surgical ablation, which made patients more susceptible to the treatment of ECV. Indeed, intra-operative radiofrequency ablation methods limited to the left atrium have proven to be efficacious for modification of the AF substrate41.
Nevertheless, the surgical procedure did not result in higher early post-operative stable conversion to SR and this might be explained by the demonstration of a bidirectional block which could be only transient requiring further “maturation” of the ablative lesions42 to alter the arrhythmia substrate sufficiently to be responsive to ECV.
In addition, left atrial LA dimensions < 45 mm (p=0.005) before ECV predicted mid-term maintenance of SR.Atrial size was more markedly reduced in patients with associated ablation than in those with isolated mitral valve surgery (40.5 ± 5.8 mm vs. 48.9 ± 8.1 mm, p<0.001) as result of a significantly higher reverse remodelling in the left atrium following surgical linear endocardial RF lesions. Enlarged left atrium LA with over-stretched myocardium and residual high wall stress might not achieve significant reverse remodelling because of the progression of myocardium damage. Nonetheless the lower atrial size in the ablation group might also be due to scarring along the ablation lines.
From our analysis it also merges that the timing between surgery and the cardioversion procedure is a matter of utmost importance. Early AF recurrence after a Maze procedure is explained by changes induced in atrial electrophysiology by myocardial edema and inflammatory response to cardiac surgery43. There
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