Surgical ablation in patients undergoing mitral valve surgery: impact of lesion set and surgical techniques on long-term success

The study by Gelsomino et al. published in December 2015 in the Europace underlines the importance of technical elements on which we want to comment.1 First, it underlines the importance of biatrial ablation lesion sets to obtain clinical success with modified Maze procedures. This is in complete concordance with the fundamental work of Cox et al.2 One cannot expect to replicate such a comprehensive pathophysiological management with only half of the work.3 The authors are right in stating the obvious. Second, regarding the mitral isthmus, the manuscript discusses the importance of unfolding the inner atrial surface to avoid ‘crevices’ and create effective electrical isolation within the tissue. This is an elementary concept, but its non-observance would inevitably lead to unsuccessful results. When the Cox-Maze III cut-and-sew procedure was performed, not only the lesions were de facto transmural, but arrhythmia surgery itself was performed only by dedicated surgeons. With advances of less cumbersome approaches using alternative energy sources, the modified procedure became more popular which increased access for patients with atrial fibrillation but also moved the technique away from expert hands.4 The electromechanical rationale behind the Maze procedure was replaced, at least sometimes, by the simple replication of a recipe. The authors are completely right in putting fundamental concepts upfront. Third, the authors introduce the fact that cryosurgery should be compared with radiofrequency regarding the proximity of the mitral annulus. This is an important element to investigate, but we propose an alternative explanation for the failure of radiofrequency procedures. The authors state that thickness of the atrioventricular groove explains why energy cannot be appropriately delivered into the tissue to create a proper transmural lesion up to the level of the annulus. This can be true. However, surgeons' fear regarding damaging the mitral annulus or posterior leaflet or the coronary arteries can overcome their fear of leaving a muscle bridge at proximity of the annulus. The desire of not doing harm to patients can sure be stronger than the desire of curing the atrial fibrillation. This state of mind is certainly prevalent amongst surgeons that have less understanding of the pathophysiological basis of arrhythmia. Unfortunately, this muscle bridge might not only leave patients with unsuccessful procedures but in fact creates more significant arrhythmias as well. Patients may then suffer from left-sided atrial flutter, which is difficult to treat medically and often worse than atrial fibrillation itself since ventricular response rate is difficult to control.5 When patients have undergone concomitant mechanical mitral valve replacement, percutaneous transseptal catheter ablation to address residual left atrial flutter can be challenging, risky, and sometimes not feasible. For that reason, using cryoablation in proximity of valvular structures and coronary arteries may lead to less injury and consequently better surgical confidence and clinical outcomes.

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