EComment. Alternative energy sources in surgery for atrial fibrillation

Abstract

In this article by MacDonald et al. [1], a great concern is the wide variety of factors coming into play at the same time in the analyzed studies. In fact, only one study with level 1 evidence was found. In this study, two randomized groups received ablation for atrial fibrillation (AF) with microwave (MW) and radiofrequency (RF) energy and at the 24-month follow-up, restoration of sinus rhythm favoured the RF over the MW group. If I were asked to evaluate the current status of different alternative energy sources used to ablate AF, I would state the following: To begin with, I should note that the surgeon has always been keenly aware of the superiority of the classic Cox-maze III “cut-and-sew” over the “electric” Cox-maze IV technique. There is no perfect alternative energy source, that is, one that might consistently generate incisions with a complete and guaranteed transmurality in the atrial tissue. In 2003, the U.S. Food and Drug Administration (FDA) cleared the Cardioblate BP System for marketing [2], which is a bipolar surgical RF ablation instrument that delivers an electrolytic irrigation solution along with its RF energy. This provides surgeons with a transmurality feedback mechanism that alerts them when an ablation line has been created through the full thickness of the tissue. So, beginning in 2004, the industry launched the widespread use of the bipolar RF devices for AF surgery. Unfortunately, microwave radiation for ablation of AF is a unipolar system, and has shown, as have all unipolar energy sources used for this aim, inconsistent results regarding the transmurality achieved [3]. Suggestions have been made about the need to create transmural lesions to cure AF, and some evidence has shown that tissue temperature is a better predictor of further lesion formation [4]. According to Cox, surgery for AF should meet the following conditions: 1) the procedure should be preferably epicardial by nature; 2) the energy source should be capable of penetrating epicardial fat and ablating all types of AF; 3) cardiopulmonary bypass must be avoided; 4) the procedure should be amenable to endoscopic or minimally invasive techniques; 5) it should be performed in less than 1 hour; 6) hospital discharge should be possible on the first postoperative day [5]. Assuming the mentioned-above criteria, the surgeon is faced with the dilemma of using bipolar devices which create transmural lesions in a systematic way, but with greater difficulty and invasiveness in its management (open approaches). While unipolar devices may be less invasive and more easily handled (thoracoscopic approaches), these are unable to provide certainty regarding the transmurality of the burn. After this discussion, I belive that the balance would tilt in favour of the use of bipolar RF instead of MW ablation. However, we have not reached the goal yet. Conflict of Interest: None declared