2004: The Year of Continuing Progress in Catheter Ablation Strategy for Atrial Fibrillation

While there was no real breakthrough in the field of catheter ablation for atrial fibrillation (AF) in 2004, there was continuous progress in that field. This progress included the emergence of other strategies for ablation and the continuous development of newer technology for facilitation of those strategies. One notable progress in ablation strategy is the evolving concept of a more extensive ablation. Promising clinical data on the outcome of linear ablation^1,2 encouraged more investigators to perform left atrial ablation rather than focal ostial pulmonary ablation. The left atrial ablation strategy involves a variety of linear ablation, typically to include two circumferential ablations around the left and right pulmonary veins, respectively, as well as posterior left atrial and mitral isthmus lines. The possible advantage of such extensive procedures over the traditional segmental ostial ablation are: 1) the elimination or reduction of non-pulmonary vein triggers,³ 2) elimination or reduction of right-left atrial connection, 3) atrial debulking,⁴ and 4) atrial denervation. The circumferential ablation method has been known for a few years,¹ and its relative safety and efficacy were recently compared to the more limited ostial segmental ablation.² The data suggest that it would be reasonable and probably advantageous to perform left atrial ablation as the first strategy for AF. It is logical to believe that the more extensive ablation is considered to be the more appropriate technique for patients with persistent and chronic AF. Many centers are, therefore, performing more persistent and chronic AF ablation in 2004. The procedure for left atrial ablation with circumferential and linear lesions typically requires anatomical mapping. Such three-dimensional electroanatomical mapping has been performed using the CARTO ® system. The system has been widely used for such purposes, namely in helping the navigation of ablation points. Another mapping system, known as the noncontact (Endocardial Solution, Inc.) technique, has also been helpful. Its newer software, NavX, also facilitates navigation and tracking of ablation sites (Figure 1). Imaging tools are also helpful in preparing ablation for AF. MRI and spiral CT are helpful imaging techniques for outlining the general anatomy of the left atrium prior to ablation. More recently, a fusion technique, whereby the MRI image is superimposed or fused into the mapping system (NavX DIF), is being investigated.⁵ The sophistication and accuracy of such a mapping system is crucial for the success in creating linear lesions using point ablation; otherwise, there is a risk for leaving gaps and promoting macroreentrant left atrial flutter or tachycardia. Another approach to AF ablation is the localization of areas of complex fragmented atrial electrogram in the left and right atria.⁶ With this approach, ablation is aimed at these areas that frequently involve areas outside the pulmonary veins. With the high associated success rate, this form of ablation is also gaining acceptance in 2004. More importantly, the data from studies involving this strategy further highlight the importance of atrial tissue itself as the trigger, promoter, or sustaining substrate for paroxysmal, and probably persistent as well as chronic AF, and is in keeping with the emerging data of the multifactorial nature of AF. The recent published data reported a high success rate in patients with paroxysmal and chronic AF, thus supporting the idea that this approach, maybe as the left atrial ablation approach, targets the electrophysiologic substrate rather than the trigger. It can be stated that, in general, the year 2004 marked another milestone in AF ablation. It confirms the importance of elimination of triggers, and it underscores the need for a strategy for elimination of electrophysiologic substrate of persistent and chronic AF. Thus, interest in linear ablation, with the ultimate goal of curing all types of AF (paroxysmal or chronic) as proposed a decade ago⁷, is increasing, and recent advancements in mapping and ablation tools have been instrumental in this shift of strategy.