Impact of catheter ablation of atrial fibrillation on the left atrium

Abstract

Although the success of pulmonary vein antrum isolation (PVAI) in eliminating atrial fibrillation (AF) has been proven, its impact on the left atrium (LA) remains uncertain. This thesis aimed to determine the impact of PVAI on LA size and function in patients with AF. The existing literature regarding the impact of catheter ablation of AF on the LA shows a great diversity. Several reasons may account for this diversity, including different imaging techniques and methods to assess LA size and function. Therefore, the first part of this thesis focused on comparing different methods to assess LA size and evaluating their accuracy in patients with AF. The first mentioned method, the LAD by echocardiography, is a rough measurement and only includes one dimension of the LA. Therefore, it should not be used as a representative for LA size. The Simpson’s rule with either CT or MRI is considered to be the gold standard for LA size assessment, since it takes into account that the LA is an asymmetrical shape. It is the method of choice for LA volume assessment in research settings. However, for clinical practice this method may consume too much time and, therefore, alternative techniques exist that closely correlate to this gold standard and which are much easier to obtain. Although these techniques have shown to underestimate true LA size, they may have enough precision for LA size assessment in clinical routine. The second part of this thesis studied the clinical implications of the LA in patients with AF and mainly focused on the impact of PVAI on the LA size and function. Two main factors may be responsible for changes in LA size and function following PVAI: 1. remodeling, 2. ablation induced LA fibrosis. This thesis has shown that the LA is influenced by both remodeling as well as ablation induced fibrosis post-ablation. PVAI resulted in a reduction of maximal LA volume in all patients, indicating an effect of ablation induced fibrosis. Minimal LA volume only decreased in patients with a successful outcome, indicating an effect of reverse atrial remodeling. As a result, LA function post-ablation was preserved in patients with a successful outcome and decreased in patients with AF recurrence. These results are of clinical importance since the LA function determines, to a certain extent, the thrombo-embolic risk within a patient. Based on the abovementioned results, it may be defensible to discontinue the anticoagulation several months after ablation in patients free of AF recurrences, because they showed a preserved LA function post-ablation. However, one must be careful because only the effect of PVAI on the LA was examined and no other ablation techniques that involve extensive additional LA ablation were examined. In addition, no different anticoagulation strategies post-ablation were analyzed. Further studies are necessary to evaluate the effects of more extensive catheter ablation in the LA on LA function and thrombo-embolic risks.