We read with interest the meta-analysis of Jeevanantham et al titled “Meta-Analysis of the Effect of Radiofrequency Catheter Ablation on Left Atrial Size, Volumes and Function in Patients With Atrial Fibrillation,” published in the May 2010 issue of The American Journal of Cardiology . The relevance of the investigators’ report is evident, because, as they correctly stated, the effects of catheter ablation on the left atrium are still unknown. After analyzing 17 reports concerning this subject, the investigators concluded that left atrial (LA) size decreases after ablation of atrial fibrillation (AF) and that LA function remains unaffected. When analyzed on the basis of AF recurrence, decrease in LA size was significant only in patients without AF recurrence. In addition, patients with AF recurrence showed a significant decrease in LA function.

Jeevanantham et al mention several limitations in their discussion, including the imaging techniques used in the different studies and, more important, the different methods to determine LA size and function. In our opinion, especially the latter deserves more attention, because the method used to determine LA size considerably affects the accuracy of the conclusions noted previously. The investigators did not consider the fact that some studies have used the accurate Simpson’s rule to determine LA volume, whereas others have used rough dimensions to estimate volume and some have measured only 1 diameter as representative of LA size. LA diameter correlates poorly with LA volume measured by Simpson’s rule and is an ill and imprecise measure of LA size. Additionally, LA size calculated by dimensions is not very suitable for patients with AF, who often have asymmetric enlargement of the left atrium, and has been shown to underestimate true LA size. To our knowledge, 4 studies have been published in which LA size was measured before and after catheter ablation of AF using the most precise method and the most accurate imaging modality (Simpson’s rule by either computed tomography or magnetic resonance imaging). Two of these studies were recently published and are not included in the meta-analysis by Jeevanantham et al. Interestingly enough, even these 4 reports provide very diverse results, thus making it difficult to come to a consistent conclusion regarding the effect of catheter ablation of AF on the left atrium.

Therefore, it must be concluded that despite the meta-analysis performed by Jeevanantham et al, the impact of catheter ablation on LA size and function remains uncertain. Furthermore, comparing studies using different imaging techniques and different methods to determine LA size seems like comparing apples and oranges.