Discussion:
Transthoracic echocardiography has the inherent advantage of being a fast bed-side tool, providing fast information about the cardiac chamber anatomy and function. Nevertheless, the quality of the acquired images may be severely compromised from the patient habitus and present significant inter-observer variability. In addition, it typically provides a 2D measure of a structure that it is not a perfect sphere, thereby potentially introducing significant error even in good quality images. On the other hand, CMR and cCT provide three-dimensional (3D) datasets of the LA.14 The acquisition of the LA geometry with all of the above-mentioned imaging modalities can vary due to the intravascular fluid state of the patient and timing of heart cycle. The current study is unique in its design for the examination of LA geometry by utilizing a near-real time invasive imaging method. 3D-RA has the inherit advantage of high-quality image acquisition of the LA, eliminating the impact of cardiac cycle and fluid status of the patient on the LA geometry. The direct and fast injection of radiopaque contrast under rapid ventricular pacing at the time point of short-term intracavitary pressure reduction allows the left atrial chamber to acquire its most spherical shape by exhausting at the same time its elastic properties, thus leading to exactly similar baseline hemodynamic conditions for each of the acquired images and allowing a more accurate and reproducible examination of geometrical parameters.22 The scope of the current study was to evaluate the alteration of the LA geometrical parameters after WACA RF-PVI in patients with recurrent AF, in a hemodynamic model that eliminates the impact of cardiac cycle and volume status of the patient.
Our entire population (n=71) showed a decrease of LA volume/LA volume-index and surface and an increase of its LA sphericity after index RF-PVI procedure. A subgroup analysis between patients with paroxysmal and persistent AF was performed and we recorded no statistical difference at baseline values of LA sphericity and volume index between patients with paroxysmal and persistent AF. After RF-PVI however, patients with paroxysmal AF showed a significant increase of their initial LA sphericity. On the other hand, patients with persistent AF also showed a tendency towards increasing of their LA sphericity, without reaching statistical significance. In accordance with previous studies we report an increase of the LA sphericity in patients with recurrent AF after initially successful RF-PVI. 12, 18
Regarding the effect of RF-PVI on LA volume and surface, there was a significant reduction of parameters after index procedure in the entire population, as well as in each series of patients with paroxysmal and persistent AF separately. There are conflicting results regarding the net effect after WACA RF-PVI on the LA volume in patients with AF recurrence. A study by Tops et al. implementing transthoracic echocardiography as imaging modality reported a reduction of the LA volume from baseline only in patients without recurrent AF after PVI.23 On the contrary, Hanazawa et al., report a significant decrease of the minimal and maximal LA volumes using 320-row cardiac MCT after RF-PVI, regardless of AF recurrences.24 Similar findings are reported by Hof et al., when he assessed the LA volume with cardiac MRI after WACA PVI.25 Our findings are in accordance with the two previously mentioned studies, confirming a significant reduction of the LA volume and surface in a series of patients failing to preserve SR after initially successful PVI. This can be explained from the net effect of WACA RF-PVI to the left atrium. The RF-lesions from the wide circumferential LA antrum isolation leads probably to shrinkage of the LA cavity.