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.