4.1 Main findings
Our main findings were as follows: (1) female sex was more prevalent, BW was lower, and the distance between the NCC and anterior LA wall was less in the LVZ Group than in the No LVZ Group; (2) the size (area) of LVZs on the anterior LA wall at LA-ascending aorta contact areas correlated negatively with the aorta-LA angle and positively with the aorta-LV angle and the NCC diameter; and (3) the aorta-LV angle correlated negatively with BW and BMI, whereas the aorta-LA angle correlated positively with BMI.
In general, LVZs are commonly seen in patients with AF. The incidence among patients with persistent AF is 35%, and among patients with paroxysmal AF, the incidence is 10%. LVZs have been shown to independently predict AF recurrence after PVI,3,12 and LVZs reflecting LA remodeling are frequently detected in the anterior LA wall.6,10,11 With the ascending aorta being the structure closest to the LA, we hypothesized that mechanical compression caused by an anatomically deviated or expanded ascending aorta leads to the development of LVZs on the anterior LA wall.6 The aorta-LA angle was narrow and the aorta-LV angle was wide in our study patients with anterior LA wall LVZs, suggesting that the ascending aorta had sunk into the anterior LA wall due a deviation in its course and distention of the NCC. These deformities might have been the result of aortic root dilation due to aging and hypertension.13,14 The NCC is adjacent to the anterior LA wall, and, because of the relatively low LA pressure, it might easily collapse against the LA. Our anatomical findings support our hypothesis. The increased LA pressure in the LVZ Group also supports our hypothesis.
The anterior LA wall LVZs were more prevalent among female patients than among male patients. Generally, the thoracic cavity is smaller in females than in males. Deviation in the course of the ascending aorta and a dilated sinus of Valsalva in patients with a relatively small thoracic cavity might increase intrathoracic pressure. Mechanical compression of the LA by the aorta might promote local myocardial fibrosis and electrophysiologic remodeling. In such cases, the intrathoracic space, which normally compensates for the pressure gradient, would be limited.
We thus suggest that dilation of the aortic root leads to the development of LVZs on the anterior LA wall. LA remodeling is generally thought to be related to the arrhythmic substrate. However, in our study, we found no association between LVZs on the anterior LA wall and AF recurrence after ablation. Remodeling of the anterior LA wall may contribute little to the arrhythmic substrate.