ICE/IVUS images analysis
Out of the 48 PV cross-sections, 3 were discarded because of poor quality and 45 (28 ICE and 17 IVUS frames) were considered adequate for quantitative analysis.
Compared to the IVUS cross-sections, the ICE ones showed larger lumen and vessel diameters and areas, larger wall thicknesses and significantly lower lumen and vessel sphericity indexes, indicative of more oval/elliptical shape of both lumen and vessel contours (Table 2). Of note, median pre- and post-ablation wall thickness index percentage (WTI%) and muscular sleeve thicknesses did not differ between ICE and IVUS-imaged PVs.
As detailed in Table 3, statistically significant increases of mean wall thickness, wall thickness index (WTI) and WTI%, suggestive of acute wall thickening, were observed after ablation in both ICE and IVUS cross-sections. A significant reduction of the thickness of the muscular sleeve was also observed after ablation [ICE cross-sections: median (IQR) percentage reduction= 8.2 (0-45.9) %; IVUS cross-sections: median (IQR) percentage reduction= 31.68 (14.54-81.64) %], with complete disappearance of the muscular sleeve after ablation in 6 PVs out of 45.
When grouping by ablation technology used for PVI (RF, cryo or laser), the increase in WTI% was observed only after RF treatment (p = 0.003) and laser treatment (p = 0.003), whilst no significant changes in wall thickness were observed after cryo ablation (p = 0.69) (Figure 3, Table 4).
A single case of vessel dissection was documented after ablation (right inferior pulmonary vein after cryoballoon ablation) (Figure 4).