The shape, length, and size of the pulmonary infundibulum vary from patient to patient and are independent of RV size [13, 14]. Therefore, the precise anatomic boundaries of the RVOT cannot be obtained by fluoroscopy alone, resulting in incomplete mapping of the SOO or damage to the thin RV free wall. This can be prevented by delineating the anatomic shell of the RVOT with the ICE before EAM (Fig. 3). The long- and short-axis views of the RVOT provide accurate boundaries of the supra- and infra-valvular regions and pulmonary semilunar leaflet. The LAD lies near the LPC and APC. It was reported that catheter ablation in the RVOT was associated with occlusion of LAD [15]. Additionally, severe pulmonary valve insufficiency with moderate proximal pulmonary artery stenosis was reported following RFCA ablation guided by EAM [16]. Complication during RVOT ablation is rare [4, 5] and is hindered by ICE assessment of the precise regional anatomy with continuous monitoring of the catheter position in critical structures such as valves and coronary arteries.
The rare but most serious complication during LVOT ablation is coronary artery injury. A recent systematic review article including 43 studies has reported three cases of coronary injury during LVOT and SoV ablation [17]. Although coronary angiography is usually performed before ablation, it is difficult to accurately determine the relationship between the actual positions of the catheter and the coronary artery during the entire cardiac cycle using fluoroscopy. Furthermore, aortic valve injuries during catheter ablation for VAs are rare but possible [18]. The short-axis view in the RV provides an accurate location of the ostium and course of the coronary arteries, as well as an excellent transverse view of the AV. Ablation at least 1 cm from the coronary ostium is generally safe [6]. Therefore, ICE use can overcome the limitations of fluoroscopy-based ablations, allowing for real-time visualization of the ablation catheter considering its proximity to the coronary artery.
ICE use also enables continuous monitoring of catheter-tissue contact, enabling effective energy delivery to the arrhythmogenic substrate. In addition, lesion formation can be identified as increased echogenicity and tissue thickness during ablation (Fig. 4) [19]. For these reasons, the utilization of ICE will enhance the effectiveness of catheter ablation.
The CARTO® 3D mapping system with the CARTOSOUND® module (Biosense Webster) can superimpose EAM on ICE-generated 3D images. There are several advantages that can be obtained by integrating ICE 3D images with EAM. First, precise delineation of the anatomic contour of the OTs using ICE enables more meticulous EAM that is essential to find SOO. Without clear anatomical boundaries, locations that are hard to reach with a mapping catheter can be omitted. However, acquisition of the anatomic shell of OT using ICE before EAM can guide EAM without missing spots. Second, the integration of 3D ICE images with EAM is particularly beneficial in mapping aortic SoV and coronary arteries that are not well visualized by fluoroscopy and EAM. When LVOT VA is suspected, the location of the aortic cusps and ostium and proximal course of the coronary arteries is initially delineated using ICE. Then, this anatomic information can be added to the 3D EAM to ensure a safe distance from coronary arteries without the need for a coronary angiogram or preprocedural imaging such as cardiac computed tomography and magnetic resonance imaging. Therefore, it will enhance the ability to map and determine the SOO of arrhythmias and reduce radiation exposure.
