Decreasing exposure to ionizing radiation during cardiac ablation has been a priority for the last 10 years. The development of electronatomical mapping systems (EAM), magnetic and robotic assisted catheter navigation, and intracardiac echocardiography (ICE) paved the way to perform increasingly more complex ablations with less radiation. Fluoroless catheter ablation, without adding prohibitive cost or procedural duration, is now a reality in the EP lab. An experienced operator proficient in ICE, with an understanding of the heart anatomy as well as the pearls and limitations of EAMs, has the necessary tools to finally free his or her back from the lead apron. In this paper, we describe the steps that, in our opinion, are needed to perform safe and effective fluoroless atrial fibrillation (AF) ablation. For simplicity, we outline the procedure in three stages: 1) placement of a coronary sinus (CS) catheter, 2) transseptal puncture, and 3) pulmonary vein (PV) antral isolation.
To perform fluoroless ablation, the operator must integrate the information provided by EAM and ICE before catheter manipulation and ablation. Commercially available EAM systems such as CARTO 3 (Biosense Webster, Inc., a Johnson & Johnson company) and EnSite NavX (St. Jude Medical) are capable of displaying real-time EP catheters on a three-dimensional shell of the left atrium (LA) and pulmonary veins with detailed accuracy. We use both systems routinely to perform AF ablation. It is our impression that most experienced operators are well familiarized with EAM, but it is the lack of ICE proficiency that prevents them from making the switch to zero fluoroscopy. Thus, in this article we will mainly focus on how to use ICE to perform AF ablation. We will not address PV signal recognition and pacing maneuvers to differentiate them from far-field signals.
Intracardiac echocardiography adds an extra layer of information and safety not achieved with EAM and fluoroscopy alone. Although the invaluable assistance of ICE to perform transseptal puncture is well recognized (Figure 1), it is frequently ignored for the rest of the procedure. ICE utilization is beyond imaging the interatrial septum (IAS). The exquisite real-time images of the LA and adjacent structures have eliminated the need in our practice to obtain cardiac CT or MRI pre-procedure to delineate the anatomy in advance or merge the images with the electronatomical map. ICE provides real-time anatomical information; thus, if the LA volume changes or our reference catheter moves during the procedure, we can quickly correct it.
Briefly, there are two types of ICE: rotational and phased-array transducers. Rotational ICE has a single rotating piezoelectric transducer that produces a circular picture perpendicular to the long axis of the catheter when driven at frequencies of 9 MHz or higher. It has a very high resolution, but lacks penetration (i.e., visualization of far-field structures). The phased-array ICE uses a 64 piezoelectric element linear array transducer and produces a sector scan perpendicular to the long axis of its shaft (Figure 2). The transducer is mounted on a deflectable catheter with motion in four planes: anterior, posterior, rightward, and leftward rotation. It has a tissue penetration of 2-15 cm. When ICE is mentioned in this paper, we will be referring to the phased-array transducer. We use the ViewFlex Plus ICE Catheter (St. Jude Medical) or SOUNDSTAR (Biosense Webster, Inc., a Johnson & Johnson company) depending on the hospital facility where the ablation is being performed.
In this paper, the image sector orientation of ICE images is from left to right (L/R) of the operator, corresponding with the anatomical position of the right and left atrium facilitating catheter navigation (Figure 2). On the contrary, we prefer to reverse the orientation of the images (R/L) when ablating ventricular tachycardia. In this orientation, the ventricular septum will be to the right side of the screen (i.e., in the anatomical position).
The rule when advancing the ICE catheter without fluoroscopy is not to push if there is any resistance, and to always have a clear echo space in front of the ICE (Figure 3A). When a 9 or 10 French (Fr) ICE catheter is used, a longer vascular sheath (41 cm) may be occasionally required to navigate the iliofemoral venous angle. The 8 Fr ICE catheter (ACUNAV and SOUNDSTAR) handles any abrupt venous turn well with careful manipulation and without the need for a long vascular sheath, with similar quality ultrasound images. However, due to its lighter weight once in the heart, it requires a gentler manipulation and has a more pronounced bouncing motion with every heartbeat. This creates a less steady picture in some patients. Nonetheless, we find the 8 Fr ACUNAV/SOUNDSTAR very easy to manipulate without fluoroscopy, with possibly less risk of cardiac perforation. The SOUNDSTAR catheter also provides integration with electronatomical mapping (Videos 1-5) by simply “drawing” the ICE contour of the LA, LAA ridge, and PVs. The esophagus is visualized as a set of “bright stripes” behind a clear space, the oblique sinus. For all these reasons, the 8 Fr SOUNDSTAR with the CARTO system is our default ICE catheter of choice. A decapolar catheter is placed in the esophagus to delineate the esophagus if EnSite NavX is used (Figure 3B).
Placement of a Coronary Sinus Catheter
Prior to CS catheter placement, a basic rudimentary geometry of the right atrium (RA) is created with the ablation catheter or the CS catheter (EnSite NavX). Subsequently, the catheter is displayed on two perpendicular views (RAO and LAO) on EAM following the same principles as when fluoroscopy is used. The ICE "home" (view of the RA and TV) helps to steer the CS catheter away from the RV, and by slightly clocking the ICE catheter, one might observe the tip of the catheter engaging the coronary sinus (Video 6). The LAA is also routinely visualized to rule out a clot before transseptal puncture. It can be imaged from the RA, LVOT, or pulmonary artery (Figure 3C). Although it is now rare since heparin is administered immediately upon sheath placement, clot formation around the long vascular sheaths is still appreciated with ICE (Video 7). Clot aspiration and repeated bolus of heparin is given until there is full resolution of clots in multiple ICE planes. Once this is confirmed, and with careful monitoring of the patient’s hemodynamics, transseptal puncture is attempted. A quick look is taken to evaluate the presence of pericardial fluid prior to accessing the left atrium.
Heparin is administered intravenously prior to performing two transseptal punctures. It is crucial to obtain an ICE view of the superior vena cava (SVC) to confirm placement of the guidewire in the SVC (Figure 4). The guidewire frequently advances into the right atrial appendage or the RVOT. If the guidewire is not clearly visualized in the SVC, the sheath and dilator should never be advanced further, or it could be catastrophic. The whole apparatus (sheath + needle + dilator) is pulled back slowly along the SVC (Video 8) to the right atrial septum guided on ICE. The tip of the dilator should be pointing towards the left atrium and not to the free wall of the SVC on ICE (Video 8). Clocking the whole apparatus will direct the tip of the dilator to the septum. While the whole apparatus is close to the interatrial septum, a slight release of the rightward rotation and clockwise motion of the ICE catheter will provide visualization of the posterior LA body and the pulmonary veins. A BRK-1 transseptal needle (St. Jude Medical) placed through the dilator can be visualized on ICE as a bright image (Video 8). Tenting should be clearly seen on ICE aiming towards the left PVs (Video 9). If the RIPV has a very low take off, the transseptal puncture can be directed lower. The direction for transseptal puncture can be safely adjusted on ICE to find the most advantageous point. The tip of the dilator occasionally slides up and down the interatrial septum, particularly if the septum is aneurismal; slight rotation of the needle while holding the sheath steady is required before advancing it. A deflectable sheath or a different curve might also help in these situations. In case of a fibrotic or double septum, ICE allows safe applications of radiofrequency (RF) energy to the puncture needle without the need to apply extreme pressure (Video 10). There is no need to mark the aorta with a pigtail or place a catheter in the His region, in our opinion. Recording LA pressure and visualization of the transseptal needle in the LA is sufficient to confirm LA access.
PV Wide Antral Isolation
The antrum of the PVs, carina, and LAA ridge are carefully delineated once in the LA by roving a 10- to 20-pole electrode catheter within the chamber with CARTO 3 or EnSite NavX. When CARTOSOUND is used, the LA and PV shells already built with the ICE catheter from the right atrium are further redefined with a contact catheter in the left atrium. As stated before, we do not perform a cardiac CT/MRI, and rely solely on ICE and EAM to define the anatomy of interest.
The sheath/ablation catheter is manipulated along the posterior wall of the LA around the left PVs and right PVs as a “first pass” to find a path with stable contact force (>10-40 grams) (Video 11), avoiding the esophagus. The veins are then isolated in couples, and if there is a middle right vein, it is usually incorporated in the wide atrial isolation within the ipsilateral veins. Ablation starts at the posterior LA from the LIPV up to the LUPV, and anteriorly from top to bottom (Figure 5). The right PVs are ablated anteriorly from low to high, and then posteriorly from top to bottom. While delivering RF energy, it is important to follow the tip of the ablation catheter and deflectable sheath not only on EAM, but on ICE as well. Thus, the ICE catheter is adjusted to image the posterior wall of the LA when ablating posteriorly around the left PVs and anteriorly (clockwise from the home view about 50 degrees with leftward rotation) when ablating around the left PV and LAA ridge (Figure 5F). In the same fashion, the ICE follows the catheter during ablation of the right PVs (Figure 6). ICE is very useful to confirm ablation is performed proximal to the ostium and on the PV side of the LAA ridge. The sheath position is also visualized on ICE, so they can be adjusted to increase or decrease contact force as needed. Frequently, ablation within the carina is needed to disrupt the connections between PVs or ablate PV triggers. At the end of the procedure, a quick sweep with the ICE catheter will exclude the presence of pericardial effusion, and confirm integrity of the mitral valve apparatus. Because our ablation lesions are quite proximal to the PVs, interrogation of the veins with Doppler to rule out PV stenosis is less frequently performed.
Finally, ICE is also extremely helpful to define the anatomy of the cavotricuspid isthmus with the presence of pouches or a prominent Eustachian ridge that frequently limits catheter contact, critical to achieving bidirectional block (Video 12).
This paper illustrates our approach at IU Health Saxony and Methodist Hospitals for using ICE in combination with EAM to perform safe and effective ablation of atrial fibrillation without fluoroscopy.
Disclosures: The authors have no conflicts of interest to report regarding the content herein.