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How to Perform Pulmonary Vein Antral Isolation for Atrial Fibrillation

Carola Gianni, MD, PhD; Marco V. Perez, MD; Amin Al-Ahmad, MD; Andrea Natale, MD

Introduction

Pulmonary vein antral isolation (PVAI) is the achievement of PV electrical isolation through ablation of the circumferential regions around the PV ostia. In addition, during early embryonic development, the PV smooth muscle cells extend over the posterior wall (PW) of the left atrium (LA), some aspects of the roof as well the right atrial septum, just anterior to the ipsilateral PVs.¹ These areas can be considered part of the PV antrum, and including them when performing PVAI targets many of the arrhythmogenic sites located in the LA, potentially modifying other factors such as neural inputs into the LA. This approach for ablation of atrial fibrillation (AF) has gained acceptance, as it has been associated with improved long-term outcomes as well as an acceptably low rate of complications.²

Preprocedural Planning

Left Atrial Imaging

All patients undergo cardiac evaluation with preprocedural imaging. A standard 2-dimensional (2D) transthoracic echocardiogram (TTE) is most commonly used. LA dimensions, morphology of the interatrial septum (for example, thickening or aneurysm Video 14.1) and other abnormalities seen on echocardiography are important to note for the procedure. In some individuals, additional imaging with either computed tomography (CT) or magnetic resonance imaging (MRI) might be also utilized. On cardiac CT or MRI, the antrum appears to be a funnel-like structure (Figure 14.1). These images also yield valuable information regarding the anatomic features of the PVs and left atrial appendage (LAA) (Figure 14.2), including abnormalities such as a common PV os, accessory PVs ( Video 14.2), or anomalous PV return.

When an electroanatomic mapping (EAM) system is used, the CT scan can either be placed for a side-to-side comparison (Figure 14.3) or superimposed on the electroanatomic map. While preoperative cardiac CT and MRI are useful in defining the antrum, they are not required to perform the procedure, mostly due to the utility of intracardiac echocardiography (ICE). Use of ICE immediately before and during ablation is helpful for anatomic orientation: it helps to define where the tubular part of the PV enters the LA and the location of the catheters in the antrum relative to the PVs (Figure 14.4; Video 14.3).

Stroke Prevention

Patients in AF undergoing PVAI will either convert to sinus rhythm during ablation or will be electrically cardioverted immediately following ablation. To minimize embolic risk, a transesophageal echocardiogram (TEE) is often performed prior to the procedure primarily to rule out the presence of a LAA clot. TEE is usually done the morning of the procedure or the day prior. Patients with a CHA₂DS₂-VASc score of 0 may undergo TEE only if AF lasts greater than 48 hours, but many patients with a CHA₂DS₂-VASc score ≥ 1 will undergo a TEE regardless of their rhythm, especially if the patient is anticoagulated with warfarin and the INRs have not been checked weekly prior to ablation. Alternatively, ICE can also sometimes be used to visualize the LAA just before obtaining transseptal access (Figure 14.5). Another important strategy to minimize the risk of periprocedural stroke is performing the procedure while on uninterrupted oral anticoagulation (therapeutic warfarin or factor Xa inhibitors); this reduces the risk of stroke without increasing the risk of bleeding.³ Keeping patients on uninterrupted anticoagulation can mitigate the use of TEE in some patients.

Procedure

The majority of our patients undergo PVAI under general anesthesia; alternatively, moderate to deep sedation/anesthesia can be employed. General anesthesia has many advantages, but the most important in this context is that it helps control respiration by eliminating deep breathing. Moreover, pain thresholds and response to sedation vary significantly, resulting in the patient moving and snoring. Therefore, catheter stability is enhanced during general anesthesia, leading to more effective energy delivery and thus reducing procedural times and improving long-term outcomes.4 A Foley urinary catheter is commonly placed in patients after sedation since the volume of fluid given during the procedure with an irrigated-tip catheter is typically up to 1 to 2 liters; however, in patients who do not need extensive ablation, we are no longer placing a urinary catheter routinely, as the current ablation catheters utilize less fluid volume. Finally, a temperature probe is placed into the esophagus to monitor both the esophageal position and the luminal temperature when ablating in the posterior aspect of the LA.

Central venous access is obtained with real-time ultrasound guidance; this reduces the number of attempts, time to access, risk of arterial puncture, and vascular complications.5 Two 8-Fr sheaths are placed in the right femoral vein and later replaced with the transseptal sheaths. An 11-Fr sheath is placed in the left femoral vein for placement of the ICE catheter. Finally, a 7-Fr sheath placed in the right internal jugular access is used to pass a 20-pole deflectable catheter positioned in the CS such that the distal 10 poles are in the CS and the proximal 10 poles are in the RA. We do not routinely place an arterial line for hemodynamic monitoring given the higher risk of hematomas in anticoagulated patients: noninvasive intermittent blood pressure monitoring every 2 to 5 minutes is generally sufficient.

After a quick assessment of the pericardial space to note the presence of any baseline effusion, a heparin bolus is given before the transseptal puncture (usually 100 U/kg up to 10,000 U with warfarin, or 12,000 to 15,000 U with factor Xa inhibitors). The goal activated clotting time (ACT) is 350 to 500 seconds. ACT is checked every 15 minutes during the procedure, and repeat small boluses might be necessary to keep the ACT at goal.

Transseptal Puncture

Two separate transseptal punctures are performed under ICE guidance. Care is taken to cross into the LA along the posterior interatrial septum, such that the left-sided PVs are in clear view ( Video 14.4). Manual pressure can be used to advance the transseptal needle within the sheath and dilator across the septum into the LA. Additionally, radiofrequency (RF) is frequently used to facilitate access, requiring less force and more control to cross into the LA. This can be done using an electrocautery pen set to cut at 20 to 40 W and applied externally near the hub when the needle is advanced out of the dilator to puncture the septum. Alternatively, a dedicated RF-powered transseptal needle is commercially available; the tip is blunted, making perforation unlikely without RF energy application. A successful transseptal puncture is confirmed with visualization of contrast or bubbles in the LA on fluoroscopy or ICE (Video 14.4), respectively. After the first transseptal puncture, the circular mapping catheter (CMC) is advanced through the transseptal sheath and fixed in one of the PVs during the second transseptal puncture to prevent losing access. Although a second transseptal sheath can be introduced via wire exchange, a separate transseptal puncture minimizes sheath-to-sheath interaction.

Selection of Transseptal Sheaths and Catheters

LA access can be obtained using a variety of transseptal sheaths. Sheaths with a moderate primary curve and no secondary curve, such as the SL-0 for the ablation catheter and a LAMP-90 for the CMC, allow easier catheter maneuverability in the posterior aspect of the LA.

The CMC is used as a roving catheter for mapping and directing the ablation catheter throughout the procedure. It should be small enough to move within the chamber easily but of a large enough diameter that it does not readily fall deep inside the PVs. In most adults, a 20-mm, 10-pole CMC provides a balance between maneuverability and size. Although the procedure may be performed without it, CMC-guided ablation allows for much more efficient targeting of electrical potentials, and it is the most effective way to confirm complete PV isolation.

RF energy delivery with open-irrigated catheters is the standard of care in performing PVAI. Open-irrigated catheters allow the use of greater power without a significant increase in temperature and clot formation, enabling more efficient and predictable energy delivery, resulting in larger ablation lesion sets. The main disadvantage of using open-irrigation catheters is a higher risk of steam pops: there is a high discrepancy between the recorded tip temperature and the actual tissue temperature, which means that steam pops might occur even with normal tip temperature. Another limitation is delivery of excessive energy to the posterior wall. This can lead to damage to the esophagus. These can be minimized with appropriate titration of energy delivery, as guided by monitoring tip temperature, impedance drop, and if available, contact force.

Our catheter of choice is a unidirectional, open-irrigated, 3.5-mm tip catheter with an F curve. A smaller curve may be considered in the minority of patients with a very small LA, while a J curve is necessary for patients with a larger LA.

Mapping

The use of 3-dimensional (3D) EAM systems has facilitated PVAI significantly. Although not necessary to perform PVAI, these systems permit efficient registration of ablation sites and documentation of the extent of antral ablation (Figure 14.6). Any EAM system may be used, with the EnSite NavX/Velocity (St. Jude Medical, St. Paul, MN) and CARTO 3 (Biosense Webster, Diamond Bar, CA) systems being the most popular. They allow near real-time display of any cardiac catheter during ablation; most important, their ability to display the CMC allows for very rapid creation of a LA volume map and facilitates the direction of the ablation catheter towards the desired poles. While maneuvering the CMC, care should be taken not to displace it anteriorly, as this can result in its entrapment in the mitral valve apparatus, a rare complication that might result in valve damage requiring open heart surgery.

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