Mapping and Ablation in Patients with LAA Closure Devices

Left atrial appendage (LAA) closure devices are becoming more commonly encountered in patients undergoing invasive procedures in the cardiac EP lab. Most common is the WATCHMAN LAA Closure Device (Boston Scientific), and in centers enrolling in the Amulet IDE clinical trial, the AMPLATZER Amulet LAA Occluder (Abbott). Patients requiring extensive left atrial ablation provide unique challenges maneuvering around the device, particularly given the importance of ablation along the LAA-PV ‘coumadin’ ridge.

For patients in the aMAZE IDE clinical trial for the LARIAT System (SentreHEART, Inc.), suture ligation of the LAA is intentionally scheduled for catheter ablation of persistent atrial fibrillation using a force-sensing irrigated RF ablation catheter with pulmonary vein isolation (PVI). In contrast to the endocardial devices, ligation of the LAA at the base provides, in our experience, improved tissue catheter contact along this ridge, which may improve effectiveness of PVI. Additionally, patients with a prior AtriClip (AtriCure, Inc.) are often brought to the EP lab for same-day or staged hybrid AF ablation (DEEP-AF clinical trial) for persistent or longstanding persistent AF. The AtriClip provides a firm backstop for contact force, and seems to be adequate for facilitating successful ablation. A smooth-walled LAA stump may be encountered after use of AtriClip or LARIAT, and can be safely mapped and ablated within. 

After WATCHMAN or AMPLATZER Amulet, we have ablated patients with persistent atrial fibrillation, including roof and septal mitral linear ablation with a catheter-only approach (Figure 1), hybrid AF ablation with the EPi-Sense Coagulation Device (AtriCure, Inc.), paroxysmal atrial fibrillation with PVI alone, and focal or re-entry LA flutter (Figures 1 and 2). In all cases (n=9), the ablation was at least past the 45-day period for post-LAAC implant TEE, and these were patients who presented to the EP lab without systemic anticoagulation on board (typically on ASA with clopidogrel, or ASA alone). All patients were successfully ablated and placed on 30 days of apixaban or rivaroxaban post ablation, given concern over endocardial thrombus formation. After 30 days, anticoagulation was discontinued. There were no device dislodgements, and our approach to the procedure when faced with an endocardial device is included below. The ability of an LAA closure device to help us manage patients with active or prior LAA thrombus has been impressive. Patients can have LAA closure followed by catheter or hybrid AF ablation, facilitating restoration of sinus rhythm; in the past, a complete open surgical Maze with LAA closure and clot extraction was their only option. Several of the patients we present had prior or active LAA thrombus, and could not be cardioverted or ablated until the LAA was closed. 

Given the recommendation for antibiotic prophylaxis up to 6 months post-LAA closure device implantation with WATCHMAN, we typically give a dose of IV cefazolin (2-3 gm) or vancomycin (weight-based) prior to vascular access. TEE is generally used to evaluate the closure device prior to transseptal access, but our preferred method for visualization during the ablation is with CARTOSOUND (Biosense Webster, Inc., a Johnson & Johnson company), AcuNav 8 Fr intracardiac echocardiography (Siemens Healthineers) through an SL-0 transseptal sheath from within the left atrium. ICE is positioned close to the RSPV, with the ultrasound beam oriented anteriorly and leftward. This provides excellent direct visualization of the LAA closure device, which can be drawn as individual point tags with contours, and aligned with a pre-procedural cardiac CT angiography (Figures 1-2, and Video 1, Video 2, Video 3, Video 4, and Video 5). For the remainder of the ablation procedure, we will minimize any fluoroscopy and generally use the CARTO map contours to avoid the LAA device. ICE is used to confirm catheter position in relation to the device when ablation is immediately adjacent to it. 

While mapping with the PENTARAY (Biosense Webster, Inc., a Johnson & Johnson company) catheter, we will add data from voltage around the edges of the device; typically, when the ablation catheter reaches the edge or crosses onto the face of either device, an abrupt drop in impedance of at least 30-50 ohms is noted. Metallic artifact on the electrode of the PENTARAY or ablation catheter is also a clue that contact has been made with the LAA device confirmed by direct visualization (Video 2). Due to low impedance limits on the RF generator, an effort to ablate on the surface of the device will typically trigger a cutoff alarm, and RF will be automatically interrupted. We commonly provide AF ablation with a zero-fluoroscopy method with ICE only; however, for post-LAA device implant cases, x-ray imaging is used to verify the initial device position and post-procedure position for comparison. Ablation can be directly observed in proximity to the edge of the LAA device (Video 3 and Video 5). 

Another consideration for subjects who have reached aspirin-only therapy following WATCHMAN or AMPLATZER Amulet implantation is the effect of ablation at the edges of the device, which may disturb the endothelial surface. It is reasonable to initiate off-label low-dose or full-dose systemic anticoagulation for 4-6 weeks to avoid initiating a device-associated thrombus that was not previously present. 

In summary, the full complement of endocardial and epicardial ablation strategies for paroxysmal or persistent atrial fibrillation and atrial flutter are possible following LAA closure device placement. This includes septal or inferior mitral valve isthmus flutter linear ablation, and ablation along the LAA-PV ridge with careful attention to avoid disturbing the edge of the LAA occluder. Our typical practice is to ablate AF with PVI first, followed by LAA closure with WATCHMAN or AMPLATZER Amulet 6 weeks after. Thus, at 90 days post ablation, systemic anticoagulation can again be discontinued long term. While we have not ablated AF and implanted an LAA occluder device during the same index procedure, growing data in support of LAA ligation with LARIAT or AtriClip may be ideally suited for future study as concomitant procedures.

Disclosure: The author has no conflicts of interest to report regarding the content herein. Outside the submitted work, Dr. Ellis reports research grants (Medtronic, Boston Scientific, AtriCure), advisory/consultant/physician proctor (Boston Scientific, Spectranetics), and Clinical Trial Steering Committee (aMAZE IDE trial) for SentreHEART, Inc.