John Day, MD, FHRS, FACC
The Journal of Innovations in Cardiac Rhythm Management
Director of Heart Rhythm Services
Intermountain Medical Center
Salt Lake City, UT
Within this issue we will visit the diverse topic of stroke prevention in atrial fibrillation (AF), a concept that continues to evolve with both mechanical and pharmacological innovation. In order to demonstrate the different treatment options for these patients, this issue offers a series of manuscripts from respected colleagues from the field, along with a commentary by our Innovative Techniques Section Editor, Samuel Asirvatham. Certainly, there are many new left atrial appendage closure (LAAC) options for stroke prevention in AF, and the content within this issue should help to outline these new and innovative approaches.
Having just returned from the 2012 Heart Rhythm Society Annual Scientific Sessions, I would like to comment on late breaking clinical trials and studies evaluating left atrial appendage closure (LAAC) devices that were presented at the conference. The first is the ASAP Trial,1 evaluating the Watchman Device (Boston Scientific, St Paul, MN), presented by Vivek Reddy, and the second is a study evaluating the LARIAT Device (SentreHEART, Inc., Redwood City, CA) presented by Randall Lee.2 I would also like to share our experience at Intermountain Medical Center in LAAC, and offer some perspectives on the direction of this procedure.
The ASAP Study, or “ASA and Plavix” Study, is critically important to the field of mechanical AF stroke prevention in that it is a feasibility study designed to evaluate whether or not the Watchman can be used in patients who cannot take warfarin. This was a non-randomized study, enrolling 150 patients from four European centers with an average CHADS score of 2.8 who had an anticoagulation contraindication. Following implantation, patients were treated with both aspirin and clopidogrel for six months, at which time the clopidogrel was discontinued and patients were continued indefinitely on aspirin. This study was unique in that prior Watchman studies required transient warfarin use following implantation before warfarin could be discontinued.
The ASAP Study demonstrated a 95% Watchman implantation success rate, which was higher than the initial Protect AF Study.3 In this rather sick cohort of patients, in which 29% had congestive heart failure, 95% were hypertensive, 42% were over age 75, 32% had diabetes, and 41% had a prior TIA or stroke, they observed 3 ischemic strokes which corresponded to 1.7 events per 100 patient years. The 1.7 strokes per 100 patient years represents a 77% reduction in the expected stroke rate based on the CHADS score. Despite not using warfarin in this high stroke risk cohort of patients, the event rate was actually lower than the Protect AF Study (2.2 strokes per 100 patient years in Protect AF) despite this group of patients having a higher average CHADS score (2.8 in ASAP versus 2.2 in Protect AF).
Clearly, the ASAP Study was remarkable in that it demonstrated a feasibility to avoiding warfarin altogether (or a comparable anticoagulant) following implantation of the Watchman. This is a huge benefit to our patients, as many have a contraindication to warfarin or one of the newer anticoagulants. Remarkably, there were no embolic strokes seen in the year of follow-up. There were two deaths that occurred more than six months following the procedure, and were unrelated to the procedure. The Watchman has been approved in Europe since 2009, and we can only hope that the FDA will soon approve this device in the United States.
We recently collaborated with 5 other centers in presenting data at the recent Heart Rhythm Society Annual Scientific Sessions in Boston discussing our results of AF ablation following implantation of the Watchman.4 In this study of 22 patients at a mean of 10 months out following Watchman placement, there were no complications or ablation challenges from the Watchman device. Interestingly, the LAA was only electrically active in 32% of the patients. If there was incomplete closure of the LAA, then the LAA was more likely to be electrically active. Despite most patients having persistent AF, the one year ablation success rate was 73%.
Another LAAC study presented as a late breaking clinical trial at HRS was titled “Percutaneous Left Atrial Appendage Exclusion Using the LARIAT in Patients with Atrial Fibrillation: Initial Clinical Experience and Long-Term Results.2” In this study, patients were enrolled if they had a warfarin contraindication and had a CHADS score of at least 1.
For those of you who may not be familiar with the LARIAT Device, it is an Endocardial/Epicardial LAAC approach. By means of a transseptal puncture, a magnetic wire is placed inside of the left atrial appendage. Then, via a percutaneous epicardial approach through the pericardial space, a second magnetic wire is introduced which “finds” the first magnetic wire in the LAA. Next, over this Endocardial/Epicardial magnetic wire bridge, a LARIAT suture is inserted over the wire in the pericardial space to find the LAA and snare it, ultimately resulting in necrosis of the LAA. Following the procedure, the only thing that remains in the body is a suture ligating the LAA. Thus, nothing is exposed on the endocardial side, and there is no need for warfarin or other anticoagulants.
In this non-randomized single center study, a total of 119 patients were evaluated for LAA ligation with the LARIAT. Due to anatomy challenges or LAA thrombus, only 89 patients (75%) could proceed to LAA ligation. Of these ligated patients, 95% had elimination of their appendage by transesophageal echocardiography. There were three procedural related complications, two of which were related to pericardial access and one with transseptal access and no device complications. While pericarditis was only seen in two patients, chest pain was observed in 25% of the patients, which was primarily due to the pericardial drain temporarily left in place immediately after the procedure. Remarkably, there were no embolic strokes seen in the year of follow-up. There were two deaths that occurred more than six months after the procedure, and were unrelated to the procedure.
This study is particularly exciting in that this LARIAT technology is currently available in the United States via a 510(K) approval process with the FDA. Thus, despite the paucity of data currently available on the LARIAT, this technology can be used today in the United States as the first approved percutaneous LAAC device. Of course, one limitation of this technology is that patients must have an intact pericardium to allow pericardial access and delivery of the LARIAT suture.
So what is our experience at the Intermountain Medical Center with the percutaneous LAAC devices? We have been implanting the Watchman Device since 2007 as part of the Protect AF Study. Following the completion of Protect AF, we have continued to implant the Watchman as part of their registry and then the Prevail Study. To date, we have implanted ninety devices. In this cohort, we have not had any cases of tamponade and have seen no embolic strokes or embolization. There were only two patients in which a Watchman could not be placed.
More recently, we have now experienced the LARIAT suture delivery device in three patients, performing percutaneous LAA ligation. All three cases were successful. One patient required a longer hospital stay due to challenges related to the temporary pericardial drain placed immediately following the procedure.
Figure : Image taken from a recent LARIAT left atrial appendage closure case at Intermountain Medical Center. The sheath on the left is endocardial via a transseptal approach, with the balloon placed at the base of the left atrial appendage. Contrast is being injected to opacity the appendage. The tip of the transseptal wire has a magnet, which is magnetically connected to an epicardial wire. The sheath on the right is inside of the pericardial space via a percutaneous approach. The LARIAT suture is being placed around the appendage from an epicardial approach.
Clearly this is an exciting time with regards to mechanical AF stroke prevention. While we have all seen countless cases where a surgeon has left a “stump” of the left atrial appendage following cardiac surgery, these percutaneous LAAC devices truly offer an advantage in that it is rare if the appendage is not perfectly closed. The greatest limitation of these LAAC devices has to do with ease of use. The Watchman is still challenging to place in many patients, and the LARIAT also presents challenges given the requirement for percutaneous pericardial space access. Prior to embarking down the LAAC road, I had no idea of just how anatomically complex the appendage is with multiple lobes and other anatomic challenges. Also, complete closure of the appendage requires strict attention to correct device placement.
In the EP world, we would also like to see a LAAC device that may be placed at the time of atrial fibrillation (AF) ablation. I worry that the Watchman or other endocardial LAAC devices, such as the Amplatzer Cardiac Plug (St. Jude Medical, Minneapolis, MN), may not be the best devices to use at the time of AF ablation. With AF ablation, we often get significant local edema along the ridge between the LAA and the left sided pulmonary veins. With this local edema, we may not get optimal closure if the endocardial LAAC device is placed at the time of AF ablation. Moreover, the long procedure times associated with AF ablation could increase the infection risk, and with an endocardial LAA device it could make future ablation of tachycardias arising from the LAA very difficult to ablate. In addition, the Amplatzer Cardiac Plug leaves a rim just outside of the LAA, which could make it even more difficult to perform AF ablation anywhere near the LAA.
On the other hand, the use of an epicardial LARIAT suture could get around this local tissue edema issue along the ridge with AF ablation. The LARIAT offers another advantage, in that the LAA tissue is necrosed, which eliminates future tachycardias arising from the LAA. However, the need for anticoagulation following AF ablation could delay the time before a pericardial drain may be pulled following the use of the LARIAT, and the necrosed LAA could lead to chronic pericarditis. Stay tuned- as this is a rapidly evolving field and future generation LAAC devices are sure to overcome many of these initial challenges.
I would also like to highlight a video presentation of a live LAAC case performed by Vivek Reddy, at the 2011 AF Innovations event, utilizing Watchman technology. The patient in this case suffered from asymptomatic paroxysmal AF. Complimentary access to this video presentation can be found on our website, www.InnovationsInCRM.com, by clicking the Innovations Case Theater link in the middle of the page and following through to the Left Atrial Appendage Closure presentation. Information on the upcoming 2012 AF Innovations event can be found at www.AfibInnovations.com.
In addition to stroke prevention, this issue of the Journal offers highly engaging manuscripts on topics such as left ventricle function recovery in a patient with mechanical prosthetic tricuspid vale, and strategies to manage complex arrhythmias following robotic cryo maze ablation procedures, to name just a few. I hope you enjoy this issue of Innovations in Cardiac Rhythm Management, and as always, your direct feedback is welcomed.