Imaging for Left Atrial Appendage Closure Procedures

Can you describe the structural heart program at HonorHealth?

Robert Burke, MD, Director of Noninvasive Cardiodiagnostics and Structural Heart Imaging: We have been performing structural heart procedures for the past 8 years, since the commercialization of transcatheter aortic valve replacement (TAVR). In addition to TAVR procedures, we do MitraClip (Abbott Vascular), Watchman (Boston Scientific), and patent foramen ovale (PFO)/atrial septal defect (ASD) closure. We participate in clinical research and were one of the biggest enrollers of the REPRISE III trial, which compared the Boston Scientific Lotus valve to the Medtronic Evolut valve. We are involved with Abbott Vascular’s Tendyne mitral replacement valve, which currently is implanted transapically.

One of our ongoing research projects is the use of Volume ICE (Siemens Healthineers) as an adjunct with MitraClip. Volume ICE is a 3D intracardiac echocardiography (ICE) catheter with a 90 x 50 degree field of view, which is more than the current standard and therefore permits improved visualization of more anatomic structures and with better detail, particularly the tricuspid valve.

We are a maximalist program, in that almost all of our TAVR procedures are done under general anesthesia and with transesophageal echocardiography (TEE) imaging. We prefer to use TEE because we believe it makes a difference in our patient outcomes, in being able to guarantee that we have the best results possible. We typically do 4 to 5 TAVR procedures per week, with over 150 cases per year, and have done about 150 MitraClip procedures. We are averaging probably 2 to 3 left atrial appendage closure (LAAC) procedures per week and thus far have done over 100 Watchman procedures. We use the cath lab at HonorHealth Scottsdale Shea Medical Center for these procedures. We have not found working in a cath lab to be a limitation at all, in terms of being able to do what is needed. We have a Siemens Artis PURE angiography system that was put in place earlier this year and that has the ability to do imaging overlay with TrueFusion (Siemens Healthineers). TrueFusion imaging, which allows overlay of echo images on fluoroscopy, can be very useful, such as for placing a marker when performing transseptal puncture. This additional ability to do overlay helps to simplify procedures and maneuvers from the standpoint of the interventional cardiologist.

What are some of the challenges of left atrial appendage closure (LAAC)?

Dr. Burke: Imaging is a huge part of the procedure. For example, to optimize the location for transseptal puncture, imaging helps you identify the appropriate low and posterior part of the fossa ovalis. This location will help provide a good trajectory, positioning the delivery catheter to enter the left atrial appendage along the left axis so the Watchman device can be successfully deployed.

David G. Rizik, MD, Director of Structural and Coronary Interventions: There are challenges to this procedure on multiple fronts. The historical domain of LAAC was that of the electrophysiologists and they carried forward from its embryonic stages (both in the clinical trials and in the initial attempts at commercialization). One of our primary goals is making certain that those patients who are eligible candidates are actually evaluated for the procedure. There are estimates that <5% of eligible patients who would benefit from Watchman undergo this procedure. Therefore, therapy awareness and triaging patients to mechanical left atrial appendage closure is critical.  Another challenge is developing a strong multidisciplinary team like all other structural disciplines. That team consists of an interventional cardiologist, an electrophysiologist, and imaging specialists. Unlike other structural procedures such as TAVR and transcatheter mitral valve intervention, LAAC is not generally dependent on the involvement of a surgeon. There are programs that do have surgical involvement, but those are less common. There is a high priority on expert involvement of imaging specialists. Since there are a number of anatomic variations in the left atrial appendage, this is key to a successful program. Studies have shown that given the technical challenges of this procedure, the learning curve may be as high as 50 cases. Our own program has benefited from Dr. Burke’s keen knowledge of all aspects of the procedure from transseptal puncture to left atrial anatomy.  Aspects such as catheter manipulation, catheter choice, and sizing are all very important, and are learned skills that benefit from a close relationship with your imaging team members in order to move your program forward. From a procedural standpoint, probably the thing that is most important and can be the hardest to learn is transseptal technique. Those who are just learning the Watchman may need to first do a primer or refresher on transseptal technique. I would say that from where I sit, optimal transseptal technique is the single most important technical aspect associated with implant success.

Dr. Burke: Imaging is essential to do a safe and accurate transseptal puncture. Interventionalists have been performing transseptal puncture well before any TEE was developed; they were doing it without any echo guidance whatsoever. But in order to make a procedure successful and safer, we need to have an idea of where we are in space. Echo imaging is essential to determining where it is most appropriate to cross the septum. The biggest bonus of having TrueFusion technology is that it allows us to work within the volume space of 3D echo along with fluoroscopy. The fusion overlay is done in real time. It does facilitate a certain degree of comfort for the interventionalist to be able to see what is going on not only on fluoroscopy, but on echo. Echo can seem a little strange as a way to visualize the anatomy, particularly because we are now looking at areas of the heart that we previously did not pay any attention to. There was either a hole in the septum or there wasn’t — it used to be a binary situation. Patients either had a PFO or didn’t, and that was mostly what we needed to know about the anatomy. With all of these different valve or device technologies, whether it is the Watchman, MitraClip, or other left-sided procedures requiring that you cross the septum, it is important to be able to visualize the septum, know your landmarks, know what is going to happen if you cross in certain areas, and what potential complications could be. Being able to work in a familiar visualization, like fluoroscopy, and add in echo at the same time using TrueFusion is a major benefit.

Dr. Rizik: I remember not so long ago that virtually all transseptal procedures were guided by fluoroscopy rather than echo guidance. It was much more challenging to predict high or low septal crossing, whether you were to anterior or posterior — therefore, there was a higher likelihood of suboptimal transseptal access. The success of a LAAC procedure is irrevocably linked to the crossing location on the septum relative to the left atrial appendage. Echocardiographic guidance gives us the ability to be very precise. To “set yourself up for success”, an accurate transseptal puncture is critical, not just for Watchman procedures, but also for transcatheter mitral therapies, along with other interventions. The ability to be very precise and more guided when performing transseptal puncture has been revolutionary for interventional cardiologists, as we are learning a whole new way of looking at transseptal technique similar to that of expert imaging physicians.

Dr. Burke: Proper positioning allows us a better opportunity to place a device accurately and with only one attempt. It is a lock-and-key type approach. By choosing the right spot on the atrial septum, the catheter, which is pre-formed with a specific curve, will enter into the left atrial appendage in a way that allows for it to chase the long axis of the left atrial appendage. There is a certain curve to the delivery catheter that will allow it to reach into the left atrial appendage, but the initial puncture must facilitate this positioning, so you don’t end up working against your equipment.

Do you see a significant amount of anatomic variability?

Dr. Rizik: Doing a TEE on a 25-year-old is probably easier than doing it on an 85-year-old. Like with every other organ system, 85-year-olds experience degenerative changes that extend to and include the esophagus. We do run into challenges with esophageal pathology. A simple one that comes to mind is the 85-year-old patient who has a hiatal hernia, which is not an unusual occurrence and does create a challenge for TEE guidance of the procedure. It is frequent that the imaging has its own set of challenges, and this is where it is essential to have an imager who is patient, and who is going to make certain that he or she gets the views that are needed.

Dr. Burke: These cases are not all textbook where you drop the probe down, see everything with one predefined view, and don’t have to think about it. There is a lot of variability with the anatomy. Some of these patients have had prior surgery, so all of the standard views are going to be off by rotation and sometimes are not obtainable at all. You need to be much more flexible in your way of approaching these cases, because they are not all going to be the same.

Are there other device options on the horizon in addition to the Watchman device?

Dr. Rizik: Several companies are currently in the development or investigational stages. Other companies are in the process of finishing clinical studies. Abbott Vascular is in the process of developing the Amulet device. And, Boston Scientific is now looking at the next generation of Watchman and even the generation after that, based on feedback from implanting physicians and imaging physicians.

What about follow-up for LAAC patients?

Dr. Burke: Follow-up is mandated by protocol. Currently the requirement is a 45-day post implant TEE, which is needed to determine whether or not there is any evidence of thrombus, if there is appropriate closure around the device and if there is any para-device leak. If we do find para-device leak, we need to quantify it, and it becomes a go/no-go situation. If there is too much leak (>5 mm), we need to continue with antithrombotic therapy, typically warfarin with a target INR of 2 to 3. If there is no evidence of leak and no evidence of clot, then we are able to discontinue the antithrombotic therapy and initiate dual antiplatelet therapy with aspirin and clopidogrel. Dual antiplatelet therapy goes until 6 months post implant, with required follow-up at one year that includes a repeat TEE.

Any final thoughts?

Dr. Burke: Understanding echo and fluoroscopy for these procedures, and particularly anything for the left-sided procedure where a transseptal puncture is required, is an area of expertise that a structural cardiologist is going to have to master. Being facile with fluoroscopic imaging and echo imaging is essential to being able to do it well, do it safely, and do it efficiently.

Dr. Rizik: Members of the Baby Boomer generation will not be turning 80 until about 2050. In the future, we are going to be doing more of these procedures, and therefore, being able to perform the implant with greater efficiency while maintaining quality will be extremely important. Having world-class imaging allows us to achieve a high degree of proficiency, efficiency, and excellence in performing these procedures. 

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Disclosures: Dr. Burke reports the following: Abbott Vascular, consulting/proctor; Boston Scientific, consulting/proctor; Edwards, consulting/proctor; Medtronic, consulting/proctor; Siemens, consulting/proctor, research support. Dr. Rizik reports the following: Abbott Vascular, Medical Advisory Board; HeartFlow, Medical Advisory Board; Boston Scientific, Executive Physician Council, grant/research support, consulting/proctor, license fees.

Dr. Robert Burke can be contacted at rburke@honorhealth.com.

Dr. David Rizik can be contacted at drizik@honorhealth.com.