There are now two transcatheter left atrial appendage (LAA) occlusion devices cleared by the U.S. Food and Drug Administration (FDA) and a couple more are expected to soon enter FDA investigational device exemption (IDE) trials. Experts presenting in LAA occlusion (LAAO) sessions at the 2022 Transcatheter Valve Therapeutics (TVT) Structural Heart in June said this offers patients more options to treat a large variety of anatomies.
LAA sessions at TVT include discussions on new devices in development, issues frequently encountered and how to over come them, and what type of imaging is best for pre-planning and procedural guidance.
In atrial fibrillation (AFib) patients, the LAA, a pocket the extends off the left atrium, has been implicated as the main source of clots that form embolisms and cause strokes. While anticoagulation therapy is the standard-of-care in AFib, there are many patients who are at a higher risk of bleeding. LAAO uses a transcatheter device implant to close the LAA in select AFib patients so they can reduce or eliminate anticoagulation drugs or other blood thinners.
The two FDA-clear LAA occluder devices in the U.S.
There are now two next generation FDA-cleared LAA occlusion (LAAO) devices – the Boston Scientific Watchman FLX and the Abbott Amulet. Both use small barbs to offer better device anchoring than the first generation LAA occluder on the market.
"These devices set a new bar," explained Devi Nair, MD, FACC, FHRS, director of cardiac electrophysiology at St. Bernard's Healthcare, Jonesboro, Arkansas. "The safety of this therapy is extremely good, and the efficacy rates are extremely good, and stroke rates are extremely low in patients who cannot tolerate anticoagulation therapy."
The first generation Watchman was cleared by the FDA in March 2015. This device has the largest amount of clinical data gathered to date. Based on operator feedback, the device was redesigned and replaced in 2020 by the new Watchman FLX. The redesign includes a better seal and anchoring for the device.
The Amulet gained FDA in August 2021. It was designed with two sealing components to better close off the LAA, rather than the single seal competent used on the Watchman. The Watchman requires the patient to continue taking anticoagulation drugs, while the Watchman's screen is endothelialized to ensure a complete closure of the LAA.
Abbott says the double sealing components of the Amulet are designed to enable patient discharge after the procedure without the need for anticoagulation. The device fits in a broad range of anatomies and has the widest range of occluder sizes on the market. It also is recapturable and repositionable to ensure optimal placement.
Remaining issues with LAA occlusion devices
Despite the good performance of the latest generation LAAO devices, some problems remain. These include peri-device leaks and device related thrombus formation. These have led to new designs for occluders working their way through pre-clinical and clinical trials. There are also issues involving imaging to properly size the devices needed for the procedure. Sometimes devices end up being undersized, which can embolism, or the device will form a poor seal.
Why pre-procedural imaging is important for LAA occluder device implants
One of the debates in sessions at TVT was whether computed tomography (CT) imaging is needed for preplanning these procedures, when transesophegeal echo (TEE) can be used for sizing and live procedural guidance. A few experts said the CT measurements are more accurate, so the cost and extra time involved for the CT is worth while.
Nair said between the two FDA-cleared devices, one might fit a patient's anatomy better than the other to achieve an optimal seal, so it is good to be able to understand the anatomy better before going into a procedure.
"Some of the software allows you to perform a virtual implant with the devices to see which one fits better and how the device sits within the appendage," she said. These include the TruePlan and FEOPS software.
If a patient can get a CT scan, there are many computational algorithms that help make these procedures so simple, Nair said. "It almost takes the surprises away, so you walk into the case knowing what anatomy you are going for, you know the dimensions, you know if the patient has a thrombus, and you know what the ideal landing zone is needed for transeptal punctures, and you know which device is a better option."
If a procedure can be pre-planned prior to getting into the cath or EP lab, she said it can cut procedure time and help eliminate the need for general anesthesia. Having CT images of the anatomy also makes it easier to use catheter-based 3D intracardiac echo (ICE) rather than needing TEE.
She said 3D/4D ICE is more expensive, but the higher image quality is needed to perform transcatheter procedures in 3D anatomy. There are three of these devices now on the market being used to guide structural heart and EP procedures, including MitraClip and LAAO procedures. Nair said you need to access the left atrium to image the LAA, but once there, she said there is not much manipulation of the catheter needed. She said 3D ice also allows for sizing of the device, which Nair said she would never try to do using 2D ICE.
However, cost is the main issue. At $3,400 for each imaging catheter, it is just not cost effective, said Rahul Sharma, MBBS, director of structural interventions at Stanford Healthcare. He said they size off of TEE.
Brijeshwar Maini, MD, regional medical director of structural heart, Tenet Florida Health, presented a case of a patient where the echo clearly was showing the wrong sizing for the occluder. In the case, they tried three different sizes until they found the actual size that proper fit. He advocated for pre-procedural CT scans.
However, if an operator is very experience and does a lot of LAA cases each year, they are probably comfortable enough and look at TEE or ICE and properly size the appendage. However, for operators that only do a small number, like five a year, they would be better off with the CT imaging.
CT has the added advantage of showing if a patient has a thrombus in the LAA prior to the procedure. This raises concerns that the clot can embolism during the procedure once catheters are inserted into the appendage. This is why CT is a standard-of-care for Jacqueline Saw, MD, interventional cardiologist at Vancouver General Hospital and St Paul’s Hospital, and clinical assistant professor at Vancouver Coastal Health Research Institute. She said it offers additional information on the patient and she also conducts all of her sizing depth measurements from the CT.
Next generation LAA occlusion devices in trials
There are several new LAAO devices in development that will try to overcome some of the issues with the current technology. A few of these are already in trials. These include the CLAAS Conformal, Laminar, LAmbre and devices that may combine ablation with LAAO. Some devices being developed are for specific LAA anatomies, she said.
Nair was involved in the early feasibility study of the Conformal device, implanting 10 of them. The device is expected to enter an FDA pivotal trial soon.
"The beauty of the device is that it comes in just two sizes, regular and large, so the sizing is very easy," Nair explained. She added the device is also more fluoro dependent, so there is less reliance on TEE.
She said the LAmbre device is also expected to begin its FDA pivotal trial soon.
"Having one device that fits all appendages would be great, but I think it will be challenging with the different variations of anatomies, with different take offs and different orientations within the left atrium," Nair explained. "But, if we can get a device that offers complete closure without having to go into the more distal parts of the appendage and is more conformable, we would be in a good place."
Related LAAO Content:
VIDEO: Advances in left atrial appendage occlusion technology — Interview with Devi Nair, MD