Left Atrial Appendage Occlusion Devices for Stroke Prevention
Atrial fibrillation patients are at five times greater risk of stroke overall. Therefore, those with stroke risk factors are put on an anticoagulant medication to prevent the formation of blood clots that can cause afib-related strokes.
Approximately 90% of the blood clots that cause afib-related strokes are formed in the left atrial appendage (LAA), a pouch or sac on the left atrium of the heart.1
An option for people who cannot take anticoagulant medications is closing or occluding the left atrial appendage using an LAA occlusion device. This procedure can be done during catheter ablation, surgical maze, or hybrid ablation procedures or may be done as a standalone procedure to help reduce the risk of stroke.
Some left atrial appendage procedures are done by electrophysiologists, and some are done by surgeons. For example, to close or occlude the left atrial appendage, electrophysiologists can use a WATCHMAN, Lariat, Sierra, LAmbre, Amulet, or Wavecrest device, and surgeons can use an AtriClip device. The purpose is to reduce your risk of stroke without the need for long-term anticoagulation.
LAA occlusion is a valuable option for patients who are not ideal candidates for taking anticoagulant medications. It can also be done as a standalone procedure for those too frail for other afib procedures.
Below are descriptions of these LAA occlusion devices.
The WATCHMAN device (Boston Scientific) received US Food and Drug Administration (FDA) approval in 2015. It is a parachute-shaped, self-expanding device that permanently closes the LAA and reduces the risk of stroke by keeping blood clots from escaping.
The safe and effective use of the WATCHMAN device for closing the LAA and preventing strokes has been shown in two key trials (PROTECT AF2 and PREVAIL3) that compared the use of the WATCHMAN device to warfarin. Together, these trials showed that the WATCHMAN device was similar to warfarin in reducing strokes, clots, and cardiovascular death.
In longer follow-up studies, the WATCHMAN device was associated with approximately an 80% reduction in hemorrhagic (bleeding) strokes and a more than 50% reduction in cardiovascular deaths.
The ASAP-TOO clinical study is assessing the safety and effectiveness of the WATCHMAN device in patients with afib who are deemed unsuitable for oral anticoagulants.
The Lariat (AtriCure) uses a loop of suture material to close off the LAA. A catheter delivers the suture loop in the procedure, slips it around the LAA, and tightens it to close off and isolate the LAA.
The LAALA-AF clinical study4 investigated the impact of adding the Lariat to close the LAA to catheter ablation in patients with persistent afib. Patients who received the Lariat were compared with persistent afib patients undergoing ablation during the same time without the use of the Lariat device.
Sixty-five percent of those who underwent ablation and LAA closure with the Lariat achieved ablation success at one year (freedom from afib and off antiarrhythmic drugs) compared to 39% with conventional ablation. In addition, more patients (33%) in the ablation group that didn’t get a Lariat underwent repeat ablations because of afib recurrence, compared to 16% of patients who received Lariat and catheter ablation.
The aMAZE clinical study examines the safety and effectiveness of the Lariat device in patients who are randomized to two treatment groups. One group includes patients who received LAA closure with the Lariat followed by catheter ablation, and the other group includes patients who received catheter ablation only (without a Lariat).
Although these studies are not stroke prevention trials—they are to determine whether isolation of the LAA can decrease the recurrence of afib—use of the Lariat has the potential to prevent strokes because it closes off the LAA.
The Sierra Ligation System device (Aegis) is similar to the Lariat. However, it closes off the LAA by placing a band around the base of the LAA and clinching it down with a lock.
The LASSO-AF clinical study is examining the safety and function of the Sierra device in closing off the LAA in patients with non-valvular afib.
The LAmbre device (Lifetech) is a self-expanding device shaped like an umbrella that closes off the LAA.
In the LAmbre study,5 successful closure of the LAA was achieved in 99% (152/153) of patients with non-valvular atrial fibrillation across 12 Chinese hospitals. After one year of follow-up, two patients had ischemic strokes, but both had a prior history of stroke. This study provided early evidence that the LAmbre device is effective for LAA closure and stroke prevention. The US FDA has approved a clinical trial in the US.
The WaveCrest device (Biosense Webster) is an implantable device with an umbrella-shaped frame that seals off the LAA so blood clots cannot escape from it.
Results from the WAVECREST 1 trial were presented at the 2014 Heart Rhythm Society Annual Scientific Sessions. The WaveCrest device was used in 73 patients with non-valvular atrial fibrillation from Europe, Australia, and New Zealand.6 The LAA was successfully closed in 93% (68/73) with few adverse events. Two patients had acute tamponade (fluid around the heart). There were no reported cases of device-related clots or strokes.
The WAVECREST 2 study will determine whether the WaveCrest device is as safe and effective for LAA closure as the WATCHMAN device.
The Amplatzer Amulet (Abbott) device is a second-generation occlusion device made up of a disc and a lobe. It conforms to the LAA opening to block it. The Amulet LAA Occluder Trial will determine whether the Amulet device is as safe and effective as the WATCHMAN device for LAA closure.
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The AtriClip (AtriCure) was the first LAA occlusion device to be approved in the US in 2010. The device is used in both open heart and closed-chest surgeries. To place the rectangular-shaped AtriClip device, which looks like a hair barrette, the surgeon positions it around the LAA and “closes” the device, much like a clamp shuts off the blood supply. This prevents blood from flowing into or out of the LAA.
The US FDA approved the AtriClip based on the results of the EXCLUDE clinical trial7 in the US. In EXCLUDE, surgeons successfully implanted the device in 95.7% (67) of patients. In addition, three months after the AtriClip was implanted, computed tomography (CT) and ultrasound scans showed complete closure of the LAA in all but one patient. Of note, stroke itself was not an endpoint in the study.
In a study of 36 patients who were followed for 3.5 years after the implantation of an AtriClip, 100% showed no clot formation in the LAA.8
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