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Page 4 of 13 Maurina et al. Mini-invasive Surg 2021;5:53 https://dx.doi.org/10.20517/2574-1225.2021.88

Marlborough, MA). This device consists of a self-expandable nitinol cage covered by a membrane of
polyethylene terephthalate (PTFE) [Figure 1] which is fully endothelialized by the heart tissue, resulting in
permanent LAA sealing. The implant procedure is performed via the femoral vein with transesophageal
echocardiography (TEE) or intracardiac echocardiography guidance, and its deployment requires a
transseptal approach [Figure 1C]. The second iteration of this device, WATCHMAN FLX, has been
available since 2019 and may overcome some limitations of the first-generation occluders, with its higher
suitability for shallower anatomies.

As of today, this device is the only LAAO device that has been prospectively compared with warfarin in two
randomized controlled trials (PROTECT-AF and PREVAIL [13,14] ) of AF patients without contraindication to
OAC. The antithrombotic protocol of these studies consisted of a post-procedural 45-day period of warfarin
anticoagulation, followed by a 6-month DAPT (aspirin and clopidogrel), which was followed by SAPT
therapy (aspirin) indefinitely. Five-year outcomes of these two trials demonstrated that LAA occlusion
provides stroke prevention in nonvalvular AF comparable to warfarin, with significant reductions in major
bleedings and all-cause mortality (HR = 0.48; P = 0.0003 and HR = 0.73; P = 0.035, respectively) .
[16]
Furthermore, the ASAP study showed that LAAO with the WATCHMAN™ can be performed even in
individuals with an absolute contraindication to OAC . Given the solid scientific evidence, the
[17]
WATCHMAN™ is a widely used device in daily clinical practice, and it was the first percutaneous device
approved for LAA occlusion in the United States (FDA approval in 2015).

The principle of the plug is also exploited by the WaveCrest® (Biosense Webster, Irvine, CA), which
obtained the CE mark in 2013 but is not FDA approved. This device may be useful in very short appendages
as it is deployed more proximal, but it is less commonly used. A prospective, multicenter, randomized trial
(NCT03302494) comparing this device and the WATCHMAN™ is currently recruiting patients in the
United States.

The pacifier principle
The “pacifier-like devices” are inspired by patent foramen ovale and atrial septal defect occluders, consisting
of a lobe that is delivered into the LAA with an additional disc to seal the LAA ostium. As for the plug
system, LAA exclusion relies on endothelialization of the device. The most widely used device is the
Amplatzer™ (Abbott Vascular, Chicago, IL; CE-approved in 2013). Although no randomized trial against
anticoagulation has been conducted, both the first (Amplatzer Cardiac Plug) and the second (Amulet)
generation of this device have shown their efficacy in reducing the risk of ischemic stroke and major
bleeding compared to the predicted risk [18,19] . Compared to the Amplatzer Cardiac Plug, the newest Amulet
has a deeper distal lobe with a more overriding proximal disc resulting in more complete LAA exclusion,
especially for deeper LAAs [Figure 2A and B]. The recently published Amulet-IDE trial confirmed this
finding, showing a higher LAA occlusion rate for the Amulet occluder compared with the WATCHMAN
(98.9% vs. 96.8%; difference = 2.03%; 95% confidence interval (CI): 0.41-3.66; P < 0.001 for noninferiority; P
= 0.003 for superiority) . As for the WATCHMAN™, Amulet deployment requires a transseptal approach
[15]
during echocardiographic guidance. In August 2021, following the results of the Amulet-IDE trial, the
Amplatzer™ Amulet received FDA approval, becoming the second percutaneous LAAO device available in
the United States.

Other Pacifiers are the LAmbre™ (Lifetech, China) and the Cardia Ultraseal™ (Cardia Inc., St Paul, MN). The
former consists of a fabric-enriched cover and an umbrella connected with a central waist , while the
[20]
Ultraseal™ is composed of a distal anchoring bulb and a proximal sail connected with an articulating joint
that allows multidirectional movements and adjustments to different LAA shapes and ostium angles . The
[21]