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Page 6 of 13 Maurina et al. Mini-invasive Surg 2021;5:53 https://dx.doi.org/10.20517/2574-1225.2021.88

[24]
after both the epicardial and endocardial magnet-tipped guidewires have been connected together . After
[24]
initial encouraging results , subsequent multicenter studies reported high periprocedural complications
with high rates of serious pericardial effusions [25,26] , which led the FDA to announce safety issues in 2015. For
this reason, the use of the LARIAT™ has been significantly reduced and this device is actually limited to rare
cases of difficult anatomies, unsuitable for fully endovascular closure. Interestingly, every device, except the
LARIAT™, is made of nitinol, a mixture of nickel and titanium; therefore, device selection in patients
severely allergic to nickel (e.g., extensive cutaneous reactions) is limited to the infrequently used ligation
system, if deemed suitable by the operator.

Thoracoscopic surgical closure
A special consideration has to be made for epicardial LAA occlusion. As many patients develop recurrent
AF after catheter ablation, may be unsuitable for the percutaneous procedure, or prefer a more durable
intervention, thoracoscopic surgical AF ablation may be a valid alternative in patients with refractory and
[27]
symptomatic AF . In these cases, since LAA electrical isolation creates an akinetic and highly
[28]
thrombogenic cul-de-sac , concomitant thoracoscopic LAA clip closure may be indicated. The AtriClip®
(AtriCure, Inc. West Chester, PA, USA) is an FDA-approved device for epicardial LAA management. This
device, consisting of a preloaded nitinol cap, is placed at the level of the epicardium at the base of the LAA,
resulting in a complete LAA exclusion . It has proven to reduce the incidence of stroke in AF patients
[28]
undergoing heart surgery . Moreover, the recent LAAOS III trial, which randomized AF patients
[29]
undergoing cardiac surgery to concomitant LAA closure (some of which with AtriClip®) or no closure,
demonstrated a relative stroke risk reduction of 33% at 3.8 years, suggesting the potential benefit of this
procedure . However, up to date, these results can be applied only to AF patients undergoing cardiac
[30]
surgery, while the potential benefit of this procedure in patients undergoing thoracoscopic AF ablation
remains hypothetical, requiring further dedicated research.

LAA imaging
Before proceeding with LAA occlusion, imaging is fundamental to assess LAA anatomy and plan the
procedure strategy. The main aspects to evaluate are the absence of LAA thrombosis and the LAA shape
and size, to check for device compatibility. TEE and computed tomography angiography (CCTA) are the
exams of choice. Even if CCTA may achieve high positive and negative predictive values and specificity,
TEE is generally considered the gold standard in ruling out LAA thrombosis.

Thrombosis is visually confirmed with a careful evaluation of LAA body through different imaging planes,
while LAA emptying velocity evaluation provides additional data about blood stasis. Low peak LAA
emptying velocity (< 40 cm/s), in fact, may indicate a pro-thrombotic state and is a strong predictor of
thrombus formation . Moreover, TEE with 3D acquisitions plays a fundamental role in evaluating LAA
[31]
anatomy and device compatibility, as it allows carefully analyzing the LAA without intravenous contrast-
medium injection. Good quality 3D images (preferably at high framerate with multi-beat acquisition) may
be post-processed to evaluate LAA depth, width, morphology, and orifice diameters. Furthermore, TEE
images are useful to choose the most suitable occluder type, with specific measurements guiding the
selection of the correct device size. In particular, the Amulet’s size is determined measuring the LAA orifice
and the device landing zone (10-12 mm inside the orifice) at different angles, while WATCHMAN requires
measurements of the orifice diameter and LAA depth.

As mentioned above, CCTA with 3D multiplanar acquisitions is a valid alternative to TEE in preprocedural
planning as it allows evaluating the LAA anatomy and provides a high level of device selection accuracy .
[32]
A small study even showed that LAA ostial perimeter measured on CCTA, compared to LAA TEE
diameter, was associated with better prediction of the optimal device size . However, it is less specific than
[33]