Based upon the increased thrombogenicity as previously described and the stasis that is manifest in the localized region on the LA and particularly the LAA, the approach to intervening to prevent stroke in association with AF could be with either of two potential options. The first approach, which is decades old with clear delineation of its benefits and risks, is to counteract the thrombogenicity resulting in the presence of the stasis by treating with anticoagulants. The range of intravenous, subcutaneous, and oral anticoagulants are all potentially successful avenues to assist in counteracting this effect. An alternative would be to eliminate the local environment where that thrombogenicity is most manifest or to prevent the emergence of thrombi from that local environment (LAA).

Although appearing simple, there are multiple limitations associated with long-term anticoagulant therapy [37]. These include:

Increased bleeding, both major and minor, is inherent to all antithrombotic therapy. In a meta-analysis including 50,578 patients from three randomized trials, Capodanno et al. [38] reported major bleeding rates of 5.0 % and 5.4 % for NOAC and warfarin, respectively. Even minor bleeding may lead to discontinuation of antithrombotic therapy and exposure to stroke risk. A local solution that offers the benefit of embolic protection in the absence of the long-term risks associated with systemic anticoagulation would be an attractive solution.

The potential avenues to remove the local environment would be to excise the LAA, to occlude its ostium therefore separating the thrombogenic environment from the left heart circulation, or to place a filter at the ostium that would prevent the emergence of thrombi that may form distally into the systemic circulation. The challenges of such an approach are multiple, with many potential pitfalls depending upon the approach that is adopted. Almost all the approaches must contend with the issue of: where is the ostium of the appendage? This leads to a number of further issues:

Based upon the distinct approaches adopted, each will have variable benefits and failures: e.g., surgical excision may leave a cul de sac or miss a proximal lobe, surgical stitching or stapling have the same issues but also residual or recurrent leak [39, 40]. Different devices (e.g., Watchman and ACP) define the ostium differently, which may be distinct to the true anatomical ostium resulting in different depths of deployment [41, 42]. This may result in device-dependent distinctions in depths of residual cul de sac and subsequent efficacy.