BACKGROUND: Percutaneous left atrial appendage occlusion (LAAO) has emerged as a nonpharmacological alternative for stroke prevention in patients with non-valvular atrial fibrillation ineligible for chronic anticoagulation therapy. Large real-world observational studies have consistently reported the efficacy of LAAO in reducing the risk of ischemic stroke and systemic embolism, compared to predicted rates, without the need for anticoagulants. Despite ongoing refinement in LAAO procedural technique, significant challenges persist. Notably, device-related thrombus (DRT) remains the main concern after LAAO. The reported incidence rate varies, ranging from 3% to 7%, and has been associated with an elevated risk of ischemic stroke and all-cause death following LAAO. Several risk factors have been identified with DRT occurrence, most of which are non-modifiable. The diagnosis of DRT is followed by an intensification of the antithrombotic treatment. However, not all DRT are resolved, with a significant number persisting or recurring upon withdrawal of anticoagulation therapy. In these situations, the antithrombotic treatment must be maintained, increasing the risk of bleeding, and mitigating the potential benefits of LAAO.

Both persistent and recurrent DRT have been linked to an increased risk of thromboembolic events when compared to resolved DRT. In the pooled analysis of data from the PROTECT-AF and PREVAIL trials, around 12% of embolic events in patients with DRT occurred in the presence of multiple DRT episodes. The incidence of persistent DRT has been reported in one out of three patients diagnosed with DRT, with DRT recurrence occurring in one out of five patients. However, the real incidence of persistent and recurrent DRT is uncertain, as current data come from retrospective studies with non-standardized imaging follow-up protocols. This situation leads to a significant number of missed cases, increases the risk of bias, and likely underestimates the rate of persistent and recurrent DRT. The timing of the imaging follow-up can significantly affect the incidence of DRT. In consecutive patients examined through a pre-specified protocol, the incidence of specific findings would be much more accurate compared to imaging examinations based exclusively on a single adverse clinical event, where the real incidence and clinical associations cannot be accurately determined.

The EHRA/EAPCI expert LAAO statement recommends imaging within 6-24 weeks and then 12 months post-procedure, with no mention of imaging follow-up in case of persistent or recurrent DRT. In contrast, the recent SCAI/HRS expert consensus statement on transcatheter LAAO suggests that repeat imaging at 45- to 90-day intervals can be conducted to assess for DRT resolution and consider the eventual cessation of anticoagulation, although there is no evidence that support this recommendation. Finally, considering the substantial rate of recurrent DRT and its clinical implications, a long-term and sequential imaging follow-up strategy may be warranted. Therefore, there is an unmet need for dedicated prospective data to determine the real incidence, related factors, and clinical impact of persistent and recurrent DRT after LAAO.