The following are key points to remember from a state-of-the-art review on the clinical impact, predictors, classification, and management of device-related thrombus (DRT) after left atrial appendage occlusion (LAAO):

1. This review provides an up-to-date overview of DRT post–left atrial appendage closure, its timing, detection, predictors, and optimal management. It also proposes a unified classification of DRT and hypoattenuated thickening (HAT) commonly encountered in post-LAAO surveillance imaging studies.
2. There is no unified definition of DRT. A thorough review of the major LAAO trial protocols reveals no consensus definition of DRT, underscoring the ambiguity of its interpretation in literature.
3. Rates of reported DRT have varied in clinical trials. In a meta-analysis of 10,154 patients who underwent post-LAAO surveillance imaging in 66 studies, the pooled incidence of DRT was 3.8% (351/10,153).
4. There was no statistically significant difference in DRT rate between the two study arms (3.4% Watchman Series [Boston Scientific, Marlborough, MA] vs. 4.8% Amulet). However, there is variation in the timing of DRT based on device used. In the Amulet arm, a majority of DRTs occurred early (<45 days), while in the Watchman arm, most were identified later than 45 days.
5. Transesophageal echocardiography (TEE) is regarded as the gold standard for device surveillance following LAAO, and for the diagnosis of DRT; however, optimized cardiac computed tomography (CCT) imaging can also be used. In general, TEE has been shown to be less sensitive than CCT in detecting and delineating peri-device leaks; both modalities appear to be comparable in the diagnosis of DRT.
6. The association between DRT and thromboembolic events has been inconsistent in the literature. Unfortunately, the limited granularity in the published literature precludes the ability to discern which specific DRT characteristics pose the highest risk of DRT-related ischemic events.
7. Prior stroke/transient ischemic attack and permanent atrial fibrillation (AF) were the most consistent patient-related DRT predictors, while implant depth was the most consistent procedural risk factor. Whether post-LAA antithrombotic regimen predicts DRT remains challenging to prove. While some studies showed a strong correlation between the type of antithrombotic therapy after the procedure and lower incidence of DRT, others showed no association.
8. Once DRT is diagnosed, resumption of anticoagulation is currently the standard of care. Numerous observational studies suggested that resumption of anticoagulation resolves DRT in >95% of cases. However, patient-level registries show less favorable results and there remains concern for recurrent DRT.
9. Advanced imaging protocols will be helpful in providing more consistent classification and interpretation of DRT and HAT. Magnetic resonance imaging using specific scan protocols that can detect methemoglobin, a component of fresh thrombus, might hold diagnostic potential at an early stage of DRT development. Similarly, computational fluid dynamics applied to CCT may further increase our ability to predict the risk of DRT in individual AF patients and could become an integral part of LAAO preplanning.
10. Changes to existing devices and new novel devices may help limit risk of DRT. The novel Watchman FLX PRO device features a fluoropolymer coating added to the fabric membrane of the device. This novel coating has in preclinical animal studies shown to inhibit thrombus formation, reduce inflammation, and facilitate endothelium ingrowth. Trials are underway to explore its clinical performance.

Clinical Topics: Interventions and Imaging

Keywords: Atrial Appendage, Coronary Occlusion, Thrombosis

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