Wern Yew Ding, MBChB

Freeman JV, Higgins AY, Wang Y, Du C, Friedman DJ, Daimee UA, Minges KE, Pereira L, Goldsweig AM, Price MJ, et al. Antithrombotic Therapy After Left Atrial Appendage Occlusion in Patients With Atrial Fibrillation. J Am Coll Cardiol. 2022;79:1785-1798.

Patients with atrial fibrillation are at an increased risk of thromboembolic complications, particularly from clot arising in the left atrial appendage. Therefore, percutaneous left atrial appendage occlusion (LAAO) lowers the risk of stroke by mechanically excluding the left atrial appendage from the systemic circulation. Nonetheless, the optimal antithrombotic regime post-device implantation remains ill-defined.

In this study, Freeman and colleagues studied the deviations from full post-procedure treatment protocols in clinical practice compared to pivotal LAAO trials, and evaluated the impact of different antithrombotic treatment patterns on the risk of adverse events. The authors utilized data from the National Cardiovascular Data Registry LAAO Registry, which serves as a formal post-market surveillance vehicle required by the U.S. Food and Drug Administration for the Watchman device. As of April 2016, U.S. hospitals were required to submit data for all Watchman procedures to the LAAO Registry to qualify for Medicare reimbursement.

For the purposes of this analysis, patients who underwent Watchman LAAO between January 2016 and November 2018 were enrolled. Patients who died during their index hospitalization, did not have successful device implantation, and who were treated with rarely used anticoagulant and antiplatelet agents were excluded. Per-protocol was defined as: 1) discharged on warfarin and aspirin; 2) first follow-up assessment at 45 days after procedure; 3) transoesophageal echocardiogram performed in follow-up window; 4) discontinuation of warfarin if residual leak <5mm and no atrial thrombus detected, or continuation of warfarin if residual leak ≥5mm or atrial thrombus detected; 5) second follow-up at 6 months; and 6) taking clopidogrel and aspirin until the second follow-up visit or warfarin and aspirin.

The final cohort comprised of 31,994 patients with a mean age of 76 years, and 41% were female. 70% had suffered prior bleeding. Only 12.2% of patients were treated with the full FDA-approved discharge and follow-up protocols, with the most common deviation due to discharge on antithrombotic medications other than warfarin and aspirin (61.5%). Antithrombotic regimes on discharge included non-vitamin K antagonist oral anticoagulant (NOAC) and aspirin (20.8%), warfarin only (13.5%), NOAC only (12.3%), and dual antiplatelet therapy (5.0%). Using a multivariable Cox frailty regression model, the adjusted risk of any adverse events through the 45-day follow-up visit was significantly lower for discharge on warfarin alone (HR 0.69 [95% CI, 0.57 – 0.84]) and NOAC alone (HR 0.73 [95% CI, 0.57 – 0.93]) compared to warfarin and aspirin. Rates of stroke or transient ischaemic attack and device-related thrombus were comparable across the groups. Warfarin alone retained lower risk at the 6-month follow-up.

Protocol deviation observed in the LAAO Registry was likely due to differences in real-world practice compared to the pivotal trials. Though patients in the pivotal trials were candidates for long-term anticoagulation, Centers for Medicare and Medicaid Services reimbursement mandates that real-world patients are deemed unable to tolerate long-term oral anticoagulation. Overall, this study provides valuable information on antithrombotic regimes post-LAAO with the Watchman device and suggests that warfarin or NOAC alone may be a suitable choice. However, there was increased rates of any readmissions with warfarin or NOAC alone that warrant further investigation. Of note, this study included only patients who underwent the older-generation device rather than the newer-generation Watchman FLX. Also, the findings may not be applicable to other devices used for LAAO.