After appendage occlusion, aspirin may be leaving lesions behind

Design

investigator-initiated, prospective, multicentre, randomised controlled trial, 1:1, open to 365 days

Population

164 patients with successful left atrial appendage occlusion confirmed at 45 days, eligible for oral anticoagulation

Primary outcome

patient-level incidence of any new silent cerebral embolic lesion on diffusion-weighted MRI

Effect

12.2% vs 31.7% (P = 0.005); MMSE difference 2.56 (95% CI 1.11-4.01) at 365 days

HALO-SCE randomised 164 patients 1:1 to half-dose rivaroxaban 10 mg daily or antiplatelet therapy, 45 days after confirmed successful left atrial appendage occlusion, with diffusion-weighted MRI and cognitive testing at 90, 180 and 365 days. New silent cerebral embolic lesions appeared in 10 of 82 (12.2%) on rivaroxaban against 26 of 82 (31.7%) on antiplatelet therapy (P = 0.005).

Cognitive scores tracked the imaging. At 365 days the between-group differences favoured rivaroxaban by 2.56 points on the Mini-Mental State Examination (95% CI 1.11-4.01) and 2.67 on the Montreal Cognitive Assessment (1.07-4.26). The composite of death, clinical thromboembolism and major bleeding was 2.4% against 11.0%, which did not reach significance (P = 0.057) in a trial of this size.

The awkward part is the population. These were patients eligible for oral anticoagulation, and appendage occlusion is usually chosen because a patient is not. Read as written, the finding is that in the subset who could take an anticoagulant and had the device anyway, a low dose after implantation beats aspirin on imaging and cognition. Read too broadly, it becomes an argument for anticoagulating people whose bleeding risk was the reason for the device.

• Record why each occlusion patient was not anticoagulated — that reason determines whether this finding applies to them
• Silent embolic lesions are an imaging endpoint; do not describe them to patients as strokes prevented
• Where anticoagulation is tolerated, review the post-45-day antithrombotic plan rather than defaulting to aspirin indefinitely
• Watch for the bleeding signal in larger trials before generalising a 164-patient result

Why it matters

It questions whether the standard post-occlusion switch to antiplatelet therapy is right for the patients who never needed to avoid anticoagulation.

Don't overread it

The primary endpoint is MRI lesions, not stroke, and the population excludes the high-bleeding-risk patients most occlusion devices are implanted in.

The statistics, in plain English

A composite outcome of 2.4% against 11.0% with P = 0.057 means the trial was too small to settle it: the direction favours rivaroxaban, but with 164 patients a handful of events either way flips the result. The imaging endpoint is significant because silent lesions are far commoner than clinical events, which is exactly why it is a surrogate rather than the answer.

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