Impact of Infarct Volume on Safety and Efficacy of Early DOAC InitiationTrial shows early blood thinners help stroke patients with heart issues

International journal of stroke : official journal of the International Stroke Society Published August 3, 2026 Study authors: Nash Philip S, Best Jonathan G, Lyon James, Ruffle James K, Amornpojnimman Thanyalak, Mendel Rom, Fo… PubMed ↗ DOI ↗ Editorial oversight: Dr. Amelia Tan, PhD · Internal Medicine & Chronic Disease

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Key Takeaway

Early DOAC initiation within 4 days is safe and effective regardless of ischemic stroke infarct volume.

Clinical management of patients presenting with acute ischemic stroke (AIS) and concurrent atrial fibrillation involves a critical decision regarding the timing of anticoagulation. A primary concern for clinicians is whether large-volume infarctions increase the risk of symptomatic intracranial hemorrhage (sICH) when direct oral anticoagulants (DOACs) are initiated promptly. This prespecified secondary analysis of a randomized controlled trial involving 3,572 patients sought to determine if infarct size influences the safety profile or clinical outcomes of early versus delayed DOAC administration.

The study compared early initiation (within 4 days of symptom onset) against delayed initiation (7-14 days). The primary endpoint was a composite of recurrent ischemic stroke, symptomatic intracranial hemorrhage, and systemic arterial embolism within a 90-day follow-up period. By stratifying results by infarct volume, researchers aimed to identify if specific patient subgroups were at higher risk for complications when treated aggressively in the acute phase.

Data analysis revealed that the timing of anticoagulation did not significantly interact with the size of the infarct. Specifically, patients with large infarctions (defined as >25 mL) did not experience a statistically significant increase in symptomatic intracranial hemorrhage compared to those with smaller lesions. The results across various volume categories—ranging from 0-5 mL to over 50 mL—showed consistent safety profiles for early intervention.

From a clinical perspective, these findings are substantial. They suggest that the presence of a large ischemic lesion is not an absolute contraindication or a reason to delay anticoagulation in patients with atrial fibrillation. The lack of interaction between infarct volume and outcome suggests that the physiological risks associated with larger strokes do not necessarily translate into increased bleeding complications when using modern DOACs.

While this was a prespecified secondary analysis, the large sample size provides high-quality evidence for clinical practice. The data indicates that clinicians can confidently initiate anticoagulation within 4 days of stroke onset for patients with atrial fibrillation, regardless of the initial imaging findings regarding infarct volume. This allows for earlier stabilization and prevention of recurrent embolic events.

In conclusion, the study reinforces a proactive approach to anticoagulation in the post-stroke period for patients with AFib. There is no evidence to suggest that delaying treatment based on the size of the initial stroke provides any safety benefit or improved clinical outcome. Standardized protocols for early DOAC initiation can be applied broadly across different infarct sizes without increasing the risk of major hemorrhage.

How this fits prior evidence

This prespecified secondary analysis of a randomized trial (n=3572) extends prior evidence on antithrombotic management in atrial fibrillation and stroke. It confirms the safety of early DOAC initiation, aligning with prior coverage that shortened dual antithrombotic therapy (1 month) is non-inferior to 12 months for efficacy with reduced bleeding. It also complements findings that implantable cardiac monitors detect high AF prevalence (21.3%) in post-stroke patients, reinforcing the need for timely anticoagulation. The result that infarct volume does not modify the treatment effect addresses a gap in prior evidence, which did not specifically examine timing by infarct size.

For people who experience an ischemic stroke caused by an irregular heartbeat known as atrial fibrillation, the timing of medication is a critical decision. Doctors must decide when to start blood-thinning medications, which are used to prevent future strokes. This research looks at whether starting these medicines quickly—within four days of the stroke—is safer and more effective than waiting a week or two, especially for patients with large areas of brain damage.

The study involved a large group of 3,572 patients who had suffered an ischemic stroke and also had atrial fibrillation. Researchers divided these patients into two groups. One group received a direct oral anticoagulant (DOAC) early, within four days of their stroke. The other group received the same type of medication but with a delay of seven to 14 days. The goal was to see if the size of the initial brain injury changed how well the medicine worked or if it increased the risk of bleeding in the brain.

The results showed that starting the blood thinner early did not change based on the size of the stroke. Whether the patient had a small, medium, or large area of damage, the timing of the medication did not show a significant difference in outcomes like recurring strokes or internal bleeding. Specifically, for patients with very large brain injuries (over 25 milliliters), there was no increase in serious bleeding when they started their medication early compared to those who waited.

It is important to remember that this specific study was a pre-specified secondary analysis of a larger trial. While the results are encouraging because they suggest that early treatment is consistent across different types of stroke sizes, it is still one piece of evidence in a complex medical field. The study does not prove that waiting is ever better; rather, it suggests that for those with large strokes, starting medication early did not lead to more bleeding than delayed starts. For patients and families right now, this means that the decision to start blood thinners quickly after a stroke is supported by data. The size of the initial brain injury does not appear to be a reason to delay treatment for those with atrial fibrillation. Patients should continue to work closely with their neurology and cardiology teams to determine the safest timing for their specific health needs.

What this means for you:

Early blood thinner use after stroke is consistent in safety and effectiveness regardless of the size of the brain injury.

Study Details

Study typeRct

Sample sizen = 3,572

EvidenceLevel 2

PublishedAug 2026

PMID41906919

View Original Abstract ↓

BACKGROUND: Randomized trials have demonstrated that early anticoagulation after acute atrial fibrillation-associated ischemic stroke is safe and non-inferior to delayed initiation. Whether anticoagulation should be delayed in people with larger infarcts is uncertain. AIMS: To investigate whether ischemic stroke infarct volume, measured precisely by segmentation, modifies the treatment effect of early anticoagulation with a direct oral anticoagulant (DOAC). METHODS: We did a prespecified secondary analysis of OPTIMAS (NCT: 03759938), a randomized, parallel-group, open-label trial with blinded outcome assessment which randomized people with acute ischemic stroke and atrial fibrillation to early initiation of any licensed DOAC, within 4 days of onset, or delayed initiation 7-14 days from onset. The primary outcome was a composite of recurrent ischemic stroke, symptomatic intracranial hemorrhage (ICH), and systemic arterial embolism within 90 days. A central neuroimaging laboratory determined infarct volume using diffusion-weighted magnetic resonance imaging (MRI) using a validated deep learning segmentation model; on computed tomography (CT), infarcts were segmented manually. We modeled infarct volume as a continuous variable using restricted cubic splines and tested for an interaction with treatment allocation in mixed effects logistic regression. RESULTS: We included 3572 participants (mean age = 78 ± 10 years, 45% female), 98.6% of the main trial population. The effect of early versus delayed anticoagulation did not vary with infarct volume (p = 0.18). Rates of the primary outcome were 17/568 (3.0%) and 12/599 (2.0%) for early versus delayed initiation with infarcts of 0-5 mL; 6/220 (2.7%) and 11/229 (4.8%) with infarcts of 5-10 mL; 13/258 (4.6%) and 10/283 (3.5%) with infarcts of 10-25 mL; 6/145 (4.1%) and 8/145 (5.5%) with infarcts of 25-50 mL; 1/93 (1.1%) and 7/94 (7.4%) with infarcts of >50 mL; and 14/481 (2.9%) and 10/430 (2.2%) in participants with no infarct visible on clinically acquired brain imaging. Corresponding odds ratios and 95% confidence intervals were 1.52 (0.71-3.20), 0.55 (0.20-1.51), 1.29 (0.55-3.00), 0.74 (0.25-2.21), 0.13 (0.02-1.11), and 1.25 (0.55-2.86), respectively. There were no increased rates of symptomatic ICH with respect to anticoagulation timing for those with large infarcts (>25 mL); there were 3/238 (1.3%) events in the early group and 5/239 (2.1%) in the delayed group. CONCLUSION: The treatment effect of early anticoagulation with a DOAC in acute ischemic stroke associated with atrial fibrillation was not modified by infarct volume. Adverse outcomes were not increased with early anticoagulation in people with larger infarcts. Our results provide no evidence that anticoagulation initiation should be delayed beyond 4 days on the basis of infarct size.

Impact of Infarct Volume on Safety and Efficacy of Early DOAC InitiationTrial shows early blood thinners help stroke patients with heart issues

How this fits prior evidence

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