Timing of Anticoagulation in Ischemic Stroke with Atrial Fibrillation
Anticoagulation should be initiated between 1 and 14 days after an ischemic stroke in patients with atrial fibrillation, with the specific timing based on stroke severity. 1, 2
Recommended Timing Based on Stroke Severity
- For patients with transient ischemic attack (TIA): Start anticoagulation 1 day after the event, after excluding intracranial hemorrhage with imaging 1, 2
- For patients with mild stroke (NIHSS <8): Start anticoagulation >3 days after the event 1, 2
- For patients with moderate stroke (NIHSS 8-15): Start anticoagulation >6-8 days after the event 1, 2
- For patients with severe stroke (NIHSS ≥16): Start anticoagulation >12-14 days after the event 1, 2
Key Principles
- Very early anticoagulation (<48 hours) should be avoided as it increases the risk of symptomatic intracranial hemorrhage without providing net benefit 1, 2
- Long-term oral anticoagulation is strongly indicated as secondary prevention in AF patients after ischemic stroke 1, 2
- Heparinoids should not be used as bridging therapy in the acute phase of ischemic stroke due to increased risk of intracranial hemorrhage 1, 2
Evaluation Before Starting Anticoagulation
- Exclude intracranial hemorrhage with CT or MRI before initiating anticoagulation 1
- For moderate to severe strokes, repeat brain imaging (CT or MRI) is recommended at day 6-12 to evaluate for hemorrhagic transformation before starting anticoagulation 1
Choice of Anticoagulant
- Direct oral anticoagulants (DOACs) are preferred over vitamin K antagonists for non-valvular atrial fibrillation due to lower risk of intracranial hemorrhage 2, 3
- For patients with mechanical heart valves or moderate to severe mitral stenosis, warfarin remains the anticoagulant of choice 3
Recent Evidence
- The OPTIMAS study is investigating whether early treatment with a DOAC (within 4 days of stroke onset) is as effective or better than delayed initiation (7-14 days) 4, 5
- Observational studies suggest that early initiation of DOACs may be safer than vitamin K antagonists 2
Special Considerations
- Infarct size is often used clinically to guide timing but is also predictive of early recurrent ischemia and hemorrhagic transformation 1, 2
- For patients with high thromboembolic risk features (left atrial/left atrial appendage thrombi, mechanical heart valves), earlier anticoagulation may be considered 6
- In patients who suffer a stroke while on anticoagulation, adherence should be assessed and therapy optimized 1
Common Pitfalls to Avoid
- Starting anticoagulation too early (<48 hours) increases hemorrhagic transformation risk 1, 2
- Delaying anticoagulation too long increases risk of recurrent ischemic stroke, which can be as high as 0.1-1.3% per day in AF patients 7
- Using heparin or LMWH as bridging therapy in the acute phase is not recommended 1
The decision on when to start anticoagulation requires balancing the risk of early recurrent stroke against the risk of hemorrhagic transformation, with stroke severity being the primary determinant of timing 1, 2.