When should heparin be started in patients with atrial fibrillation who have suffered a stroke?

Timing of Heparin Initiation in Atrial Fibrillation Patients with Stroke

In patients with atrial fibrillation who have suffered an acute ischemic stroke, heparin should NOT be started very early (<48 hours after stroke onset) due to increased risk of hemorrhagic transformation without clear benefit. 1

Initial Management Approach

• Very early anticoagulation (within 48 hours) using heparinoids or vitamin K antagonists should be avoided in patients with AF who have had an acute ischemic stroke 1
• Heparinoids should not be used as bridging therapy in the acute phase of ischemic stroke as they appear to increase the risk of symptomatic intracranial hemorrhage without net benefit 1
• The optimal timing of anticoagulation after acute ischemic stroke is unknown, but current evidence suggests delaying initiation beyond the acute phase 1, 2

Timing Recommendations Based on Stroke Severity

• For patients with AF and acute ischemic stroke, oral anticoagulation should usually be started within 2 weeks of the stroke event 1
• For patients at high risk of hemorrhagic conversion, it is reasonable to delay initiation of oral anticoagulation beyond 14 days 1
• For patients at low risk of hemorrhagic conversion, it may be reasonable to initiate anticoagulation between 2-14 days after the index event 1

Factors Affecting Timing Decision

• Infarct size is an important consideration - larger infarcts have higher risk of hemorrhagic transformation and may require longer delays before anticoagulation 1, 2
• Normal baseline CT findings and age younger than 70 years have been associated with better neurological recovery with early heparin treatment 1
• Presence of cerebral microbleeds, thrombolytic therapy, and large ischemic lesions increase the risk of hemorrhagic transformation 2

Heparin Administration When Indicated

• When heparin is administered, close monitoring of aPTT is necessary to lessen the risk of hemorrhagic complications 1
• Target aPTT should be 1.5 to 2.0 times control values 1
• Initial heparin infusion rates of 9.7-11.0 units/kg/hour without a bolus can result in therapeutic levels of anticoagulation without increasing bleeding risk 3
• Higher initial infusion rates (>11.0 units/kg/hour) are associated with increased bleeding risk (OR 1.95% CI 1.06-3.59) 3

Long-term Anticoagulation

• Long-term oral anticoagulation is strongly indicated as secondary prevention in AF patients with stroke 1
• Direct oral anticoagulants (DOACs) are preferred over warfarin for patients without moderate to severe mitral stenosis or mechanical heart valves 1
• For patients who cannot take oral anticoagulants, left atrial appendage occlusion may be considered 1

Ongoing Research

• The OPTIMAS trial is currently investigating whether early treatment with a DOAC (within four days of stroke onset) is as effective or better than delayed initiation (7-14 days from onset) in AF patients with acute ischemic stroke 4
• Early use of NOACs shows promise but requires further testing in randomized controlled trials 1

Common Pitfalls to Avoid

• Initiating parenteral anticoagulation within 48 hours of stroke onset, which increases risk of hemorrhagic transformation 1
• Delaying anticoagulation unnecessarily in patients at low risk for hemorrhagic transformation, leaving them vulnerable to recurrent stroke 1
• Inadequate monitoring of aPTT when heparin is administered, which can lead to either insufficient anticoagulation (increasing stroke risk) or excessive anticoagulation (increasing bleeding risk) 1