Are there indications for anticoagulation (blood clot prevention) after a watershed stroke?

From the Guidelines

Anticoagulation is generally not indicated after a watershed stroke unless there is a specific cardioembolic source identified. Watershed strokes typically occur due to hypoperfusion or hemodynamic compromise rather than embolism, making antiplatelet therapy the preferred approach in most cases. For secondary prevention after watershed stroke, antiplatelet medications such as aspirin (81-325 mg daily), clopidogrel (75 mg daily), or aspirin plus extended-release dipyridamole are typically recommended, as supported by the Canadian Stroke Best Practice Recommendations, sixth edition practice guidelines, update 2017 1.

Key Considerations

• The selection of an antiplatelet agent should be individualized based on patient risk factor profiles, cost, tolerance, and other clinical characteristics, as recommended by the American Heart Association/American Stroke Association guidelines 1.
• If the watershed stroke occurred in the setting of large vessel stenosis (such as carotid artery stenosis), aggressive management of this underlying cause is essential, which may include carotid endarterectomy or stenting in appropriate cases.
• Anticoagulation with warfarin, direct oral anticoagulants (DOACs) like apixaban or rivaroxaban would only be indicated if a cardioembolic source such as atrial fibrillation, mechanical heart valve, or left ventricular thrombus is discovered, as anticoagulants carry a higher bleeding risk without providing additional benefit over antiplatelet therapy in this specific stroke mechanism.

Evidence-Based Recommendations

• All patients with ischemic stroke or transient ischemic attack should be prescribed antiplatelet therapy for secondary prevention of recurrent stroke unless there is an indication for anticoagulation, with acetylsalicylic acid (80–325 mg daily), combined acetylsalicylic acid (25 mg) and extended-release dipyridamole (25 mg/200 mg twice daily), or clopidogrel (75 mg daily) being appropriate options 1.
• Short-term concurrent use of acetylsalicylic acid and clopidogrel (up to 21 days) has not shown an increased risk of bleeding and may be protective following minor stroke or transient ischemic attack, but longer-term use is not recommended due to an increased risk of bleeding and mortality 1.

From the Research

Indications for Anticoagulation after Watershed Stroke

• The provided studies do not directly address the indications for anticoagulation after a watershed stroke.
• However, studies such as 2 and 3 discuss the timing of anticoagulation initiation after acute ischemic stroke in patients with atrial fibrillation, which may be relevant to some cases of watershed stroke.
• According to 2, the optimal time to initiate anticoagulant therapy after acute ischemic stroke in patients with atrial fibrillation is uncertain, and the risk of hemorrhagic transformation and recurrent ischemic stroke must be considered.
• Study 3 found that the recommended time frame of 4-14 days to start oral anticoagulation was not associated with reduced ischemic and hemorrhagic outcomes in patients with cardioembolic stroke.
• Watershed strokes are often caused by cerebral hypoperfusion or arterial embolism, as described in 4, and the pathophysiological mechanism of brain injury production is not fully defined.
• The study 5 highlights the importance of oral anticoagulation in preventing strokes secondary to atrial fibrillation, but does not specifically address watershed strokes.
• Study 6 discusses a classic watershed infarct as a consequence of severe hypotension, but does not provide information on anticoagulation therapy.
• In summary, while there is no direct evidence on indications for anticoagulation after watershed stroke, studies on anticoagulation timing in acute ischemic stroke and atrial fibrillation may provide some relevant insights 2, 3, 5.