Should anticoagulation be initiated immediately in a patient with a watershed stroke?

From the Guidelines

Anticoagulation should not be initiated immediately in a patient with a watershed stroke, but rather considered after 1-2 weeks if there's a cardioembolic source or other specific indications for anticoagulation. The standard acute treatment for ischemic stroke, including watershed infarcts, typically involves antiplatelet therapy such as aspirin (initial dose 325 mg, followed by 81 mg daily) unless contraindicated 1. Watershed strokes occur at the border zones between major cerebral arterial territories and are usually caused by hypoperfusion or microemboli rather than large vessel occlusion. Anticoagulants like heparin or warfarin carry a significant risk of hemorrhagic transformation in acute stroke and have not been shown to improve outcomes in most stroke types.

According to the most recent guidelines, oral anticoagulation should usually be started within 2 weeks of acute ischemic stroke, but the optimal timing within this period is not known 1. It's also important to note that anticoagulation with NOACs soon after stroke (earlier than 1 week) has not been tested in randomized trials, but shows promise in observational studies 1. Initial management should focus on maintaining adequate cerebral perfusion, controlling blood pressure (avoiding excessive lowering), and addressing the underlying cause of hypoperfusion such as severe carotid stenosis or cardiac dysfunction.

Some key considerations for initiating anticoagulation include:

• The presence of a cardioembolic source, such as atrial fibrillation
• The size and location of the infarct
• The risk of hemorrhagic transformation
• The patient's overall clinical condition and comorbidities In general, the decision to initiate anticoagulation should be made on a case-by-case basis, taking into account the individual patient's risk factors and clinical presentation 1.

From the Research

Anticoagulation in Watershed Stroke

• The decision to initiate anticoagulation in a patient with a watershed stroke depends on various factors, including the presence of atrial fibrillation, stroke severity, and the risk of hemorrhagic transformation 2.
• According to the study by 2, in patients with small acute ischemic stroke (AIS) without hemorrhagic transformation, 51% of stroke neurologists elected to start anticoagulation within 96 hours.
• However, with increased stroke severity and asymptomatic hemorrhagic transformation, only 29% and 26% of stroke neurologists, respectively, chose to anticoagulate within 7 days 2.
• The study by 3 suggests that patients with ischemic stroke and atrial fibrillation may benefit from the initiation of a direct oral anticoagulant (DOAC) without bridging therapy, as it is associated with a lower risk of recurrent ischemic events.

Timing of Anticoagulation

• The optimal timing of anticoagulation in patients with watershed stroke is not well established, and there is a lack of consensus among stroke neurologists regarding the timing of anticoagulation for secondary stroke prevention in patients with AIS due to paroxysmal atrial fibrillation 2.
• The study by 4 highlights the uncertainty surrounding the management of anticoagulation in patients with atrial fibrillation who have suffered an acute cardioembolic stroke, and whether warfarin should be temporarily stopped or continued.
• The study by 5 found that patients with atrial fibrillation who have an ischemic stroke despite previous oral anticoagulation are at a higher risk for recurrent ischemic stroke, and better prevention strategies are needed for this high-risk patient group.

Anticoagulation Choice

• The choice of anticoagulant is also an important consideration, with DOACs being the preferred anticoagulation strategy in patients with AIS due to paroxysmal atrial fibrillation 2.
• The study by 3 found that DOAC treatment was associated with a lower risk of recurrent ischemic events compared to warfarin, but not delayed symptomatic intracranial hemorrhage.
• The study by 6 found that underuse of anticoagulation is a common contributor to ischemic strokes and transient ischemic attacks in patients with atrial fibrillation, and that infrequent paroxysms of AF, previous bleeding episodes, and patient decline/independent discontinuation of treatment were the most frequently documented reasons for withholding oral anticoagulation.