What is the role of prophylactic antiplatelets, such as aspirin (acetylsalicylic acid), in managing unruptured internal carotid artery (ICA) aneurysms?

Prophylactic Antiplatelets in ICA Aneurysm

For unruptured internal carotid artery (ICA) aneurysms managed conservatively (not undergoing intervention), aspirin 75-100 mg daily is recommended based on the same rationale as asymptomatic carotid stenosis—to reduce overall cardiovascular mortality and stroke risk. 1

Conservative Management of Unruptured ICA Aneurysms

Asymptomatic Unruptured Aneurysms

• Aspirin 75-100 mg daily should be initiated for patients with unruptured ICA aneurysms who are being observed without intervention, following the same Grade 2B recommendation as asymptomatic carotid stenosis. 1
• The rationale is that these patients have underlying atherosclerotic vascular disease and benefit from cardiovascular risk reduction, with aspirin reducing total mortality over 10 years regardless of cardiovascular risk profile. 1
• The benefit must be weighed against bleeding risk—in moderate to high cardiovascular risk patients, the reduction in MI is closely balanced with increased major bleeding. 1

Dosing Considerations

• Low-dose aspirin (75-100 mg daily) is superior to higher doses for vascular protection. 1
• The Aspirin and Carotid Endarterectomy trial demonstrated that low-dose aspirin (81-325 mg) resulted in significantly lower rates of stroke, MI, and death compared to high-dose aspirin (650-1,300 mg) at 3 months (6.2% vs 8.4%, P=0.03). 1
• Higher aspirin doses may paradoxically reduce efficacy by inhibiting arterial prostacyclin production. 2

Aneurysms Undergoing Endovascular Treatment

Flow Diversion or Stent-Assisted Coiling

• Dual antiplatelet therapy (DAPT) with aspirin and clopidogrel is standard for patients undergoing flow diversion or stent-assisted coiling of ICA aneurysms to prevent thromboembolic complications. 3, 4
• Antiplatelet therapy administered before and after coil embolization significantly reduces symptomatic thromboembolic complications from 16% (no therapy) to 1.9% (P=0.004). 4
• DAPT should be continued for 1-3 months post-procedure, then transitioned to single antiplatelet therapy indefinitely. 5

Special Circumstances

• In patients who cannot tolerate DAPT due to bleeding disorders, aspirin monotherapy may be considered for flow diversion, though this is based on limited case report evidence. 3
• For blood blister-like aneurysms treated with overlapping stents, appropriate adjustment of antiplatelet therapy may improve healing in recurrent cases. 6

Critical Pitfalls to Avoid

Masking Progressive Disease

• Aspirin may mask symptoms of progressive carotid atherosclerosis by preventing platelet aggregation and embolization, potentially allowing dangerous progression to critical stenosis without warning symptoms. 2
• A retrospective study found 27 patients on aspirin (325-1,300 mg daily) for symptomatic carotid disease developed crescendo symptoms or stroke despite compliance, with angiography revealing progression to ≥90% stenosis. 2
• Regular surveillance imaging is essential in patients with ICA aneurysms on aspirin therapy to detect silent progression of disease. 5

Bleeding Risk Assessment

• Do not initiate aspirin in patients at very high bleeding risk without careful consideration of cardiovascular benefit versus hemorrhagic risk. 1, 7
• Patients with hereditary hemorrhagic telangiectasia or bleeding disorders require individualized approaches, potentially using aspirin monotherapy instead of DAPT for endovascular procedures. 3

Premature Discontinuation After Intervention

• Never discontinue DAPT prematurely after stent-assisted procedures—this dramatically increases stent thrombosis risk. 5
• Maintain DAPT for the full recommended 1-3 month duration before transitioning to monotherapy. 5

Monitoring Strategy

• Annual follow-up is mandatory to assess cardiovascular risk factors, treatment compliance, and neurological symptoms. 5
• After endovascular treatment, duplex ultrasound surveillance within the first month is recommended. 5
• Hemoglobin levels and clinical bleeding parameters should be monitored in patients on antiplatelet therapy. 8