Why are patients with vertebral artery dissection started on Aspirin (acetylsalicylic acid) and Plavix (clopidogrel)?

Management of Vertebral Artery Dissection with Aspirin and Plavix

Patients with vertebral artery dissection are treated with dual antiplatelet therapy (aspirin and clopidogrel/Plavix) to prevent thromboembolic complications that can lead to ischemic stroke, which is a major cause of morbidity and mortality in these patients.

Pathophysiology and Risk of Stroke

Vertebral artery dissection creates a false lumen within the arterial wall that can:

• Form a thrombus that may embolize distally
• Cause stenosis or occlusion of the true lumen
• Lead to cerebral or retinal ischemia in 50-95% of cases 1

Evidence-Based Treatment Approach

Initial Antithrombotic Therapy

1. First-line therapy options:

   • Either antiplatelet therapy or anticoagulation is recommended for at least 3 months in patients with ischemic stroke or TIA and extracranial vertebral artery dissection 1
   • The American Heart Association/American Stroke Association guidelines state: "In patients with ischemic stroke or TIA and extracranial carotid or vertebral artery dissection, either antiplatelet therapy or oral anticoagulants are recommended for at least 3 months" 1

2. Antiplatelet vs. Anticoagulation:

   • The CADISS randomized trial (2015) found no significant difference between antiplatelet and anticoagulant therapy in preventing recurrent stroke in cervical artery dissection 2
   • Recurrent stroke was rare in both treatment groups (2% overall) 2
   • A 2013 study specifically on vertebral artery dissection also found no difference between aspirin and anticoagulation 3

Rationale for Dual Antiplatelet Therapy

While guidelines don't specifically mandate dual antiplatelet therapy for vertebral artery dissection, the use of aspirin plus clopidogrel (Plavix) is often preferred because:

1. Enhanced platelet inhibition: Dual therapy provides more complete inhibition of platelet aggregation through complementary mechanisms:

   • Aspirin inhibits thromboxane A2 production
   • Clopidogrel blocks ADP-mediated platelet activation

2. Established benefit in similar conditions: Guidelines recommend DAPT for minor ischemic stroke or high-risk TIA, which shares pathophysiological features with dissection 1

3. Lower bleeding risk: Compared to anticoagulation, antiplatelet therapy may have a more favorable bleeding profile, especially important if there's extension of dissection intracranially 1

Treatment Protocol

1. Acute phase (first 24 hours):

   • Confirm diagnosis with CTA or MRA
   • Rule out subarachnoid hemorrhage
   • Loading doses:
     • Aspirin 160-325 mg
     • Clopidogrel 300-600 mg

2. Maintenance therapy:

   • Aspirin 81-325 mg daily
   • Clopidogrel 75 mg daily
   • Duration: typically 3 months 1

3. Long-term management:

   • After 3 months, transition to single antiplatelet therapy (aspirin 81-325 mg daily or clopidogrel 75 mg daily) 1
   • Regular imaging surveillance to assess healing

Special Considerations

• Monitoring: Regular clinical and imaging follow-up to assess for:

  • Healing of dissection
  • Development of pseudoaneurysm
  • Recurrent symptoms

• Caution: Anticoagulation may adversely influence outcomes if there is intracranial extension of the dissection with risk of subarachnoid hemorrhage 1

• Recurrence risk: Some patients have experienced recurrence when stopping antiplatelet therapy 4, suggesting the importance of appropriate duration of treatment

Conclusion

While both antiplatelet therapy and anticoagulation are supported by guidelines for vertebral artery dissection, dual antiplatelet therapy with aspirin and clopidogrel offers effective protection against thromboembolic complications with potentially lower bleeding risk compared to anticoagulation. The treatment duration should be at least 3 months, followed by long-term single antiplatelet therapy.