What are the treatment recommendations for patients with symptomatic carotid stenosis based on the Nascet (North American Symptomatic Carotid Endarterectomy Trial) trial?

Treatment Recommendations for Symptomatic Carotid Stenosis Based on NASCET Trial

Carotid endarterectomy (CEA) is strongly recommended for patients with symptomatic carotid stenosis of 70-99%, as it significantly reduces the risk of ipsilateral stroke compared to medical therapy alone. 1

NASCET Trial Summary and Key Findings

The North American Symptomatic Carotid Endarterectomy Trial (NASCET) was a landmark study that evaluated the efficacy of CEA in patients with symptomatic carotid stenosis. The trial had several important findings:

Severe Stenosis (70-99%)

• The trial was stopped early after 18 months for patients with 70-99% stenosis due to clear benefit of CEA
• 2-year cumulative risk of ipsilateral stroke: 9% with CEA vs. 26% with medical therapy alone
• Absolute risk reduction: 17% in favor of surgical management 1
• This represents a highly significant benefit that has shaped clinical practice

Moderate Stenosis (50-69%)

• CEA showed moderate benefit for patients with 50-69% stenosis
• 5-year rate of ipsilateral stroke: 15.7% with CEA vs. 22% with medical therapy
• Number needed to treat: 15 patients over 5 years to prevent one stroke 1
• Benefit was greatest among men, patients with recent stroke as the qualifying event, and patients with hemispheric symptoms 2

Mild Stenosis (<50%)

• No significant benefit was found for CEA in patients with less than 50% stenosis 1, 2

Measurement Method Considerations

The NASCET method of measuring stenosis is critical to understand when interpreting results:

• NASCET method: Compares the narrowest diameter to the normal distal internal carotid artery
• This differs from the European Carotid Surgery Trial (ECST) method, which used the estimated carotid bulb diameter as reference
• A conversion table exists between the two methods (e.g., 70% stenosis by ECST equals approximately 40% by NASCET) 1

Current Treatment Recommendations

Based on the NASCET findings and subsequent guidelines:

1. For 70-99% symptomatic stenosis:

   • CEA is strongly recommended and should be performed urgently 1
   • Ideally within the first days following a non-disabling stroke or TIA, and within 14 days of the ischemic event 1
   • The benefit is durable, with protection against stroke maintained for at least 8 years 2

2. For 50-69% symptomatic stenosis:

   • CEA should be considered but with more careful patient selection
   • Greatest benefit in men, those with recent stroke, and hemispheric symptoms 2
   • Surgical expertise is particularly important in this group 2

3. For <50% symptomatic stenosis:

   • Medical therapy is recommended as CEA provides no significant benefit 1, 2

Important Considerations for Implementation

• Surgical expertise matters: CEA should be performed by surgeons/centers with low perioperative complication rates (ideally <6-7% combined perioperative stroke and death rates) 1
• Timing is critical: Early intervention (within days to 2 weeks) provides the greatest benefit for symptomatic patients 1
• Age considerations: CEA is generally more appropriate than carotid stenting for patients over 70 years 1
• Alternative for non-surgical candidates: Carotid stenting may be considered for patients who are not candidates for CEA due to technical, anatomical, or medical reasons 1

Pitfalls to Avoid

• Inappropriate patient selection: Patients with near-occlusion (99% stenosis with collapse of distal vessel) may not benefit as much from CEA 1
• Delayed intervention: The benefit of CEA diminishes with time from the symptomatic event
• Inadequate surgical expertise: Outcomes are highly dependent on surgical skill and perioperative care
• Inconsistent measurement methods: Using different methods to measure stenosis (NASCET vs. ECST) can lead to inappropriate treatment decisions 1

The NASCET trial fundamentally changed the management of carotid stenosis, establishing CEA as a proven intervention for stroke prevention in appropriately selected symptomatic patients with significant carotid stenosis.