Is a CPT 37215 trans catheter stent medically necessary for a patient with 75-80% stenosis of the right internal carotid artery (ICA) and no documented operative institution and surgical provider complication rates?

Medical Necessity Assessment for Carotid Artery Stenting in Asymptomatic 75% ICA Stenosis

This carotid artery stenting procedure cannot be certified as medically necessary because the operative institution and surgical provider have not documented complication rates below the required 3% threshold for asymptomatic patients. 1

Critical Missing Documentation

The MCG criteria explicitly require that the operative institution and surgical provider demonstrate known complication rates (stroke and mortality) less than 3% at 30 days post-procedure in asymptomatic patients. 1 This is not merely a documentation formality—it represents a fundamental safety requirement that determines whether the intervention provides net benefit over medical management alone.

Without documented institutional and provider-specific complication rates, the procedure fails to meet evidence-based safety standards and should not proceed. 1

Why This Requirement Exists

Modern Medical Therapy Has Changed the Risk-Benefit Calculation

• The annual stroke risk in asymptomatic severe carotid stenosis managed with contemporary best medical therapy has fallen to ≤1% per year. 2
• In the Asymptomatic Carotid Surgery Trial (ACST), patients on lipid-lowering therapy had only 0.6% per year absolute benefit from carotid endarterectomy compared to 1.5% per year in those not on statins. 2
• Modern optimal medical therapy (antiplatelet agents, statins, blood pressure control, diabetes management, smoking cessation) may have further reduced stroke risk compared to older clinical trials, potentially obviating the need for carotid revascularization in many patients. 2

Procedural Risk Must Be Exceptionally Low to Justify Intervention

• The perioperative risk of stroke or death with carotid endarterectomy is approximately 1.5-3% in asymptomatic patients. 2
• For carotid artery stenting specifically, the perioperative risk is higher at approximately 2.2-4%. 2
• If the institutional complication rate exceeds 3%, the immediate procedural risk may equal or exceed the 5-year stroke risk with medical therapy alone, eliminating any potential benefit. 1

Guideline-Based Requirements for Asymptomatic Carotid Stenosis

Canadian Stroke Best Practice Recommendations (2018)

Carotid stenting may be considered in patients with 60-99% carotid stenosis who are not operative candidates for technical, anatomic, or medical reasons provided there is a less than 3% risk of peri-procedural morbidity and mortality. 1

Additionally, carotid stenting should be performed by an interventionist/center with expertise that routinely audits their performance results, especially perioperative stroke and death rates. 1

American Heart Association/American Stroke Association Guidelines (2011)

• Prophylactic carotid endarterectomy performed with <3% morbidity and mortality can be useful in highly selected patients with asymptomatic carotid stenosis (minimum 60% by angiography, 70% by validated Doppler ultrasound). 1
• The cited 3% threshold for complication rates may actually be high because of interim advances in medical therapy since the original trials. 1
• In carefully selected patients, carotid endarterectomy should be performed by a surgeon who routinely audits their performance results and demonstrates a less than 3% risk of peri-operative morbidity and mortality. 1

Multi-Society Guidelines (2011)

Carotid artery stenting is reasonable when performed by operators with established periprocedural morbidity and mortality rates of 4-6%, similar to that observed in trials comparing CAS and CEA. 1 However, this applies to symptomatic patients—the threshold for asymptomatic patients remains <3%. 1

This Patient's Clinical Context

Patient Meets Some Criteria

• Stenosis severity: 75-80% right ICA stenosis meets the ≥70% threshold. 1
• Life expectancy: At 58 years old without significant past medical history, likely exceeds 5 years. 1
• Patient preference: Carotid artery stenting preferred after discussion. 1
• Medical management: Patient will receive appropriate antiplatelet therapy (Plavix). 1

Critical Gap: Symptomatic vs. Asymptomatic Status

The documentation describes "intermittent severe headache associated with intermittent numbness, tingling and weakness of left upper extremity and face." This raises a crucial question: Are these symptoms truly attributable to the right ICA stenosis, making this a symptomatic case?

• Cluster headaches are listed as a separate diagnosis and are typically not caused by carotid stenosis. 1
• Intermittent left-sided weakness and numbness could represent transient ischemic attacks from the right ICA stenosis. 1
• If these represent true TIAs within the past 6 months, this becomes a symptomatic case with different risk-benefit calculations and potentially higher acceptable complication rates (up to 6%). 1

However, the MCG criteria being applied are for asymptomatic patients, which maintains the <3% complication rate requirement. 1

What Must Happen Before Proceeding

Required Documentation

1. Institutional complication rates: The hospital must provide audited data showing 30-day stroke and mortality rates <3% for asymptomatic carotid stenting procedures. 1

2. Provider-specific complication rates: The interventionalist must demonstrate personal complication rates <3% in asymptomatic patients. 1

3. Clarification of symptom status: Neurology should definitively determine whether the left-sided symptoms represent true TIAs attributable to the right ICA stenosis (making this symptomatic) or are unrelated (keeping this asymptomatic). 1

If Symptomatic Status Confirmed

If the patient is truly symptomatic with recent TIA:

• The acceptable complication rate threshold increases to <6%. 1
• The benefit of intervention is substantially greater (17% absolute risk reduction in NASCET trial for 70-99% stenosis). 1
• Intervention should occur within 2 weeks of symptoms when indicated. 1

If Asymptomatic Status Confirmed

If the patient is truly asymptomatic:

• The <3% complication rate documentation remains mandatory. 1
• Consider whether intensive medical therapy alone might be superior given modern stroke prevention strategies. 2
• Ensure the patient understands that with optimal medical therapy, their annual stroke risk is approximately 1%, and the procedure itself carries 2-4% immediate risk. 2

Common Pitfalls to Avoid

Do not proceed with intervention based solely on stenosis severity. The degree of stenosis (75-80%) meets anatomic criteria, but this alone does not justify intervention in asymptomatic patients without documented low complication rates. 1

Do not assume all institutions and operators meet the <3% threshold. Real-world complication rates vary widely—a 10-state survey found rates ranging from 1.4% to 6.0% for carotid endarterectomy in asymptomatic patients. 1

Do not overlook the importance of optimal medical therapy. Regardless of whether intervention proceeds, this patient requires aggressive risk factor modification including antiplatelet therapy, statin therapy, blood pressure control, and lifestyle modifications. 2

Do not confuse symptomatic and asymptomatic criteria. The distinction fundamentally changes the risk-benefit calculation and acceptable complication thresholds. 1

Recommendation

Deny authorization for carotid artery stenting until the operative institution and surgical provider document complication rates <3% for asymptomatic patients. 1 Simultaneously, request neurology clarification on whether the patient's symptoms represent true TIAs attributable to the right ICA stenosis, which would reclassify this as a symptomatic case with different criteria. 1 Ensure the patient is initiated on optimal medical therapy regardless of intervention decision. 2