Anatomic Criteria for Transcarotid Artery Revascularization (TCAR)
TCAR requires specific anatomic parameters: a minimum 5 cm distance from clavicle to carotid bifurcation, common carotid artery (CCA) diameter ≥6 mm, internal carotid artery (ICA) diameter between 4-9 mm, and absence of significant atherosclerotic plaque at the intended CCA puncture site.
Core Anatomic Requirements
The anatomic eligibility for TCAR is defined by four critical measurements 1, 2:
Essential Criteria:
- Clavicle-to-bifurcation distance: ≥5 cm (this is the most common limiting factor, present in approximately 75% of patients) 2
- CCA diameter: ≥6 mm (nearly universal, present in 100% of eligible patients) 2
- ICA diameter: 4-9 mm (also nearly universal at 100%) 2
- CCA access site: Must lack significant atherosclerotic plaque at the intended puncture location (present in 96% of patients) 2
Additional Anatomic Considerations:
- Bifurcation anatomy: Must be favorable for stenting (unfavorable anatomy present in only 7% of cases) 2
- Lesion location: The carotid stenosis must be accessible proximal to the bifurcation for adequate sheath placement
Clinical Context
Approximately 68-72% of patients with carotid stenosis meet these anatomic criteria for TCAR 1, 2. The most frequent anatomic exclusion is insufficient clavicle-to-bifurcation distance, followed by significant plaque at the access site 1.
Patient Factors Associated with TCAR Ineligibility:
Workarounds for Unfavorable Anatomy
When standard anatomic criteria are not met, particularly for insufficient clavicle-to-bifurcation distance or unsuitable CCA access, a prosthetic conduit can be used to extend TCAR eligibility. This involves anastomosing a 6 mm prosthetic graft (typically Dacron) to the CCA in an end-to-side fashion, allowing stent delivery through the conduit, which is then ligated and oversewn 3, 4. This technique achieves 100% technical success with no increase in stroke rates and comparable procedure times 4.
Conduit Technique Indications:
- Clavicle-to-bifurcation distance <5 cm 4
- CCA diameter <6 mm 4
- Significant atherosclerotic disease at intended access site 4
Comparison with Other Modalities
TCAR fills a critical gap between carotid endarterectomy (CEA) and transfemoral carotid artery stenting (TFCAS):
- 21% of patients are ineligible for CEA due to lesions extending above C2 1
- 35% of patients are ineligible for TFCAS due to hostile aortic arch anatomy or severe ICA tortuosity 1
- 69% of patients at high anatomic risk for TFCAS remain eligible for TCAR 2
Common Pitfalls:
- Failing to measure the clavicle-to-bifurcation distance preoperatively—this is the single most common reason for TCAR ineligibility
- Overlooking significant plaque at the CCA access site, which can complicate sheath insertion
- Not considering prosthetic conduit options when standard anatomy is borderline or unfavorable
The anatomic assessment should be performed using computed tomography angiography (CTA) of the neck and chest to accurately measure all required parameters before procedure planning 1, 2.