# Transcarotid Artery Revascularization (TCAR)

## Overview

Transcarotid Artery Revascularization (TCAR) is a hybrid technique for carotid revascularization that combines direct surgical access to the carotid artery with endovascular stent deployment, performed under flow reversal neuroprotection. This approach was developed to mitigate the embolic risks associated with transfemoral carotid artery stenting (CAS), which arise primarily from catheter navigation through the aortic arch. TCAR utilizes the ENROUTE Transcarotid Neuroprotection System, produced by Silk Road Medical, and received FDA approval in 2015. Since then, it has been rapidly adopted across the United States. TCAR represents a "best of both worlds" strategy by integrating the surgical control of direct carotid access with the minimally invasive benefits of endovascular stent placement.

## Rationale

The rationale behind TCAR stems from the limitations of existing carotid revascularization methods. Transfemoral CAS carries a significant embolic risk during navigation of the aortic arch, especially in elderly patients with atheromatous or complex arch anatomy. Carotid endarterectomy (CEA), while effective, is an open surgical procedure associated with higher cardiac risk, wound complications, and potential cranial nerve injury. TCAR circumvents these issues by eliminating the need to navigate the aortic arch through direct access to the common carotid artery (CCA) in the neck. Additionally, the use of flow reversal during stenting actively removes embolic debris before it can reach the brain, enhancing neuroprotection.

## Principles of Flow Reversal Neuroprotection

The flow reversal neuroprotection mechanism in TCAR is based on the Mo.Ma concept of proximal protection. The ENROUTE system establishes a circuit whereby an arterial sheath is placed directly into the CCA through a small neck incision. The CCA is then clamped proximally to the sheath, causing blood to flow retrograde from the internal carotid artery (ICA) through the sheath. This blood passes through an inline filter designed to capture embolic debris before the filtered blood is returned to the patient via a femoral venous sheath. The net effect is that any debris generated during stenting flows away from the brain through the reversed ICA flow. This flow reversal is maintained continuously during the critical procedural steps, including lesion crossing, pre-dilation, stenting, and post-dilation.

<image>Schematic diagram of the TCAR flow reversal circuit showing the direct CCA arterial sheath, proximal CCA clamp, retrograde flow from the ICA through the external filter, and return of filtered blood via the femoral venous sheath, with arrows indicating the direction of blood flow during the procedure</image>

## Technique

### Preoperative Preparation

Prior to the procedure, patients are started on dual antiplatelet therapy, typically aspirin and clopidogrel, at least three days before intervention. Standard cerebrovascular imaging, such as computed tomography angiography (CTA) or magnetic resonance angiography (MRA), is performed to assess vascular anatomy. Duplex ultrasound is also used to confirm the degree of stenosis and to evaluate the CCA for suitability as a sheath placement site.

### Procedural Steps

The procedure begins with a small, 2-3 cm transverse incision at the base of the neck, just above the clavicle. This allows exposure of the CCA below the omohyoid muscle with significantly less dissection than required for CEA, as there is no need to expose the carotid bifurcation, internal carotid artery, or cranial nerves. Femoral venous access is then obtained, usually via the right common femoral vein, with an 8 French sheath placed to serve as the return circuit.

Next, an arteriotomy is made in the CCA, and the ENROUTE arterial sheath is inserted directly into the artery. The CCA is clamped proximally to the sheath to establish flow reversal. The arterial sheath is connected to the venous sheath through the filter circuit, initiating retrograde blood flow from the ICA through the filter and back to the venous system.

Under flow reversal, a guidewire is advanced through the stenotic lesion into the distal ICA. Pre-dilation is performed using a low-profile balloon angioplasty. The ENROUTE transcarotid stent, which is self-expanding with a nitinol open-cell design, is then deployed across the lesion. Alternative self-expanding carotid stents may also be used. Post-dilation with balloon angioplasty within the stent follows to optimize stent expansion.

Completion angiography is performed through the arterial sheath to confirm adequate revascularization. Finally, antegrade flow is restored by releasing the CCA clamp, the sheath is removed, and the arteriotomy is closed. The small neck incision is then closed, resulting in a minimal wound.

### Key Technical Advantages

TCAR offers several technical advantages. By avoiding navigation through the aortic arch, it eliminates the highest-risk portion of transfemoral CAS. Direct arterial puncture provides excellent pushability and control, and the shorter working distance compared to the transfemoral approach facilitates precise device manipulation. Continuous flow reversal during the procedure offers superior neuroprotection compared to distal filter devices used in traditional CAS.

## ROADSTER Trials

### ROADSTER 1 (2015)

The initial evaluation of TCAR was conducted in the ROADSTER 1 trial, a prospective, multicenter, single-arm study involving 141 patients who were at high surgical risk and had symptomatic carotid stenosis of 50% or greater or asymptomatic stenosis of 80% or greater. The combined endpoint of stroke, death, or myocardial infarction (MI) at 30 days was 3.5%, with a stroke rate of 1.4%, which was the lowest reported for any carotid stenting trial at that time.

### ROADSTER 2 (2020)

ROADSTER 2 expanded enrollment to 632 patients with broader inclusion criteria. The 30-day stroke or death rate was 2.9%, and the stroke rate in asymptomatic patients was 0.6%. These results compared favorably to benchmarks for both CEA and transfemoral CAS, supporting the safety and efficacy of TCAR.

<image>Intraoperative photograph of TCAR procedure showing the small cervical incision at the base of the neck, the ENROUTE arterial sheath inserted into the CCA, the proximal CCA clamp, and the external flow reversal circuit with inline filter connected to the femoral venous return line</image>

## Indications

The indications for TCAR align with those for carotid revascularization in general, including symptomatic stenosis of 50% or greater and asymptomatic stenosis of 60-80% or greater. TCAR is particularly well suited for high surgical risk patients, who are traditional candidates for CAS, as well as standard-risk patients for whom both CEA and TCAR are viable options. It is especially advantageous in patients with unfavorable aortic arch anatomy, such as Type II or III arches or bovine arch variants, and in elderly patients over 70 years old, where transfemoral CAS outcomes tend to be poorer. TCAR is also indicated for recurrent stenosis after prior CEA and in patients with prior neck radiation. However, adequate CCA anatomy is required for sheath placement; the procedure is not suitable if the CCA is heavily calcified, tortuous, or previously stented.

## Contraindications

Contraindications to TCAR include severe disease of the CCA at the intended sheath insertion site, prior CCA stenting, a CCA that is too short to allow clamp placement, severe contrast allergy, inability to tolerate dual antiplatelet therapy, and complete occlusion of the ICA.

## Outcomes vs. CEA and Transfemoral CAS

When comparing outcomes, TCAR demonstrates favorable results relative to both CEA and transfemoral CAS. The 30-day stroke rate for CEA ranges from 1.4% to 2.3%, for transfemoral CAS from 3.2% to 4.1%, and for TCAR from 0.6% to 1.4%. The 30-day myocardial infarction rate is 1.1-2.3% for CEA, 0.5-1.1% for transfemoral CAS, and 0.4-1.0% for TCAR. Cranial nerve injury occurs in 4-8% of CEA cases, is nearly absent in transfemoral CAS, and occurs in less than 1% of TCAR cases. Wound complications are reported in 5-10% of CEA, less than 1% of transfemoral CAS, and 2-3% of TCAR procedures. Real-world data from the Vascular Quality Initiative (VQI) confirms the low stroke rates observed with TCAR. Overall, TCAR appears to combine the neuroprotection superiority of transfemoral CAS with the minimally invasive advantages of CEA.

| Outcome | CEA | Transfemoral CAS | TCAR |
|---------|-----|-----------------|------|
| 30-day stroke | 1.4–2.3% | 3.2–4.1% | 0.6–1.4% |
| 30-day MI | 1.1–2.3% | 0.5–1.1% | 0.4–1.0% |
| Cranial nerve injury | 4–8% | ~0% | <1% |
| Wound complications | 5–10% | <1% | 2–3% |
| Arch navigation required | No | Yes (highest risk step) | No |
| Neuroprotection method | N/A (direct plaque removal) | Distal filter or proximal occlusion | Flow reversal (continuous) |

## Controversies

Despite its advantages, TCAR faces several controversies. Long-term data on durability and stroke prevention beyond five years are still maturing, given that TCAR is a relatively new procedure. There has been no head-to-head randomized trial comparing TCAR directly with CEA in standard-risk patients. The procedure requires specific training and credentialing, and there is a learning curve for operators. TCAR devices are more expensive than the equipment used for CEA, which may impact cost-effectiveness. Although adoption is rapidly increasing in the United States, TCAR is less widely adopted internationally. Additionally, the role of any carotid revascularization procedure—including CEA, CAS, or TCAR—in asymptomatic disease remains debated, especially in the context of modern medical therapy.

## Clinical Pearls

TCAR effectively eliminates the most dangerous aspect of transfemoral CAS—navigation through the aortic arch—which accounts for its lower stroke rates. The small neck incision required for TCAR results in minimal risk to cranial nerves compared to CEA. This technique is particularly beneficial for patients over 70 years of age and those with hostile arch anatomy, where transfemoral CAS carries the highest complication rates. It is essential to establish dual antiplatelet therapy before the procedure and verify patient compliance. Preoperative imaging must confirm that the CCA is adequate for sheath placement. Although flow reversal is generally well tolerated, patients may experience transient neurological symptoms during reversal, so tolerance should be tested before proceeding. Importantly, TCAR is not simply "stenting through the neck"; the critical differentiator is the flow reversal neuroprotection system that ensures embolic debris is diverted away from the brain.

## References
- Kashyap VS, et al. TCAR with dynamic flow reversal: 30-day outcomes from the ROADSTER multicenter trial. J Vasc Surg. 2015;62(5):1227-1235.
- Kashyap VS, et al. Safety and effectiveness of TCAR (ROADSTER 2). J Vasc Surg. 2020;72(5):1350-1361.
- Malas MB, et al. Comparison of TCAR with CEA and TF-CAS (VQI analysis). J Vasc Surg. 2019;69(1):92-100.
- Schermerhorn ML, et al. TCAR in the VQI: outcomes and trends. J Vasc Surg. 2020;72(5):1362-1370.
- Naylor AR, et al. ESVS 2023 Guidelines on Carotid and Vertebral Artery Disease. Eur J Vasc Endovasc Surg. 2023;65(1):7-111.