Transcarotid Artery Revascularization With Flow Reversal: Bypassing the Arch and Limiting Distal Emboli

Over the past decade, carotid stenting has been gradually welcomed as an additional tool for carotid revascularization. The major drawbacks of this procedure are the need for access through what maybe challenging anatomy and the potential for distal embolic events. Distal protection devices have ameliorated this risk to a large degree, but their ability to capture all debris is not foolproof. Additionally, the risk of gaining access to the common carotid artery (CCA) with a sheath in challenging and atherosclerotic anatomy has raised concern and may explain why carotid stenting risk rises sharply in patients’ seventh and eighth decades of life. Transcarotid access has been utilized over the years with some success by achieving flow reversal by creating a shunt between the common carotid and internal jugular vein.1 The degree of flow reversal, however, was modest and could not be regulated effectively. The transcarotid revascularization (TCAR) procedure with the ENROUTE transcarotid neuroprotection system2 (Sunnyvale, California) is an innovative flow reversal system that utilizes direct carotid access via the creation of an arteriovenous shunt with the femoral vein and achieves flow reversal that can be regulated. The technique effectively “marries” the concept of carotid clamping and back bleeding of carotid endarterectomy (CEA), with stenting. The PROOF study is the first human phase 3 trial of the device that recently reported safety and efficacy in 75 patients.3 The PROOF study was conducted as a prospective, single arm, open label phase 3 study in Germany. Inclusion criteria were symptomatic or asymptomatic high-grade stenosis in patients over 21 yr of age and a minimum distance of 5 cm between the clavicle and carotid bifurcation in order to allow convenient access and device manipulation. Pertinent exclusion criteria were atrial fibrillation, evidence of stroke in previous 30 d, plaque in CCA at the planned access site, prior ipsilateral carotid stent, patient enrollment in another trial, and a planned procedure. Of 99 screened patients, 96 consented but 21 had to be excluded. Five of 96 were excluded due to CCA disease, 3 due to atrial fibrillation, and 1 due to a prior stent. It is interesting to note that 3/96 were excluded due to “scheduling or surgeon availability” and 2 due to “abnormal blood tests.” The nature of the latter is not described (whether platelet inhibition or systemic issues such as renal dysfunction etc.). Seventy-five patients were finally enrolled and treated between 2009 and 2012 with various stents. Patients received a variety of different stents that were commercially available, delivered by the ENROUTE transcarotid access sheath with flow reversal for cerebral protection. Eight patients underwent a transcranial Doppler examination to monitor the presence of microemboli during the procedure and to measure middle cerebral artery velocity, before, during, and after the procedure. Diffusion-weighted magnetic resonance imaging (DWI) was used in 56/75 patients before and after the surgery. Transcranial Doppler and DWI imaging data were analyzed by 2 independent and separate core laboratories each. Primary endpoints were composite of major stroke, myocardial infarction, or death within 30 d, as in prior trials of carotid stenting. The parameters used to measure the technical efficacy of the TCAR included acute device success, procedure success, and tolerance to reverse flow. Briefly, the procedure was done with a small cervical cut down incision in the supraclavicular area, dissection of CCA, and securing with a vessel loop. Micropuncture technique is used to obtain access with an 8-Fr sheath in the CCA with care being taken to ensure that the sheath tip is below the plaque. Venous access is obtained in either femoral vein. The 2 sheaths are connected with a large bore flow line with the in-line flow controller. After the shunt is established, the CCA proximal to sheath puncture site is clamped with the vessel loop and/or a vascular clamp, thus establishing flow reversal that is manipulated with the flow controller. The latter can be set to high flow reversal during high-risk maneuvers such as balloon angioplasty, stent deployment, or CCA clamp release. Stent deployment proceeds in standard fashion. Adequate heparinization is ensured throughout. A purse-string suture at the arteriotomy site taken before sheath insertion is used from hemostasis at conclusion. Neurological examinations are conducted through the procedure. Right- and left-sided disease were nearly equally distributed. Mean severity of stenosis was 85% (standard deviation of 8.8). Mean lesion length was 14.4 mm (standard deviation of 7.6). Thirty- three of 75 plaques were severely calcified. Fifty-five of 75 were over 70 yr of age (6 over 80 yr). Thirty of 75 (40%) had contralateral carotid stenosis but the degrees were not mentioned. Acute device success was achieved in 68 (90.6%) of patients. In the remaining, 7 acute device failures (nearly 10%) were encountered: 3 were deemed as device malfunctions, 1 had dissection on guidewire insertion, and 3 had “unfavorable CCA anatomy.” Reverse flow was established in 71 (94.6%) patients. The remaining 4 (5.4%) had a bailout procedure with transfemoral carotid artery stenting (3) and CEA (1). There is no indication if they presented with symptomatic or asymptomatic stenosis. Five of 75 had transient altered consciousness during flow reversal, and this was managed with less time on reversal. Average reverse flow time was 19.1 ± 8.2 min allowing for a successful treatment. No primary endpoint events were reported. Ten of 56 who underwent DWI showed new ipsilateral lesions (17.9%). Over the 30 d of follow-up, major bleeding events 2 d post procedure were noted in 2 patients: 1 gastrointestinal from antiplatelets and another intracerebral hemorrhage during procedure (this was the patient who underwent CEA bailout). Two of 75 (2.7%) had vocal cord paralysis that persisted at 6 mo. A minor contralateral stroke was also reported. Of the 79 adverse events documented, 33 were procedural related and 8 were device related. Prior and ongoing studies suggest that direct CCA access along with flow reversal may be a good option for high-risk cases. While the acute device success rate and the need for bailout are far from perfect in this study, the overall stroke rate is very encouraging and very competitive with prior carotid stenting studies. This is especially impressive since cases in this study may have been more challenging and higher risk that what has been studied in randomized trials. From a technical standpoint, this approach is a welcome addition to the carotid revascularization tool box and may expand indications particularly for asymptomatic patients.