Randomised, controlled trials have shown that periprocedural rates of minor stroke are higher with carotid artery stenting than with endarterectomy. Also, diffusion-weighted magnetic resonance imaging has shown that more silent new ischaemic brain lesions develop after stenting as compared to endarterectomy. “However, carotid endarterectomy is associated with a higher myocardial infarction rate (that impacts significantly on four-year mortality) than carotid artery stenting. It is also associated with significantly higher cranial nerve injury than stenting. In the CREST trial, these injuries were motor and remained unresolved at six months in 2% of patients. There is clear room for improvement for both carotid artery stenting and endarterectomy,” Sumaira Macdonald, Newcastle, UK, told Interventional News.
At the recent VIVA meeting in Las Vegas, USA, Macdonald told delegates that flow-altered short transcervical carotid artery stenting (FAST-CAS) has been shown to be a safe and feasible method for carotid revascularisation.“The low rate of myocardial infarction and cranial nerve injury with this technique is commensurate with transfemoral carotid artery stenting and shows improvement over carotid endarterectomy. The low rate of stroke/death and new diffusion-weighted magnetic resonance imaging lesions is commensurate with carotid endarterectomy and shows improvement over transfemoral carotid artery stenting,” said Macdonald.
Macdonald was presenting on Silk Road Medical’s PROOF (Embolic protection system: first-in-man) study, a single-arm first-in-man study using the Michi Neuroprotection System from two centres in Dusseldorf, Germany. The system is a new transcervical access and cerebral embolic protection system which enables stent implantation under high flow rate reverse flow, also known as flow-altered short transcervical carotid artery stenting.
“The access point for transcervical carotid artery stenting is just above the clavicle, between the two heads of the sternomastoid and directly into the common carotid artery. It is a 2–3cm incision. There are few complications relating to the cutdown but these would include potential damage to the vagus nerve, bleeding, haematoma and infection. The rates of these complications were exceedingly low, or absent, in PROOF,” she said.
Patients needed to have been over 21 years of age, with either symptomatic and asymptomatic carotid artery stenosis and over 5cm of space between the clavicle and carotid bifurcation, to be included in the PROOF study. Patients were excluded if they were considered anatomically high-risk (such as if they had had previous radiation treatment to the neck or radical neck dissection, tracheostomy or tracheal stoma etc), if they had a chronic total occlusion or a previously placed stent in the target vessel, had had atrial fibrillation within 90 days, common carotid artery disease, stroke within 30 days, or ipsilateral stroke with fluctuating neurologic symptoms within one year.
Of the 65 patients enrolled, 28 (43%) were female; the average age was 72.4 years and 25 (38%) patients were over 75 years of age. There were 12 symptomatic patients (18%) and five (8%) with contralateral occlusion. Eighteen patients (28%) were diabetic, two had had a recent myocardial infarction and 12 (18%) had congestive heart failure.
Procedural results
Macdonald stated that there was acute device success in 60 patients (92%). Two early failures were due to a blunt transition between the dilator and sheath of the Michi system and this was subsequently modified. The tolerance to reverse flow per protocol was 100% in the 61 patients assessed. The investigators found that tolerance to reverse flow could not be assessed in one subject who was placed under general anaesthesia prior to the procedure due to a high degree of agitation, and in three patients in whom a flow reversal circuit was not established. These patients were converted to either transcervical or transfemoral carotid artery stenting using a filter-based embolic protection system. There was investigator-reported transient intolerance in five (7.7%) cases, all of which resolved. “These were reported more frequently early in the learning curve—subsequently the operators learned to be tolerant of the patients’ intolerance,” said Macdonald.
The PROOF safety results showed that 61 (94%) patients completed 30-day follow up. “None of the patients had a major stroke, myocardial infarction and death from the index procedure through to the 30-day post-procedural period. There was one minor contralateral stroke reported at 30 days in a patient who had a negative post-procedural diffusion-weighted magnetic resonance imaging scan. This was considered to be related to neither the procedure nor the Michi system by the adjudicating committee. There was also one case of cranial nerve injury however these data are monitored, but not yet adjudicated,” said Macdonald.
Macdonald emphasised that larger, multicentre studies, such as the ongoing LOTUS study, which will involve a majority population of patients who are recently symptomatic, and the ROADSTER study in the USA, were necessary to confirm initial results. The PROOF first-in-man experience of 44 patients was published in the Journal of Vascular Surgery by Lazlo Pinter et al.
She also shared the PROOF diffusion-weighted imaging substudy which analysed information from the baseline scan (within 72 hours of the procedure) and the post-procedure scan (performed within 12–48 hours after the procedure). These scans were submitted for blinded evaluation by two independent neuroradiologists at a US Corelab. “These were data from 48 patients in this study and eight (16.7%) had new lesions,” she noted.
Macdonald noted that in the International Carotid Stenting Study (ICSS), which used a transfemoral stenting approach, with primarily distal filters as embolic protection, 50% of 124 patients developed new lesions. In the ICSS carotid endareterectomy group, where the embolic protection was a clamp and backbleed, 17% of 107 patients developed new diffusion-weighted imaging lesions. “In the PROOF study where the stenting approach was transcervical and the embolic protection was proximal high flow rate flow reversal, 17% of the 48 patients studied had new diffusion-weighted imaging lesions, which was equivalent to carotid endarterectomy for the first time for any carotid stenting strategy,” she said.
