In Leicester, UK, rapid-access surgery for symptomatic carotid stenosis has been offered since October 2008. Ross Naylor reviews the practical lessons that have been learned with the experience. He discussed this topic at CX35 on Tuesday.

By Ross Naylor

When the trials randomised “recently symptomatic” patients to carotid endarterectomy or medical therapy, symptoms had to have occurred

Consequently, there has been a move towards performing surgery as soon as possible after the index event (ie treating transient ischaemic attack on a par with unstable angina). NICE advise that patients should undergo surgery

Some surgical/interventional colleagues have not actively embraced the move towards expedited intervention. For them, patients benefit from a period of stabilisation and assessment (in order to reduce procedural risk), while others believe that intervening early is associated with an unacceptably high procedural risk that may negate any benefit conferred through early intervention. The reality is, however, that the surgeon who operates within two weeks with a 10% procedural risk is still likely to prevent more strokes (in the long term) than the surgeon who defers surgery for four weeks and then operates with a 0% risk!

The Leicester Unit has offered a rapid-access surgery service since October 2008. All patients are seen in a 24/7 cerebrovascular clinic and those with 50–99% stenoses are transferred to the Vascular Unit for expedited surgery. 400+ symptomatic patients have now been treated (12%

First; it is not unusual (in the hyper-acute setting) for the duplex operator to comment that there is a critical stenosis that does not appear to open out into a normal calibre vessel. In the past (when patients were randomised some time after the index event), this might have been diagnosed as “near occlusion” (little benefit from surgery), but this is not the case in the hyper-acute setting. The diagnostic “give-away” is that high velocities are maintained across the stenosis (even if the distal lumen cannot be visualised) and CT angiography almost always shows a reconstructable vessel. In “near occlusion”, there are very low systolic velicities and little or no diastolic flow. Accordingly, corroborative imaging is mandatory (in the hyper-acute period) before recommending against urgent carotid surgery.

Second; anyone setting up this kind of service better get used to seeing recurrent events in up to 15% of patients between admission and surgery (despite being on antiplatelet and statin therapy). Up to 40% of patients referred acutely will have spontaneous embolisation on transcranial Doppler. Recurrent events (prior to surgery) were rarely encountered in the past, largely because patients were not referred so quickly.

Third; patients undergoing surgery (using general anaesthetic) with a pre-existing neurological deficit will almost always suffer a transient worsening of their deficit postoperatively. In the past, this was an indication for re-exploration. The “key” to management is how quickly the patient recovers from anaesthesia. If it is relatively quick, they will return to their pre-operative neurological status within an hour or so. Accordingly, it is important to warn recovery staff who may otherwise be alarmed at the apparent neurological deterioration.

Fourth; be prepared to adopt even more obsessive attention to surgical technique. We have found that careless skin preparation can trigger embolisation and transcranial Doppler is invaluable in warning of the embolising (unstable) patient during carotid mobilisation.

Fifth; be prepared to encounter a higher prevalence of post-endarterectomy hypertension (25% in theatre recovery, 25% back on the ward). This is usually seen in patients with poorly controlled blood pressure pre-operatively and it is essential that medical/nursing staff have guidelines for managing this condition. If you are going to treat patients in the hyper-acute period, you cannot adopt an ad hoc approach to blood pressure management, as patients will be subject to a greater risk of hyperperfusion stroke or intracranial haemorrhage.

Finally; (and contrary to what has previously been expected), our experience of operating in the hyperacute period has not been associated with a significant increase in procedural risk.

However; if you still harbour doubts about the benefit of intervening in the hyperacute period, ask yourself how you would want to be treated should you suffer a transient ischaemic attack and have a significant carotid stenosis?

Thought so! Don’t your patients deserve the same?

Following carotid intervention, the number of detectable diffusion-weight magnetic resonance imaging (DW-MRI) lesions is an order of magnitude greater than adverse clinical event (stroke/death). This lends credence to the use of DW-MRI as a surrogate endpoint allowing comparisons of interventional strategies in studies with reduced sample size, wrote Sumaira Macdonald, Newcastle, UK. She discussed this topic at CX35 on Tuesday 9 April.

By Sumaira Macdonald

The International Carotid Stenting Study (ICSS) sub-study comparing DW-MRI lesions in patients undergoing largely filter-protected carotid stenting and carotid endarterectomy demonstrated significantly fewer DW-MRI lesions after carotid endarterectomy, implying superior of control of procedural microemboli. Sixty-two of 124 (50%) patients undergoing distal filter-protected transfemoral carotid artery stenting and 18 of 107 patients undergoing carotid endarterectomy (17%) had new DW-MRI lesions (p<0.0001). Individual lesions were smaller in the carotid artery stenting group than in the carotid endarterectomy group (p<0.0001). Of the DW-MRI positive scans following carotid artery stenting, 25 (34%) resulted from unprotected carotid artery stenting and 37 (75%) resulted from filter-protected carotid artery stenting (p<0.019). Total lesion volume per patient did not differ significantly between patients undergoing carotid artery stenting and those undergoing carotid endarterectomy.

Two small randomised trials compared proximal embolic protection (Medtronic MoMa) with distal filters during carotid artery stenting. There were substantial or significant reductions in DW-MRI lesions for the MoMa compared with filter protection.

There were significantly fewer DW-MRI lesions in the MoMa group ipsilateral to the carotid lesion (p<0.0002) but no difference in the DW-MRI lesions in the contralateral hemisphere, implying the embolic penalty associated with catheterisation of the arch/great vessel origins for transfemoral carotid artery stenting. There was also a significant difference in favour of the MoMa system for lesion volume 0 [0 to 0.84] vs. 0.47 [0 to 2.4cm3] (p<0.0001).

The PROOF first-in-man analysis of high flow rate flow reversal via direct common carotid artery access (MICHI System) evaluated 65 patients, 48 of who had pre- and post-carotid artery stenting DW-MRI read by two independent US neuroradiologists. Eight of 48 patients had new DW-MRI lesions (16.7%).

Another study examined patients undergoing transcervical carotid artery stenting with flow reversal or distal filter-protected transfemoral carotid artery stenting. DW-MRI lesions were found in four of 64 transcervical (12.9%) and in 11 transfemoral (33.3%) patients (p=0.03). In multivariate analysis, age (relative risk, 1.022; p<.001), symptomatic status (relative risk, 4.109; p<.001), and open-cell vs. closed-cell stent design (relative risk, 2.01; p<.001) were associated with a higher risk of lesions in the transfemoral group but not in the transcervical group.

The low rates of DW-MRI lesions in studies of carotid artery stenting with flow reversal via direct carotid access are commensurate with carotid endarterectomy, presumably resulting from more effective embolic control and avoidance of catheterisation of the arch.

A prospective study of 110 patients undergoing filter-protected transfemoral carotid artery stenting investigated the fate of silent DW-MRI lesions. Twelve of 30 DWI lesions persisted, resulting in a lesion reversibility rate of 60%. Seventy-five per cent (12/16) of the cortical lesions disappeared while only 30% (3/10) of subcortical lesions disappeared. Eighty-three per cent (14/17) of lesions measuring 0–5mm disappeared while only 31% (4/13) of lesions measuring >5mm disappeared. It was concluded that a large number of silent ischaemic lesions visualised on the DWI images post-carotid artery stenting disappear within months and therefore the extent of permanent carotid artery stenting-related cerebral damage may be overestimated.

The most recent analyses of the ICSS sub-study data set revealed that patients in the carotid artery stenting group had more acute (relative risk 8.8, 95% CI 4.4-17.5, p<0.001) and persisting lesions (relative risk 4.2, 1.6-11.1; p=0.005) than patients in the carotid endarterectomy group. However, the rate of conversion from acute to persisting lesions was lower in the carotid artery stenting group than in the carotid endarterectomy group (RR 0.4, 0.2-0.8; p=0.007).

Systematic reviews have failed to provide consistent data across included studies comparing cognitive outcomes following carotid artery stenting and carotid endarterectomy.

Of 1,713 patients included in the ICSS, 140 of 177 patients enrolled in two Dutch centres had neuropsychometric testing at baseline and 120 at follow-up. Ten domains were examined, including executive function. There were no significant difference in overall cognition between patients undergoing carotid artery stenting and carotid endarterectomy despite the impressive difference in DW-MRI lesions counts between carotid artery stenting and carotid endarterectomy.

“Standard” filter-protected transfemoral carotid artery stenting generates more DW-MRI lesions than carotid endarterectomy but technical modifications (proximal embolic protection, direct carotid access) allow carotid artery stenting to more effectively compete where microemboli are concerned. Clinical correlation, with regards cognitive function is poor, implying either that a large number of DWI lesions are clinically irrelevant or that neuropsychometry is a blunt tool. DW-MRI is a reasonable secondary endpoint for carotid interventions, but without watertight clinical inference, the use of DW-MRI as a primary endpoint remains an unproven convenience.

On Tuesday 9 April, in the CX Non-Cardiovascular Adavanced Imaging Day session, Roger Greenhalgh, London, UK, introduced the speakers from the respective companies who spoke about building a hybrid operating room, the financial implications of doing so, and laser-guided hybrid suites.

In the afternoon session, chaired by John Primrose, president of the association of Surgeons of Great Britain and Ireland, showed delegates on the following topics:

• Florian Gebhard, Ulm, Germany—Making the hybrid operating room cost effective: the multidisciplinary hybrid operating room, and improving trauma care
• Manuel Ritter, Mannheirn, Germany— Radiation safety: management of dose in the hybrid operating room, and improvement of PCNL by Uro-Dyna computed tomography (CT)
• Helmut Isringhaus, Völkinghaus, Germany—Minimally-invasive resection of small lung nodules guided by fluoroscopy
• Javier Fandino, Aarau, Switzerland—Concept and applications of the hybrid operating room in cerebrovascular surgery
• Dogu Teber, Heidelberg, Germany—Laparoscopic partial nephrectomy in kidney cancer guided by Dyna CT/laparoscopy image diffusion
• Marco van Strijen, Nieuwegien, The Netherlands,—Advanced image guidance in renal tumour ablations
• Beat Müller, Heidelberg, Germany—Image-guided partial liver resection in hepatocellular carcinoma
• Alexander Schramm, Ulm, Germany—First experience of maxillofacial surgery in a hybrid operating room
• Chrisitan Raftopoulos, Brussels, Belgium—The hybrid operating room for neurosurgery
• Hicham Kobeiter, Créteil, France—Advanced image guidance for transcatheter arterial tumour embolisation using EmboGuide