Report – On the Cutting Edge: ongoing research into intracranial thrombus

Day 3. Wenesday, 5 October

The last day of the Stroke Live Course began with a lecture by Dr J. Blasco (Barcelona, Spain) focusing on the influence of mechanical thrombectomy (MT) on endothelial cells. He first emphasized that the use of rtPA may have some downsides, mainly blood-brain barrier disruption, increased endothelial permeability, brain edema or direct neurotoxic effect. Stent-retrievers may have some downsides as well, one of them being endothelial damage. He then mentioned some studies on this topic before going on to describe his own study analyzing the impact of gadolinium vessel enhancement (GVE) after mechanical thrombectomy. In this study, his team used a combination of TOF and FLAIR gadolinium sequences, demonstrating nicely that GVE was present in more than 50% of the patients after MT. This presence was associated with a previous use of rtPA and the number of passes of the device. Severe BBB was present in 45% of patients and associated with ICH and poor clinical outcome.

After this introduction, Dr R. Bourcier (Nantes, France) spoke about his own original research work that focused on the potential opportunity of detecting thrombus composition by imaging tools. Specifically, he and his team questioned whether the susceptibility vessel sign (SVS) was a reliable marker to predict thrombus composition. He first showed that SVS could appear differently depending on the specific MRI machine used in its detection – even for the same clot. Thus, he highlighted the need for a reliable and quantitative tool to predict thrombus composition. Different MRI sequences have been tested by his team with one of these sequences being able to give them the mean T2* relaxation time; a low mean relaxation time being associated with a lower number of attempts of MT than a higher relaxation time.

 

On clots

David Vale from Neuravi followed with an interesting presentation focusing on in vitro modelling of the intracranial clot, a topic which is his company’s main research field and in which they have developed their expertise. Indeed, today Neuravi is able to produce several clot analogs. He first mentioned some studies on intracranial thrombus, showing that many variables could be implicated in explaining varying clot compositions (age, environment, etc…). Furthermore, he highlighted that, besides clot biological composition, mechanical properties (compression, friction) could also influence the success of MT. Demonstrations using silicon models followed, illustrating the different MT procedures using different clot models.

Dr. Raul Nogueira (Atlanta, GA, USA) then performed a quick review of different studies focusing on clot composition, and exposed his viewpoint concerning the influence of thrombus burden and stroke outcome.

 

Clinical cases

Pr Vincent Costalat (Montpellier, France) presented the first clinical case of the day, a vertebro-basilar ischemic stroke (baseline NIHSS = 5), explored by CT and CTA. CTA showed a distal and top basilar occlusion. Secondary clinical worsening occurred with NIHSS at 9. Complete MRI was not possible here because of the patient’s agitation. Only DWI was performed, which appeared normal. Access was performed coaxially using a Neuron Max with a long vertebral catheter. A quick survey was launched by V. Costalat where he asked the audience whether or not they performed a microcatheter injection after passing through the thrombus. In this particular case, use of this injection appeared mandatory because the anatomy was tricky, difficult to depict, with the microcatheter being first localized in a thalamoperforating artery. In this case, both a distal aspiration catheter and a Solitaire stent retriever were employed, with complete reperfusion after one pass.

The neuro-interventional team from Denver, CO, USA then presented SLICE’s last day’s most difficult case. This concerned an 80-year-old woman with acute speech difficulties and secondary clinical worsening NIHSS (28). CTP showed a substantial perfusion mismatch between TMax and CBV. At initial management, a T carotid occlusion was suspected. In fact, the intracranial lesion was associated with a chronic carotid bulb occlusion. Even after multiple attempts with different wires and catheters, it was impossible to reach the intracranial part of the carotid artery, leading to the decision to stop the procedure.

The stroke neurologist Dr Bertrand Lapergue (Foch Hospital, Suresnes, France), presented the ASTER study, sharing with us its design and purpose. This study compares first pass use of the ADAPT technique as opposed to stent retrievers. Inclusion in this randomized trial are now complete and results will probably be published soon.

Dr Don Frei from the neuro-interventional team of Denver, CO, USA, presented arguments in favor of using first pass aspiration, illustrating his talk with some successful cases realized using the Penumbra ACE 68.

Dr Gascou (Montpellier, France) demonstrated silicon cases performed with 5MAX and ACE. He first presented a Montpellier aspiration technique protocol, avoiding going through the thrombus in order to lower the risk of distal emboli. He demonstrated that this approach was difficult with the stiffer ACE 68, which needed more support. It should be noted that with this latter catheter the thrombus was completely ingested by aspiration before retrieval.

The afternoon case session began with a right tandem stroke presented by the team from Atlanta (GA, USA) with the first run showing a stenosis of the carotid bulb. The strategy here consisted of inflating a balloon guide catheter (BGC) just before the stenosis and then advancing the BGC under manual aspiration to clean the potential clot attached there. No intermediate catheter was used to reach the intracranial circulation and, after deployment of the Solitaire stent retriever, retrieval was performed through the stenosis and the BGC below.

Vincent Costalat suggested first securely advancing an intermediate catheter after the stenosis allowing for multiple attempts of thrombectomy without crossing the culprit stenosis. An open debate followed with a very rich exchange between the expert panel and audience concerning both stenting and the required antiplatelet medication. In this case, after the first retrieval achieved a substantial intracranial reperfusion, a SPIDER protection device was placed in the cervical carotid and angioplasty was subsequently performed before stenting with a VIA 6.30. The massive stroke on day MRI reminds us that infarct core assessment is mandatory before stent delivery (and antiplatelet loading, etc…).

Next, a lecture by Olav Jansen (Kiel, Germany) focused on possible approaches to tandem lesions, highlighting several of the problems encountered when facing these lesions. He performed a quick review of the literature on this topic, especially a recent article published in AJNR suggesting that cervical carotid stenting plus MT was effective and not associated with an increase of sICH rates compared to MT alone.

Dr Omer Eker (Montpellier, France), in a very clear presentation, emphasized that it was important and required to classify tandem occlusions according to their etiology (atherosclerotic, dissection, embolic, web). He presented Montpellier’s revascularization strategy when facing tandem occlusions along with the design of his study which compared three groups of patients: tandem atherosclerotic occlusions, dissection associated tandems and isolated MCA occlusions. The main results showed that a first pass proximal approach in this setting was significantly associated with the risk of symptomatic intracranial hemorrhage. Regarding demographic data, atherosclerotic tandem patients were older and presented with more cardiovascular risk factors.

In the last “silicon” session of the day, Dr Gascou showed an interesting model of tandem occlusions. Dr Anderssen from the Karolinska Institute (Sweden) presented his point of view when faced with these kinds of lesions: first, inflate the BGC in the common carotid artery; second, go through the lesion using a long microwire with a 21 microcatheter. His preference was the use of a triaxial system with an intermediate catheter distal to the carotid and, if he is unable to go through the cervical lesion (a very rare situation in his experience), he performs an angioplasty using a small balloon (2-3 mm), with the BGC remaining inflated.

A quick presentation by V. Costalat followed and focused on large strokes. Results suggest that ischemic stroke patients with ASPECT scores of 5 or less on admission MRI should not automatically be ineligible for endovascular therapy. Indeed, thrombectomy may be effective in patients of less than 70-years-old with ASPECT scores of 4 to 5, with good clinical outcomes achieved at 90 days in 43.6% of these patients. Older patients and patients with lower ASPECT scores should be considered for thrombectomy on an individual basis taking into consideration their comorbidities and pre-stroke status.

The last case of the day – and the last of this year’s SLICE meeting as well – came from the Montpellier, France team of interventional neuroradiologists and concerned a right MCA occlusion. The first aspiration with a Sofia 6 Fr catheter led to a partial reperfusion of the MCA territory, with a persistent prefrontal defect. The second attempt, with a stent retriever, unfortunately, did not allow for clot retrieval and resulted in a TICI 0 reperfusion, probably by proximal migration. A third attempt, deploying a stent retriever in a stem artery supplying the precentral and central artery, led to a TICI 2A reperfusion. A vasospasm was suspected at this point, and Nimodipine was administered. After five minutes, a control angiogram showed a TICI 3 reperfusion.

To close this rich last day of SLICE, Patrick A. Brouwer from the Karolinska Institute (Sweden) and Alain Bonafe from Montpellier (France) gave their opinions regarding the endovascular skills needed in order to effectively preform mechanical thrombectomy. This is an ongoing and open debate with Prof. Bonafe offering us with a quick review of the “European Recommendations on Organization of Interventional Care in Acute Stroke”, recently published in the Interventional Journal of Stroke.

 

Until next year…

This very successful second SLICE Meeting thus came to an end. It offered all of us a unique opportunity to explore and discuss the various aspects of critical stroke care including wide-ranging discussions on ischemic stroke patients – from their diagnosis to their treatment – including patient workflow at local and regional levels…anesthesiology management was also very much a part of these discussions. Perspectives offered by a vast range of challenging future studies were presented as well, for instance on large volume strokes and low NIHSS to cite just two of them.

This second edition allowed for the different contributors and attendees to share their experiences together.

Thank you all for your participation which made this second edition so alive….see you at SLICE 2017!

 

Cyril Dargazanli, MD

Cyril Dargazanli