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The third and final day of SLICE 2019 opened with a morning session entirely dedicated to thrombus. In this session, Doctors Jean-Phillippe Desilles, Cyril Dargazanli, Heleen Van Beusekom and Simon F. de Meyer gave us an update on recent findings about the microanatomy and the composition of intracerebral clots.
According to these findings, the thrombi have a core – a shell structure – and it is the shell which protects the clot against thrombolysis. The identification of various clot components such as extracellular DNA (the neutrophil extracellular traps – NETs) or von Willebrandt factor (vWF) might lead to the development of new thrombolytic drugs or the association of existing drugs with others such as DNAse or ADAMTS 13 (degrading the vWF) in order to achieve better efficiency of IVT.
Regarding mechanical thrombectomy (MT), Arturo Consoli presented the contribution of DSA to clot imaging. Despite being indirect, DSA gives useful real-time information about the occlusion at different levels – the global, regional, and focal one – all these levels being useful in planning the MT procedure.
For example, stent retrievers perform less well in tortious vessels, whereas contact aspiration has best results if the angle of attachment with the clot is close to 180°. Moreover, according to the aspect of the occlusion, contact aspiration performs better in regular occlusions and stent retrievers in irregular occlusions, especially if they bear a “claw shape”.
While DSA only gives information about morphology, MRI may also provide insight into clot composition as Doctor Romain Bourcier underlined in his talk.
The MRI can depict red-blood-cell-rich clots by a susceptibility vessel sign (SVS) on the gradient echo sequence and this type of clot is significantly associated with higher reperfusion rates in EVT and a better functional outcome. Based on these considerations, Dr. Bourcier presented a new clinical trial, the Vector trial, in which the modality of EVT is tailored to the results of the MRI. A fibrin-rich clot, devoid of the SVS, will be treated by contact aspiration first and a stent retriever will be used in first place when the clots are seen with an SVS.
Doctor Charles Majoie presented the contribution of the CT and CTA to clot imaging. Not only can it assess the clot length and location, its distance to ICA bifurcation, and clot burden, but it can also show the clot density giving an idea of its composition: a hyperdense thrombus is red blood cell rich whereas a hypodense is fibrin rich. However, a calcified clot, very difficult to retrieve by MT, is very dense on CT but is missed on MR. Moreover, Doctor Majoie defines permeability as the clot’s quality of being penetrable. This reflects “empty” spaces inside the thrombus (contrast uptake) and might give contact surface for IVT.
After Doctor JR MacCarthy demonstrated in vitro the relation between clot composition and its mechanical features, Franz Bozsak, engineer and co-founder of the company Sensome, gave us insights on how we might be able to easily analyze the composition of a clot in vivo, during MT. The company is developing a 0,014’’ micro-guidewire equipped with an array of 3 impedance sensors close to its distal tip.
Once placed in the thrombus, the application of low and high frequency currents enables it to characterize the tissue composition. The data are transmitted by Bluetooth to an external computer and processed with a machine learning algorithm in order to recognize tissues. By moving the microwire it is also possible to determine the exact clot length.
Moreover, the sensors, being placed in such a way as to cover 360°, might be possible to analyze not only the thrombus itself but also the vessel wall.
In the afternoon session, Doctor Osama Zaidat presented the importance of the first pass effect in thrombectomy. This was nicely illustrated by a recorded stroke case from the Montpellier team, a severe wake-up stroke caused by an M1 occlusion. The combination of a 9 Fr balloon guiding catheter, an Embotrap stent retriever and a distal aspiration (Sofia) allowed for a very good revascularization with TICI 2c being obtained after the first pass.
Doctor Francisco Mont’Alverde discussed an interesting case of aggressive cerebral venous thrombosis in a young patient and proposed an algorithm for its management and the place of endovascular treatment.
The day concluded with a series of workshops: small groups where we worked on unsolved questions about stroke management. The results of these – “our choices while awaiting evidence” – were shared with all participants animating more lively discussions between the faculty.
Léon IKKA