Thrombus retrieval

There are several techniques available for mechanical thrombolysis. The most common is probing the thrombus with a microguidewire. This technique appears to be useful in facilitating chemical thrombolysis. Alternatively, a snare (e.g., Amplatz Goose-Neck Microsnare, Microvena, White Bear Lake, MN) can be used for multiple passes through the occlusion to disrupt the thrombus. " A snare can also be used for clot retrieval, mostly in simations in which the clot has a firm consistency or contains solid material. ... 

The Penumbra stroke system (Penumbra Inc., San Leandro, CA) includes two different revascularization options (1) thrombus debulking and aspiration may be achieved by a reperfusion catheter that aspirates the clot while a separator device fragments it, and (2) direct thrombus extraction may be performed by a ring retriever while a balloon guide catheter is used to temporarily arrest flow. This system has been tested in a pilot trial in Europe. Twenty patients (mean NIHSS 21) with a total of 21 vessel occlusions (7 ICA, 5 MCA, and 9 Basilar) were treated up to 8 hours after symptom onset. Recanalization prior to lA lysis was achieved in all cases (48% TIMI 2 52% TIMI 3). Seven patients were also treated with lA UK or rt-PA. Good outcome at 30 days (defined as mRS < 2 or NIHSS 4-point improvement) was demonstrated in 42%. The mortality rate was 45%, but there were no device-related deaths. There was one asymptomatic SAH and three symptomatic ICHs. A prospective, single-arm, multicenter trial is being conducted in the United States and Europe currently. 

KerberCW, Barr ID, Berger RM, Chopko BW. Snare retrieval of intracranial thrombus in patients with acute stroke. J Vase Interv Radiol 2002 13 1269-1274. 

Figure 6. Characteristic plaque debris retrieved by a filtration device. ALS amorphous lipid substance, FC foam cell, T thrombus. Arrows point to cholesterol crystals (by permission from Skyschally111 ).

A rapid, minimally invasive in vivo animal model was developed to evaluate continuously the process of thrombosis on biomaterials. Goats subjected acutely to bilateral polyethylene catheters are monitored for net retention of luln-oxine platelets on the separate catheters. Comparisons between continuous scintigraphic monitoring of platelet retention and thrombus recovered at catheter retrieval show that platelet retention and thrombus growth are dynamic processes for at least the first few hours of implantation, and that platelet retention is predictive for thrombus size. Mean recovered thrombus weight is 23 mg cm, which corresponds to a 44% increase in effective radius of the catheter-thrombus combination. 

Figure 4. Correlation of thrombus platelet concentration and thrombus weight. The positive correlation suggests that thrombus weight can be predicted from the number of platelets retained. These thrombi were retrieved 2-3 h after catheter placement. Conditions m =0.80 and r = 0.90.

The Catch device (Balt Extrusion, Montmorency, Erance) is a distally closed, self-expanding nitinol cage that has also been used for thrombectomy with promising results [32]. A comparison between the MERCI and the Catch devices in an animal model has demonstrated superiority of the MERCI Retriever, which resulted in higher rates of overall recanalization (90% vs. 70%), higher chances of recanalization at the first attempt, and a lower rate of thrombus fragmentation/ distal embolization [33]. 

Fig. 13.4 Combined MERCI thrombectomy and balloon angioplasty for treatment of acute atherosclerotic occlusion, (a) Baseline angiogram demonstrates complete occlusion of the midsegment of the basilar artery black arrow). Note the PICA-anteiior-inferior cerebellar artery (AICA) collaterals (white arrow) with reconstitution of flow at the distal basilar artery, (b) Native image demonstrates the MERCI device deployed distally to the occlusion (white arrow), (c) Photograph of the retrieved thrombus that caused the occlusion (black arrow). It presumably originated...

Patients have a limited 3-h window starting at the onset of stroke symptoms to be treated with clot-dissolving (thrombolytic) drugs [42]. However, there is strict exclusion criteria for patients to be treated with thrombolytic drugs in an effort to prevent potential intracerebral and gastrointenstinal hemorrhaging associated with the treatment. Therefore researchers have proposed nonpharmaceutical treatments to retrieve the clot mechanically, in which blood flow would be restored immediately compared to therapeutic clot dissolution. Consequently, the FDA has approved the use of mechanical devices to retrieve a thrombus [43,44],... 

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