Vessels Occlusion

Coagulation summarizes the mechanisms involved in stopping bleeding due to an injured or defective vessel wall. Coagulation is characterized by procoagulatory and anticoagulatory factors that are in balance under normal conditions. Vessel injuries are occluded by the coagulation system and spontaneous vessel occlusions dissolved by the fibrinolytic cascade. 

Thrombosis is an imbalance toward the clotting capacity of the blood that leads to vessel occlusion by a clot. The clot prohibits ftuther blood flow and can so cause pathological sequelae dependent on its localization. 

A significant neurologic deficit expected to result in long-term disability, and attributable to large vessel occlusion (basilar, vertebral, internal carotid, or middle cerebral artery M1 or M2 branches). 

The data for the use of GP Ilb/Illa inhibitors in conjunction with lAT are even more scant, and are limited to case reports. Intravenous abciximab has been successfully used as adjunctive therapy to lA rt-PA or UK in cases of acute stroke. Desh-mukh et al. reported on 21 patients with large vessel occlusion refractory to lAT with rt-PA who were treated with IV and/or lA abciximab, eptifibatide, or tirofiban. Twelve patients also received IV rt-PA and 18 patients underwent balloon angioplasty. Complete or partial recanalization was achieved in 17 of 21 patients. Three patients (14%) had asymptomatic ICH, but there were no cases of symptomatic ICH. Mangiafico et al. described 21 stroke patients treated with an intravenous bolus of tirofiban and heparin followed by lA urokinase. Nineteen of these patients also underwent balloon angioplasty. TIMI 2-3 flow was achieved in 17 of 21 patients. ICH occurred in 5 of 21 patients (3 symptomatic ICH and 2 SAH), and was fatal in 3... 

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. 

Bose A, Jansen O. Clinical safety and performance of the penumbra stroke system a novel device for the treatment of acute stroke due to large vessel occlusive disease. European Stroke Conference Brussels, Belgium May 2006. 

In one study, patients with significant diffusion-perfusion mismatch on MRI, large vessel occlusive disease, and fluctuating neurological deficits were found to be more likely to respond. Induced hypertension correlated with improved cortical cerebral... 

Blaser T, Hofmann K, Buerger T, Effenberger O, Wallesch CW, Goertler M. Risk of stroke, transient ischemic attack, and vessel occlusion before endarterectomy in patients with symptomatic severe carotid stenosis. Stroke 2002 33 1057-1062. 

Although several approaches to stroke classification have been described, the most common mechanism-based classification in current use is the system described by the TOAST investigators." This classification describes five major subtypes of ischemic stroke based on the results of neuroimaging and other medical investigations, namely (1) LAA, (2) cardioembolism, (3) small-vessel occlusion, (4) stroke of other determined etiology, and (5) stroke of undetermined etiology. Inter-rater reliability of the TOAST scheme has been reported as moderate-to-substantial K 0.5-0.7). 

Intra-arterial thrombolytics may improve outcomes in selected patients with acute ischemic stroke due to large-vessel occlusion. Patients in the Prolyse in Acute Cerebral Thromboembolism II (PROACT II) trial were given 9 mg prourokinase (r-pro UK)... 

Almost all patients with TTP have a deficiency in protease activity. As a result, TTP is associated with the presence of unusually large vWF (uLvWF) multimers in the circulation. These uLvWF multimers can bind to GPIb/IX receptor complex on platelets under conditions of high shear stress in the microcirculation and can also bind to the GPIIb/ina receptor on activated platelets, causing aggregation of platelets and subsequent blood vessel occlusion (69). 

Vascular imaging allows determination of supply vessel occlusions, the presence of clots and wall abnormalities, such as atherosclerotic plaques and possible plaque ulceration, and, if they exist, to assess their effect on blood flow. 

To provide optimal immunosuppressant effects, sirolimus is typically combined with glucocorticoids or other immunosuppressants. Sirolimus exerts a number of other beneficial effects, including the ability to inhibit smooth muscle proliferation in blood vessel walls. For this reason, sirolimus is sometimes incorporated into drug-eluting stents that is, a supportive tubular structure (stent) is placed in the lumen of a partially occluded artery, and the drug is released slowly from the stent to help reduce vessel occlusion.64... 

Van Belle E, Abolmaali K, Bauters C, McFadden ER Lablanche JM, Bertrand ME. Restenosis, late vessel occlusion and left ventricular function six months after balloon angioplasty in diabetic patients. J Am Coll Cardiol 1999 34 476-485. 

Large Vessel Occlusive Disease of the Anterior Circulation 4... 

The presence and extent of the ischaemic penumbra is time-dependent. However, stroke is a heterogeneous disorder, and survival of the penumbra can vary from less than 3 h to well beyond 48 h from patient to patient (Darby et al. 1999 Read et al. 2000). Penumbral survival is dependent upon many factors, such as location of vessel occlusion, state of collateral blood... 

Perfusion imaging (PI) is complementary to DWI in acute stroke assessment. In animal models, PI lesions are visible immediately after vessel occlusion and resolve rapidly after successful thrombolysis or reperfusion (Muller et al. 1995 Yenari et al. 1997). In stroke patients, serial PI studies can document... 

Furthermore, a number of groups have now demonstrated that patients with distal vessel occlusion (including those without visible MRA lesions) have more complete reperfusion in response to tPA compared to those with proximal occlusion (Linfante et al. 2002 Neumann-Haefelin et al. 2004 Parsons... 

Fig. 3.10. Patient received intravenous tPA following MRI. PI map is a colour coded MTT map where mildly hypoperfused tissue is light blue, moderate hypoperfusion is green, and severe is red. Despite no visible vessel occlusion on acute MRA, there is still significant tissue at risk. Following thrombolysis, there is complete reperfusion and all mismatch tissue is salvaged from infarction on follow-up imaging...

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