Evaluation of Merci Retriever by Experimental Modeling

The Merci Retriever is the first device for mechanical embolus removal in patients with cerebral ischemia. Use of the device was evaluated using experimental models. Three stroke model systems were created: silicone embolism model with flow system, pig embolism model, and silicone-pig tortuous artery model. The series of extraction procedures (capture, retrieval, and aspiration) was examined in the models under flow control. Coagulated blood clot was adopted as embolic material, to simulate embolic stroke of the carotid or middle cerebral arteries. Retrieval of the clot was successful in only one of six trials in the silicone model of the carotid artery, as the clot easily worked free from the helical tip. Aspiration was successful in three of the six trials. Retrieval was successful in two of four trials in the middle cerebral artery and aspiration was successful in two. Retrieval was successful in all five trials in the pig embolism model, and three of five trials in the silicone-pig tortuous artery model. The Merci Retriever does not always retain the embolism, and the helix tends to distort in acute or rough lumen. Aspiration is not always successful.

Catheter-based recanalization techniques for acute ischemic stroke

Recent advances in endovascular interventional therapies have revolutionized the management of acute ischemic stroke. For patients who present with occluded circle of Willis vessels, timely and successful arterial recanalization is the best predictor of clinical improvement. Diagnostic neuroimaging has advanced noninvasive tools--namely, transcranial Doppler, CT angiography, and MR angiography--to screen individuals with acute neurologic syndromes rapidly for arterial occlusion, and hence to exclude from treatment those who are unlikely to benefit from or could be harmed by arterial recanalization strategies. Intra-arterial thrombolysis has been proven to be of benefit in large clinical trials. Moreover, the US Food and Drug Administration has recently approved the use of a mechanical clot retrieval device for acute embolic stroke, and a number of other similar strategies are under various stages of investigation. This article reviews the diagnostic and interventional approach to the management of large vessel embolic stroke.

AngioJet rheolytic thrombectomy versus local intrapulmonary thrombolysis in massive pulmonary embolism: a retrospective data analysis

PURPOSE

To compare the efficacy of full-dose local intrapulmonary thrombolysis (LIT) versus AngioJet rheolytic thrombectomy (ART) in the treatment of massive pulmonary embolism.

METHODS

A retrospective review was conducted of 8 consecutive patients (5 women; mean age 66.0+/-5.9 years, range 56-74) who underwent LIT with high-dose intrapulmonary urokinase (4400 IU/kg over 10 minutes followed by a 2000-IU/kg/h infusion) and a subsequent 6 consecutive patients (4 men; mean age of 59.2+/-17.0 years, range 26-69) who underwent ART plus adjunctive low-dose urokinase infusions (100,000 IU) until hemodynamic recovery was achieved. Pre and postprocedural Miller scores were calculated, and relative Miller score improvement, total urokinase doses, and duration of therapy were compared.

RESULTS

Hemodynamic stability was restored in all 8 LIT patients and in 5 (83%) of the 6 ART patients; 1 (16.7%) patient died during the ART procedure due to recurrent MPE. In the LIT group, the mean Miller score prior to intervention was 17.38+/-2.67, which was reduced to 6.13+/-1.46 after the intervention (p<0.0001) compared to scores of 18.83+/-2.86 and 6.83+/-2.79, respectively, in the ART group (p<0.0001). The mean urokinase dose was 2.07+/-0.44 million IU in the LIT group versus 0.70+/-0.36 million IU in the ART group (p<0.0001). The mean duration of therapy was 11.45+/-2.94 hours in the LIT group versus 3.37+/-1.41 hours in the ART group (p<0.0001). No significant difference in relative Miller score improvement was observed.

CONCLUSION

By accelerating the fragmentation of thrombus, ART plus adjunctive low-dose urokinase seems to be more rapidly effective compared to LIT. ART achieves both rapid cardiovascular relief and reduces the dose of thrombolytic agent necessary in patients with massive pulmonary embolism.

Mechanical Embolectomy

Mechanical embolectomy in acute ischemic stroke employs the use of novel endovascular devices to revascularize occluded intracerebral arteries. Devices like the Merci Retiever and other endovascular snares, laser thrombectomy and rheolytic/obliterative microcatheters, intracranial balloon angioplasty and stenting, and intra-arterial and transcranial ultrasound-enhanced chemical thrombolysis are intended to improve tissue rescue and diminish reperfusion hemorrhage while broadening the population eligible for therapy. Patient selection with MRI- and CT-based stroke protocols can detect tissue at risk and may obviate the classic limitations of the stroke therapeutic time window. These devices are being developed and modified at a rapid pace, requiring mounting endovascular expertise, and are being used successfully alone or in conjunction with chemical thrombolysis with relative safety.

The Incidence of Emboli during Cardiac Surgery: A Histopathologic Analysis of 2297 Patients

OBJECTIVE

Manipulation of the atherosclerotic aorta during cardiac surgery is assumed to cause embolization, which can contribute to adverse outcomes. Recently, as a result of worldwide trials deploying the Embol-X intraaortic filter during cardiac surgery, such emboli were captured and processed for histopathologic analysis.

METHODS

Filters with a pore size of 120 microns were placed in 2297 patients who underwent the following operations: coronary artery bypass grafting (CABG) (70%), valve (17%), combination CABG/valve (11%), and other (2%).

RESULTS

The filters captured at least one embolus in 98% of the patients. An average of 8.3 particles was captured per filter (range of 0-74). The surface area of the emboli was on an average 5.8 mm2 (range of 0-188 mm2). Histologic analysis of the captured particles indicated that in 79% of the filters fibrous atheromata were noted, in 44% there were platelets and fibrin, 8% had red blood cell thrombus, 3% had fibro-fatty/adventitial tissue, 2% had other material including cartilage, myocardium, lung, suture, and a teflon pledget. Of the patients enrolled, 1569 were high-risk. The average number of particles captured in the high-risk patients was 8.5 versus 5.8 for the low- to moderate-risk patients (P < .0001). Concomitantly,there was an increase in the embolic burden between the higher- and lower-risk patients (surface area 6.6 vs. 4.0 mm2, P < .0001).

CONCLUSION

These data show the ubiquitous incidence of emboli during cardiac procedures. Intraaortic filtration should reduce adverse outcomes as was demonstrated for the high-risk patients in this study. Aortic manipulation during cardiac surgery can cause embolization and increase morbidity. The use of an intraaortic filter can decrease the embolic burden. We now report the histopathologic analysis of these emboli.

[Treatment of acute myocardial infarction due to embolism by a thromboaspiration catheter]

Although rare, coronary embolism poses a therapeutic problem. Thromboaspiration is an elegant alternative to implantation of a stent. The place of stenting in acute myocardial infarction depends on the results of randomised trials. The authors report the case of a 69 year old woman who presented with an apico-lateral infarction probably due to a coronary embolism after postoperative thrombosis of a mechanical mitral valve prosthesis. The authors performed a percutaneous revascularisation by thromboaspiration with a good result.

MERCI 1: a phase 1 study of Mechanical Embolus Removal in Cerebral Ischemia

BACKGROUND AND PURPOSE

To report the result of the Mechanical Embolus Removal in Cerebral Ischemia (MERCI) 1 study, a phase 1 trial to evaluate the safety and efficacy of mechanical embolectomy in the cerebral vasculature.

METHODS

MERCI 1 enrolled 30 patients in 7 US centers. Main inclusion criteria were: National Institutes of Health Stroke Scale score (NIHSS) > or =10; treatment performed within 8 hours from symptoms onset and contra-indication to intravenous thrombolysis; no large hypodensity on computed tomography; and occlusion of a major cerebral artery on the angiogram. Safety was defined by the absence of vascular injury or symptomatic intracranial hemorrhage. Efficacy was assessed by recanalization rate and clinical outcome at 1 month. Significant recovery was defined as 30-day modified Rankin of 0 to 2 in patients with baseline NIHSS 10 to 20 and 30-day modified Rankin of 0 to 3 in patients with baseline NIHSS >20. The procedures were performed with the Merci Retrieval System, a system specially designed for intracranial embolectomy.

RESULTS

Twenty-eight patients were treated. Median NIHSS was 22. Median time from onset to completion of treatment was 6 hours and 15 minutes. Successful recanalization with mechanical embolectomy only was achieved in 12 (43%) patients, and with additional intra-arterial tissue plasminogen activator in 18 (64%) patients. There was one procedure related technical complication, with no clinical consequence. Twelve asymptomatic and no symptomatic intracranial hemorrhages occurred. At 1 month, 9 of 8 revascularized patients and 0 of 10 nonrevascularized patients had achieved significant recovery.

CONCLUSIONS

This phase 1 study shows that cerebral embolectomy with the Merci Retriever was safe and that successful recanalization could benefit a significant number of patients, even when performed in an extended 8-hour time window.

Thrombectomy for Acute Internal Carotid Thrombosis: Five Thrombectomy Devices Compared

OBJECTIVE

To test the safety and efficiency of commercially available thrombectomy catheters in clearing simulated internal carotid artery (ICA) thrombosis.

DESIGN

Comparative in vitro study.

MATERIALS AND METHODS

A model of the ICA was filled with human thrombus, the 'circle of Willis' back pressure was set at either 10 or 30 cm of water. Five thrombectomy devices (Hydrolyser, Clot Buster, Acolysis System, AngioJet and Fogarty embolectomy catheter) were compared for (i) efficiency at removing thrombus, (ii) pressure changes at the tip of each device, and (iii) distal embolisation by flow cytometry.

RESULTS

Thrombus clearance was greatest with the AngioJet (median 95%, range 92-97%) and least with the Acolysis System (median 34%, range 12-50%). The Clot Buster and Hydrolyser were safest as they produced only negative tip pressures, the AngioJet and Balloon catheter produced positive and negative pressures risking distal embolisation. The Acolysis system produced no pressure change during use. Distal embolisation (of particles between 5 and 40 microm diameter) was greatest with the Fogarty balloon catheter at 10 cm water (P<0.05) and least with the Hydrolyser and Clot Buster.

CONCLUSION

Balloon embolectomy for ICA thrombosis risks further embolic cerebral damage. The Hydrolyser and the Clot Buster show the greatest promise for ICA thrombectomy.

An update on bronchial blockers during lung separation techniques in adults

Techniques for one-lung ventilation (OLV) can be accomplished in two ways: The first involves the use of a double-lumen endotracheal tube (DLT). The second involves blockade of a mainstem bronchus (bronchial blockers). Bronchial blockade technology is on the rise, and in some specific clinical situations (e.g., management of the difficult airway during OLV or selective lobar blockade) it can offer more as an alternative to achieve OLV in adults. Special emphasis on newer information for the use of Fogarty embolectomy catheter as a bronchial blocker, the torque control blocker Univent, and the wire-guided endobronchial blocker (Arndt blocker) is included. Also this review describes placement, positioning, complications, ventilation modalities, and airflow resistances of all three bronchial blockers. Finally, the bronchial blockers can be used in many cases that require OLV, taking into consideration that bronchial blockers require longer time for placement, assisted suction to expedite lung collapse, and the use of fiberoptic bronchoscopy. The current use of bronchial blockers, supported by scientific evidence, dictates that bronchial blockers should be available in any service that performs lung separation techniques.

Fluoroscopy-assisted dual-catheter thromboembolectomy: a new technique useful in patients with embolization to arteries of disproportionate diameters

Distal embolization is a complication of aortoiliac aneurysm repair. Fluoroscopy-assisted catheter thromboembolectomy is useful in removing popliteal and tibial emboli from the femoral approach. Concomitant presence of aortoiliac and popliteal aneurysms, a known association, may present a difficult challenge to embolus extraction. Currently available embolectomy catheters large enough for thrombus extraction from a popliteal aneurysm are too large for safe tibial artery cannulation, and tibial balloon catheters cannot be enlarged sufficiently to transfer the thrombus through the aneurysmal popliteal segment. We treated a patient who embolized to his popliteal aneurysm and distal tibial circulation following aortoiliac aneurysm repair. A fluoroscopy-assisted dual-catheter technique was used to extract the thrombus through the femoral approach, eliminating the need for direct popliteal or tibial exploration. This technique uses two balloon catheters of graduated size, maneuvered concurrently under fluoroscopic guidance into the tibial and popliteal circulation. The smaller tibial catheter is inflated, and thrombus is withdrawn into the popliteal segment. The larger popliteal balloon catheter is then inflated distal to the smaller catheter, and both catheters are withdrawn simultaneously to deliver the clot through the femoral arteriotomy. This technique can be useful for successful balloon catheter extraction of thrombus via remote access, in an arterial system with variable diameter, eliminating the need for direct popliteal or tibial exploration.

Peripheral arterial applications of percutaneous mechanical thrombectomy

Various devices have been introduced for the purpose of percutaneous mechanical thrombectomy (PMT). These devices show promise as a valuable treatment option in acute arterial thrombotic occlusions, in addition to the gold-standard surgical method, the Fogarty balloon embolectomy, and local fibrinolysis therapy. Local fibrinolytic therapy cannot be used in the presence of contraindications, and can be time-consuming in limb threatening situations. Surgical intervention can also result in intimal vessel wall injury and is of limited value in infrageniculate occlusions. In this review, currently available PMT devices for peripheral arterial applications will be introduced, and their advantages, drawbacks and finally the reported clinical experience with these devices will be presented.

Treatment of basilar artery embolism with a mechanical extraction device: necessity of flow reversal

BACKGROUND AND PURPOSE

The success of local fibrinolysis in vertebrobasilar thromboembolism depends on the volume and composition of the clot. Since thrombolysis can also be time consuming and cause bleeding, we investigated the feasibility of a mechanical clot retraction device based on a nitinol basket advanced through a microcatheter.

METHODS

Five patients with acute embolism of the basilar artery who presented with progressive stroke and impaired consciousness were included in a multicenter study (Neuronet Evaluation in Embolic Stroke Disease [NEED]). In 3 patients flow reversal was induced with the use of silicone balloons or coaxial catheters. Three patients required additional fibrinolysis.

RESULTS

The device failed to retrieve the clots in our first 2 patients with distal basilar artery embolism. After successful recanalization by local fibrinolysis, both patients survived, 1 disabled and 1 with little residual impairment. In the next 3 patients the anterograde flow in the basilar artery was reversed during the short retraction period by temporarily blocking the vertebral or subclavian arteries. Two of these patients were completely recanalized by solely mechanical means; the third patient needed additional fibrinolysis before also being recanalized. All 3 patients survived: 1 remained disabled, 1 had almost a full recovery, and 1 became asymptomatic the day after the procedure.

CONCLUSIONS

Mechanical thrombus extraction seems to be a feasible method for preventing infarction by rapid, complete, and safe recanalization of the basilar artery. We recommend the use of flow control to support retrieval of the thrombus (which the proximal flow would otherwise keep in place like a cork) and to protect the distal vessels from embolization by fragments.

[Thrombectomy and embolectomy using the adherent clot catheter]

The efficacy of the Adherent Cloth Catheter is demonstrated on the three above described cases. The different mechanism of function on contrary to the classic Fogarty Catheter enables us to remove the older, strongly adherent thrombus from prothesis, artery or vein. The catheter is a functional instrument not only for vascular surgery, but also for invasive angiology.

Acute ischemia of the upper extremity: long-term results following thrombembolectomy with the Fogarty catheter

OBJECTIVE

In 1962, the procedure of arterial thrombembolectomy with the Fogarty catheter was established. Numerous studies have been published studying thrombembolectomies of the lower extremities. Limited information, however, is available following thrombembolectomy of the upper extremity after arterial occlusion. The aim of the present study, therefore, was to determine long-term results (3-5 years after thrombembolectomy) following thrombembolectomy of the upper extremity with the Fogarty catheter in a large retrospective clinical study.

DESIGN

In the present study, 251 patients were encountered. Over a period of 20 years, 283 thrombembolectomies with the Fogarty catheter were performed on the upper extremity at the surgical department of the University of Munich.

MAIN OUTCOME MEASUREMENTS

The appearance of local and general complications in the postoperative phase, as well as long-term results, were evaluated.

RESULTS

The results indicate that general complications - i.e., cardiac insufficiency, cerebral ischemia, etc. - occurred in 18 patients (7.2%). Local complications - i.e., wound infection, persistence of ischemia, or hematoma - were evident in 51 patients (20.3%). Re-occlusion following thrombembolectomy was found in 21 patients (8.8%). The affected extremity had to be amputated in five cases (2.0%), and 14 patients (5.6%) died during the postoperative phase. As a result of multimorbidity of the patients and average age at the time of surgery (73 years), 40% of the patients had died before the date of examination. Nonetheless, 111 patients of the 117 living patients showed no complaints or minor coldness and pain following heavy exercise.

CONCLUSIONS

The results of the present study indicate that, in most cases, thrombembolectomy with the Fogarty catheter represents a successful surgical method for the acute treatment of arterial occlusion of the upper extremity.

Comparison of three mechanical thrombus removal devices in thrombosed canine iliac arteries

PURPOSE

To assess and compare intimal and medial vascular damage caused by three mechanical wall-contact thrombectomy devices: Fogarty embolectomy catheter, Arrow-Trerotola peripheral thrombectomy device, and MTI-Castañeda over-the-wire brush.

MATERIALS AND METHODS

Bilateral external iliac arteries of 15 canines were thrombosed before mechanical thrombolysis. Ten thrombosed arteries were randomly assigned to receive each device. Animals were sacrificed immediately, and histologic assessment of endothelial and medial damage in the vessels was performed.

RESULTS

The vascular damage found with all devices extended into the tunica media. The Fogarty embolectomy catheter and the Arrow-Trerotola device caused significantly more damage than the Castañeda brush.

CONCLUSION

All devices caused lesions extending into the media. Previous research has shown that the extent and depth of the vascular lesion may be contributing factors in promoting early atherosclerotic and accelerated hyperplastic intimal and medial changes. These findings warrant further study of these devices in an atherosclerotic model with longer follow-up.

Transvenous Catheter Embolectomy

Transvenous pulmonary embolectomy was first described in 1969 by Greenfield and associates who designed a special catheter for the aspiration of thrombi in the pulmonary circulatory system. This technique was applied in 64 patients with massive pulmonary embolism (PE) with a 70 to 72% survival rate. However, it is difficult to implement and has not gained widespread acceptance. More recently, several other catheter devices have been used in patients with PE. The total number of patients reported does not exceed 100. Relative angiographic improvement varies between 10 and 49%, but hemodynamic improvement is not observed or not measured in most patients and mortality varies between 9 and 30%. Fibrinolysis was associated with mechanical thrombectomy in 54% of the patients, making the results difficult to interpret. Transvenous pulmonary embolectomy remains an experimental procedure and should been attempted only in the very few patients with PE, uncontrolled cardiogenic shock, and absolute contraindication to fibrinolytic treatment. Animal models are required to compare the different devices available.

Transcatheter snare removal of acute middle cerebral artery thromboembolism: technical case report

OBJECTIVE AND IMPORTANCE

We describe the case of a patient in whom a snare designed for the removal of foreign bodies was successfully used to retrieve a thromboembolism from the middle cerebral artery. This technique can be used to reestablish blood flow when maximal pharmacological therapies have failed.

CLINICAL PRESENTATION

A 38-year-old man with scrotal squamous cell carcinoma presented with the abrupt onset of left hemiparesis and numbness. Computed tomography of the head showed no hemorrhage or hypodensity, and right middle cerebral artery thrombosis was suspected.

INTERVENTION

Cerebral angiography demonstrated a near-total occlusion of the right middle cerebral artery at the M1-M2 junction. The administration of intra-arterial urokinase, systemic heparin, and systemic abciximab, and mechanical maceration failed to lyse the clot. A 4-mm goose-neck snare was guided through a microcatheter, and the clot was snared and withdrawn. Immediate postoperative angiography demonstrated the reconstitution of normal flow. Pathological examination of the snared material was consistent with clot. By postoperative Day 5, the patient had regained full strength, except for the fingers of the left hand, which remained moderately weak. Computed tomography demonstrated a right insular and extreme capsular infarct.

CONCLUSION

To our knowledge, this is the first reported use of a snare to remove clot in the setting of thromboembolic stroke. As the use of intra-arterial thrombolysis increases, transcatheter snare removal of pharmacologically resistant clot may be considered as a salvage strategy.