Current status of percutaneous mechanical thrombectomy. Part I. General principles

Design and Characterization of an Ultrasound Transducer for Combined Histotripsy-Thrombolytic Therapy

Chronic thrombi of the deep veins of the leg are resistant to dissolution or removal by current interventions and can act as thrombogenic sources. Histotripsy, a focused ultrasound therapy, uses the mechanical activity of bubble clouds to liquefy target tissues. In vitro experiments have shown that histotripsy enhances thrombolytic agent recombinant tissue plasminogen activator in a highly retracted clot model resistant to lytic therapy alone. Although these results are promising, further refinement of the acoustic source is necessary for in vivo studies and clinical translation. The source parameters for use in vivo were defined, and a transducer was fabricated for transcutaneous exposure of porcine and human iliofemoral deep-vein thrombosis (DVT) as the target. Based on the design criteria, a 1.5-MHz elliptical source with a 6-cm focal length and a focal gain of 60 was selected. The source was characterized by fiber-optic hydrophone and holography. High-speed photography showed that the cavitation cloud could be confined to dimensions smaller than the specified vessel lumen. The source was also demonstrated in vitro to create confined lesions within clots. The results support that this design offers an appropriate clinical prototype for combined histotripsy-thrombolytic therapy.

Contrast enhanced sonothrombolysis using streptokinase loaded phase change nano-droplets for potential treatment of deep venous thrombosis

Current thrombolytic therapies for deep venous thrombosis are limited due to the wide side effect profile. Contrast mediated sonothrombolysis is a promising approach for thrombus treatment. The current study examines the effectiveness of in vitro streptokinase (SK) loaded phase-change nanodroplet (PCND) mediated sonothrombolysis at 7 MHz for the diagnosis of deep venous thrombosis. Lecithin shell and perfluorohexane core nanodroplets were prepared via the thin-film hydration method and morphologically characterized. Sonothrombolysis was performed at 7 MHz at different mechanical indexes of samples i.e., only sonothrombolysis, PCND mediated sonothrombolysis, sonothrombolysis with SK and SK loaded PCND mediated sonothrombolysis. Thrombolysis efficacy was assessed by measuring clot weight changes during 30 min US exposure, recording the mean gray intensity from the US images of the clot by computer software ImageJ, and spectrophotometric quantification of the hemoglobin in the clot lysate. In 15 minutes of sonothrombolysis performed at high mechanical index (0.9 and 1.2), SK loaded PCNDs showed a 48.61% and 74.29% reduction of mean gray intensity. At 0.9 and 1.2 MI, 86% and 92% weight loss was noted for SK-loaded PCNDs in confidence with spectrophotometric results. A significant difference (P < 0.05) was noted for SK-loaded PCND mediated sonothrombolysis compared to other groups. Loading of SK inside the PCNDs enhanced the efficacy of sonothrombolysis. An increase in MI and time also increased the efficacy of sonothrombolysis. This in vitro study showed the potential use of SK-loaded perfluorohexane core PCNDs as sonothrombolytic agents for deep venous thrombosis.

Contrast enhanced sonothrombolysis using streptokinase loaded phase change nano-droplets.

Aspiration thrombectomy for the management of acute deep venous thrombosis in the setting of venous thoracic outlet syndrome

Objectives

Venous thoracic outlet syndrome, known by the eponym Paget–Schroetter syndrome, is seen in healthy, young individuals with “effort-induced thrombosis.” Endovascular therapies, including catheter-directed thrombolysis, have been described in the acute management of the upper extremity deep venous thrombosis; however, we assessed the technical success of treating this entity using a mechanical aspiration thrombectomy system.

Methods

This was a multi-center retrospective review of patients with venous thoracic outlet syndrome with acute thrombosis treated with the Indigo continuous aspiration mechanical thrombectomy system. Charts from patients with venous thoracic outlet syndrome and acute deep venous thrombosis treated with this system at our institution along with three data sharing locations were reviewed for demographics, deep venous thrombosis risk factors, imaging modalities used for diagnosis, extent of axillosubclavian deep venous thrombosis, treatment details, adjunctive therapies, and complications. The primary outcome was technical success (resolution of >70% of thrombus).

Results

There were 16 patients (50% male) with a mean age of 33 years (range 17–69 years). Six patients had underlying venous thromboembolism risk factors including use of contraceptives ( n = 2), prior deep venous thrombosis ( n = 3), and known thrombophilia ( n = 1). Fifteen patients had complete venous occlusion, and the extent of venous involvement included subclavian ( n = 14), axillary ( n = 16), and brachial ( n = 7). The majority (81.25%) of patients were treated in a single setting, and technical success was achieved in all cases with the use of adjunctive therapies. Only three patients required additional overnight thrombolytic therapy.

Conclusions

The Penumbra Indigo system, often in combination with adjunctive catheter-directed thrombolysis and venoplasty, is a safe and effective device for the treatment of acute upper extremity deep venous thrombosis in the setting of Paget–Schroetter syndrome. No patients experienced central embolization or post-operative renal insufficiency. One-third of patients avoided any additional catheter-directed thrombolysis exposure, and technical success was achieved in all cases. A single bleeding complication was observed in a patient undergoing overnight adjunctive catheter-directed thrombolysis. All patients maintained patency until time of first rib resection.

Endovascular treatment of pulmonary embolism: Selective review of available techniques

Acute pulmonary embolism (PE) is the third most common cause of death in hospitalized patients. The development of sophisticated diagnostic and therapeutic modalities for PE, including endovascular therapy, affords a certain level of complexity to the treatment of patients with this important clinical entity. Furthermore, the lack of level I evidence for the safety and effectiveness of catheter directed therapy brings controversy to a promising treatment approach. In this review paper, we discuss the pathophysiology and clinical presentation of PE, review the medical and surgical treatment of the condition, and describe in detail the tools that are available for the endovascular therapy of PE, including mechanical thrombectomy, suction thrombectomy, and fibrinolytic therapy. We also review the literature available to date on these methods, and describe the function of the Pulmonary Embolism Response Team.

Thermal Changes during Rheolytic Mechanical Thrombectomy

PURPOSE

To characterize thermal changes induced by rheolytic thrombectomy (RT) within an ex vivo venous model and evaluate resultant changes of endothelial and vessel wall injury.

MATERIALS AND METHODS

Patent human saphenous vein segments without thrombus were mounted in an ex vivo perfusion system with a temperature probe apposed to the adventitial surface. RT was performed over a guide wire to facilitate device centering. Continuous RT was performed for 4 minutes with temperature recorded every 10 seconds. Pulsed RT was performed for eight cycles of 30 seconds followed by 10 seconds of deactivation. Mean temperature increase, maximum temperature (Tmax), intimal/medial thickness, endothelial cell staining (CD31), and heat shock protein 90 (HSP90) expression were compared between untreated and RT-treated venous segments.

RESULTS

Continuous RT produced a mean 7.6°C increase in temperature above baseline with mean Tmax of 44.1°C. Pulsed RT produced a mean 7.3°C increase in temperature and mean Tmax of 43.8°C. Differences in mean temperature increase (P = .66) and Tmax (P = .71) between the two groups were not statistically significant. RT-treated segments showed intima/media thinning (0.32 mm before RT and 0.18 mm after RT; P = .004) and reduction in intact endothelium (38.8% before RT and 13.8% after RT; P = .002). Staining for HSP90 showed a 3.1% increase in expression after RT (P = .31).

CONCLUSIONS

RT in this venous model showed reproducible increases in vessel temperature and evidence of endothelial and vessel wall injury. Avoiding prolonged RT application to a focal vascular segment during clinical use may be beneficial.

Mechanical thrombectomy-assisted thrombolysis for acute symptomatic portal and superior mesenteric venous thrombosis

Acute portal vein and mesenteric vein thrombosis (PVMVT) can cause acute mesenteric ischemia and be fatal with mortality rate of 37%-76%. Therefore, early diagnosis and prompt venous revascularization are warranted in patients with acute symptomatic PVMVT. Due to advances in catheter-directed treatment, endovascular treatment has been used for revascularization of affected vessels in PVMVT. We report two cases of symptomatic PVMVT treated successfully by transhepatic percutaneous mechanical thrombectomy-assisted thrombolysis.

Recanalization of acute and subacute venous and synthetic bypass-graft occlusions with a mechanical rotational catheter

PURPOSE

Percutaneous mechanical thrombectomy (PMT) is now established as an alternative treatment of acute arterial occlusions in addition to fibrinolysis and surgical thrombectomy. The objective of this retrospective study was the investigation of a rotational atherothrombectomy catheter in terms of safety and efficacy in the treatment of acute and subacute femoropopliteal bypass occlusions.

MATERIALS AND METHODS

Forty-two patients (average age 65.8 ± 9.1 years) with acute (<14 days [n = 31]) and subacute (14-42 days [n = 11]) femoropopliteal bypass occlusions were treated consecutively with a rotational debulking and removal catheter (Straub Rotarex). The average occlusion length was 28.4 ± 2.9 (24-34) cm. Thirty-four (81%) patients underwent venous bypass, and 8 (19%) patients underwent polytetrafluoroethylene bypass.

RESULTS

The technical success rate was 97.6% (41 of 42). In 1 patient, blood flow could not be restored despite the use of the atherothrombectomy system. The average catheter intervention time was 6.9 ± 2.1 (4-9) min. Ankle-brachial index increased from 0.39 ± 0.13 to 0.83 ± 0.11 at discharge and to 0.82 ± 0.17 after 1 month (p < 0.05). There were a total of 2 (4.8%) peri-interventional complications: One patient developed a distal embolism, which was successfully treated with local lysis, and another patient had a small perforation at the distal anastomosis, which was successfully treated with a stent.

CONCLUSION

PMT with the Rotarex atherothrombectomy catheter represents a safe and effective option in the treatment of acute and subacute femoropopliteal bypass occlusions because it can quickly restore blood flow.

Noninvasive treatment of deep venous thrombosis using pulsed ultrasound cavitation therapy (histotripsy) in a porcine model

PURPOSE

This study evaluated histotripsy as a noninvasive, image-guided method of thrombolysis in a porcine model of deep vein thrombosis. Histotripsy therapy uses short, high-intensity, focused ultrasound pulses to cause mechanical breakdown of targeted soft tissue by acoustic cavitation, which is guided by real-time ultrasound imaging. This is an in vivo feasibility study of histotripsy thrombolysis.

METHODS AND MATERIALS

Acute thrombi were formed in the femoral vein of juvenile pigs weighing 30-40 kg by balloon occlusion with two catheters and thrombin infusion. A 10-cm-diameter 1-MHz focused transducer was used for therapy. An 8-MHz ultrasound imager was used to align the clot with the therapy focus. Therapy consisted of five cycle pulses delivered at a rate of 1 kHz and peak negative pressure between 14 and 19 MPa. The focus was scanned along the long axis of the vessel to treat the entire visible clot during ultrasound exposure. The targeted region identified by a hyperechoic cavitation bubble cloud was visualized via ultrasound during treatment.

RESULTS

Thrombus breakdown was apparent as a decrease in echogenicity within the vessel in 10 of 12 cases and in 7 cases improved flow through the vein as measured by color Doppler. Vessel histology found denudation of vascular endothelium and small pockets of hemorrhage in the vessel adventitia and underlying muscle and fatty tissue, but perforation of the vessel wall was never observed.

CONCLUSIONS

The results indicate histotripsy has potential for development as a noninvasive treatment for deep vein thrombosis.

Recanalisation of thrombotic arterial occlusions with rotational thrombectomy

PURPOSE

This study sought to assess the effectiveness of rotational thrombectomy (RT) with the Rotarex device in the treatment of thrombotic occlusions in native arteries, by-pass grafts, stents and stent-grafts.

MATERIALS AND METHODS

Over the last 4 years, 22 patients (14 men and 8 women; mean age 62.6 years) affected by 5 acute (<14 days) thrombotic occlusions of the native arteries (4 plaque thromboses in the common iliac artery and one on a dissection intimal flap of the external iliac artery), 17 subacute and chronic thromboses affecting 4 femoro-popliteal by-pass grafts, 10 stents (7 in the common iliac artery and 3 in the superficial femoral artery) and 3 stents-grafts were studied. Acute thromboses of native arteries were follow-up with colour-Doppler ultrasound (US) examination at 1 and 3 months. Subacute and chronic thrombotic occlusions were follow-up with colour-Doppler US examination at 1, 3, 6 and 12 months and yearly thereafter.

RESULTS

Immediate technical success was achieved without any need for additional procedures in all acute occlusions of native arteries (4/22 cases). In the subacute and chronic occlusions, the procedure was completed with percutaneous transluminal angioplasty (PTA) (8/22), cutting balloon (6/22) and stenting (5/22). The complication rate was 4.8% (1 rupture of the external iliac artery repaired with a stent-graft).

CONCLUSIONS

Arterial recanalisation with RT is the treatment of choice for acute thrombosis of healthy native arteries (4-7 mm); the treatment of thrombosis complicating calcified plaques or dissection intimal flaps may cause rupture of the arterial wall. In subacute and chronic occlusions of by-pass grafts, stents and stent grafts, additional procedures are necessary to achieve complete recanalisation.

Acute kidney injury caused by intravascular hemolysis after mechanical thrombectomy

BACKGROUND

A 43-year-old African-American female (gravida 5 para 0) with an 8-week intrauterine pregnancy presented to the emergency room with crampy abdominal pain, shortness of breath, and shoulder pain. She had normal renal function on admission. CT angiography of the chest revealed bilateral pulmonary emboli; therefore, the AngioJet (Possis Medical, Inc., Minneapolis, MN) device was used to perform mechanical thrombolysis. The patient subsequently developed hyperkalemia, red urine and anuria.

INVESTIGATIONS

Physical examination, measurement of serum creatinine level and electrolytes, dipstick urinalysis and centrifugation of urine and blood.

DIAGNOSIS

Acute kidney injury due to hemoglobinuria as a result of non-immune-mediated intravascular hemolysis following the use of a percutaneous mechanical thrombectomy device (AngioJet).

MANAGEMENT

Hydration, alkalinization of urine and initiation of hemodialysis (temporarily switched to continuous venovenous hemodiafiltration). Urine output improved after the 20th day of hospitalization, at which point dialysis was discontinued. The patient's renal function completely recovered by day 25.

[Venous interventions--part 1: techniques and lower torso thromboses]

Venous thrombosis is one of the most common vascular diseases. Without treatment, pulmonary embolism is a potentially life-threatening complication. Long-term complications are chronic venous insufficiency and post-thrombotic syndrome. Medical anticoagulation is currently the standard therapy, since it prevents appositional thrombus growth although it usually can not prevent the development of post-thrombotic syndrome. The structure of the thrombotic material often leads to partial recanalisation with residual stenosis. Early and sufficient systemic thrombolysis with adequate concentration may achieve disintegration of the thrombus and preservation of venous valve function. Supplementary to conservative therapy, local catheter thrombolysis is possible even in cases with contraindications for a systemic thrombolysis therapy. Additional interventional techniques reduce the required concentration of the thrombolytic. Venous stenosis can be treated by balloon angioplasty and stent implantation. This article reviews the different percutaneous treatment options as well as their application and usefulness in thrombosis of the lower torso.

Catheter Embolectomy for Acute Pulmonary Embolism

Massive pulmonary embolism (PE) is a life-threatening condition with a high early mortality rate due to acute right ventricular failure and cardiogenic shock. As soon as the diagnosis is suspected, an IV bolus of unfractionated heparin should be administered. In addition to anticoagulation, rapid initiation of systemic thrombolysis is potentially life-saving and therefore is standard therapy. Many patients with massive PE cannot receive thrombolysis because of an increased bleeding risk, such as prior surgery, trauma, or cancer. In these patients, catheter or surgical embolectomy are helpful for rapidly reversing right ventricular failure. Catheter thrombectomy appears to be particularly useful if surgical embolectomy is not available or the patient has contraindications to surgery. Although no controlled clinical trials are available, data from cohort studies indicate that the clinical outcomes after surgical and catheter embolectomy may be comparable.

Evaluation of a Newly Developed Percutaneous Thrombectomy Basket Device in Sheep With Central Pulmonary Embolisms

OBJECTIVE

The authors studied the development of a thrombectomy device that is adequately steerable and quickly placeable in case of extensive pulmonary embolism.

MATERIALS AND METHODS

The device consists of a self-expandable nitinol basket mounted at a catheter-tip, which allows suction and extraction of thrombus material. Five in vitro tests were performed followed by tests in 6 sheep. In vivo thrombus material was introduced through a jugular vein to produce pulmonary embolism. After catheter insertion over the right femoral vein, the basket was placed adjacent to the pulmonary embolus and the extraction procedure was performed.

RESULTS

In in vitro tests, the extracted thrombus amount varied between 60% and 95%. In animal experiments, the extracted amount varied between 30% and 95% as determined angiographically. Limiting factors were steerability and optimal positioning of the basket in relation to the embolus.

CONCLUSIONS

Extraction of pulmonary embolism with the self-expanding suction basket is feasible. However, successful recanalization is limited by catheter maneuverability in the pulmonary arterial system.

Septic Thrombosis of the Inferior Vena Cava Treated with Percutaneous Mechanical Thrombectomy

The present report describes a patient with septic thrombosis of the inferior vena cava (IVC) related to a subhepatic abscess adjacent to the IVC. Despite prolonged antimicrobial therapy and systemic anticoagulation, sepsis and septic embolism persisted while the size of the thrombus increased. Percutaneous mechanical thrombectomy was performed, resulting in removal of the infected thrombus and complete clinical recovery.

Recanalization of acute and subacute femoropopliteal artery occlusions with the rotarex catheter: one year follow-up, single center experience

PURPOSE

To assess the efficacy and safety of a new rotational catheter for percutaneous removal of fresh and organized thrombi in the femoropopliteal artery.

METHODS

Forty-one limbs in 38 patients (age 56--90 years, mean 75.6 years) with acute, subacute or chronic femoropopliteal occlusions of 1--180 days' duration (mean 31.6 days) were treated with the Rotarex device. The Fontaine stage was mainly IIB (Rutherford 2--3, 22 patients) or III (Rutherford 4, 14 patients). The length of occlusion varied from 2 to 35 cm (mean 13.1 cm). After recanalization percutaneous transluminal angioplasty (PTA) was performed if there was a residual stenosis of >25%. Patients were followed up with color Doppler ultrasound at 48 hr and clinically with Doppler pressures and oscillometry at 3, 6, and 12 months.

RESULTS

After an average of two passages with the Rotarex catheter all but two limbs required PTA for residual stenosis >25%. Five patients needed additional stenting. Major complications were one groin hematoma requiring blood transfusion and one arteriovenous fistula spontaneously thrombosing after unsuccessful primary prolonged balloon dilation. Distal embolizations occurred in 10 patients; 6 clinically relevant emboli were aspirated. All occlusions were technically successfully recanalised there were 2 early reocclusions after 1 day and two at 2 weeks. Brachial-ankle indices improved from an average of 0.41 before to 0.93 after recanalization. Primary and secondary patency rates were 62% / 84% after 6 months and 39% / 68% after 1 year. The amputation-free survival at 12 months was 100%.

CONCLUSION

The Rotarex mechanical thrombectomy device is an efficient, quick, easy to handle, and safe tool for the treatment of acute, subacute or even chronic peripheral arterial thromboembolic occlusions. It can be used for short or long occlusions with equal success, provided the obstruction is not heavily calcified and has been safely passed with a guidewire first.

Mechanical Thrombectomy of Acute Iliofemoral Deep Vein Thrombosis with Use of an Arrow-Trerotola Percutaneous Thrombectomy Device

PURPOSE

To evaluate the immediate and 1-year clinical outcomes of mechanical thrombectomy with use of the Arrow-Trerotola percutaneous thrombectomy device (PTD) with or without low-dose urokinase in the treatment of acute iliofemoral deep vein thrombosis (DVT).

MATERIALS AND METHODS

Mechanical thrombectomy with the PTD was performed in 25 patients with acute iliofemoral DVT. Thrombolytic therapy with low-dose urokinase was used in all patients without contraindications (n = 20). Other therapies used in combination included inferior vena cava filter insertion (n = 5), sheath aspiration thrombectomy (n = 25), and angioplasty and stent placement (n = 20).

RESULTS

Initial technical and clinical success was achieved in all cases. In the 20 patients who had no contraindications to the use of urokinase, the dosage of urokinase did not exceed 1 million IU (range, 360,000-1,000,000 IU; mean, 640,000 IU). The mean time of urokinase infusion was 16 hours (range, 12-20). In five patients who had a contraindication to the use of urokinase, mechanical thrombectomy with the PTD was successful without the use of urokinase. There were no major complications. Primary patency of the stent-implanted common iliac vein segment was achieved at 1 year in 17 of 20 patients (85%). The overall 1-year clinical success rate was 92% (23 of 25 patients). Valvular insufficiency occurred in two patients (8%).

CONCLUSION

The PTD is an effective mechanical thrombectomy device in the treatment of acute iliofemoral DVT with or without adjunctive urokinase thrombolysis.

Hemolysis during percutaneous mechanical thrombectomy can mimic a hemolytic transfusion reaction

BACKGROUND

Interventional radiologists have developed percutaneous mechanical thrombectomy (PMT) devices to remove intravascular thrombi. Hemolysis, secondary to thrombus destruction from these devices, has been described in radiology journals, but similar reports appear to be lacking in the transfusion medicine literature. Two cases of hemolysis after PMT are described that involved the transfusion service, one of which was reported as a hemolytic transfusion reaction.

CASE REPORTS

The first patient received 4 units of red cells (RBCs) during a thrombectomy and subsequent placement of a transjugular intrahepatic portosystemic shunt. The patient developed hemoglobinuria, and it was reported to the blood bank as a possible hemolytic transfusion reaction. After RBC mismatch and bacterial contamination were excluded, the hemolysis was attributed to thrombectomy-related mechanical hemolysis. In the second case, a hemolyzed sample was sent to the blood bank for a type and cross-match. Upon requesting that the sample be redrawn, it was learned that the sample was obtained after PMT.

CONCLUSION

Patients who have undergone PMT can have clinical and laboratory findings suggestive of hemolytic transfusion reactions. Although interventional radiologists are familiar with these side effects, the blood bank profession needs to be aware that these procedures cause nonimmune hemolysis and must consider this possibility when evaluating transfusion reactions in these patients.

Percutaneous Venous Thrombectomy Using the Arrow-Trerotola Percutaneous Thrombolytic Device (PTD) with Temporary Caval Filtration: In Vitro Investigations

PURPOSE

To evaluate the size and quantity of downstream emboli after thrombectomy using the Arrow-Trerotola Percutaneous Thrombolytic Device (PTD) with or without temporary filtration for extensive iliofemoral and iliocaval thrombi in an in vitro flow model.

METHODS

Iliocaval thrombi were simulated by clotted bovine blood in a flow model (semilucent silicone tubings, diameter 12-16 mm). Five experimental set-ups were performed 10 times each; thrombus particles and distribution were measured in the effluent. First, after retrograde insertion, mechanical thrombectomy was performed using the PTD alone. Then a modified self-expanding tulip-shaped temporary vena cava stent filter was inserted additionally at the beginning of each declotting procedure and removed immediately after the intervention without any manipulation within or at the filter itself. In a third step, the filter was filled with thrombus only. Here, two experiments were performed: Careful closure within the flow circuit without any additional fragmentation procedure and running the PTD within the filter lumen, respectively. In the final set-up, mechanical thrombectomy was performed within the thrombus-filled tubing as well as in the filter lumen. The latter was closed at the end of the procedure and both devices were removed from the flow circuit.

RESULTS

Running the PTD in the flow circuit without filter protection led to a fragmentation of 67.9% (+/-7.14%) of the clot into particles < or =500 microm; restoration of flow was established in all cases. Additional placement of the filter safely allowed maceration of 82.9% (+/-5.59%) of the thrombus. Controlled closure of the thrombus-filled filter within the flow circuit without additional mechanical treatment broke up 75.2% (+/-10.49%), while additional mechanical thrombectomy by running the PTD within the occluded filter led to dissolution of 90.4% (+/-3.99%) of the initial clot. In the final set-up, an overall fragmentation rate of 99.6% (+/-0.44%) was achieved.

CONCLUSIONS

The combined use of the Arrow-Trerotola PTD and a temporary vena cava stent filter proved to be effective for even large clot removal in this experimental set-up.

Venous thromboembolism in the intensive care unit

Most ICU patients have a significant number of risk factors for VTE. The high incidence of DVT in the ICU population and the recognition of a high incidence of PE at autopsy confirm this. We have alluded to the difficulty of clinical diagnosis of VTE and the need for diagnostic investigations. We have reviewed currently available diagnostic investigations with regard to their sensitivity and specificity and their practicability in ICU patients, and have formulated recommended diagnostic algorithms (Figs. 4 and 5). The most important factor in the management of VTE is prevention. In the ICU, all patients are at high risk for VTE, and therefore, at a minimum should receive subcutaneous prophylactic heparin unless it is contraindicated. Alternative methods of prophylaxis are available, and should be considered for patients who have contraindications to heparin.

Early experience with a rotational thrombectomy device for treatment of acute and subacute infra-aortic arterial occlusions

PURPOSE

To evaluate a rotational thrombectomy device in the treatment of acute and subacute/chronic thrombotic infra-aortic occlusions of native vessels and bypass grafts.

METHODS

From July 2000 to February 2002, 98 patients (65 men; mean age 66+/-9 years, range 47-90) with 100 thrombotic occlusions (mean age of occlusion 31+/-33 days, range 0-140) measuring an average of 21+/-11 cm long (range 2-40) were treated with rotational thrombectomy (Rotarex). There were 33 acute (</=14 days) thrombotic/embolic native artery occlusions (group I), 58 subacute/chronic (>14 days) native artery occlusions (group II), and 9 acute bypass graft occlusions (group III).

RESULTS

The device activation time was 4.9+/-1.4 minutes, during which 4.0+/-1.4 passes of the device were performed. The amount of aspirated fluid was 240+/-119 mL. Slightly less than half the arteries (48%) were stented. Primary success (residual stenosis <30%) was achieved in 92% (94% for group I, 93% for group II, and 78% for group III; 100% for the ipsilateral approach, 56% for the crossover approach). Among the 18 complications, 3 were serious (2 amputations after unsuccessful intervention and 1 death); there were 8 vessel perforations and 7 cases of peripheral embolization. Thirty-day survival and limb salvage was 88% for group I, 100% for group II, and 66% for group III.

CONCLUSIONS

The device is an easy-to-handle, useful tool for ipsilateral treatment of acute and subacute thrombotic arterial and bypass graft occlusions. The use of this device is limited by the 8-F diameter of the catheter and the limited capacity for crossover interventions.

Applications of percutaneous mechanical thrombectomy in pulmonary embolism

Percutaneous mechanical thrombectomy (PMT) has matured into a reliable and valuable therapeutic tool in acute vascular diseases. PMT devices are designed to achieve rapid clearance of acute occlusion in large arteries and veins. This article provides a summary of cumulated experience on pulmonary embolism (PE) treatment with PMT devices. PMT devices are a heterogeneous group of devices that uses different forms of energy. Most of the devices do not totally eliminate thrombus rather fragment in small particles. The rationale of PMT is based on the rapid relief of central pulmonary obstruction. PMT in massive PE provides efficacious and safe debulking of centrally located thrombus in PE, lowering pulmonary artery pressures and improving hemodynamics and blood oxygenation. This results in lowering mortality if compared with natural history of PE, and reduced procedure time if compared with pharmacological thrombolysis. The clinical indications for percutaneous intervention in PE are discussed in the text.

Low-power transverse ultrasonic treatment of portal vein thrombosis in an animal model

PURPOSE

The authors have recently developed a small-diameter, thin, flexible ultrasonic catheter device that permits the removal of thrombus by low-power transverse ultrasonic cavitation energy. In this study, the authors sought to determine whether this device could be used to eliminate portal vein thrombosis in an animal model.

MATERIALS AND METHODS

In five anesthetized pigs, a total of six occlusions of the left portal vein were achieved with use of autologous clot with (n = 2) or without (n = 4) thrombin injection (250 U) introduced via a 7-F transhepatic catheter/sheath system. Angiographic examination documented complete occlusion of this vessel. The 75-cm-long, 21-gauge ultrasonic catheter (Resolution) was introduced into the clot under angiographic guidance via the transhepatic sheath. Transverse-wave ultrasonic energy was then delivered from the distal 5 cm of the probe at 3.5 W +/- 10% power for up to 6 minutes. Repeat angiographic studies were performed to document patency. After the procedure, gross and histopathologic examinations were performed.

RESULTS

Restoration of patency of the main left portal vein was documented in all cases at angiography, with no evidence of residual clot fragments in the major branches. However, side branches demonstrated small thrombotic plugs on pathologic examination. No complications such as perforation of the vessel adjacent to the active ultrasonic tip were encountered. Virtually all thrombolysis was documented to occur within the first minute of energy application. At gross pathologic examination, there was no evidence of damage to the portal vein, and histopathologic examination demonstrated minimal intimal disruption without damage to the media.

CONCLUSIONS

This preliminary animal study suggests the feasibility of a percutaneous transhepatic approach to the treatment of portal vein thrombosis with use of low-power ultrasonic cavitation energy. With further study, this method may have potential for the treatment of thrombotic disease, thereby offering novel therapy to patients with thrombotic vascular occlusions.

Comparison of a new recirculation thrombectomy catheter with other devices of the same type: in vitro and in vivo evaluations

RATIONALE AND OBJECTIVES

To compare a new 7 Fr. Helix thrombectomy catheter with Amplatz thrombectomy devices (ATD) with respect to clot fragmentation efficiency, hemolytic potential, and risk for vascular trauma.

MATERIALS AND METHODS

Particle size was evaluated following the maceration of 8-to-10-day-old clots, each weighing 6 +/- 0.01 g. The clots were macerated using devices of various sizes, including the 7-Fr. Helix thrombectomy catheter, the 7-Fr. over-the-wire (OTW), 8-Fr. ATD and the 6-Fr. ATD. The number of particles by weight was quantified. The 7-Fr. Helix and the 8-Fr. ATD were tested in the native iliac vein of six dogs without presence of clots. Blood samples were obtained before, during, and at 1, 3, 6, 24, and 48 hours after the procedure, to monitor the hemolytic effects. The treated iliac veins were examined histologically.

RESULTS

Most of the clot was fragmented into particles <10 microm. The mean percentage by weight of the original clot that remained as particles larger than 10 microm was 1.59% in the 7-Fr. Helix group. This was significantly less than 3.10% with the 6-Fr. ATD, 2.57% with 7-Fr. OTW and 2.44% in the 8-Fr. ATD group (<0.01). In vivo results showed a higher plasma free hemoglobin (PFH) level starting 5 minutes after initiating the ATD activation, reaching its peak after completion of the activation, and declining afterward, with return to the baseline at 24 hours. The haptoglobin level tended to decline slightly at 10 minutes, reaching its lowest level at 24 hours, and starting to recover at 48 hours. A similar pattern of PFH and haptoglobin changes was found in both groups. There were no significant differences regarding hemolytic effect of the two tested devices. No significant changes of creatinine were observed for up to 48 hours after procedures. Focal microthrombosis was seen in two sites of two vessels treated with the 7-Fr. Helix and a focal injury of a venous valve was noted in the 8-Fr. ATD group. The media and internal elastic lamina (IEL) were intact in all cases.

CONCLUSION

The newly designed 7-Fr. Helix is more effective in fragmentation in vitro clots than the 6 Fr. ATD, 7-Fr. OTW and the 8-Fr. ATD. The 7-Fr. Helix and the 8-Fr. ATD produced hemolytic effects, but they appeared to be tolerated by the animals. The in vivo results indicated that the 7-Fr. Helix appears to be as safe as the 8-Fr. ATD.

Percutaneous thrombolysis of thrombosed haemodialysis access grafts: comparison of three mechanical devices

BACKGROUND

Percutaneous thrombolysis has become an accepted treatment of thrombosed haemodialysis grafts. Several devices have been developed for mechanical thrombolysis, which macerate the clot using different mechanisms such as aspiration and fragmentation. The aim of our study was to compare the efficacy of three devices for mechanical thrombolysis in removing the thrombus from thrombosed haemodialysis access grafts and to determine the initial technical and clinical success, complication rates of each device, and graft patency after the procedure.

METHODS

Thrombolysis (i.e. clot removal followed by percutaneous transluminal angioplasty (PTA)) was performed in 68 thrombosed haemodialysis grafts using the Cragg brush catheter combined with urokinase in 13, the Hydrolyser in 18 and the Arrow-Trerotola Percutaneous Thrombolytic Device (PTD) in 37. Clot removal scores (CRS, the ability to thoroughly remove clot from the access), initial technical success, clinical success, patency at 30, 60, and 90 days, and complication rates were evaluated.

RESULTS

CRS for the Cragg brush, Hydrolyser and PTD were good in 92, 44, and 95% of cases, respectively. Initial technical (85, 83, and 95%) and clinical success (62, 67, and 86%), mean patency rates at 30 (73, 60, and 55%), 60 (61, 53, and 49%), and 90 (49, 40, and 43%) days, stenosis after PTA (33, 46, and 21%) and complication rates (8, 6, and 0%) were not different for the three devices. Success rates and graft patency depended on the effect of PTA, irrespective of the device used.

CONCLUSIONS

The rotational devices removed clots more effectively than the Hydrolyser, with the PTD having the advantage of not requiring urokinase. However, the result of PTA in the treatment of underlying stenoses was the only predictive value for graft patency.

Prototype percutaneous thrombolytic device: preclinical testing in subacute inferior vena caval thrombosis in a pig model

PURPOSE

To develop an animal model of subacute inferior vena caval (IVC) thrombosis and apply this model in evaluating the safety and efficacy of a prototype percutaneous thrombolytic device for restoring patency.

MATERIALS AND METHODS

In 11 pigs, a stent with a ligature in the middle was placed in the IVC. Thrombin was injected to induce thrombosis. Hemostasis was achieved by using an occlusion balloon. The stent was ligated to prevent thrombus migration. Five to 8 days after thrombus induction, the ligature was broken and the stent fully deployed. In 10 animals, thrombectomy was performed by using the percutaneous thrombolytic device. A vena caval filter was inserted at the beginning of each declotting procedure. Thrombus removal percentage was estimated and pulmonary angiograms obtained to detect embolism before and after thrombectomy. The IVC was analyzed histologically. To determine thrombus composition, one animal was sacrificed without thrombectomy. Concerning procedural safety, failure of the stent delivery system, stent migration, and venous perforation due to balloon inflation and the stent placement or thrombectomy procedure were evaluated.

RESULTS

Thrombus creation was successful in all animals. Fragmentation led to 75%--100% thrombus removal with flow restoration in all cases. There were no episodes of stent delivery failure, stent migration, or venous perforation. No significant pulmonary embolism was observed. In one case, a vessel dissection was identified at histologic examination.

CONCLUSION

In this animal model of IVC thrombosis, the percutaneous thrombolytic device is effective and safe for clot removal.

Rheolytic catheter and thrombolysis of dural venous sinus thrombosis: a case series

OBJECTIVE

The high morbidity and mortality rates associated with dural sinus thrombosis may be heightened by a delay in diagnosis, which necessitates prompt and effective treatment. Traditional treatment consists of the initiation of systemic anticoagulation with heparin and, more recently, regional thrombolysis with direct endovascular infusion of thrombolytic agents. We report our experience in a series of five patients in whom we accomplished mechanical clot lysis with the combination of a rheolytic device and balloon catheters.

METHODS

Five patients with dural sinus thrombosis were treated with a combination of pharmacological and mechanical thrombolysis with the 5-French Angiolet rheolytic catheter (Possis Medical, Minneapolis, MN) and balloon catheters. The success of the procedure was determined by resolution of or improvement in the patient's neurological examination results and imaging features.

RESULTS

All five patients demonstrated immediate improvement as observed on imaging studies or in terms of neurological status. Three patients required more than one intervention, and all but one patient continued to improve after the final intervention. Two of the five patients continued to experience mild residual neurological deficits, and two patients experienced complete recovery. The fifth patient had a delayed recurrence of thrombosis that required multiple interventions, and the patient has significant neurological deficits. Navigation of the dural sinuses was possible in all patients with the use of a microcatheter and was possible to a variable degree with the rheolytic catheter. Known complications of the procedures included two pseudoaneurysms at the femoral puncture site.

CONCLUSION

Mechanical clot lysis is a powerful technique for immediate restoration of antegrade venous flow in dural sinus thrombosis. In most patients, the superior sagittal sinuses and contralateral transverse sinuses could be accessed with the 5-French rheolytic catheter.

Interventional therapy for pulmonary embolism

Venous thromboembolism is a common cause of death. Acute massive pulmonary embolism (PE) is life-threatening and may require vigorous more invasive treatment. Several risk factors are related to increased incidence of massive PE. Anticoagulation is the most traditional treatment for PE but may not suffice in cases of massive PE. Systemic thrombolytic therapy, catheter-directed thrombolysis, percutaneous embolectomy, and more recently, percutaneous thrombus fragmentation techniques with a multitude of devices are now available to treat the most severe cases of massive PE. Successful treatment of PE includes implementation of a treatment protocol and the use of associated techniques and devices.

Mechanical thrombectomy in patients with deep venous thrombosis

PURPOSE

To report our experience with mechanical thrombectomy in proximal deep vein thrombosis (DVT).

METHODS

Eighteen patients with a mean (+/- SD) age of 37.6 +/- 16.1 years who presented with DVT in the iliac and femoral vein (n = 3), inferior vena cava (n = 5), or inferior vena cava and iliac vein (n = 10), were treated with the Amplatz Thrombectomy Device after insertion of a temporary caval filter.

RESULTS

Successful recanalization was achieved in 15 of 18 patients (83%). Overall, the percentage of thrombus removed was 66 +/- 29%: 73 +/- 30% at caval level and 55 +/- 36% at iliofemoral level. Complementary interventions (seven patients) were balloon angioplasty (n = 2), angioplasty and stenting (n = 2), thrombo-aspiration alone (n = 1), thrombo-aspiration, balloon angioplasty, and permanent filter (n = 1), and permanent filter alone (n = 1). There was one in-hospital death. Follow-up was obtained at a mean of 29.6 months; three patients had died (two cancers, one myocardial infarction); 10 had no or minimal sequelae; one had post-phlebitic limb.

CONCLUSION

Mechanical thrombectomy is a potential therapeutic option in patients presenting with proximal DVT.

Creation of radiopaque thrombi for in vivo experiments

PURPOSE

A number of percutaneous thrombectomy devices are undergoing investigation for treatment of patients with venous thromboembolism. Use of radiopaque thrombus to monitor thrombus delivery and assess thrombectomy has been previously reported. The purpose of this project was to quantitatively test the effect of mixing different ratios of blood and contrast material to facilitate maximum thrombus formation and radiopacity.

MATERIALS AND METHODS

The following ratios of blood and contrast material were mixed: 2 mL blood to 8 mL contrast material (ratio = 0.25), 4 mL blood to 6 mL contrast material (ratio = 0.67), 6 mL blood to 4 mL contrast material (ratio = 1.5), and 8 mL blood to 2 mL contrast material (ratio = 4). Contrast material was added at day 0, 3, or 6. Each sample received one of two ionic contrast agents to opacify the clots. At day 14, thrombus mass and opacity were determined.

RESULTS

Three combinations of blood and contrast material produced maximum thrombus and radiopacity. These were sodium iothalamate 30% with a ratio of 4 with contrast material added on day 0 and sodium iothalamate 60% with a ratio of 1.5 with contrast material added on day 3 or 6.

CONCLUSIONS

When forming radiopaque thrombi, significant differences can result from the ratio of blood to contrast material used. Contrast material type can also affect radiopacity and mass formed. The use of optimal ratios of blood to contrast material should maximize device evaluation with minimal wasting of valuable resources such as test subjects, physician time, and equipment.

Mechanical thrombolysis of thrombosed hemodialysis native fistulas with use of the Arrow-Trerotola percutaneous thrombolytic device: our preliminary experience

PURPOSE

To evaluate the feasibility of use of the Arrow-Trerotola percutaneous thrombolytic device (PTD) in the treatment of thrombosed hemodialysis native fistula occlusions.

MATERIALS AND METHODS

Ten patients with native fistula occlusion underwent mechanical thrombolysis with use of the PTD. The standard PTD was used in seven patients and the over-the-wire device was used in three patients. Major outcomes of our study included procedure time, clinical success, complication rate, and 3- and 6-month patency rates.

RESULTS

The technical success rate was 100% and the clinical success rate was 90% (9 of 10). In all 10 cases, the procedure was associated with angioplasty. There were no major complications. The mean time of successful procedures was 126.1 minutes. The 3- and 6-month primary patency rates were 70% and 60%, respectively; the assisted primary patency rate at 6 months was 80%.

CONCLUSION

The PTD is an effective mechanical device for percutaneous treatment of thrombosed hemodialysis access. Our clinically successful initial experience with the PTD shows that the technique is rapid and safe for treatment of native fistula occlusions.

Percutaneous venous thrombectomy with the use of a balloon sheath: first in vitro investigations of a new low-tech concept

RATIONALE AND OBJECTIVES

To test mechanical thrombectomy of extensive iliofemoral and iliocaval thrombi in an in vitro flow model with the use of 12F and 18F balloon sheaths.

METHODS

Newly developed 12F and 18F sheaths were evaluated in four vessel models (simulation of femoral, iliofemoral, iliocaval, and caval thrombi by clotted bovine blood in a flow model). After retrograde insertion of the sheath and blocking of the vessel proximal to the thrombus by inflating the balloon, mechanical fragmentation was performed coaxially through the sheath lumen by using a 7F pigtail rotation device. With an occlusion balloon catheter, residual thrombi were withdrawn to the orifice of the sheath and aspirated. Twelve silicone tubes occluded by thrombi were recanalized in each setting. In the latex model, seven recanalizations were performed.

RESULTS

All clots were removed completely within a treatment duration of 2 to 14 minutes. Fluid loss during the procedure was 29.6 to 129.3 mL for the femoral flow model, 61.9 to 137.2 mL for the iliofemoral model, 74.5 to 163.4 mL for the iliocaval model, and 102.7 to 236.7 mL for the caval model. No fragments were washed downstream. In four settings, small residual thrombi were attached to the balloon after deflation of the sheath.

CONCLUSIONS

Clot amounts up to 171 g were removed quickly and completely by using these large-caliber balloon sheaths. Fluid loss from aspiration was negligible. Balloon occlusion prevented embolization of thrombus fragments proximal to the sheath. Further studies are needed to prove the efficacy of this technique in vivo.

Mid-term follow-up after percutaneous hydrodynamic thrombectomy in lower limb ischemia: initial experience with two-dimensional MR imaging and three-dimensional MR angiography

PURPOSE

To assess noninvasively mid-term patency, reocclusion, and mid-term changes of the arterial wall after percutaneous hydrodynamic thrombectomy in patients with acute lower limb ischemia using magnetic resonance (MR) imaging/MR angiography (MRA).

MATERIALS AND METHODS

Arterial wall and luminal changes were evaluated in 16 patients (10 men, six women; mean age, 70 years), with a minimum follow-up of 12 months after percutaneous thrombectomy with a hydrodynamic catheter for acute lower limb ischemia (embolic, n = 5; thrombotic, n = 11). Adjunctive PTA was performed in 44%. The mean follow-up was 23 months +/- 7.6 (range, 12-33 months). MR imaging and MRA were performed on a 1.0 T system using an extremity coil and two-dimensional (2D) time-of-flight, turbo spin echo, 2D gradient echo, and contrast enhanced three-dimensional (3D) gradient echo sequences.

RESULTS

In one patient, a complete reocclusion was noted and, in two patients, a hemodynamically insignificant restenosis (< or = 50%) was identified with MR imaging. This was in accordance with color flow duplex sonography, physical examination, ankle/brachial index measurements, and the treadmill test. The MR morphometry documented an increase of the entire vessel area from 48.9 mm2 +/- 3.3 (control segments) to 55.5 mm2 +/- 2.8 at the treated segments (+13.3%; P < .05). The vessel wall area increased from 31.7 mm2 +/- 1.8 to 39.4 mm2 +/- 2.3 (+24.4%; P < .05). The mean area stenosis grade was 12%.

CONCLUSION

MR imaging with use of morphometric analysis is a possible tool to noninvasively determine the mid-term patency and restenosis/reocclusion and remodeling process after percutaneous thrombectomy and other interventional procedures.

Hydraulic analysis of the functional properties of saline-jet aspiration thrombectomy catheters

The purpose of this paper is to clarify the functional properties of a saline-jet aspiration thrombectomy catheter based on hydraulics. This catheter, developed by the authors, aspirates intravascular thrombi by means of the effect of a high-speed jet. We have derived the relationships between Qs, Qa, and p(n), where Qs is the water supply rate, Qa is the water aspiration rate and p(n) is the negative pressure created in the distal lumen of the catheter. The relationships are represented by simple equations using c1 and c2, where c1 and c2 are coefficients proper to the catheter. We have obtained c1 and c2 experimentally for three types of catheter with different distal shapes. Two practical conclusions are derived from this study. First, making a short taper at the distal end increases the negative pressure created and is advantageous for thrombus aspiration. Second, making the diameter of the inner tube and nozzle smaller is essential for improving the aspiration ability of the catheter.