Zhong Qian

Endovascular Treatment of Complicated Type-B Aortic Dissection with Stent-Grafts: Midterm Results

PURPOSE To report the midterm results of the endovascular treatment of complicated type-B aortic dissection with use of stent-grafts. MATERIALS AND METHODS Ten patients with acute (n = 4) or chronic (n = 6) complicated type-B dissection were treated with custom-made stent-grafts. Indications for treatment included uncontrollable hypertension with dissection extension (n = 3), renal ischemia (n = 1), and false lumen aneurysm (n = 6). Stainless-steel Z-stents covered with polyester grafts were placed in the initial six patients. Nitinol stents covered with ultrathin polytetrafluoroethylene were used in the remaining four patients. The patients were followed-up with helical computed tomography for a maximum of 30 months (mean, 20 mo). RESULTS There was one technical failure related to the access site. Early complications included deep venous thrombosis (n = 1) and embolic stroke (n = 1). Complete thrombosis of the thoracic false lumen was achieved in six patients and partial thrombosis was achieved in three. Aneurysms developed at the ends of the stainless-steel stents in two patients, requiring additional stent-graft placement. Despite successful remodeling of the thoracic aorta, three of four patients with distal reentry into the abdominal aorta experienced progressive abdominal aortic aneurysm (AAA). AAA rupture developed in two patients; one rupture was fatal and the other was treated with emergency surgery. CONCLUSIONS Endovascular treatment of complicated type-B aortic dissection is technically feasible and effective. Closely monitoring the treated aorta is essential to detect early aneurysm formation at the ends of rigid stents. Despite adequate sealing of the tears in the thoracic aorta, dissection with distal reentry phenomenon into the abdominal aorta may evolve into AAA with late rupture.

Hemolytic Effect of the Amplatz Thrombectomy Device

PURPOSE The hemolytic effect of the Amplatz thrombectomy device (ATD) was evaluated in nine dogs and in nine patients. MATERIALS AND METHODS The device was activated for 1-2 minutes in the abdominal aorta, inferior vena cava, or femoral artery of nine dogs. The device was activated for 1-4 minutes in the nine patients in occluded lower extremity bypass grafts (n = 5), native superficial femoral artery (n = 1), a pulmonary artery embolus (n = 1), a portocaval shunt (n = 1), and an iliac vein stent (n = 1). Patients were examined for laboratory evidence of hemolysis following mechanical thrombectomy. RESULTS In all dogs haptoglobin level decreased, free hemoglobin level in the plasma increased, and hemoglobinuria was present. There was no change in renal function. The level of haptoglobin decreased and the level of plasma free hemoglobin increased in eight patients, with hemoglobinuria detected in one. More hemolysis was observed in the animals than in the patients. CONCLUSION The ATD has a definite transient hemolytic effect. Until further studied, it should not be used in children and should be used with caution in patients who are anemic, hypoxemic, or have potentially reversible renal insufficiency. Activation time should be monitored closely because hemolysis probably increases with increasing activation time.

Bifurcated Endoprosthesis for Treatment of Aortoiliac Occlusive Lesions

Purpose: To report our initial experience with a bifurcated endoprosthesis in the management of aortoiliac occlusive disease. Methods: From May 2001 to February 2004, 112 patients were referred to our institution for the management of aortoiliac disease. Among these, 5 (6%) patients (3 men; mean age 57.8 years) with severe ischemia owing to TASC C or D iliac occlusions were selected for endovascular treatment with a bifurcated stent-graft. An Excluder stent-graft was placed after preliminary recanalization (thrombolysis and/or balloon dilation) the day before. The patients were followed clinically and ultrasonographically every 3 months during the first year and semiannually thereafter. Results: Technical success was achieved in all patients. Endovascular aortoiliac bifurcation reconstruction restored iliac artery flow immediately in all cases. There were no procedurerelated complications. The mean ankle-brachial index (ABI) was significantly improved, from 0.66±0.04 before the procedure to 0.94±0.06 immediately after the procedure (p < 0.01). The aortoiliac reconstructions remained patent during the mean 17-month follow-up (range 3–36), and the ABIs were stable. There was no mortality or amputation required in this series. Conclusions: Endovascular placement of a bifurcated stent-graft appears to be technically feasible, effective, and safe in the management of aortoiliac occlusive disease.

In vitro and in vivo experimental evaluation of a new vena caval filter.

PURPOSE A new stainless steel (MP35N alloy) vena cava filter without a central stasis point was evaluated in vitro and in vivo. MATERIALS AND METHODS The clot-trapping efficiency and hemodynamic flow pattern of the filter were assessed in a flow model and were compared with those of currently available commercial filters including the Vena Tech-LGM, Simon nitinol, Greenfield, and Birds Nest filters. The new filter was placed in the inferior vena cava (IVC) of 31 dogs; 21 of the 31 dogs were followed up with cavography for up to 3 months. At the termination of the study, the filters and IVCs were examined grossly and histologically. An in vivo clot-trapping test was carried out in five dogs. RESULTS The least turbulence was noted with the new filter and the titanium Greenfield filter. The stainless steel Greenfield and Simon nitinol filters caused major flow disturbances. Migration within 5 cm of initial placement occurred in two animals (9.5%). There were no IVC thromboses, perforations, or filter embolizations. An in vivo clot-trapping study showed an 80% efficiency for small thrombi (3 x 20 mm) and 100% efficiency for large thrombi (6 x 20 mm) with the new filter. The Simon and the new filter had the best clot-trapping capabilities. The Vena Tech-LGM and Birds Nest filters were slightly inferior and the Greenfield filter demonstrated by far the lowest trapping capacity. CONCLUSION The new vena cava filter is easily introduced percutaneously through a 12-F sheath and appears to be very promising due to its high filtering capability, low turbulence, nonmagnetic properties, good mechanical stability, and hypothrombogenicity. Clinical trials are warranted.

An animal model of abdominal aortic aneurysm created with peritoneal patch: technique and initial results.

AbstractThe purpose of this study was to develop an abdominal aortic aneurysm model that more closely resembles the morphology of human aneurysms with potential for further growth of the sac. An infrarenal abdominal aortic aneurysm (AAA) model was created with a double-layered peritoneal patch in 27 domestic swine. The patch, measuring in average from 6 to 12 cm in length and from 2 to 3 cm in width, was sutured to the edge of an aortotomy. Pre- and postsurgical digital subtraction aortograms (DSA) were obtained to document the appearance and dimensions of the aneurysm. All animals were followed with DSA for up to 5 months. Laparoscopic examination enhanced by the use of laparoscopic ultrasound was also carried out in 2 animals to assess the aneurysm at 30 and 60 days following surgery. Histological examination was performed on 4 animals. All the animals that underwent the surgical creation of the AAA survived the surgical procedure. Postsurgical DSA demonstrated the presence of the AAA in all animals, defined as more than 50% increase in diameter. The aneurysmal mean diameter increased from the baseline of 10.27 ± 1.24 to 16.69 ± 2.29 mm immediately after surgery, to 27.6 ± 6.59 mm at 14 days, 32.45 ± 8.76 mm at 30 days (p < 0.01), and subsequently decreased to 25.98 ± 3.75 mm at 60 days. A total of 15 animals died of aneurysmal rupture that occurred more frequently in the long aneurysms (≥6 cm in length) than the short aneurysms (<6 cm in length) during the first 2 weeks after surgery (p < 0.05). No rupture occurred beyond 16 days after surgery. Four animals survived and underwent 60-day angiographic follow-up. Laparoscopic follow-up showed strong pulses, a reddish external appearance and undetectable suture lines on the aneurysmal wall. On pathology, the patches were well incorporated into the aortic wall, the luminal wall appeared almost completely endothelialized, and cellular and matrix proliferation were noted in the aneurysmal wall. A reproducible technique for the creation of an infrarenal AAA model was developed using a peritoneal patch in swine. The aneurysm model proved to have potential for further growth of the sac and a tendency to rupture. Because of the growth potential, this might be a better model than those with a noncompliant aneurysmal wall for the preclinical evaluation of stent-graft devices.

Transcatheter Occlusion of Patent Ductus Arteriosus Using a Newly Developed Self-expanding Device: Evaluation in a Canine Model

RATIONALE AND OBJECTIVES.A new occlusion device designed for use in a patent ductus arteriosus was tested in an animal model. METHODS.The device consists of a self-expanding conicalshaped stainless steel mesh, with hooks encircling the expanding end acting to secure the device within the ductus. A screw thread at the apex allows attachment to a stylet, and a 6 F delivery system is used. Placement of the device was attempted in 20 canines that previously had a vascular graft surgically inserted between the descending thoracic aorta and main pulmonary artery, creating the patent ductus model. Angiographic follow-up at regular intervals was performed over a 3-month period. RESULTS.Early cases resulted in device misplacement and migration because of inaccurate assessment of ductus position and size. In 15 canines the device was placed within the ductus and regularly assessed over the 3-month placement period. Ductus occlusion occurred within 1 week in 12 of 13 dogs (92%) when device placement was considered ideal. In two dogs where significant protrusion of the device from the ductus was evident (either into the aorta or main pulmonary artery) ductus closure was delayed but present by 3 months, resulting in a 93% overall closure rate at this time. In one dog, the ductus remained partially opened. CONCLUSIONS.This self-expanding patent ductus arteriosus occlusion device is promising. The 6 F delivery system is advantageous over other devices currently available, making it more suited for use in the pediatric population. Accurate assessment of the ductus is imperative, however, to enable correct device sizing. The screw thread system allows the device to be repositioned if desired prior to deployment.

A modified technique to minimize filter tilting during deployment of the Günther Tulip filter: in vitro study.

With an in vitro model of the inferior vena cava, it was demonstrated that slight tension on the introducer during quick release of the jugular Günther Tulip filter led to less tilting of the filter compared with the technique recommended by the manufacturer. This technique may be useful to minimize significant filter tilting that may be associated with decreased filtration efficiency, and difficulty or impossibility of future filter retrieval.

Can Labeled Single-Use Devices Be Reused? An Old Question in the New Era

REPROCESSING and reuse of medical single-use devices (SUDs) such as catheters and guide wires are gaining popularity as a result of the escalating cost of health care. A recent survey revealed that approximately 20%–30% of hospitals in the United States reprocess SUDs (1). The figures are likely underestimated because hospitals tend not to report their use of reprocessed SUDs. According to the United States General Accounting Office, substantial cost savings can be achieved by reprocessing SUDs because the cost of in-house reprocessing can be less than 10% of the cost of a new device and the cost of third-party reprocessing is approximately 50% of the cost of a new device (1). The legitimate questions here are: 1. Is it safe and economically sound to use reprocessed SUDs? 2. Are reprocessed SUDs as good as the original devices in terms of chemical and physical characteristics? 3. How should reprocessing be regulated to ensure public health? The answers to these questions depend on to whom they are addressed. Most of the opposition against reprocessing of SUDs comes from the original equipment manufacturers (OEMs), whereas the medical community is generally supportive of reprocessing (2). Commentary in the English literature on this subject is relatively sparse. Despite extensive debate in cardiologic publications, there is little pertinent information in interventional journals. Therefore, we are providing our colleagues with insight into the historic and current status of the reprocessing and reuse of SUDs. This commentary is not intended to represent our endorsement or opposition to the practice of reprocessing SUDs.

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

Qian Z, Kvamme P, Raghed D, et al. Comparison of a new recirculation thrombectomy catheter with other devices of the same type: in vitro and in vivo evaluations. Invest Radiol 2002;37:503–511. Raionale 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 &mgr;m. The mean percentage by weight of the original clot that remained as particles larger than10 &mgr;m 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 implantation of non-small-cell lung carcinoma: Technique and observations

RATIONALE AND OBJECTIVES The authors performed this study to determine whether intrathoracic inoculation of non-small-cell lung carcinoma with fluoroscopic guidance would provide for more accurate implantation. MATERIALS AND METHODS A tumor cell inoculum (2 x 10(6) cells per 0.15 mL) was injected percutaneously under fluoroscopic guidance at the posterior midaxillary line in 22 athymic nude mice. The mice underwent imaging with a mammographic unit at 3, 5, and 8 weeks after implantation. The mice were sacrificed at 8 weeks, and autopsy was performed to determine tumor yield. RESULTS The use of a percutaneous technique under fluoroscopic guidance greatly facilitated the accurate implantation of xenografts. Tumor growth was seen at radiography in 18 of the 22 (82%) mice at 8 weeks. Necropsy revealed a 100% tumor yield. Histologic examination confirmed adenocarcinoma of the lung. The average number of tumors found in the lung parenchyma was 1.05 +/- 0.35; the average number of tumors found in the mediastinum was 0.59 +/- 0.67. The average tumor weight was 389 mg +/- 64.3. The average tumor size was 300 mm3 +/- 66.23. CONCLUSION With fluoroscopic guidance, percutaneous implantation of tumor cells in athymic nude mice is simple and effective.