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 Bird's 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 Bird's 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.

Evaluation of a new vascular occlusion device.

RATIONALE AND OBJECTIVES: A new vascular occlusion device was tested in canine femoral and iliac arteries and in an animal model of a patent ductus arteriosus (PDA). METHODS: Four variations of the vascular plug were placed into 18 iliac or femoral arteries of 17 mongrel dogs. Follow-up angiography was performed 1 hour and, if necessary, 2 hours after placement in all animals, 14 of which were then killed. Three dogs were followed angiographically for 2 weeks to 3 months. The "butterfly" plug was then tested in a canine model of a PDA. RESULTS: All plugs contained thrombi, and 12 of the 18 devices caused complete or nearly complete vascular occlusion within 2 hours. In one dog, one vascular plug had eroded through the vessel wall at 3 months without clinical sequelae. Successful PDA occlusion was achieved in 1 or 2 days in 6 of 8 dogs. Three misplacements occurred, one of which resulted in death. DISCUSSION: The balloon-expandable vascular plug appears to be a promising device for occlusion of blood vessels. Migration has not been observed once the device is placed, thus, sizing of the device appears less critical than with coils. However, modification of the delivery system and considerably more experience with the device are necessary to reduce the risk of misplacement.

A stepless needle-dilator for expedient percutaneous catheterization: technical note.

A new stepless needle-dilator is described which allows arterial puncture and dilation in a single step using a single wall puncture technique. The new needle-dilator causes significantly less arterial damage than a conventional dilator (p less than 0.05). Additionally, time and cost savings are realized by clinical users.

The biocompatibility of compressed collagen foam plugs.

The tissue reaction to reexpanded, purified bovine collagen sponge placed percutaneously into the lung, pleural space, liver, kidney, and muscle was studied in dogs and rabbits. In addition, the biocompatibility and radiopacity of tantalum-treated collagen foam plugs was examined. No adverse effects were found. We believe that collagen plugs may be of use in occluding needle tracts from biopsy sites to prevent complications such as bleeding or pneumothoraces.

Atheroablation with the Kensey catheter: a pathologic study.

The mode of action of the Kensey catheter, a new atheroablation device, was investigated. Fresh above-the-knee amputated legs were used for recanalization of the superficial femoral artery. The variables used were identical to those of clinical trials, including a rotational speed of 50,000 rpm and an injection rate of 40 mL/min. The debris produced by the catheter was studied cytologically, and the arterial segments were examined histologically. The particle size in the debris ranged from 1 to 2,000 microns. The softer plaques produced a fine fibrin dust background with long strips of intima ranging from 10 to 2,000 microns. Complicated calcified plaques produced larger background material (10-120 microns) but smaller strips of intima (50-800 microns). Dissections and perforations occurred. Some of the debris produced by the atheroablation process was used to embolize a canine heart and kidney. Small focal infarctions were found in the heart, and large and multiple infarcts were seen in the kidney. In clinical studies the debris appears to be tolerated in the lower extremities. Its safety in the kidney and heart are questioned.

Histologic evidence of angiographic catheter-induced vascular trauma: a comparison of conventional and deformable soft-tip catheters.

Catheter-related complications associated with coronary arteriography remain an iatrogenic hazard with life-threatening consequences. Because such complications may be related to catheter-tip-induced vascular trauma during coronary angiography or percutaneous transluminal coronary angioplasty (PTCA), several types of deformable, soft-tip angiographic catheters have been developed. The following study was undertaken to evaluate the effects of one of these catheters, as well as of conventional catheters, in canine arteries. Ten dogs were catheterized, five with a conventional angiographic catheter and five with a deformable soft-tip catheter (Angiomedics SOFTIP model), all in the Judkins left 3.5 configuration. The left coronary artery (LCA) was subjected to repeated catheterization; the instruments were also advanced and withdrawn through various segments of the thoracic and abdominal aorta and the right iliac artery. Forty-five arterial tissue sections were collected; these were subjected to histologic analysis 2 weeks after catheterization. When catheterized with the soft-tip instrument, muscular arteries such as the LCA and the right iliac artery had an 86% reduction in subintimal lesions with a disrupted or split internal elastic membrane, compared to muscular arteries catheterized with a conventional instrument (p <.017). Moreover, two medial tears were produced by the conventional catheters. On a scale of 1 to 3 (3 being the most severe), the average severity of muscular arterial lesions observed after use of the soft-tip catheter was 1.0, whereas the average severity associated with conventional catheters was 2.0 (p <.02). No significant differences were observed in elastic (aortic) segments. Therefore, this study showed that subacute, subintimal vascular lesions induced by conventional angiographic catheters are more frequent, more serious, and more likely to penetrate the internal elastic membrane than are lesions produced by soft-tip catheters. Obviously, then, soft-tip catheters offer a safer, less traumatic approach to diagnostic and interventional cardiology.

Acute and long-term effects of massive balloon dilation on the aortic wall and vasa vasorum.

To investigate the acute and long-term effects on the vasa vasorum after massive overdilation, canine aortic segments were dilated with Gruentzig balloon catheters to more than 100% over normal size. In the acute study, the significant lumen increase was the result of intimal and medial rupture with stretching and thinning of the adventitia. In these areas, the vasa vasorum were stretched and severed, causing adventitial hemorrhage. In the chronic study, areas of previous subtotal wall rupture with adventitial thinning were repaired by scar tissue. This repair included formation of a neomedia, hyperplasia of the adventitia, and proliferation of the vasa vasorum. No progression of luminal dilatation was seen. This study showed that in subtotal aortic wall rupture, even a severely damaged adventitia is capable of preserving the lumen from further dilatation and rupture until healing. Blood flow to the damaged vessel wall was reestablished by revascularization via capillary budding in the aortic wall.

Modified sheath introducer for reduced arterial damage.

An introducer-sheath dilator is described, which was modified to protect the leading lip of the sheath during insertion, thus reducing arterial damage. The new sheath and a standard sheath were inserted into the femoral arteries of six dogs. Subsequent histologic examination of the arteries proved the new sheath to be both safe and effective.

Improved vessel dilator for percutaneous catheterization.

Three commercial vessel dilators and a dilator of an improved design were tested during percutaneous catheterization in 16 mongrel dogs to evaluate arterial damage produced with their use. The results indicate that, although all dilators often produce arterial damage, the improved design produced much less damage. In addition, lesions were less severe overall. The dilator has been safely and successfully used in patients for percutaneous vessel catheterization for the past 30 years at the authors' institution.

A less traumatic catheter for coronary arteriography.

A deformable soft-tipped angiographic catheter has been designed and developed to reduce vascular trauma during coronary arteriography. In order to test the ability of the catheter tip glide over vascular endothelium, the coefficient of resistance was tested using fresh human aortic tissue. The mean frictional coefficients of resistance (FRc) for the soft-tipped catheter, as compared with two commonly used catheters (N = 10/group), were .78 +/- .08 units for the soft-tipped catheter and 1.10 +/- .10 (p less than .006) and .98 +/- .10 (p less than .034) for the conventional catheters. This demonstrates a significant 23% reduction in FRc with the soft-tipped catheter. The ease of penetration into a wax media was also measured using the soft-tipped catheter and compared with the same two conventional catheters. The indentation depths for the soft-tipped catheter and the two other catheter groups (N = 7/group) were 140 +/- 18 micron, 246 +/- 15 micron and 318 +/- 20 micron, respectively. This represents a 56% decrease in indentation depth with the soft-tipped catheter. Histologic studies in canines have demonstrated considerably less endothelial damage and subsequent intimal proliferation in the aorta and coronary ostia with the soft-tipped catheters compared with control catheters. It is concluded that a soft-tipped angiographic catheter is less traumatic to vascular tissue and may offer a safer approach to intravascular studies.

Nephrotoxicity of contrast media assessed by occlusion arteriography.

The authors describe an experimental model for the study of nephrotoxicity induced by contrast media, based on a standardized injection combined with occlusion of the renal artery so as to expose the kidney to a high concentration of contrast medium for ten minutes. Iopamidol, ioxaglate, and both isosmolar and hyperosmolar saline were well tolerated, but diatrizoate caused marked radiological and pathological changes. This model may be helpful in studies of the mechanisms underlying contrast medium nephrotoxicity and evaluating differences in toxicity between contrast agents.

Long-term patency of the ductus arteriosus after balloon dilatation: an experimental study.

Balloon dilatation of the ductus arteriosus was carried out in vivo in eight piglets that were 12 to 16 days old. The ductus was functionally closed in all animals before dilatation. Long-term patency for periods of up to 6 months after the procedure was demonstrated in six animals by angiography, Doppler ultrasound examination, and at autopsy. The presence of hemodynamically significant shunts was indicated by clinical development of heart failure, pulmonary infections, and left ventricular hypertrophy. These results confirm the value of this laboratory preparation to create left-to-right shunts at the ductus level.

Renal ablation using hot contrast medium: an experimental study. Work in progress.

Ablation of the kidney was attempted in 12 dogs by injecting 10-30 ml of heated (100 degrees C) contrast medium (Hypaque-60, diatrizoate meglumine) into the renal artery. Complete renal ablation without collateralization was demonstrated. Hot contrast medium is an effective embolic agent, and its use is associated with few of the drawbacks of presently used techniques.

Patency of the ductus arteriosus after balloon dilatation: an experimental study.

Balloon dilatation of the ductus arteriosus was carried out in vivo in newborn pigs and on postmortem specimens from humans and piglets. The ductus was functionally closed in all newborn animals but patency resulted in all animals after balloon dilatation. Left-to-right shunts of 50% to 70% were found with anatomic lumen sizes of 3 to 5 mm. Patency was demonstrated up to 6 weeks after dilatation. Histologic examination showed splitting of the internal elastic layer and media, areas of hemorrhage confined to the media, and preservation of the adventitia. Mediastinal hemorrhage did not occur. This new technique is useful as an animal model of patent ductus arteriosus and could theoretically be used for palliative treatment of ductus-dependent congenital heart disease.

Spermatic vein obliteration using hot contrast medium in dogs.

Obliteration of varicoceles in men with infertility has been shown to improve semen quality and increase fertility rates. Many current techniques involve complex procedures and specialized equipment and may be associated with adverse effects. Transcatheter thermal vessel occlusion was utilized for spermatic vein obliteration in dogs. Diatrizoate (76%) contrast medium at a temperature of 100 degrees C was injected into canine spermatic veins. Follow-up venography and histologic examination revealed thrombosis of the injected veins without damage to the surrounding tissues in all cases. Clinical and laboratory examination of the animals revealed no adverse systemic effects. It is concluded that transcatheter thermal venous occlusion is an effective technique for spermatic vein occlusion in a canine model.

Work in progress. Transcatheter thermal venous occlusion: a new technique.

Diatrizoate (76%) contrast agent heated to 100 degrees C was injected into the veins of dogs and one human volunteer for the nonsurgical occlusion of the vessels. Follow-up venograms and histologic examinations, at intervals varying from one day to four weeks later, revealed thrombosis of the injected veins in all animals. Thrombosis occurred one to five days after injection of contrast agent. The authors conclude that hot contrast medium is a safe and convenient agent for inducing thrombosis. It is much easier to use than mechanical devices, tissue glues, and plastics, which involve complex procedures and specialized equipment. In contrast to other sclerosing agents, hot contrast agent is rapidly converted into a nonsclerosing agent by cooling. The new technique allows a more controlled thermal injury to the vascular wall and is under fluoroscopic control.

Transluminal dilatation of coarctation of the abdominal aorta. An experimental study in dogs.

The optimal treatment for recurrent coarctation of the aorta remains undefined. Recurrent stenosis following surgical repair occurs in 6-48% of cases involving the thoracic aorta. Because of the high morbidity and mortality associated with surgery, an alternate approach such as transluminal angioplasty is desirable. To evaluate this possibility, the authors created several experimental lesions to test their capability for dilatation, using the percutaneous transluminal technique. The results indicate that balloon dilatation of coarctation after end-to-end anastomosis is difficult or impossible. Dilatation of other types of suture lines may also be difficult due to the large amount of fibrous tissue at the anastomotic site, which is not amenable to balloon dilatation. Thus surgery remains the preferred form of therapy.

The mechanism of angioplasty. Dilatation of iliac cadaver arteries with intravascular pressure control.

A model was developed which allows the dilatation of iliac cadaver arteries under normal blood pressure conditions (mean pressure 100 mmHg). Segments of the iliac artery were put under pressure and dilated with balloons under similar conditions as in clinical practice. Purposely oversized balloons were used because most of the arteries did not contain severely stenotic plaques and consequently the commercially available balloons had no effect because of their comparatively small diameter. In spite of the use of oversized balloons, the cadaver arteries could not be significant dilated. Rupture of the intima and media was almost invariably present. Leakage of distending fluid through the adventitia occurred commonly. The "therapeutic range" between minimal dilation and partial or total rupture in postmortem studies is small.

Mural thrombosis of the left atrium following replacement of the mitral valve.

The nature and incidence of postoperative mural thrombosis of the septal and/or posterior walls of the left atrium were studied in autopsy specimens of hearts from patients in whom the mitral valve had been replaced by a prosthesis 1 day or longer before death. The cases were divided into length of postoperative period as follows; Group I, 1 to 60 days, 57 cases; Group II, 61 days or longer, 36 cases. In Group I mural thrombus of the septal and/or posterior walls of the left atrium was found in 35 of 57 patients (61%). Thrombi against the septal wall tended to be broad and flat. Thrombi involving the posterior wall tended to be multifocal. In Group II, lesions interpreted as old thrombi of the atrial septum were found in 23 of 36 subjects (64%). Grossly, the old lesions were represented by gray nodularity. Histologically such lesions were consistent with organized thrombi. Superimposed recent thrombosis occurred in some cases. Systemic embolism occurred in each group. In the cases in which left-sided thrombi were restricted to the septal and/or posterior walls of the left atrium, systemic embolism was observed in 10 of 23 cases in Group I (43%) and in two of seven cases in Group II (29%). Obstruction of the mitral prosthesis by bulky mural thrombosis originating at the septal wall of the left atrium was observed in one case. The study suggests that the process of postoperative mural thrombosis of the septal and posterior walls of the left atrium may result from trauma to these structures during the operative procedure.