Antiembolic filters: the state of the art.
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Humans↗
Biomedical subjects
L J Greenfield
Publications and source records attributed to L J Greenfield.
Evolution of venous interruption for pulmonary thromboembolism.
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Evaluation Studies as Topic↗
Late results of suprarenal Greenfield vena cava filter placement.
Placement of the Greenfield filter above the renal veins was necessary in 71 (9%) of 821 total patients in the filter registries of two institutions. The status of 60 patients (85%) could be verified, with follow-up data ranging from 18 months to 16 years (average, 53 months). Of 24 deaths (34%), none was from recurrent embolism or renal failure; death was most commonly associated with a malignant neoplasm. The recurrent embolism rate was 4%, identical to the infrarenal experience. Duplex evaluation of the filters in 22 patients, representing the majority (61%) of living patients, showed that all the filters were patent. Sixteen patients (41%) had lower-extremity edema that predated filter insertion, and in no patient did the results of noninvasive venous studies worsen. Filter fracture (two patients) or distal migration (two patients) had no clinical sequelae, and there was no evidence of renal dysfunction. For thrombus extending to the level of the renal veins or within them and for pregnant patients or women of childbearing age, suprarenal placement of the Greenfield filter is safe and effective, with no filter obstruction seen in follow-up extending to 16 years.
Adolescent↗
Endovascular therapy of venous thromboembolic disease.
This article discusses the background and status of inferior vena caval filtration and transvenous catheter techniques for pulmonary embolectomy in the management of venous thromboembolic disease.
Catheterization↗
N-acyl 3-alkylidenyl- and 3-alkyl azetidin-2-ones: a new class of monocyclic beta-lactam antibacterial agents. 1. Structure-activity relationships of 3-isopropylidene and 3-isopropyl analogs.
The synthesis and antibacterial activity of a series of N-acyl 3-isopropylidenyl- and 3-isopropyl 2-azetidinones having potent in vitro antibacterial activity, particularly against anaerobic organisms, is described. A distinguishing structural feature of these compounds is the lack of any ionizable moiety appendant to the lactam nitrogen.
Anti-Bacterial Agents↗
Experimental embolic capture by asymmetric Greenfield filters.
An uncommon complication of percutaneous insertion of the titanium Greenfield filter is angulation at discharge with clustering of the limbs to one side of the vena cava. Potential adverse effects of this asymmetry were tested in a perfusion system with cadaver venae cavae. The stainless-steel Greenfield filter (SGF) was compared with the modified-hook titanium model (TGF-MH) and a percutaneous modified-hook model of the SGF (SGF-MH) with flexible plastic emboli in four sizes and varied sequences. There were 458 runs comprised of 2203 embolic events, with an overall successful capture rate of 81% despite tilting, asymmetry, and accelerated flow rates from 1.0 to 2.5 L/min. Significant differences were observed in vena cava with diameters greater than 22 mm where capture rate was 76% as opposed to 86% in venae cavae less than 22 mm (p = 0.01). Larger emboli (8 x 25 mm and 8 x 100 mm) were trapped uniformly, whereas smaller emboli (5 x 10 mm) had 59% capture (p = 0.001). Similarly, the capture rate was less when smaller emboli were released before the larger ones (71% vs 87%; p = 0.001). Capture in small versus large venae cavae was not significantly different for the SGF (75%) or TGF-MH (84% vs 87%) but differed for the SGF-MH (98% vs 67%; p less than 0.001). Logistic regression was used to develop a mathematic model for interaction of the variables and determined two first-order interactions: caval size and limb position and caval size and type of filter.(ABSTRACT TRUNCATED AT 250 WORDS)
Cadaver↗
Quantitative increases in surgical house officer clinical activity as the basis for increased work loads in a university hospital.
BACKGROUND: House officer (HO) work loads, particularly work hours, have been the subject of considerable controversy. The hypothesis of this study was that a disproportionate work burden has been placed on HOs in teaching hospitals because of increased obligatory clinical activities and increased educational expectations. METHODS: Factors directly and indirectly affecting care of surgical patients were related to individual HO efforts at the University of Michigan from 1981 to 1991. Data regarding clinical activity and support services were abstracted for analysis from hospital year-end reports, personnel rosters, and educational logs and correlated with the number of surgical HOs. RESULTS: The total numbers of HOs in the Department of Surgery were relatively constant (122 +/- 4) throughout the study interval. Increases that occurred in annual hospital admissions (7615 to 10,651), discharges (7909 to 11,176), clinic visits (53,251 to 86,111), total operations (6789 to 16,526), and operating room hours (24,175 to 62,429) were significant (r greater than 0.9; p less than 0.001 in each category). The acuity of inpatient hospital care increased twofold, as measured by a case mix index, and was accompanied by a 125% increase in the number of surgical intensive care unit beds. During the study period, department of surgery faculty increased 49% (59 to 88), clinical nursing staff increased 118% (821 to 1794), hospital administrative staff increased 59% (2086 to 3320), and hospital support staff increased 53% (4134 to 6342). The number of students in each University of Michigan Medical School class, a group that might defray certain HO work loads, decreased significantly by 16% (226 to 189) during this time (r = -0.76; p less than 0.02). CONCLUSIONS: Disproportionate increases in work demands have been placed on surgical HOs compared with other health care team members during the past decade. Calculated work loads increased from 91.2 hr/wk/HO in 1981 to 110.9 hr/wk/HO in 1991. Balancing the increasing service activities with educational needs of surgical HOs remains a substantial challenge to be addressed by educators.
Employee Performance Appraisal↗
Lower extremity arterial disease in systemic lupus erythematosus.
Lupus vasculitis primarily affects microvascular circulation, and large-vessel thrombosis is a rare complication of this disease. Large-vessel occlusive disease in systemic lupus erythematosus is most likely related to hypercoagulability in addition to immune complex-mediated endothelial damage. We describe the 11th and 12th patients reported to have systemic lupus erythematosus and macrovascular occlusive disease of the lower extremities. Our experience and a review of the literature suggest that, while aortoiliac disease is amenable to bypass or endarterectomy, infrainguinal disease is rarely correctable surgically, and amputation becomes necessary in most of these patients.
Adolescent↗
Assessment of vena caval filters.
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Evaluation Studies as Topic↗
Evaluation of the inferior vena cava with intravascular US after Greenfield filter placement.
An animal model was used to evaluate the utility of intravascular ultrasound (US) imaging of the inferior vena cava (IVC) following Greenfield filter placement. Ten Greenfield filters were placed in the IVCs of five sheep and three dogs. Experimentally induced thrombi were injected into four filters at the time of placement. Intravascular US and cavography were performed 4 weeks after filter implant. The imaging studies were evaluated for demonstration of filter position, orientation, and leg distribution, as well as prediction of caval wall penetration by filter hooks. Experimentally induced and spontaneous intrafilter thrombi were also imaged. Findings were compared with those of postmortem examination. Exact filter position and orientation were most simply and accurately demonstrated on radiographs. Filter leg distribution and extent of intrafilter thrombus were best evaluated on intravascular US images. The prevalence of caval wall penetration was underestimated with both studies. The results of this animal study suggest that the information about the IVC provided at cavography and intravascular US following Greenfield filter placement may be complementary.
Animals↗
Clinical characteristics and surgical management of vascular complications in patients undergoing cardiac catheterization: interventional versus diagnostic procedures.
The purpose of this report is to define the clinical characteristics and outcome of surgical management of vascular complications after interventional cardiac catheterization and to contrast them to those after diagnostic cardiac catheterization. From October 1985 to December 1989, 101 patients were treated for 106 vascular complications after 1866 interventional and 5046 diagnostic cardiac catheterizations at the University of Michigan Medical Center. Interventional catheterizations resulted in 69 vascular complications in 64 patients (frequency 3.4%). The most common interventions included coronary angioplasty (34), of which 10 required percutaneous partial cardiopulmonary bypass, intraaortic balloon pump placement (14), and aortic valvuloplasty (11). Interventional catheter-related complications included hemorrhage (33), arterial thrombosis (18), pseudoaneurysm formation (12), catheter embolization (2), thromboembolism (2), as well as arteriovenous fistula, pseudoaneurysm, and arterial dissection (1 each). Fifteen of these 69 patients (24%) had suffered acute myocardial infarction just before their catheterization. Surgical repair was performed under local anesthesia in 70% of patients. Major vascular reconstructions were required in 9% of patients. Three percent of the involved lower extremities had to be amputated because of complications occurring after arterial puncture. Eight percent of the patients incurring vascular complications after interventional procedures died after operation. Diagnostic catheterizations resulted in 37 vascular complications in 37 patients (frequency 0.7%). In contrast to diagnostic cardiac catheterization, vascular complications after interventional cardiac catheterization occurred more frequently, were most often due to hemorrhage at the vascular access site, and occurred in high-risk, critically ill patients.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Results of a multicenter study of the modified hook-titanium Greenfield filter.
Initial efforts to modify the stainless steel Greenfield filter for percutaneous insertion led to development of a titanium Greenfield filter, which could be inserted by use of a 12F carrier. This device functioned well as a filter but had an unacceptable 30% rate of migration, tilting, and penetration. Therefore a titanium Greenfield filter with modified hooks was developed and has been tested in 186 patients at 10 institutions. Successful placement occurred in 181 (97%); placement of the remainder was precluded by unfavorable anatomy. A contraindication to anticoagulation was the most frequent indication for insertion (75%). All but two were inserted percutaneously, predominantly via the right femoral vein (70%). Initial incomplete opening was seen in four patients (2%), which was corrected by guide wire manipulation and asymmetry of the legs in 10 (5.4%). Insertion site hematoma occurred in one patient, and apical penetration of the cava during insertion occurred in a second patient. Both events were without sequelae. Follow-up examinations were performed at 30 days at which time 35 deaths had occurred. Recurrent embolism was suspected in six patients (3%) and two of three deaths were confirmed by autopsy. Filter movement greater than 9 mm was seen in 13 patients, (11%) and increase in base diameter greater than or equal to 5 mm was seen in 17 patients (14%). CT scanning showed evidence of caval penetration in only one patient (0.8%). Insertion site venous thrombosis was seen in 4/46 (8.7%) patients screened. The modified hook titanium Greenfield filter is inserted percutaneously or operatively through a sheath, eliminating concern for misplacement from premature discharge.(ABSTRACT TRUNCATED AT 250 WORDS)
Adolescent↗
Deep venous thrombosis in the baboon: an experimental model.
Experimental models of deep venous thrombosis, heretofore, have not been available for laboratory studies. This investigation establishes a novel model of venous thrombosis by inhibiting the protein C system combined with venous stasis and subtle venous injury. Ten adolescent baboons were studied in pairs, with one animal receiving saline solution (B2, B4, B6, B8, B10) and one being exposed to thrombogenic reagents (B1, B3, B5, B7, B9). These reagents represented a combination of a monoclonal antibody (HPC4) to protein C, 1 to 4 mg/kg administered over 5 minutes, and tumor necrosis factor administered over 3 minutes at a dose of 150 micrograms/kg through a catheter placed into the left superficial femoral vein with distal ligation. To encourage stasis, a pediatric size blood pressure cuff was inflated to 40 mm Hg on the right thigh for 50 minutes of every hour during the first experimental day (day 1) in B5 to B10. The animals were observed for a 6-hour period on day 1 and then for an 11- to 15-day period until sacrifice. Hemodynamic and hematologic parameters were recorded along with duplex imaging of the iliac veins and inferior vena cava on a daily basis. Venography was performed on day 1, day 4, and the day of sacrifice. At sacrifice the entire iliac and vena caval system was carefully dissected, opened, and photographed. Experimental animals given the HPC4 and tumor necrosis factor developed left iliac vein thrombosis extending into the inferior vena cava. Duplex imaging, venography, and autopsy revealed that control animals receiving saline solution never developed comparable thrombus. Experimental subjects exhibited thrombus on duplex imaging by day 4 (B1), day 3 (B3), day 2 (B5), 120 minutes (B7), and 360 minutes (B9) after receiving HPC4 and tumor necrosis factor. Venograms performed on day 1 exhibited thrombus in B5, B7, and B9. The extent of thrombus, the timing of its occurrence, and its effect on the animals' left leg followed a dose-dependent relationship for the animals in which the occlusive blood pressure cuff was used. Significantly greater declines in blood pressure, white blood cell count, and platelet count were found in affected animals given HPC4 and tumor necrosis factor reagents as compared to control subjects. All affected animals demonstrated the appearance of fibrin split products and a markedly prolonged prothrombin time. This investigation, for the first time, establishes a reproducible model of deep venous thrombosis involving inhibition of protein C that will facilitate further laboratory studies on venous thrombosis.
Animals↗
Catheter pulmonary embolectomy.
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Catheterization, Swan-Ganz↗
Evaluation of a new percutaneous stainless steel Greenfield filter by intravascular ultrasonography.
The standard stainless steel Greenfield filter was modified by extending the limbs at the apex to permit loading into a 12F carrier for percutaneous insertion. This model was tested for fixation and resolution of experimental embolism in dogs (six filters in four dogs) and sheep (eight suprarenal filters in eight sheep). Serial radiographs and venacavography at 2 and 4 weeks allowed measurement of migration and suspected caval penetration, confirmed by direct examination at autopsy. Caval penetration was graded according to visibility of point (0), hook (1+), or limb (2+) for each limb of the filter. Oxidized cellulose-induced thrombi were injected and trapped in two dogs and four sheep without proximal filter displacement or thrombus propagation. Thrombi showed incomplete resolution during 4 weeks' observation by interval venacavography and subsequent autopsy but no tendency for proximal propagation. Distal migration occurred in four of six filters in dogs, and caval wall penetration was seen (score 1.8/filter). Less migration was seen in sheep (2/8), but there was evidence of hook penetration in four animals (score 0.88/filter). Intravascular ultrasonography, 20 MHz, with a 6.5 F catheter assembly successfully visualized all 10 filters in which it was attempted and showed thrombi attached to the filter or caval wall, all of which were confirmed at explant. No thrombi were missed; however, intravascular ultrasonography was limited in assessment of caval wall penetration by lack of position control and reverberation artifact. Although it performs well as a filter, the elasticity of the percutaneous stainless steel greenfield filter allows distal migration and caval penetration comparable to the titanium Greenfield filter and will require further modification of hook design to improve performance.
Animals↗
Transatrial interruption of the inferior vena cava.
Transatrial placement of a Greenfield filter at the time of cardiac surgery was performed on three patients with recent femoral venous thrombosis and unstable angina, and at the time of pulmonary embolectomy on four others. The filter carrier was passed through the right atrial cannulation site under fluoroscopic guidance into the inferior vena cava. A preliminary venacavogram was performed through the carrier or a previously placed angiographic catheter. Two complications were encountered: the first was misplacement of a filter in the right renal vein before routine venacavography was employed; the second was caudal displacement of a filter by a right atrial venous drainage cannula that projected into the inferior vena cava. The latter complication can be prevented by the use of a right atrial "sump" drain that does not protrude into the inferior vena cava.
Angina, Unstable↗
Long-term results of aortoiliac reconstruction.
To facilitate evaluation of new and evolving interventional strategies in the management of aortoiliac occlusive disease, the collective long-term experience with traditional operative reconstruction was reviewed. Endarterectomy, currently the procedure of choice for a limited number of patients with disease localized to the aorta and common iliac arteries, has demonstrated 10-year primary patency rates of 48%-77%. By comparison, prosthetic in situ replacement or bypass grafting, commonly performed for more extensive lesions and in the presence of aneurysmal degeneration or total occlusion of the aorta, has yielded 10-year primary patency rates of 62%-79%. Cumulative graft patency can often be extended by means of thrombectomy, thrombolysis, and repair of thrombosed graft limbs, with 20-year extended cumulative patency rates of 49%-68%. The long-term success of operative reconstruction is highly dependent on the extent of coexistent peripheral occlusive disease, with progression of outflow disease representing the single most important factor associated with thrombosis of endarterectomy sites or prosthetic bypass grafts. Further improvements in long-term outcome for all modes of intervention in aortoiliac occlusive disease require increased attention to the minimization of risk factors associated with the underlying atherosclerotic disease process.
Angioplasty, Balloon↗