Simon Nitinol Inferior Vena Cava Filter: Initial Clinical Experience
Transcription
Simon Nitinol Inferior Vena Cava Filter: Initial Clinical Experience
Morris Simon, MD #{149} Christos A. Athanasoulis, David H. Porter, MD #{149} Barbara H. Byse, MD Dan E. Orron, MD #{149} Arthur C. Waitman, MD Simon Initial Work Nitinol Clinical Kim, Kleshinski, MD #{149} Fred L. Steinberg, BS #{149}Stuart Geller, MD Cava MD #{149} #{149} Filter: in Progress’ Index terms: Embolism, pulmonary, 60.72 nae cavae, filters #{149} Venae cavae, interventiona! procedure, 982.1299 #{149} Venae cavae, stenosis obstruction, 982.458 1989; #{149} Ducksoo Inferior Vena Experience The Simon nitinol filter for percutaneous interruption of the vena cava to prevent pulmonary embolism is currently undergoing a multicenter clinical trial. Preliminary clinical results are reported as work in progress. The results in 44 patients at two centers are analyzed in detail, and major events are reported from 103 patients in 17 centers in the United States during a 10-month penod. The filter was successfully inserted via the femoral or jugular route in all patients through a 9-F catheter. The placement procedure was easy and without significant complications. Follow-up studies included plain radiography, ultrasonography, magnetic resonance (MR) imaging, and clinical evaluation. No filter migration or perforation occurred among the 103 patients. Symptomatic occlusions occurred in 7%-9%, comparable to other series, and some asymptomatic occlusions were detected with MR imaging only. The implications of occlusion of the filter are discussed. Radiology MD #{149} Stephen 172:99-103 T Simon HE filter) nitino! for monamy filter the embolism going tional clinical study (SNF prevention is currently trial in the under- in a multi-instituUnited States, with 17 participating centers. At this time, a total of 103 filters have been placed in patients. This filter is presently classified device as an by the Administration not include other cal data cava since already ty and filter in current published exist regarding of these The SNF exploits ma! shape-memory of vena chinisafe- ticipating the unique properties themof ni- into complex warmed alloy a previously rigid (1,2). this material to stainless that can man studies proved in animal (3,4). of comparable and hu- saline or it is warmed to body temperaassumes its filter shape, and locks into lungs. cm has a 28-mm en overlapping verging a legs The hoops, with up to a clinical trial. to trap filter dome and terminal is 3.8 with has hooks AND METHODS population 18 women, consisted ranging of 26 in age sev- six dito the procedure Hospital from Eighof the and 26 at Massachu(MCH) between February and November 1988. Appropniate informed consent was obtained from all from the lower limbs or pelprevent the emboli from the hong, easily through for delivery cava (IVC). It is designed study and underwent setts Ceneral infu- Here, tune, reaching to a broad 19 to 96 years (median, 62 years). teen patients underwent placement SNF at Beth Israel Hospital (BIH), when A cold place. in the The men Ve- emboli vis and adapt widths Patients imprinted, filter shape Biocompatibility has steel can cava PATIENTS as a soft, straight set of wires cooled but is instantly trans- formed filter data of the major complications of fibten placement that would be reportable to the study monitor in a total of 103 patients from all 17 centers par- did any the The range devices. a nickel-titanium exist when Drug trial with extensive efficacy tinol, and The filter. maximum of 28 mm. This preliminary progress report focuses on detailed early clinical mesults of placement of the SNF in 44 patients. We also report follow-up investigational Food (FDA). randomization vena use, U.S. sion allows it to pass standard 9-F catheter into the inferior vena #{149} engage the vena cava wall (Fig 1). The legs serve as a coarse first filter, while the dome forms a fine second or of pul- patients. The clinical indications for filter ment were those generally accepted IVC filter placement (5). The major cations were pulmonary embolism tensive deep anticoagulant venous thrombosis or thrombolytic was contraindicated, cations, or failed resulted to prevent bolism. proportion The high placements MGH in neunosurgical placefor mdion ex- when therapy in complirecurrent emof filter patients at is noteworthy. Methods I From the Department of Radiology, Beth Israel Hospital. Harvard Medical School, 330 Brookline Ave. Boston, MA 021 15 (MS., D.K., D.H.P., 5K., D.E.O.), and the Department of Radiology, Massachusetts General Hospital, Boston (C.A.A., F.L.S., B.H.B., S.C., A.C.W.). From the 1988 RSNA annual meeting. Received December 5, 1988; revision requested January 17, 1989; revision received February 14; accepted February 17. Address reprint requests to MS. Nitinol Medical Technologies (NMT), Woburn, Mass, is the manufacturer of the Simon nitinol filter and is responsible for the conduct of the clinical trial under Food and Drug Administration Investigational Device Exemption no. G870093. MS. is the Scientific Director of NMT, and C.A.A. is a member of the Board of Advisors. All authors are in full compliance with established guidelines at their respective institutions for disclosure of financial interest related to research projects. ©RSNA, 1989 See also the editorial by Yune (15-16) and article by Epstein et a! (105-1 10) in this issue. insertion dune line procedure-Before is started, is cooled at least catheter a 500 mL in a bucket the procebag of normal saof ice chips for half an hour. The 9-F delivery is inserted percutaneously into Abbreviations: FDA = Food inferior vena era! Hospital, a BIH = Beth Israel Hospital, and Drug Administration, IVC cava, MGH Massachusetts GenSNF = Simon nitinol filter. 99 common or jugular with the iliac vein via a standard femonal venipunctune, on either side, Se!dingen technique. The cathe- ten is first used vena cavognam of the renal Table 1 Summary of Preliminary Results of SNF Placement in 103 Patients at 17 to obtain a preliminary to determine the position veins and to ensure that Centers the Results vena cava does not exceed 28 mm in width, after correction for magnification. The presence anatomic of thrombi anomalies on significant is also shown. catheter tip is then repositioned low the lowest rena! vein, the cation for the filter dome. The filter comes It is received tube section in the of the delivery system infused and is feederThe cold through the stor- via a sideport at the rate of about per second to cool and soften the filter. The storage tube is then connected directly to the 9-F catheter so that the cold saline infuses into with requires the tip of the catheter. about six forward This strokes of the feeder pump handle. Finally, a single backward stroke of the storage tube and catheter unsheaths the filter and releases it into the IVC. It is instantaneously trans- formed into its expanded filter shape locks into place. The catheter is then and pulled ye- back nogram slightly, and is obtained is removed pressed and in the dune requires skills and complete, and the only including grams, if cine ing is used. the final po- manner. routine takes both site is com- The proce- vena and jugular minutes and plain radiography ly after placement angiography. to cavoimag- delivery sys- that the jugular and its filter is be performed through Follow-up-The initial and follow-up examinations were directed toward the detection of complications at the venipuncture site, such as venous thrombosis hemorrhage, and at the filter site, in- cluding filter migration, penetration or perforation of the vena cava wall, misplacement, filter tilting, or crossing of the filter legs. Possible recurrent pulmonary embolism and systemic effects of the nitinol material were also evaluated with clinical and laboratory methods. In addition, partial on complete occlusion of the filter due to trapped embohi, an anticipated sequela of filter placement, was also diagnosed clinically on by means of noninvasive imaging, including magnetic resonance (MR) imaging. 100 #{149} Radiology of the again and Chest ti!ation/perfusion Migrations Cranial 0 Caudal 0 Recurrent pulmonary embolism Symptomatic 0(1) 2 Asymptomatic filter shortat 3 and 6 also optional studies. enhanced with formed only The clinical when and scanning Vena contrast yen- were was clinically bolytic were requires therapy medications prescribed. of anticoagulant at the time that major or other The use or on throm- of filter place- in- RESULTS ic recurrent in progress and thus, only limitreported. Of the 103 centers, there were and no deaths me(Table 1). There was case of symptomat- pulmonary embolism, and two patients had confirmed asymptomatic pulmonary embolism. Theme were seven cases of confirmed symptomatic IVC occlusion and two possible IVC occlusions detected on the basis of clinical findings only. Of the 44 patients studied in Boston, 10 have undergone in parentheses with clinically represent suspected Table 2 Summary of Preliminary Results SNF Placement in 44 Patients of No. of Patients Results Entry a 3-month complications site thrombus Hemorrhage Failuretointroduce Major misplacement Leg penetration Migration Tilting of dome* Spindle formationt Leg crossingl 5 0 0 0 0 0 24 1 4 (2) IVC patency Patent with Occlusion Occlusion require- ment or subsequently was based purely on clinical considerations and was not fluenced by the protocol. The trial is now data are incomplete; ed trends can be patients at all 17 no filter migrations bated to the filter one unconfirmed to filter Note-Numbers additional patients findings only. Perioperative complications at all centers be reported immediately to the study monitor. These included filter migrations, recurrent pulmonary embolism, IVC occlusions, and filter-related deaths. follow-up 7 (2) 3 0 indicated. at 3 and 6 but was not a protocol therapies withholding related per- months included history, physical examination of the puncture site and lower limbs, plain radiography of the filter negion, and laboratory tests of blood and urine for liven and kidney function and blood clotting. Autopsy examination of the vena cava and filter of patients who died during the course of the 6-month study or later, due to any cause, was en- protocol Deaths cavography material examination Symptomatic Asymptomatic ultrasite radiography lung the same catheter by means of a retrograde injection of contrast medium just above the filter. and (top) from months. Optional studies included sound (US) imaging of the puncture The study preloaded for a feet-first delivery from above. After a jugular delivery, follow-up can a 9-F catheter form viewed the side (night). Protocol requirements included clinical history and physical examination, documentation of the placement procedure, No The femoral in its extended ment. angiognaphic 30-45 or digital-subtraction tems are identical, except catheten system is longer venognaphy form for passage through and in its fully expanded the end (left) and from counaged whether there is Finally, the catheter puncture usual typically a follow-up to check sition of the filter any leg penetration. is shown and filter region, computed tomography (CT), MR imaging, or digital-subtraction the IVC for a few seconds. Typically, less than 150 mL of saline is required for filter delivery, an insufficient amount to affect patient temperatune. The filter is then advanced napidly through the catheter until its tip aligns The SNF of Patients IVC occlusion storage- with a telescoping and pusher wire. is briefly age tube 10 drops just beoptimal lo- 1. to be delivered. preloaded preassemb!ed pump section saline ready Figure The No. thrombus (symptomatic) (asymptomatic) Recurrent pulmonary embolism Symptomatic Asymptomatic Deaths 5 [11J 3 (2)[7-1 3 [7] 1] 0(1) 1 Related to filter Unrelated to filter 0 7 Note-Numbers in parentheses represent patients with clinically suspected findings only. Numbers in brackets are percentages. * Dome tilting of up to 30#{176} occurs as a normal adaptation to a small IVC lumen. It does not affect filtering efficiency, since the dome hole sizes are unaffected. t Spindle formation is an intermediate stage of dome recovery that may occur in very small venae cavae. I Leg crossing occurred in the first four patients due to a pusher wire problem that has been corrected. follow-up 6-month abdominal were and four have completed follow-up (Table 2). Initial madiogmaphs of the filter obtained in all 44 patients; en underwent abdominal phy at 3 months, and four months. Ultrasound studies a sev- madiograat 6 of the puncture patients 3 months sites were performed in 18 soon after placement, five at and two at 6 months. US studies of the IVC and filter region proved technically difficult due to wide variations in build and bowel contents in individual patients but July 1989 were attempted in nine patients in the early period after placement, in five patients at 3 months, and in two The filter tip was properly positioned within 3 cm of the lowest menal vein in all patients, except three at 6 months. three patients. in whom it was delivered slightly lower than planned due to early opemator inexperience. In two cases, the dome appeared to engage the infemior edge of the lowest renal vein without affecting renal venous meturn. It should be noted that in large aging CT was performed Twenty-five MR examinations Ti-weighted gradient-echo formed with sequences sequence nongated or a new fast were per- in 21 patients. MR imaging appears to be a promising sive method for determining tency of the vena cava and menting thrombi captured tem or complete cava was the occlusion (6). In seven only by referring One patient in im- noninvathe pafor docuin the filof the patients, telephone physician vena follow-up interview or patient. refused of all follow-up ex- aminations. Seven patients hated to the filter died of causes unmeplacement during the trial period. None tients died of pulmonary One autopsy study of these paembolism. was obtained dun- ing the study period and showed no thrombus in the filter. A second autopsy was performed on a patient aften the 6-month study period and showed an organized thrombus attached to the legs-a result that confirmed findings of an earlier followup MR imaging study-as well as a more recent thrombus captured in the filter dome. Forty-one filters were delivered by the femomal route, 29 on the right and 12 on the left, and three were delivened by the jugular route, two on the might, and one via the left extemnal jugular vein. The filter-placement procedume was well tolerated by all 44 patients. Theme introduction. with material starting the Some early problems caused difficulty in filter movement out of the storage tube, were and no failures some leg of cross- venae cavae, mally descends aging or CT. Theme embolism for venotomy femonal vein Theme was no clinical evidence matoma formation at the venous tion or new ed subsequently in one developed disseminated agulation. formation Volume patient who vascular co- No arteriovenous or air embolism 172 devel- #{149} Number fistula occurred. 1 filter mito secure who has been frequency. of cannot be In the the have chanical track (measured raised passage has of been been large in with recurrent bohism (10). Other tilting, misplacement, Ques- the me- Greenfield shown emboli filled resulting about (9). fil- to allow once clot, its the apex a condition em- pulmonary problems included caudal or cranial migration, perforation and fracture of the Greenfield filter, and thrombosis at the entry site (11,12). IVC occlusion is reported to occur in about 5% of patients For tigatons (13). these have reasons, attempted a number to of invesdevelop sembhed. The through delivery is accomplished a 9-F (3-mm outside catheter; thus, angiographic phications at the puncture mized. The clinical trial femonal then or side, jugular but com- site are is limited vein access diameter) local approach to the minito a on central ei- ye- nous system may eventually via a number of alternative veins. The external jugular been used in one patient. cial requirement cold saline be gained peripheral vein has The only speinfusion of a is the solution during the brief passage of the filter through the catheter. During the clinical trial a number of new observations and insights have emerged about the filter placement and the capture of embo!i en route to the lungs. These relate to tenting of the vena cava wall, tilting of the dome, and occlusion of the filter by thrombus. Local tenting of the vena cava wall due to pressure by the rim of the filter dome was observed frequently, particulanly in venae smaller cavae, but ap- peared to have no significant hemodynamic impact or ill effects. The tented portion fills in within a few months due to development of a slightly thicker neointima at the points of contact just within the outer rim so that the rim may appear to lie just outside the main column of contrast medium on follow-up venograms. Similarly, though rarely, the distal end of a filter leg may appear to lie alongside the lumen. Earlier animal experiments have documented that this effect is due to a longitudinal crease formed by the legs in the vena cava wall and covered with endothelium. The leg ends have not penetrated the vena cava wall. The dome of the filter frequently was observed to be tilted about 20#{176}-25#{176} toward the wall of the vein, particularly outside about of the dila- to ac- sheath, efficacy which filter increasing requires diameter been the percuta- Greenfield venipuncture in outside large houses with this a 29-F or the years, introduction 9.6 mm has recent of jugular to insert that performed However, diameter) ten, the capsule commodate tions of in order insertion thrombosis in paanticoagulant thrombus was not- patients surgical neous withdrawal, no instances given anticoagulant on thrombolytic drugs or for whom such drugs have failed (7). In the United States, the only device currently available for clinical use is the Gmeenfield filter (8). At the time of its introduction in 1973, placement of the Gneenfield filter required filter. of venous not receiving Femomal were It is now widely accepted that vena cava filters have become the method of choice for the prevention of pulmonary folded opment tients therapy. nor- during DISCUSSION ing resulted in the first four patients, without clinical effect. These early problems were resolved by minor design changes of the feeder system. catheter filter 2 cm of either cranial or caudal gmation. The device appears itself well. delivery puncture site. Five of the 18 patients studied with US in the days following the procedure showed some local thrombosis. Three patients were symptomatic. This finding could represent local thrombus formation due to intimal injury, thrombus peeled off of the catheter surface during tip of the about dome formation as the catheter is being withdrawn. It is possible to readvance the filter upward to its optimal position before the legs are released, but this is not recommended because of the risk of damage to the venous endothelium. In smaller venae cavae, the filter dome commonly assumed a slightly tilted position. Penetration of the vena cava wall by the filter legs did not occur. Theme was no clinical evidence of metropemitoneal hemorrhage, nor was any seen in patients followed up with MR im- metal of he- the proved filter devices that are easier to insert, have lower complication rates, and produce a more effective mechanical filtering action. The SNF is one of these. Others include the bird’s nest filten, the Amplatz filter, and the Gunther filter (14-16). The SNF is distinguished by its ease of insertion and mechanical effectiveness. The device is pmehoaded to eliminate handling of the filter device, and the delivery system is preas- im- in small is due venae to the cavae dome (Fig 2). geometry, This result which is more easily accommodated in a confined space if the dome is slightly indined rather than perfectly transverse. However, such sloping does not impair the filtering efficiency of the filter because the size of the openings in the dome remain unchanged. Fewer openings of a given size are required to subdivide a smaller IVC cross section. This contrasts with the Greenfield filter, in which tilting enlarges the size of the openings between some of the legs and Radiology . 101 thus reduces of the device, the mechanical an effect well ed in in vitro studies (17). efficiency document- Portions of the dome loops or legs that are in contact with the wall of the vena cava become covered by a neointimal layer within 2 weeks (3). Traditionally, cava occlusion filter has been ous complication. designed to trap order to prevent of a vena regarded as a semi- However, the SNF is embohi in the IVC in them from reaching the lungs. We would therefore argue that filter occlusion should be considered an unfortunate but expected event in a small but the patients significant percentage in our study. Occlusion of is certainly preferable to pulmonary embohism, the potentially fatal alternative. Partial or complete occlusion may be associated with obstructive symptoms of variable severity, depending on the size of the emboli, the completeness obstruction, and the state of the eral venous return. The symptoms usually transient, with recovery weeks or months ization collateral the as lysis and of occlusion recanal- thus of that pnimar- ily reflects the recurrence rate of pulmonamy embolism and the size of the embohi in a given patient population rather than any defect of filter design or performance. The frequency of recurrent pulmonary embolism in patients such as ours who cannot receive anticoagulant ment, and thus the potential clot treatcap- ture rate determine indirectly. of the filter, is difficult to and can be estimated only Before the use of anticoagumortality due to pulmonary emwas reported to be about 30% lants, bolism (18), while the current tients treated with py is only 8% (19). b. Figure 2. monly assumed Radiographs of filter dome venae cavae in smaller in a central mortality in anticoagulant This difference pa- theraof seems that some large single embohi or several smaller embohi can be massive enough to cause a symptomatic occlusion when captured in the filter. Furthemmore, since improved imaging methods indicate that complete occlusion may occur without symptoms if good venous collaterals exist, the total number of complete occlusions is probably higher than previously reported. In the BIH/MGH subseries, five of the nized with 44 patients collateral (11%) had lower-limb swell- ing. MR imaging showed filling defects in the filters in these patients, which could represent captured embohi. Three of 44 patients (7%) showed complete occlusion (Table 2). In addition, two patients had clinical findings that may have been due to IVC occlusion, but this aging sion result was studies. rate in not confirmed The the with symptomatic BIH/MGH im- occluseries is thus Since less than one-third of significant pulmonary embohi are lethal, there must be at least three times this number of clinically significant recurrent embohi, or more than 66%. It seems clear that once a patient has had a single episode of embolism and remains untreated with anticoaguhants, the probability of a recurrence is very high. This is supported by autopsy studies of pulmonary embolism (20, 21) and a 7%-11% (three plus a possible two of 44 patients), and the overall symptomatic occlusion rate is 7%-9% (seven plus a possible two of 103 patients in all 17 participating centers), findings comparable to those previously reported by other investigators. Another three completely asymptomatic patients also showed complete occlusion, which would not have been detected without a routine MR imaging follow-up study. To our knowledge, this is the first chinical study in which it has been possible to use noninvasive MR imaging to assess the presence of thrombus in a vena clinical cava 22% thus represents the recurrence rate hism, anticoagulants when study probable of pulmonary of the Gunther fatal emboare not used. filter with contrast material-enhanced CT, which showed thrombi in 39% of the filters studied at an arbitrary point of time in the follow-up period (22). Clinical reports of patients with filtens in place indicate that 5%-10% experience symptoms and signs of IVC occlusion (22). In view of the estimated high embolism recurrence rate, it 102 . Radiology position (a) and in a tilted position corn- (b). of cohlatare in of the IVC or enlargement vessels occur. We believe frequency a. filter, since the SNF is nonfemro- as filling defects when contrast material-enhanced digital-subtraction or complete with total US also veins will not generally with mild asymptomatic leg swelling, or associated can be recog- multiple allow sionally, may be large. plain recurrent or large that clusion MR five of the of were obstruction pathways Thus, to of of have been studies of an of through be missed to collateral the ye- rate the rate selection clots filter. clinically, filter of the in (22). do not cannot In fact, beto too raise or, perhaps, allowed to and van- We indicate be used should These fil- at a rate reported being me- popu- receive efficiency. patient of various filters occlusion the prone prevalence occlusions and thus filter tions more occlusions other low that complete thrombosis who 5%-10% compare three patients. the in patients these failure with that Symptomatic hieve filter in be the embolism lations with (27). reflects current for interest venous it is likely occlusion images neurosurgical extensive nous persist occlusion. signs of oc- patients tend with can MR patients It is of were ex- veins be severe confirmed eight patients develop our complete clinical imaging. occlusion could embolism that three that with size (25,26). had had Occaveins if the collateral there may no symptoms Five patients and embohi. collateral swelling showed of of collat- small pulmonary or months tens. and This lower-limb Such if adequate Generally, two (24). However, are compromised, weeks occlusion passage one significant emboli, are may of the vena of flow on MR asymptomatic exist. em- embohi occlusion absence veins imaging within a large small A complete be eral contrast, of images. may thai Small In cause cava ous problems. weeks. on cluster on or or with MR Recovery occurs bolus magnetic (23). This suggests that the true total occlusion rate for other IVC filters may be greater than previously reported without MR imaging. Partial or complete filter occlusion may cause various transient but nonleclinical angiography, vena cavography or duplex US. days imaged CT, quesof pass emboli may routine fol- July 1989 low-up ventilation /perfusion chide studies are rarely used radionu(28). Even deaths due to pulmonary embolism may be ascribed to the known undemlying cardiac disease or malignancy, as autopsies are performed in only a small percentage of fatalities in hospitals. The possibility of local thrombosis occurring tion on the filter to a metallic itself device as a reac- in the blood- stream is difficult to rule out with certainty. This would be difficult or impossible to distinguish from captured emboli from the veins of the lower limb or even from the catheter surface during withdrawal. The nitinol matemiah of the SNF has been shown to have low thrombogenicity ments (3). Furthermore, jomity of SNFs free, in animal expemisince the ma- in humans inherent remain thrombogenicity anticoagulation high probability remains the most occlusion. All attempts to successful. There tion one or significant filter dome pletehy in an In this SNFs and treatment, of recurrent likely cause the embolism of filter small the surface livery catheter of recurrent thrombus the (29). was very low. Pulmonary embowas suspected in one of 103 paon the basis of clinical findings a change in the pattern of abnorfindings on ventilation/perfusion Another patient was asympto- pulmonary embo- matic, but new perfusion defects observed on a routine follow-up In conclusion, with the cedure is simple, significant puncture SNF were perfu- weeks. A vena cavogmam a thin thrombus extendfilter from clot contained deaths were attributable embolism of filter our initial for percutaneous pleted one and detailed 11. to 39% in a contrast CT study of another 14. and 15. complete report trial study of the is com- bird’s Ind) 16. U for clinical since this nest has filter been (Cook, 18. 19. Bloom- 20. panel 21. recommended approval by an FDA article was submitted. Acknowledgments: We are indebted to the many unnamed investigators currently participating in the clinical trial of the SNF at numerous centers in the United States. Their interest and dedication in the exploration of new interventional developments and in the pursual of the demanding protocols necessary to obtain meaningful data have been remarkable. We thank Anne Maloney, RT, Beth Israel Hospital, and Joseph DeBenedeto, RT, Massachusetts Genera! Hospital, and their staff for technical assistance, and Claire Martinez, BA, for manuscript preparation. 1. The A 2. pro- insertion quick, and relatively free of complications at the venisite due to the small size of Simon 3. 4. vena M, Kaplow cava filter R, Salzman using E, Freiman thermal shape 23. 24. 1K, Zairnovskii VA, Khrnelevskaia WA. MR angiography refocusing. J Comput with Assist 12:377-382. Denny DF Jr. Dorfrnan CS, Gronan JJ, Greenwood LH, Morse 55, Yoselevitz M. Greenfield filter: percutaneous placement in 50 patients. AJR 1988; 150:427-429. Greenfield U, McCurdy JR. Brown PP, Ellains RC. A new intracaval filter permitting continued flow and resolution of ernboli. Surgery 1973; 73:599-606. Tadavarthy SM, Castaneda-Zuniga W, SaloE. et al. Kimray-Greenfield vena cava filter: percutaneous introduction. Radiology 1984; 151:525-526. Bounameaux H, Velebit V, Battikha J, Schneider PAZ, Bisetti A, Krahenbuhl B. Recurrent, fatal pulmonary embolism despite inferior vena cava interruption with the Greenfield filter. Vasa 1987; 16:84-85. Carabassi RA plications encountered III, Moritz filter. Am MJ, Jarrell with J Surg BE. Corn- the use of the 1987; 154:163- Kantor A, G!anz S. Gordon DH, Sclafani SJ. Percutaneous insertion of the Kimray-Greenfield filter. Greenfield AJR 1987; U, Peyton 149:1065-1066. R, Crute S. Barmes R. Greenfield vena cava filter experience. Arch Surg 1981; 116:1451-1456. Roehm JOF, Johnsrude IS, Barth MH, Gianturco C. The bird’s nest inferior vena cava filter: progress report. Radiology 1988; 168:745-749. Darcy MD, Hunter DW, Lund GB, Cardella JF. Amp!atz retrievable vena cava filter. Semin Interventional Radiol 1986; 3:214-219. Gunther RW, Schild H, Fries A, Storkel S. Vena caval filter to prevent pulmonary embolism: experimental study. Radiology 1985; 156:315-320. Katsamouris AA, Waltman AC, Delichatsios MA, Athanasoulis CA. Inferior vena cava filtens: in vitro comparison of clot trapping and flow dynamics. Radiology 1988; 166:361-366. Barnitt DW, Jordan SC. Anticoagulant drugs in treatment of pulmonary embolism: a controlled trial. Lancet 1960; 1:1309-1312. Urokinase pulmonary embolism trial: a na- tional cooperative study. Circulation 1973; 47(suppl 2):1-l08. Freiman DC, Suyemoto J. Wessler S. Frequency of pulmonary thromboembolism in man. N Engl J Med 1965; 272:1278-1280. Smith GT, Dammin GJ, Dexter L. Postmortern arteniographic studies of the human lung in pulmonary embolization. JAMA 1964; 188:143-151. Fobbe F, Dietzel M, Konth R, et al. Gunther vena caval filter: results of long term followup. AJR 1988; 151:1031-1034. Teitelbaum GP, Ortega HV, Vinitski 5, et al. Low-artifact intravascular devices: MR ima Kakkar Sung 26. the deep veins of the leg. Ann R Coil Engi 1969; 45:257-276. Mahorner H, Castleberry JW. Coleman Attempts to restore which are the site veins 28. VV. The problems of thrombosis function of massive in major thrombosis. in WO. Ann Surg 1957; 146:510-522. Swann KW, Black PM. Deep vein thrombosis and pulmonary emboli in neurosurgical patients: a review. J Neurosurg 1984; 89:1-10. Sharma GVRK, Tow DE, Panisi AF, Sasahara AA. 29. - ing evaluation. Radiology 1988; 168:713-71 Ferris EJ, Vittimberga FJ, Byrne JJ. Nabseth DC. Shapiro JH. The inferior vena cava after ligation and plication. Radiology 1967; 89:110. 25. D. mem- ory alloy: experimental aspects. Radiology 1977; 125:87-94. Palestrant AM. Prince MR. Simon M. Cornparative in vitro evaluation of the nitinol inferior vena cava filter. Radiology 1982; 145:351-355. Prince MR. Salzrnan EW, Schoen FJ, Palestrant M, Simon M. Local intravascular effects of the nitinol wire blood clot filter. Invest Radiol 1988; 23:294-300. Rabkin 22. 27. References 1988; Greenfield 168. 13. Since this article was submitted, migration of a SNF has occurred will be included in a future meThe or experience filter 10. for and J Vasc 1:377-382. rnonowitz fill- in 25%-29% of 44) of pa- of the clinical when the in 1989. ington, placement. is encouraging. 9. de- rate complication 8. port. hism hism tients and mal scans. any 7. 12. detailed 1984; Tomogr of thromIn our we demonstrated tients, comparable material-enhanced Surg ADDENDUM layer withdrawal pulmonary filter. series, Laub GA. Kaiser gradient motion 17. The to recurrent BIH/MGH 6. of 103 patients, demonstration in the Greenfield U. Current indications results of Greenfield filter placement. com- of the small-bore during sion scan at 2 demonstrated ing above the within it. No noninvasive vena ture site within a week of the procedune could represent venipunctume trauma, coincidental venous thrombofrom series 5. the dehiv- symptomatic occlusion occurred in 7%9%, a finding comparable to those in published series of other filters. All patients showed marked clinical improvement over a period of weeks or months.The use of MR imaging permits of the results SNF is planned Only ly rare after an initial problem with pusher wire was corrected. Some thrombus developing at the venipunc- of the operator and requires no assembly. The requirement is the infusaline while the filter is bethrough the catheter. complete vena cava occlumay be symptomatic or is regarded by the auexpected effect of successful thromboembohi in the fil- ten. In the larger A more extremely or stripping system only special sion of cold ing advanced Partial or sion, which asymptomatic, thors as an trapping of emy The the filter, filter. insert the filter were was no filter migra- misplacement. failed to form catheter. handles ing defects or occlusions (11 plus a possible two cava, and its intermediate spindle shape was considered satisfactory. Crossing of the filter legs was extreme- sis, introducer never boembohi of the nitinol wire seems unlikely. population of patients with without clot- the Diagnosis of pulmonary embolism. Ann Rev Med 1977; 28:159-166. Siegelman 55. Caplan LH, Annes GP. Complications of catheter angiography: study with oscillometry and “pullout” angiograms. Radiology 1968; 91:251-253. II, Maksirnovich IV, Rabkin Dl, Khasenov BP. Experimental basis and first clinical trial of xray intravascular blood vessel prosthesis. Vestn Rentgenol Radiol 1984; 4:59-64. Volume 172 #{149} Number 1 Radiology . 103