INSTITUTE OF RENTGENOLOGY UNIVERSITY MEDICAL CENTER LJUBLJANA
SELF EXPANDING METALLIC STENTS
Pavcnik D, Surlan M
Abstract - Between September and December 1989 four patients with stenosis of the tracheobronchial tree and obstruction of vena cava superior were treated with self expanding metallic stent. Stents were successfully placed in each patient.
Alle are clasified as cured. For venography before and after stent placement lohexol 350 was used.
UDC: 616.23-007.271-089.819.5
Key words: tracheal stenosis, superior vena cava syndrome, metallic stents Case report
Radiol lugosl 1990; 24: 147-50.
lntroduction - In 1969, Charles Dotter first publiched data demonstrating long term patency of intravascular stents in dogs (1, 2). Since Dotter's initial success, others have reported long term patency without significant luminal narrowing in a variety of stents placed in several tubular structures (3, 4, 5, 6, 8, 9, 10, 11, 12). In our patients we used the expandable metallic stent created by one of the pioneers of Interventional Radiology, Cesare Gianturco. His devices have been responsible for opening the door to lnterventional Radiology. Among his inventions are the embolic coils, the self-expanding stainless steel stents, the bird's nest vena cava filters, the U-inverted-U balloon assisted stents, patent ductus occluders and septal defect occluders.
Materials and methods - In three patients with stenosis of the tracheobronchial tree and in one patients with vena cava superior (VCS) obstruction due to sarcoidosis Gianturco stents were placed. The procedure was performed per-cutaneously in patients with vena cava superior obstruction and transendoscopically in other patients. In all four cases stenosis was first dilated with a PTA balloon catheter to allow passage of
Received: March 3, 1990 - Accepted: March 26, 1990
the guiding sheath. The stents opened the stricture segment in all cases.
The expandable metallic stent is constructed of stainless steel wire bent in a zig-zag pattern and encircled to form a cylilnder (5). The stent is compressed and introduced through a Teflon catheter of 10-12 F caliber. The stent is advanced until it reaches the tip of the catheter by using a pusher catheter. It is released from the catheter by withdrawing the catheter while holding the pusher catheter against the stent. Upon release, the stent expands or attempts to expand to its original diameter creating the expansile force to allow the expansion of the vessel against the extrinsic, stenotic force (12).
Results - Clinical trials of the Gianturco expandable metallic stent have been conducted also in our institution in Ljubljana. The stent has been evaluated in the tracheobronchial tree and vena cava. To date, the stents opened stenosis in all cases and after at least 3 months, they have remained patent without migration or other complications.
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PavCnik D, Surlan M. Self expanding metallic stents
Case report (1) - A 41-year old patient developed superior vena cava obstruction secondary to compression by fibrosis due to sarcoidosis. Clinical findings were facial swelling, distention of the veins of the neck and headache. On phlebography, a contrast medium (lohexol 350) injection into the vena cava superior led to immediate filling of the vena azygos with reversed flow direction. Flebogram showed the superior vena cava obstruction (Fig. 1). The procedure
balloon was introduced, and after the second inflation the result was satisfactory. A double stent was placed (Fig. 2) and immediate clinical
Fig. 1 - Vena cava superior obstruction (arrows)
was performed percutaneously through the right femoral vein. First an introducer sheath was inserted into the femoral vein. For crosing the tight stenosis of vena cava superior we used 0,035 inch. movable core straight guidewire and straight 5 F catheter. Once the diagnostic catheter had crossed the obstruction, the catheter was exchanged for dilatation balloon catheter (6 mm diameter).
Before PTA, 5000 units of Heparin was injected through the sheath side arm. After PTA, the balloon catheter was wtihdrawn while the guide-wire was kept in place. Then a longer 20 mm
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Fig. 2 - Double self expandable stent in vena cava superior
improvement was accomplished. Aspirin and per-santine have been given for three months. To date, stent provides good patency of VCS (Fig. 3).
Case report (2) - A 58-year old patient developed stenosios of the right bronchus which resulted from fibrosis due to surgery. To overcome this problem we used PTA balloon catheter and two self-expanding stents. This patient has been followed for 4 months. Follow up exams indicate that stents conform to the luminal surface, are stable, and remain patent. The patient is asymptomatic and this indicates that stent can effectively dilate the brbnchus.
Rad'o' lugosl 1990: 24: 147-50.
PavčniK D, šurlan M. Self expanding metallic stents
Fig. 3 - Patent stent in vena cava superior
Disscusion - Gianturco self expandable metallic stent has been evaluated in several tubular structures including the arteries and aorta (12), the veins and vena cava, the tracheobranchial tree (11), the bile ducts (5), and the ureter (4). In the blood vessels, local expansion with neointi-mal proliferation covering the stents was observed. The stent was incorporated in the wall of the blood vessel. In stenotic veins and vena cava, the stents dilated the vessels and decreased the pressure gradient across the stenoses (3). The stent was also placed in the intrahepatic segment of the vena cava inferior in a patient with Budd-Chiarri syndrome (4). When placed in the tracheobronchial three the stent created focal dilatation and inflammation with mucosal secretion covering the stent. There was no obstruction or peforation of the trachea (11).
Percutaneous biliar drainage is the usual form of biliary decompression in patients with obstructive jaundice secondary to neoplastic involvement of the bile ducts. However, there are many comlications associated with currently used decompression techniques. Catheter drainage sy-
stem whether external or internal-external may migrate, be associated with infection, or become blocked. The use of indwelling endoprosthesis has not overcome all the problems, and removal of malfunctioning prostheses may be impossible.
Self expandable stents placed in common bile duct opened the strictured segment and remained patent without migration or other complications up to one year (4, 5).
Placement of the stent in the ureter resulted in mucosol proliferation which caused obstruction of the ureter in some cases.
Conclusion - Interventional radiology has provided a promising nonsurgical treatment of vascular and bronchotracheal strictures with Gian-turco self expandable metallic stents. The work of many investigators (3, 5, 6, 11, 12) as well as our own results demonstrate that these newly developed self expandable stents will improve the treatment of strictures in several tubular structures.
Povzetek
SAMORAZTEGLJIVE KOVINSKE PROTEZE
V času od septembra do decembra 1989 smo zdravili štiri bolnike, ki so imeli zožitev traheobronhialnega vejevja in obstrukcijo vene cave sup, s samorazteglji-vim kovinskim stentom. Pri vseh bolnikih je bila vstavitev uspešna.
Vse bolnike smo opredelili kot ozdravljene. pri veno-grafiji, opravljeni pred in po vstavitvi stenta smo uporabili lohexoi 350.
References
1.	Dotter CT. Transluminally placed coilspring en-darterial tube grafts: long term patency in canine popliteal artery. lnvest Radiol 1969; 4:329.
2.	Dotter CT et al. Transluminal expandable nitinol coil stent grafting: preliminary report. Radiology 1983; 147:259-60.
3.	Charnsangavej C, Carrasco CH, Wallace S et al. Stenosis of the vena cava, Preliminary assesment of treatment with expandable metallic stents. Radiology 1986; 161 :295-8.
4.	Charnsangavej C. Gianturco expandable metallic stent. XIII. Meeting on lnterventional Radiology, Orlando; 1988:172-4.
5.	Carrasco CH, Wallace S, Charnsangavej C et al. Expandable biliary endoprosthesis: An experimental study. AJR 1985; 145:1279-81.
6.	Duprat G Jr, Wright KC, Charnsangavej C et al. Flexible balloon-expanded stent for small vessels. Work in progress. Radiology 1987; 162:276-8.
7.	Duprat G Jr, Wright KC, Charnsangavej C et al. Selfexpanding metallic stents for small vessels: an experimental evaluation. Radiology 1987; 162:469-72.
8.	Palmaz JC, Sibbit RR, Reuter R, Tio FO, Rice WJ. Expandable intraluminal graft: preliminary study. Work in progress. Radiology 1985; 156:73-7.
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Pavčnik D, šurlan M. Self expanding metallic stents
9.	Rousseau H, Puel J, Joffre F, Sigwart U, Dobouc-her C, Imbert C, Knight C, Knopf L, Wallsten H. Self-expanding endovascular prosthesis: an experimental study. Radiology 1987; 164:709-14.
10.	Strecker EP, Berg G, Weber H, Bohl M, Schneider B. Experimentelle Untersuchungen mit einer neuen perkutan einfuhrbaren und aufdehnbaren Gefassendo-prothese. Fortschritte Rontgenstrahlen 1987; 147:66972.
11.	Wallace MJ, Charnsangavej C, Ogawa K et al. Tracheobrachial tree: Expandable metallic stents used
in experimental and clinical applications. Radiology 1986; 158:309-12.
12. Wright KC, Wallace S, Charnsangavej C et al. Percutaneous endovascular stents: an experimental evaluation. Radiology 1985; 156:69-72.
Author's address: Doc. dr. Dušan Pavčnik, dr. med., Institut of Rentgenology, University Medical Center, Zaloška 7, 61000 Ljubljana.

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