The past 25 years have witnessed experimental efforts at catheter-based management of aortic, pulmonary and venous valve regurgitation. This chapter describes the initial designs and experimental evolution of a bioprosthetic venous valve that can be implanted by using a transcatheter technique. An evaluation of a percutaneously placed bioprosthetic, bicuspid venous valve (BBVV) consisting of a square stent and small intestinal submucosa (SIS) covering was performed in 15 sheep. Of 30 BBVVs placed into the jugular veins, 28 exhibited good valve function on immediate venograms, and 25 on venograms prior to sacrifice. Gross and histologic examinations demonstrated incorporation of remodeled and endothelialized SIS BBVVs into the vein wall. Minimally invasive placed square stent based SIS valve is a promising one-way, competent valve.Proteklih 25 godina bili smo svjedoci eksperimentalnih pokušaja u liječenju aortne i pulmonalne regurgitacije te insuficijencije venskih zalistaka pomoću katetera. U ovom članku opisuju se početne zamisli i eksperimentalni razvoj bioprotetskih venskih valvula koje se mogu ugraditi transkateterskom metodom. Procjena perkutano postavljene bioprotetske bikuspidne venske valvule (BBVV), koja se sastoji od četverokutnog stenta i pokrova submukoze tankog crijeva (SIS), učinjena je na 15 ovaca. Od 30 BBVV-a postavljenih u jugularnu venu 28 je imalo urednu funkciju na venogramima učinjenima odmah poslije zahvata, a 25 na venogramima učinjenima prije žrtvovanja životinja. Makroskopska i histološka analiza pokazale su uklapanje remodeliranogi endoteliziranog SIS-BBVV-a u vensku stjenku. Valvula koja sadrži četverokutni stent i SIS, postavljena uz minimalnu invazivnost, jednosmjerna je valvula od koje se može očekivati uspješnost

Dusan Pavcnik

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Acta clin Croat 2002; 41 (Suppl): 93-97 Original Scientific Paper93Correspondence to: D. Pavcnik, M.D., Ph.D., Dotter InterventionalInstitute, Oregon Health Sciences University, L342, 3181 SW SamJackson Park Road, Portland, Oregon, 97201(503) 494-8396 phone, (503) 494-4258 fax;e-mail: pavcnikd@ohsu.eduAcknowledgment: The author thanks Martina Basin Pavcnik, DMD,and Sheri Imai, BS, for their assistance.CHRONIC VENOUS INSUFFICIENCY AND BIOPROSTHETICBICUSPID SQUARE STENT BASED VENOUS VALVEFOR TRANSCATHETER PLACEMENTDusan PavcnikDotter Interventional Institute, Oregon Health Sciences University, Portland, Oregon, USASUMMARY ∑ The past 25 years have witnessed experimental efforts at catheter-based manage-ment of aortic, pulmonary and venous valve regurgitation. This chapter describes the initial designsand experimental evolution of a bioprosthetic venous valve that can be implanted by using atranscatheter technique. An evaluation of a percutaneously placed bioprosthetic, bicuspid venous valve(BBVV) consisting of a square stent and small intestinal submucosa (SIS) covering was performed in15 sheep. Of  30 BBVVs placed into the jugular veins, 28 exhibited good valve function on immedi-ate venograms, and 25 on venograms prior to sacrifice. Gross and histologic examinations demon-strated incorporation of remodeled and endothelialized SIS BBVVs into the vein wall. Minimallyinvasive placed square stent based SIS valve is a promising one-way, competent valve.Venous stasis or chronic venous insufficiency is theresult of valvular reflux, obstruction or both. Reflux in thevenous system is due to incompetent or destroyed valves.Primary valvular incompetence (PVI) is the result of adilated valvular ring, redundancy or dysplasia of the valveleaflets. In PVI, valves have smooth, thin wavy leaflets incontrast to the thickened, deformed valve cusps associatedwith secondary valvular insufficiency (SVI). SVI is asso-ciated with a history of post-thrombotic event in etiology;valve dysfunction causing stasis may also be a predispos-ing factor to thrombosis1.Chronic venous insufficiency (CVI) is a clinical con-dition characterized by lower extremity venous hyperten-sion2. Normal valve function and structure, combined withfoot and muscle pump action, comprise a complex hemo-dynamic system required for efficient venous emptying ofcalf veins in the upright position. William Harvey initiallyevaluated the function of  venous valves in 16283, how-ever, more than 300 years had passed before Eiseman andMalette4 reported their experimental attempt at venousvalve repair. Then, 25 years ago, Kistner5 first describedvenous valve repair in human beings. Internal valvulo-plasty results for carefully selected patients with PVI show70%-80% of good long term clinical  and duplex follow-up, however, only 37%-100% of valve transplantation and17%-66% of transposition procedures for CVI have goodlong term patency6.The challenge of correcting valvular incompetence hasrecently included application of endovascular technique.Newer approaches to restoration of valve competence in-clude implantation of axillary vein valves or cryopreservedvalves and experimental work with canine jugular vein-stent and cryopreserved vein stent combinations7.A percutaneous, minimally invasive, outpatient treat-ment of symptomatic reflux is an attractive concept. In1981, Charles Dotter8 suggested transcatheter venousD. Pavcnik 3rd Congress of Croatian Society of Radiology with International Participation94 Acta clin Croat, Vol. ??, No. ?, 2002valve placement: “Catheter based devices have met clini-cal success in the closure of patent ductus arteriosus andatrial septal defects. Why not catheter-placed prostheticvalves?”  In  1993, Uflacker reported percutaneous place-ment in the inferior vena cava of pigs of a monocuspvenous valve consisting of a single body Z stent withpolyetherurethane or polytetrafluoroethylene (PTFE)membrane9. Two more recent experimental studies haveemployed catheter insertion of bovine jugular venousvalves mounted within an expandable stent10,11. Thorpeat al. have also described promising short-term experi-mental results with catheter insertion of a bicuspid venousvalve made from the porcine small intestinal submucosa(SIS) mounted on a single body Z stent base12.In 2000, Bonhoeffer et al.13 reported first successfulpercutaneous valve replacement in a failed conduit fromthe right ventricle to the pulmonary artery in a 12-year-old boy. They used bovine jugular vein valve mountedinside stent.Square stent based venous valveRecently, Pavcnik et al. have reported results of long-term experimental study that are encouraging for the clini-cal application of manufactured square stent venous valve(Fig. 1). The square stent venous valves appear to undergoremodeling with recipient’s own cells and function with-out the need for anticoagulants. Therefore they have thepotential to treat chronic venous insufficiency by replac-ing valves that are destroyed from thrombophlebitis orthat are incompetent14-16.After deployment, the square stent based valve self-expanded and appeared to function in the same manneras a natural venous valve. The bioprosthetic bicuspidvenous valve (BBVV) was open during continuousantegrade flow. When retrograde pressure was applied, theBBVVs closed, and the two SIS leaflets sealed againsteach other preventing retrograde flow through the valve(Fig. 2).  BBVVs placed into jugular veins centrally (closerto heart) or across the native valve (NV) took over thefunction of these valves. All 16 BBVVs placed across theNVs were functional with minimally thickened leafletsafter one, three and six months (Fig. 3). Twelve BBVVsplaced centrally to the NV had leaflets thickened to amean of 750 µ. This suggests that when replacing thefunction of the natural valve in their location, BBVVs havebest chance to function.A manufactured, percutaneously implantable, non-immunogenic venous valve that remains patent and com-petent over time is an attractive alternative to direct venousvalvular reconstruction or transplantation. The combina-tion of a square stent and the biomaterial SIS14-16. permitsmanufacture of a bicuspid venous valve that is anatomicallyand functionally similar to the NV. Attached to a squarestent, SIS provides an effective bioscaffold for attraction ofhost cells. The BVV incorporated into a vein wall consistsof two cusps, the valvular agger and the valvular sinus (Fig.4). The cusp consists of a free border (SIS) and parietal part(vein wall). The SIS used in these experiments was 120 to180 ì thick and was approximately 4 and 6 times thickerthan the NV (30 µ)16.At the BBVV agger, where the SIS leaflets were at-tached to the vein wall, the SIS membranes were thick-Fig. 1 Square stent based SIS venous valve.  A)  Non-restricted square stent based valve 20 mm long with 4 barbs for vein 14-15 mm indiameter. A retention wire pusher connected to one barb retains valve. B)  Valve front loaded into a 9 Fr guiding catheter.D. Pavcnik 3rd Congress of Croatian Society of Radiology with International ParticipationActa clin Croat, Vol. ??, No. ?, 2002 95Fig. 2 Function of the square stent based SIS venous valve placed into both external jugular veins. A) Jugular venogram with injectiondistal to the valve demonstrates valve patency. This is analogous to the animal standing upright. B) High volume injection central to thevalve demonstrates closure of the valve with no leak. Valves must function in this manner to prevent cephalic reflux when the animal low-ers its head to eat or drink.ened. This chronic inflammation and cellular ingrowtharound sutures and the stent wires created a seal betweenthe vein wall and the two valve pockets15,16.  Parietal bor-ders of BVV sinuses consisted of natural vein wall withintact endothelium preventing local thrombosis (Fig. 3).Out of 30 BVVs with 60 cusps, only one pocket of a singlemisaligned BVV thrombosed. This suggests the SIS valveis resistant to thrombosis. Venous endothelial cells wereattached to SIS one month after implantation. As thisprocess continued, other cells infiltrated the SIS, and theingrowth of host cells allowed for incorporation of thevalve and its borders into the vein wall16.D. Pavcnik 3rd Congress of Croatian Society of Radiology with International Participation96 Acta clin Croat, Vol. ??, No. ?, 2002The BBVVs described herein demonstrate several ad-vantages over other prosthetic venous valves9-13. These in-clude simple introduction with valve self-expansion andself-attachment by barbs to the vein wall. The valve appearsstable and does not spontaneously migrate. The 9 Fr sizeof the delivery catheter for BVV is smaller than that fordelivery of a monocusp valve9.   It is, however, much smallerthan the 16 Fr size for the bicuspid SIS covered Z stentvalve12 and the 18 Fr size required for insertion of a stentmounted bovine jugular vein valve10,11,13. Another advan-tage of the square stent based SIS valve is its availability indifferent size for various vein diameters. They may also notrequire anticoagulation. The results of this study are encour-aging and warrant an experimental trial in humans15,16.Fig. 3 Square stent based SIS valve 3 months after implantation in animal.  A)  Axial view from above shows incorporation of the bicuspidvalve into vein wall. B) Longitudinal microscopic view of both SIS leaflets. C)  High magnification of the SIS leaflet shows that the mem-brane has been fully penetrated and reorganized by host cells, including fibrocytes, plasma cells, lymphocytes and endothelial cells. (Hema-toxylin & eosin stain original magnification 400 x).Fig. 4 Square stent based SIS valve at 6 months.  A) longitudinal cross-section shows an incorporated valve with two cusps and two si-nuses. B) Longitudinal microscopic view of both remodeled SIS leaflets.D. Pavcnik 3rd Congress of Croatian Society of Radiology with International ParticipationActa clin Croat, Vol. ??, No. ?, 2002 97SaæetakKRONI»NA VENSKA INSUFICIJENCIJA I TRANSKATETERSKO POSTAVLJANJE BIOPROTETSKEBIKUSPIDNE VENSKE VALVULE S »ETVEROKUTNIM STENTOMD. PavcnikProteklih 25 godina bili smo svjedoci eksperimentalnih pokuπaja u lijeËenju aortne i pulmonalne regurgitacije te insuficijencijevenskih zalistaka pomoæu katetera. U ovom Ëlanku opisuju se poËetne zamisli i eksperimentalni razvoj bioprotetskih venskihvalvula koje se mogu ugraditi transkateterskom metodom. Procjena perkutano postavljene bioprotetske bikuspidne venskevalvule (BBVV), koja se sastoji od Ëetverokutnog stenta i pokrova submukoze tankog crijeva (SIS), uËinjena je na 15 ovaca.Od 30 BBVV-a postavljenih u jugularnu venu 28 je imalo urednu funkciju na venogramima uËinjenima odmah poslije zahvata,a 25 na venogramima uËinjenima prije ærtvovanja æivotinja. Makroskopska i histoloπka analiza pokazale su uklapanje remodeliranogi endoteliziranog SIS-BBVV-a u vensku stijenku. Valvula koja sadræi Ëetverokutni stent i SIS, postavljena uz minimalnuinvazivnost, jednosmjerna je valvula od koje se moæe oËekivati uspjeπnost.Although a great deal of work remains to be done,these early results indicate that the development of a bio-logical prosthetic, pulmonary and venous valve fortranscatheter placement is more than feasible.References1. RAJU S. Venous insufficiency of the lower limb and stasis ulceration:changing concept and management. Ann Surg 1983:197;6:688-97.2. SCHURR HJ, SMITH PD. Pathogenesis of venous ulceration.Phlebology 1992: (Suppl 1):13-6.3. HARVEY W. An anatomical description concerning the move-ment of the heart and blood in living creatures (Whitteridge Gtranslation). Oxford, UK: Blackwell Scientific Publications, 1976.4. EISMAN B, MALETTE W. An operative technique for the con-struction of venous valve. Surg Gynecol Obstet 1953;97:731-4.5. KISTNER RL. Surgical repair of the incompetent femoral valve.Arch Surg 1975;110:1336-42.6. AKESSON H, RISBORG B, BJORGELL O. External supportvalvuloplasty in the treatment of chronic deep vein incompetencein the legs. Int Angiol 1998;18:233-8.7. BERGAN JJ. Prospects for minimal invasion in venous disease.Vasc Surg 1999;33:247-9.8. DOTTER ChT. Interventional radiology ∑ review of an emerg-ing field. Semin Radiol 1981;16:7-12.9. UFLACKER R. Percutaneously introduced artificial venous valve:experimental use in pigs. The 1993 Annual Meeting of the West-ern Angiographic & Interventional Society, Portland, OR. AbstractBook 1993:30.10. GOMEZ-JORGE J, VENBRUX AC, MAGEE C.  Percutane-ous development of a valved bovine jugular vein in the swine venoussystem: a potential treatment for venous insufficiency. J Vasc IntervRadiol 2000:11:931-6.11. BONHOEFFER P, BOUDJEMLINE Y, SALIBA Z, HAUSSEAO, AGGOUN Y, BONNET D, SIDI D, KACHANNER J.Transcatheter implantation of a bovine valve in pulmonary posi-tion: a lamb study. Circulation 2000;102:813-6.12. THORPE PE, OSSE FJ, CORREA LO. The valve-stent: devel-opment of a percutaneous prosthesis for treatment of valvular in-sufficiency. The 12th Annual Meeting of the American VenousForum, Phoenix, Arizona.  Abstract Book 2000:82.13. BONHOEFFER P, BOUDJEMLINE Y, SALIBA Z, MERCKYJ, AGGOUN Y, BONNET D, ACAR P, LE BIDOIS J, SIDI D,KACHANNER J. Percutaneous replacement of pulmonary valvein a right-ventricle to pulmonary-artery prosthetic conduit withvalve dysfunction. Lancet 2000;356:1403-5.14. PAVCNIK D, UCHIDA BT, KELLER FS, CORLESS C,RÖSCH J. Retrievable IVC square stent filter: experimental study.Cardiovasc Intervent Radiol 1999;22:239-45.15. PAVCNIK D, UCHIDA B, TIMMERMANS HA, KELLER FS,RÖSCH J. Square stent: a new self-expandable endoluminal deviceand its applications. Cardiovasc Intervent Radiol 2001;24:207-17.16. PAVCNIK D, UCHIDA B, TIMMERMANS HA, CORLESSCL , O’HARA M, TOYOTA N, MONETA GL, KELLER FS,RÖSCH J. Percutaneous bioprosthetic venous valve: a long termstudy in sheep. J Vasc Surg 2002;35 (in press).

Kronična venska insuficijencija i transkatetersko postavljanje bioprotetske bikuspidne venske valvule s četverokutnim stentom

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