ORIGINAL ARTICLE
A new vascular substitute: femoral artery angioplasty in dogs using
sugarcane biopolymer membrane patch – hemodynamic and histopathologic
evaluation
Silvio Romero de Barros MarquesI; Esdras Marques LinsII; Jos• Lamartine de Andrade
AguiarIII; Maria Claudia Sodr• AlbuquerqueIV; Renata de Oliveira RossiterV; Luciano Tavares MontenegroVI; Roberto Jos• VieiraVI
I Professor, Vascular Surgery, Cent ro de Ciências da Saúde ( CCS) , Universidade Federal de
Pernam buco ( UFPE) , Recife, PE, Brazil.
I I Physician. Subst it ut e professor, Depart m ent of Surgery, CCS- UFPE, Recife, PE, Brazil. I I I Physician. Associat e professor, Depart m ent of Surgery, CCS, UFPE, Recife, PE, Brazil. I V Subst it ut e professor, Depart m ent of Surgery, CCS, UFPE, Recife, PE, Brazil.
VResident in Pat hology, Hospit al das Clínicas, UFPE, Recife, PE, Brazil.
VI Physician. Associat e professor, Depart m ent of Pat hology, CCS, UFPE, Recife, PE, Brazil.
Correspondence
J Vasc Bras. 2007; 6( 4) : 309- 15.
RESUMO
Contexto:A obt enção de um subst it ut o art erial ideal para o em prego nas reconst ruções das art érias de pequeno e m édio calibre é ainda o principal obj et ivo da m aioria das pesquisas cient íficas
desenvolvidas no cam po dos subst it ut os vasculares. A m em brana de biopolím ero de cana- de- açúcar pode ser de grande ut ilidade para a realização das reconst ruções art eriais em vasos de calibre inferior a 4 m m e assim perm it ir o t rat am ent o de doenças que afet am m ilhões de pessoas no Brasil e em t odo o m undo.
Objetivo: Avaliar do pont o de vist a hem odinâm ico e hist opat ológico o com port am ent o da m em brana do biopolím ero de cana- de- açúcar quando ut ilizada com rem endo em art erioplast ias fem orais em cães.
percut ânea das art érias fem orais. Os anim ais foram subm et idos à dissecção das art érias fem orais, m edido o diâm et ro art erial e realizada velocim et ria Doppler t rans- operat ória em pont os proxim al e dist al à art erioplast ia. A seguir foi realizada laparot om ia e exposição da aort a abdom inal para acesso art eriográfico. Os segm ent os das art érias fem orais com os rem endos foram ret irados para est udo hist opat ológico e os anim ais foram m ort os com dose t óxica de anest ésico.
Result a dos: No período de avaliação de 180 dias, nos dois grupos, não foram observados casos de infecção da ferida operat ória, dilat ação, rupt ura, falso- aneurism a ou t rom bose. Nos dois grupos foi encont rada, na superfície ext erna dos rem endos, um a respost a inflam at ória crônica com neut rófilos e linfócit os além de fibrose. Na superfície int erna dos rem endos, em am bos os grupos, foi encont rada fibrose. No grupo cont role ocorreu invasão dos rem endos de e- PTFE por fibroblast os.
Conclusões: Com base nos result ados obt idos com o m odelo experim ent al ut ilizado, durant e o período de observação de 180 dias, conclui- se que a m em brana do biopolím ero de cana- de- açúcar const it ui- se em um subst it ut o art erial adequado quando ut ilizado sob form a de rem endos em art érias fem orais de cães.
Pa la vra s- cha ve: Prót ese vascular, im plant e de prót ese vascular, bioprót ese e cana- de- açúcar.
ABSTRACT
Ba ck ground: Achievem ent of an ideal art erial subst it ut e t o be used in t he reconst ruct ion of sm all-and m edium - caliber art eries is st ill t he m ain obj ect ive of m ost scient ific research st udies developed in t he area of vascular subst it ut es. Sugarcane biopolym er m em brane could be ext rem ely useful t o perform vascular reconst ruct ion in art eries wit h diam et er sm aller t han 4 m m , allowing t reat m ent of diseases t hat affect m illions of people in Brazil and worldwide.
Obj e ct ive : To evaluat e t he hem odynam ic and hist opat hologic behavior of sugarcane biopolym er m em brane when used as a pat ch in fem oral art ery angioplast y in dogs.
M et hod: Eight adult m ongrel dogs, under general anest hesia, underwent percut aneous Doppler velocim et ry of t he left and right fem oral art eries for preoperat ive cont rol at t he Healt h Sciences Cent er Experim ent al Research Laborat ory of Universidade Federal de Pernam buco. Aft er being disinfect ed, t he dogs underwent fem oral art ery pat ch angioplast y using a sugarcane m em brane biopolym er pat ch on t he left side and an expanded PTFE ( e- PTFE) pat ch on t he right side. The dogs underwent daily clinical evaluat ion for t he first week and weekly t hereaft er. Clinical evaluat ion consist ed of an exam inat ion of fem oral art ery pulses, gait assessm ent and verificat ion as t o whet her t here was any pulsat ile t um or, bruising, hem orrhage or surgical wound infect ion. One hundred and eight y days aft er t he angioplast ies, percut aneous Doppler velocim et ry of t he fem oral art eries was perform ed under general anest hesia. Next , t he dogs underwent dissect ion of t he fem oral art eries, m easurem ent of t he art erial diam et er and perioperat ive Doppler velocim et ry proxim ally and dist ally t o t he art ery
angioplast y. Laparot om y was t hen perform ed t o expose t he abdom inal aort a for angiographic access. The fem oral art ery segm ent s wit h pat ches were harvest ed for hist opat hologic analysis, and t he anim als were sacrificed under a t oxic dosage of anest het ic.
Re sult s: At 180 days, no cases of surgical wound infect ion, aneurysm , rupt ure, pseudoaneurysm or t hrom bosis were observed in eit her group. A chronic inflam m at ory react ion wit h lym phocyt es and neut rophils was seen in bot h groups on t he out er surface of pat ches. Fibrosis was seen on t he inner and out er surfaces of t he pat ches. I nvasion by fibroblast s of all e- PTFE pat ches occurred in t he cont rol group.
Conclusions: Based on t he result s obt ained wit h t he experim ent al m odel em ployed, for a 180- day period, it m ay be concluded t hat t he sugarcane biopolym er m em brane is an adequat e art erial subst it ut e when used as a pat ch in fem oral art ery angioplast y in dogs.
I nt roduct ion
Closure of art eriot om ies, using varied t echniques, m ay cause reduct ion in vascular lum en, especially in sm all- diam et er art eries. That reduct ion is a lim it ing fact or for art erial reconst ruct ion t hat can, however, be avoided using a pat ch.1 - 5
The concept of pat ch angioplast y was first est ablished by Carrel & Gut hrie in 1906. Despit e having t heir foundat ions well est ablished, t his surgical t echnique only st art ed being widely used aft er t he descript ion perform ed by Dos Sant os, in 1946, of t he endart erect om y t echnique and of t he st udies by Senning and Crawford et al., in 1959, who independent ly report ed experim ent al and clinical use of pat ch graft s, confirm ing t he hypot hesis t hat t hey widened vascular lum en and avoided st enosis aft er an art eriot om y.2 - 4 , 6
Several t ypes of m at erials have been used as pat ches in angioplast ies. Nowadays, t he m ost widely used are aut ogenous veins, biological graft s of bovine pericardium and synt het ic Dacron and expanded polyt et rafluoroet hylene ( e- PTFE) pat ches. Aut ogenous veins are m ore indicat ed for sm all- and
m edium - diam et er angioplast ies, whereas t he bovine pericardium and synt het ic pat ches are m ore used in large- diam et er art eries.7 - 1 1
An ext racellular polysaccharide produced by bact erial synt hesis based on sugar cane m olasses has been recent ly developed at Est ação Experim ent al de Cana- de- Açúcar de Carpina of Universidade Federal Rural de Pernam buco.1 2
The m em branes form ed based on t hat polym er were processed for applicat ion as surgical graft at t he Experim ent al Surgery Sect or of t he Cent er of Healt h Sciences at Universidade Federal de Pernam buco. They were evaluat ed by laborat ory t est s and present ed flexibilit y, low t oxicit y, biocom pat ibilit y and resist ance against rupt ure.1 3
Such m em brane has been used in m any areas of experim ent al surgery: healing of skin wounds; in uret eral reconst ruct ion; as a subst it ut e of t ym panic m em brane; am ong ot hers. However, t here is no report of st udies on it s behavior as an art erial subst it ut e, except in a m ast er's t hesis developed by our group.1 4 - 1 8
Following t he line of research using t he sugarcane biopolym er m em brane in several experim ent s of reconst ruct ive surgery of organs and t issues, t his st udy aim s at evaluat ing, from t he hem odynam ic and hist opat hologic perspect ive, t he behavior of t hat m em brane as an art erial wall subst it ut e as pat ches in t he fem oral art ery of dogs.
M et hod
Bet ween January 2005 and June 2006, eight dogs ( Canis fam iliaris) were used, one fem ale and seven m ales, m ean body weight of 15.4 kg.
The anim als were kept in an experim ent al laborat ory for 21 days before st art ing t he st udy. They were given chow diet , rabies vaccine and verm icide.
Fast ing for solid foods occurred over t he 24 hours preceding t he surgery for all anim als.
( 2.5 m g/ kg) and pancuronium brom ide ( 0.2 m g/ kg) . Aft er inguinal t richot om y, percut aneous Doppler velocim et ry was perform ed in t he fem oral art eries and, next , disinfect ion using Povidine®, and t hen
t he surgical sit es were disinfect ed.
Longit udinal 5- cm skin incisions were t hen perform ed in inguinal regions t o expose t he left and right fem oral art eries. Aft er exposure, art erial diam et ers were m easured using a m anual pachym et er.
Next , longit udinal art eriot om ies were perform ed by rem oving an ellipt ic fragm ent of t he art erial wall m easuring 1.5 cm in diam et er and a diam et er equal t o 1/ 3 of t he art erial diam et er. To correct art erial wall defect s, fem oral angioplast ies using e- PTFE pat ches on t he right side and sugarcane biopolym er m em brane pat ches on t he left side were perform ed using a cardiovascular polypropylene cont inuous 7- 0 sut ure ( Figure 1) .
Aft er anest het ic recovery, t he anim als were sent t o independent cages in t he experim ent al laborat ory. Solid foods were released 8 hours aft er t he surgery.
Over t he first post operat ive week, t he dogs were subm it t ed t o daily and weekly clinical assessm ent st art ing on t he eight h day. Clinical assessm ent consist ed of t he exam inat ion of fem oral pulses, walking and presence of pulsat ile t um or, hem at om a or hem orrhage and surgical wound infect ion. Six m ont hs aft er t he surgery, t he dogs were subm it t ed t o a new surgery. Preoperat ive cares and
Next , t he dogs were subm it t ed t o laparot om y for exposure and punct ure of t he abdom inal aort a using an 18- gauge Jelco®, followed by iodinat ed- cont rast art eriographies ( Conray®) . Aft er art eriography
and m acroscopic evaluat ion, all art erial segm ent s having pat ches were rem oved for hist opat hologic t est s. The m at erial was st ained wit h hem at oxylin- eosin and picrosirius ( Figure 2) .
The experim ent s perform ed were dist ribut ed int o t wo random ly est ablished groups: Group I , eight art erial pat ches using t he biopolym er ( experim ent al group) ; Group I I , eight art erial pat ches using e-PTFE ( cont rol group) . I n t his st udy, each anim al was it s own cont rol.
The research prot ocol was sent for appraisal of t he Bioet hics Com m it t ee at Universidade Federal de Pernam buco, which approved it wit hout rest rict ions.
Significance level used for all st at ist ical t est s was 5% . The dat a were included in an Excel spreadsheet and analyzed using t he soft ware St at ist ical Package for t he Social Sciences ( SPSS) version 11.
Result s
All anim als survived t he est ablished period of 180 days for clinical observat ion and second surgery. There were no cases of infect ion, dilat at ion or aneurysm , rupt ure or pseudoaneurysm and t hrom bosis in any group ( Figure 3) .
I n assessm ent s before and aft er t he art erioplast y, Doppler sign in t he left and right fem oral art eries was present and had t hree- phase wave flow.
Art eriography showed t hat t he fem oral art eries in t he cont rol and experim ent al group had no
Measurem ent of art erial diam et ers before and 180 days aft er angioplast ies did not show st at ist ically significant differences ( p > 0.05, using t he signed- rank Wilcoxon t est ) ( Table 1) .
Discussion
All current subst it ut es have m aj or lim it at ions. Aut ogenous veins are scarce, biological graft s have high rat es of aneurysm al dilat at ion and calcificat ion, and synt het ic graft s are expensive and have low resist ance t o infect ion. Thus, search for an ideal subst it ut e rem ains, especially for applicat ion in sm all-and m edium - diam et er art eries. This m at erial m ust have proper t echnical qualit ies t o be used in hum an beings, in associat ion wit h a low product ion cost , so t hat it can be widely used.7 - 1 1
Nowadays, m any research st udies have evaluat ed use of new m at erials for subst it ut ion of blood vessels. Som e of t hem have been direct ed t o t he st udy of m at erials produced based on subst ances synt hesized by m icroorganism s, such as bact erial cellulose, which was used in t he product ion of t ubular graft s by Klem m et al., in 2001, for subst it ut ion of t he carot id art ery in rat s.1 9
it has been used in experim ent al st udies t o evaluat e new art erial pat ches.2 0 - 2 9
The m ain com plicat ions result ing from t he use of art erial pat ches are t he sam e seen in t ubular graft s: t hrom bosis, rupt ure and pseudoaneurysm , dilat at ion and surgical wound infect ion.2 0 - 2 9
Such com plicat ions did not occur in t he present st udy. The result s were confirm ed by clinical assessm ent and by Doppler velocim et ry, as well as by art eriography. Absence of dilat at ion in t he fem oral art eries aft er im plant at ion of t he pat ches was also confirm ed by m easurem ent of fem oral art ery diam et ers at t he pat ch im plant at ion sit e. Associat ion bet ween Doppler flowm et ry and art eriography allowed proper assessm ent of collat eral circulat ion, since it allowed analysis bot h of m orphology and charact erist ics of blood flow in fem oral art eries.
Com plicat ions result ing from use of art erial pat ches can be caused by failure of m at erial used as a pat ch, as observed by Pena & Husni, who report ed 20% of t hrom bosis in fem oral angioplast ies wit h Dacron pat ches in dogs and by McCready et al., when using porcine int est inal subm ucosa as a pat ch in carot id angioplast ies and obt aining 10% of pseudoaneurysm s.2 4 , 2 9
Sim ilarly, Menon et al. found 35% of t hrom bosis in fem oral and carot id angioplast ies using Dacron pat ches com pared wit h 25% of t hrom bosis using aut ogenous vein pat ches, showing superiorit y of t he lat t er.2 2
The healing process of sugarcane m em brane pat ches was charact erized by presence of a chronic inflam m at ory react ion in t he ext ernal surface m ediat ed by lym phocyt es and neut rophils, as well as fibrosis. I n t he int ernal surface of t hese pat ches, t here was developm ent of an int im al layer form ed by fibrosis. That process is sim ilar t o t hat observed in healing of synt het ic m at erials, such as e- PTFE.9
-1 -1 , 2 8
Also sim ilarly t o e- PTFE pat ches, focuses of degenerat ive process wit h loss of int egrit y were not observed in sugarcane m em brane pat ches, as in aut ogenous art ery or vein pat ches. I n bot h groups, rare presence of m acrophages confirm s low rat e of ant igens in t hose m at erials. There were no focuses of calcificat ion, as observed in biological graft healing.2 0 , 2 2 , 2 4 , 2 8
Different ly of e- PTFE pat ches, sugarcane m em brane pat ches did not allow invasion by fibroblast s. Penet rat ion of cells in e- PTFE pat ches occurs due t o presence of m icropores in t heir st ruct ure. That process has been described in t he lit erat ure and is im port ant for a com plet e healing of pat ches. The sugarcane biopolym er m em brane has no pores and, t herefore, did not allow invasion by fibroblast s, but t he new int im al and advent it ia layers were st rongly at t ached, respect ively, t o t he int ernal and ext ernal pat ch walls.9 - 1 1 , 3 0 , 3 1
Conclusion
Based on t he result s obt ained wit h t he experim ent al m odel used, over a 180- day observat ion period, it can be concluded t hat t he sugarcane biopolym er m em brane is a proper art erial subst it ut e when used as pat ches in t he fem oral art ery of dogs.
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Correspondence: Esdras Marques Lins
