Usability of Ringed Polytetrafluoroethylene
Grafts for Middle Hepatic Vein Reconstruction
During Living Donor Liver Transplantation
Shin Hwang,* Dong-Hwan Jung,* Tae-Yong Ha, Chul-Soo Ahn, Deok-Bog Moon, Ki-Hun Kim,
Gi-Won Song, Gil-Chun Park, Sung-Won Jung, Sam-Youl Yoon, Jung-Man Namgoong,
Chun-Soo Park, Yo-Han Park, Hyeong-Woo Park, Hyo-Jun Lee, and Sung-Gyu Lee
Division of Liver Transplantation and Hepatobiliary Surgery, Department of Surgery, Asan Medical Center,
University of Ulsan College of Medicine, Seoul, Korea
Large vein allografts are suitable for middle hepatic vein (MHV) reconstruction, but their supply is often limited. Although poly-
tetrafluoroethylene (PTFE) grafts are unlimitedly available, their long-term patency is relatively poor. We intended to enhance
the clinical usability of PTFE grafts for MHV reconstruction during living donor liver transplantation (LDLT). Two sequential
studies were performed. First, PTFE grafts were implanted as inferior vena cava replacements into dogs. Second, in a 1-year
prospective clinical trial of 262 adults undergoing LDLT with a modified right lobe, MHV reconstruction with PTFE grafts was
compared with other types of reconstruction, and the outcomes were evaluated. In the animal study, PTFE grafts induced
strong inflammatory reactions and luminal thrombus formation, but the endothelial lining was well developed. In the clinical
study, the reconstruction techniques were revised to make a composite PTFE graft with an artery patch on the basis of the
results of the animal study. MHVs were reconstructed with cryopreserved iliac veins (n ¼ 122), iliac arteries (n ¼ 43), aortas
(n ¼ 13), and PTFE (n ¼ 84), and these reconstructions yielded 6-month patency rates of 75.3%, 35.2%, 92.3%, and 76.6%,
respectively. The overall 6-month patency rates for the iliac vein and PTFE grafts were similar (P ¼ 0.92), but the 6-month pat-
ency rates with vein segment 5 were 51.0% and 34.7%, respectively (P ¼ 0.001). The overall graft and patient survival rates
did not differ among these 4 groups. In conclusion, ringed PTFE grafts combined with small vessel patches showed high pat-
ency rates comparable to those of iliac vein grafts; thus, they can be used for MHV reconstruction when other sizable vessel
allografts are not available. Liver Transpl 18:955-965, 2012. V
C 2012 AASLD.
Received December 6, 2011; accepted March 19, 2012.
Middle hepatic vein (MHV) reconstruction with an
interposition vessel graft has been established as a
standard procedure for living donor liver transplanta-
tion (LDLT) with a right lobe graft when the donor’s
MHV trunk is preserved in the donor’s remnant liver.
Materials used to date for this type of venous vascular
reconstruction have included various types of homolo-
gous and autologous vessel grafts.1-5
increase in the number of adult LDLT procedures and
the relatively limited number of vessel allografts have
Abbreviations: CT, computed tomography; GRWR, graft-to-recipient weight ratio; IVC, inferior vena cava; LDLT, living donor liver
transplantation; MELD, Model for End-Stage Liver Disease; MHV, middle hepatic vein; PTFE, polytetrafluoroethylene; V5, hepatic
vein branch segment 5; V8, hepatic vein branch segment 8.
This study was registered at ClinicalTrials.gov (NCT01205802). It was terminated in advance because the final goal was met early
during the study period.
This study was supported by research funds from the Asan Institute of Life Science (grant 2007-246 to Shin Hwang).
*These authors contributed equally to this work.
Address reprint requests to Sung-Gyu Lee, M.D., F.A.C.S., Division of Liver Transplantation and Hepatobiliary Surgery, Department of Surgery,
Asan Medical Center, University of Ulsan College of Medicine, 388-1 Poongnap-Dong, Songpa-Gu, Seoul, Korea 138-736. Telephone:
82-2-3010-3485; FAX: 82-2-474-9027; E-mail: email@example.com
View this article online at wileyonlinelibrary.com.
LIVER TRANSPLANTATION.DOI 10.1002/lt. Published on behalf of the American Association for the Study of Liver Diseases
LIVER TRANSPLANTATION 18:955-965, 2012
C 2012 American Association for the Study of Liver Diseases.
led us to search for new vessel substitutes.6Although
thin-walled, expanded polytetrafluoroethylene (PTFE)
grafts have been used for MHV reconstruction, their
patency rates appear to be insufficiently low.7Using
PTFE grafts for MHV reconstruction in a small num-
ber of patients undergoing LDLT and nontransplant
surgery, however, we have found that although their
long-term patency is much lower than that of allo-
grafts, the late occlusion of PTFE grafts is not signifi-
cantly associated with patient survival outcomes.
Because of the advantage of prosthetic vessel grafts
(ie, their unlimited availability), we performed 2
sequential studies to assess the clinical usability of
ringed, expanded PTFE grafts for MHV reconstruction
during LDLT. The first study was performed with a
expanded PTFE grafts after implantation. The second
was a prospective clinical trial designed to determine
whether these grafts can maintain luminal flow for a
sufficiently long period of time.
what occursat these
PART 1. ANIMAL STUDY FOR
ASSESSING CHANGES AT IMPLANTED
Materials and Methods
The animal experiment involved the replacement of
the infrarenal inferior vena cava (IVC) through the
interposition of a cold-preserved IVC allograft or an
expanded PTFE graft, 4 weeks of waiting, and gross
and histological examinations of the vessel grafts after
harvesting. This study protocol was approved by our
institutional ethics board for animal experimentation.
We used 11 male dogs weighing 25 to 30 kg each.
infrarenal IVC was isolated by the ligation of multiple
lumbar veins. After the clamping of both ends of the
infrarenal IVC, a 5- to 6-cm-long segment was excised
from each. This segmental defect was replaced by an
IVC allograft in 3 dogs and by an expanded PTFE graft
in 5 dogs. The IVC allografts had been harvested 1
week earlier from 3 other dogs and had been pre-
served in a cold histidine-tryptophan-ketoglutarate
solution (Alsbach-H€ ahnlein Co., Germany). The size of
the IVC graft was matched to each native IVC. Each
PTFE graft was made of thin-walled, expanded PTFE
with a 14-mm inner diameter and a 15-mm outer di-
ameter (Gore-Tex, WL Gore & Associates, Inc.). The
anastomosis was made with continuous running
sutures (6-0 monofilaments). None of these animals
received antiplatelet or anticoagulation therapy, and
none experienced any serious surgical complications.
After 4 weeks, the dogs were sacrificed, and their
IVCs, including the interposed grafts and anastomo-
ses, were harvested.
The luminal patency of each graft portion was eval-
uated with Doppler ultrasonography during the heart-
beating state, and a morphometric assessment was
performed after IVC harvesting. The mean outer and
general anesthesia, the
inner diameters were calculated after multiple meas-
urements along the longitudinal lengths of the grafts.
Tissue samples were fixed in a 10% formalin solution
and were histologically evaluated after routine hema-
toxylin-eosin staining, Masson trichrome staining for
collagen and muscle fibers, and Verhoeff–Van Gieson
staining for elastic fibers. The tissue samples were
also assessed immunohistochemically by incubation
with a mouse antibody to proliferating cell nuclear
marker for cellular proliferation; with a mouse anti-
body to a-actin (Dako, Carpinteria, CA), which is a
marker for smooth muscle cells within the vessel; and
with a rabbit antibody to von Willebrand factor
(Dako), which is a marker for vascular endothelial
cells. Median values were determined, and the groups
were compared statistically with Mann-Whitney U
tests. A P value < 0.05 was regarded as statistically
Blood flow through the IVC grafts was maintained in
all 8 dogs, and this resulted in a 1-month patency
rate of 100%. Anastomotic and luminal stenoses were
greater in the PTFE group versus the allograft group
(Fig. 1). More than half of each PTFE graft lumen was
filled with thrombus. Morphometric changes in the
graft diameters and histological findings are summar-
izedin Table 1. More severe
observed in the PTFE group. Immunohistochemical
staining showed scant cellular proliferation at allo-
grafts but more active replication at PTFE grafts. The
endothelial lining at the luminal surface was well
developed in both groups.
PART 2. PROSPECTIVE CLINICAL
STUDY OF THE PATENCY OF
IMPLANTED RINGED PTFE GRAFTS
Patients and Methods
Conclusions from the Preceding Animal Study
The results of the animal study led to 3 important
conclusions. First, the PTFE grafts induced strong
inflammatory tissue reactions at the anastomotic
sites, and this may have led to early severe narrowing
of the anastomosis. Because this type of anastomotic
stenosis appears to be inevitable with PTFE grafts, a
wider anastomosis would likely alleviate the stenosis-
inducing effects of severe inflammation. Second, pro-
gressive luminal thrombus formation led to early nar-
rowing of the effective lumen, although the endothelial
lining was well formed. Thrombus formation appears
to be alleviated by the application of sufficient antipla-
telet and anticoagulation therapy. The effective lumen
may be enlarged with a larger caliber PTFE graft,
although this may increase the risk of thrombus for-
mation because of the diameter-dependent decrease
in the flow velocity. Third, expanded PTFE grafts are
flexible and are, therefore, vulnerable to buckling,
956 HWANG ET AL.LIVER TRANSPLANTATION, August 2012
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