Experimental and clinical results of grafts in the venous system: a current review

Review article: History of venous trauma

ABSTRACT

This is a literature review on the history of venous trauma since the 1800s, especially that to the common femoral, femoral and popliteal veins, with focus on the early 1900s, World War I, World War II, Korean War, Vietnam War, and then civilian and military reviews (1960-2020). In the latter two groups, tables were used to summarize the following: incidence of venous repair versus ligation, management of popliteal venous injuries, patency of venous repairs when assessed <30 days from operation, patency of venous repairs when assessed >30 days from operation, clinical assessment (edema or not) after ligation versus repair, incidence of deep venous thrombosis after ligation versus repair, and incidence of pulmonary embolism after ligation versus repair.There is a lack of the following in the literature on the management of venous injuries over the past 80 years: standard definition of magnitude of venous injury in operative reports, accepted indications for venous repair, standard postoperative management, and timing and mode of early and later postoperative assessment.Multiple factors have entered into the decision on venous ligation versus repair after trauma for the past 60 years, but a surgeon's training and local management protocols have the most influence in both civilian and military centers. Ligation of venous injuries, particularly those in the lower extremities, is well tolerated in civilian trauma, although there is the usual lack of short- and long-term follow-up as noted in many of the articles reviewed.

LEVEL OF EVIDENCE

Review article, levels IV and V.

New Directions in the Use of Carbon as Vascular Graft Material

Carbon has been used to improve the thromboresistance of synthetic vascular prostheses, and for this pur pose, dacron grafts have been coated with carbon. Owing to the contradic tory results reported in the literature, a new kind of vascular conduit, ex clusively textured from carbon fi bers, has been developed. The pres ent research study was undertaken to compare carbon and expanded poly tetrafluoroethylene (e-PTFE) grafts when used as vascular substitutes. Fifty-six experimental animals were divided into four equal groups and underwent substitution of segments of infrarenal aorta or inferior vena cava (IVC), through use of either carbon or e-PTFE grafts. Prosthetic segments were removed fifteen sec onds, or sixty minutes, or seven, fif teen, thirty, sixty, or one hundred twenty days after implantation. Spec imens were examined by light and scanning electron microscopy. Cumu lative patency rates, calculated by the life-table method at 120 days after surgery, were 72% for aortic carbon grafts, 41 % for aortic e-PTFE grafts, and 0% for both carbon and e-PTFE grafts implanted on the IVC. Carbon conduits performed significantly bet ter than e-PTFE conduits when used as small-caliber arterial substitutes (p < 0.05). Fifteen seconds after blood contact, the inner surface of carbon prostheses, regardless of the implantation site, was covered with a thin proteinaceous layer, whereas e- PTFE grafts appeared almost com pletely free from hematic deposits.

One hour after implantation, a red thrombus was found to overlay the luminal surface of both carbon and e- PTFE prostheses. This layer ap peared to be thicker on the e-PTFE grafts than on the carbon grafts and thicker on the venous grafts than on the arterial. The endothelialization process of the blood-prosthesis inter face seemed to be slightly more rapid on the carbon than on the e-PTFE aortic grafts. In conclusion, this new carbon graft would appear to possess promising specifications, making it suitable for small-caliber arterial (but not venous) replacement.

Effect of Endothelial Seeding and Graft Material on the Patency Rate of Venous Grafts

Because prosthetic grafting to the venous system has a low patency rate, endothelial cell seeding has been used to enhance this rate. The effects of heterologous (porcine) or homolo gous (canine omental) endothelial seeding and of graft material (dacron or polytetrafluoroethylene—PTFE) on the patency rate of venous grafts were evaluated in this study.

Fifty-three grafts (10 cm x 8 mm ID) were inserted in dogs' vena cava. All animals were treated with aspi rin. Patency rate was evaluated at day 4 (cavography) or at day 32 (his tology).

The authors found that: (1) da cron grafts provided a poor venous conduit for seeding purposes; (2) PTFE grafts, whether seeded with omental canine or porcine endothelial cells, had a consistently high patency rate; and (3) although further studies would be needed, heterologous and homologous cell seeding might repre sent acceptable alternatives to autolo gous seeding.

Venographic Changes Associated with Seeded and Nonseeded Vena Cava Grafting

Thirty-four mongrel dogs had their inferior vena cava replaced by a 10 cm porcine endothelial cell seeded or nonseeded polytetrafluroethylene graft. Graft patency at four days (documented by cavograms) was then correlated with that noted at the time of sacrifice (day 32). The overall day 32 patency rate was 32 %. Grafts seeded and treated with aspirin had the highest patency rate. Collaterals were noted on all cavograms showing clotted grafts and on none of the patent grafts. Large collaterals were seen in 25% of the subjects, and moderate and minimal collateralization occurred in 75% of the cases. No correlation was noted between graft occlusion and symptomatology.

Experimental Inferior Caval Replacement with Mesothelium

Thrombo-resistance of mesothelial grafts was evaluated by replacing the inferior vena cava in 16 dogs. In 10 dogs, treated by antiplatelet aggregation agents, uniform graft thrombosis happened within 15 days. In six other dogs, the addition of an arterio-venous fistula produced conditions of flow (1385 ± 178 ml/min; mean ± s.e.m.) and velocity (17.1 ± 4.5 cm/s) closer to human values and markedly improved the patency rates (four patent over six up to 6 months P < 0.02). Light microscopy and scanning electron microscopy studies performed on the patent grafts showed well preserved mesothelial cells. Mesothelial fibrinolytic activity was 1160 ± 257 tissue activator units/g tissue before and 846 ± 142 activator units/g tissue after implantation (P = n.s.). Prostaglandin synthesis by native mesothelium was respectively 252 ± 103 and 7 ± 3 pg/ml/mg wet tissue/min for 6-keto-PGF1α and TXB2. The synthesis was reduced for 6-keto-PGF1α in the patent grafts but unaltered for TXB2, This work puts forward the suggestion that mesothelium is a promising venous substitute in conditions of high flow.

Hyaluronan-based scaffold for in vivo regeneration of the rat vena cava: Preliminary results in an animal model

The aim of this study was to develop a prosthetic graft that could perform as a small-diameter vascular conduit for vein regeneration. The difficulty of obtaining significant long-term patency and good wall mechanical strength in vivo has been a significant obstacle in achieving small-diameter vein prostheses. Fifteen Male Wistar rats weighing 250-350 g were used. Tubular structures of hyaluronan (HYAFF-11 tubules, 2 mm diameter, and 1.5 cm length) were implanted in the vena cava of rats as temporary absorbable guides to promote regeneration of veins. Performance was assessed at 30, 60, and 90 days after surgery by histology (hematoxylin-eosin and Weighert solution) and immunohistochemistry (antibodies to von Willebrand factor and to Myosin Light-Chain Kinase). These experiments resulted in two novel findings: (1) sequential regeneration of vascular components led to complete vein wall regeneration 30 days after surgery; (2) the biomaterial used created the ideal environment for the delicate regeneration process during the critical initial phases, yet its biodegradability allowed for complete degradation of the construct 4 months after implantation, at which time, a new vein remained to connect the vein stumps. This work demonstrates the complete vena cava regeneration inside the hyaluronic acid-based prosthesis, opening new perspective of microsurgical applications, like replantation of the upper limb, elongation of vascular pedicle of free flaps, cardiovascular surgery, and pediatric microvascular surgery.

An Experimental Model for the Treatment of Lethal Bleeding Injury to the Juxtahepatic Vena Cava With Stent Graft

BACKGROUND

Juxtahepatic vein injuries present a high mortality rate. Our objectives were to develop an experimental model of endovascular lethal injury of the juxtahepatic inferior vena cava (JHIVC) and to evaluate its hemodynamic alterations; to treat the lesion with volume replacement, and a stent graft (SG); and to follow the animals after treatment.

METHODS

Twenty dogs were anesthetized and monitored [heart rate (HR), mean arterial pressure (MAP), vesical and peritoneal pressures], and submitted to a JHIVC endovascular injury. After volume replacement the dogs were divided into two groups: control (GI) and experimental (GII). GI was observed until death. GII was treated with SG and followed by Doppler ultrasound (DUS) and cavography for 4 (GIIA), and 8 weeks (GIIB), and then sacrificed and IVC and SG were analyzed.

RESULTS

GI presented increased abdominal pressures, arterial hypotension, and death after 80 minutes. GII had a 100% survival rate till sacrifice, without clinical repercussions. At DUS and cavography all SG were patent, with monophasic pulsatile flow. On US, SG diameters after 2, 4, and 8 weeks did not show differences. On cavography IVC diameters presented no difference between groups GIIA and GIIB throughout the experiment. These data analyzed for the GII as a whole, showed statistically significant differences. Average lumen diameter reduction of SG was 27.43+/-20,00%. Pressure values in the IVC cranially, caudally to the SG, and inside the SG, did not show differences. In the IVC with the SG we observed a thicker neointima layer, and the injury in the media layer was covered with fibroconnective tissue.

CONCLUSIONS

We developed an experimental dog model of endovascular lethal injury of the JHIVC with significant increase in abdominal pressures, and a mortality rate of 100%. The treatment of this lesion with SG resulted in a thickened neointima layer, and a 27% reduction in the JHIVC lumen diameter, without clinical repercussion, and with a 100% survival rate.

Aneurysm of the iliofemoral vein

In this clinical case we report the use of the superficial femoral vein as an autologous venous interposition graft for the reconstruction of the iliofemoral vein in a 21-year-old female who presented with an asymptomatic primary aneurysm of the left iliofemoral vein. The choice of surgical technique used is discussed.

Experimental microvenous reconstructions with Gore-Tex polytetrafluoroethylene prosthesis implanted by means of the sleeve anastomotic technique

Polytetrafluoroethylene (PTFE) prostheses (Gore-Tex; ID, 1 mm; length, 5-7 mm; wall thickness, 0.2 mm; fibril length, 30 microns, n = 28) were implanted into the rat femoral vein by means of the sleeve anastomotic technique to enhance the patency rate. In the control group, PTFE prostheses (n = 8) were implanted by means of the end-to-end technique. In the experimental group patency and healing of the PTFE prostheses were evaluated at 1 day (n = 4), 1 week (n = 6), 3 weeks (n = 6), 6 weeks (n = 6), and 12 weeks (n = 6) after implantation by means of macroscopic inspection and routine light and scanning electron microscopy. All prostheses, except one at 1 week after implantation, were patent at the time of removal. All of the microvenous prostheses were completely covered by an endothelial layer at 3, 6, and 12 weeks after implantation. Occasionally some smooth muscle-like cells could be found underneath this endothelial layer, but stenosis was never observed at the anastomotic sites. Only scarce tissue ingrowth was observed in the wall of the PTFE prostheses. In the control group, all prostheses, except one prosthesis after 3 weeks, were found to be occluded. An occlusive mural thrombus was found firmly attached at the anastomoses at 1 day, and an organized thrombus at 3 weeks after implantation. The patent prosthesis demonstrated complete endothelial healing. These results demonstrate the importance of the sleeve anastomotic technique and the potential of PTFE prostheses as a microvenous conduit when implanted by means of the sleeve anastomotic technique in experimental reconstructive microvascular procedures.

Management of venous trauma

There has been considerable interest in the management of injured extremity veins since the American experience during the Vietnam War. Fortunately, there are an increasing number of reports from civilian experience in the United States that add valuable information. Although the controversy continues, it appears that there is merit in repair of many injured lower-extremity veins, particularly the popliteal vein when it is a single return conduit, assuming that the patient's general condition will permit, in an attempt to prevent acute venous hypertension initially and chronic venous hypertension subsequently. Figure 1 identifies the recovery potential that exists even if the initial venous repair fails. In contrast to thrombosis in the arterial system, recanalization is the rule in venous thrombosis. Patent valves can exist above and below the rather localized area of thrombosis. It appears that recanalization will prevent the problems of chronic venous insufficiency. It is obvious that many patients do well for years; however, the sequelae of acute venous hypertension may be more demonstrable after 10 or 15 years. There has not been similar evidence supporting a more aggressive approach in general in upper-extremity veins. However, it should be appreciated that a return pathway must remain patent, as noted in replantation of extremities. Obviously, there are differences in military and civilian wounds, with the former usually having more extensive soft-tissue destruction and obliteration of collateral veins and lymphatic channels. Unfortunately, many civilian gunshot wounds are being seen in the United States that are similar to the military type. We must not forget the lessons of the past, and we must continue to analyze our experience in the management of injured veins under a variety of conditions.

Evaluation of peritoneal tube grafts in the inferior vena cava of the pig

A tube graft 2.5 or 5 cm long, was constructed from the peritoneum of the anterior abdominal wall of 12 pigs. It was anastomosed end-to-end as an interposition graft in the infrarenal vena cava. The observation period was 4 months. Three of the six short grafts were venographically patent at 2 weeks, while all the long grafts were occluded. After 4 months two short grafts had recanalized, giving a patency rate of five out of six short grafts. No long grafts recanalized. In three of the patent specimens no clear tissue changes were found with light microscopy, while in the others changes of inflammation and fibrosis were noted. Scanning electron microscopy revealed good 'endothelialization' in two specimens, and partial 'endothelialization' in the others. No dilatation or severe stenosis of the patent grafts was seen. The occluded grafts remained only as a fibrous strand with sutures.

Late Thrombogenicity of Grafts in the Venous System

Although some previous experiments have demonstrated encouraging early results with venous vascular prosthesis, the long-term results have not been sufficiently investigated. The late thrombogenicity of 12 autogenous vein grafts and eight polytetrafluoroethylene (PTFE) grafts, three of which had been subjected to endothelial seeding, was evaluated 6 months after implantation in the canine venous system by determination of the survival time of the indium-labelled autogenous platelets and of the light and electron microscopic appearance of the graft-to-blood interface.

Twelve dogs receiving autogenous vein grafts had a platelet half-life of 64 ± 13 (mean ± s.d.) hours and a completely thrombus-free internal graft surface covered by a smooth endothelium. The platelet half-life in five dogs with non-seeded PTFE grafts was significantly ( P < 0.01) shorter (44 ± 11h). The PTFE-to-blood interface consisted of a 100- to 170-μm-thick pseudointima with a thrombus-free surface area of 25-90% and substantial endothelial coverage in only two animals. Three dogs receiving endothelial-seeded PTFE grafts had a platelet half-life of 38, 46 and 53h, respectively, a 10- to 80-μm-thick pseudointima covered with typical endothelium, and a thrombus-free surface area of 90-100%.

Our results demonstrate that PTFE grafts are still thrombogenic at 6 months following implantation in the canine venous system. Therefore, additional measures are required to maintain graft patency. Our limited experience with endothelial seeding does not allow any definite conclusions, but our findings indicate that this procedure might be beneficial.

Surgical treatment of idiopathic mediastinal fibrosis: report of five cases

Idiopathic mediastinal fibrosis is a rare disease of unknown aetiology. It is a benign condition in which abnormal proliferation of fibrous tissue occurs within the mediastinum, leading to constriction and obliteration of local structures, particularly the great veins. It is a rare cause of superior vena caval obstruction (1-2%) but one that is potentially amenable to surgical palliation. The results of venous reconstruction in five patients with superior vena caval obstruction secondary to idiopathic mediastinal fibrosis are reported. Reversed autogenous saphenous vein grafts were used in two patients, woven silicone rubber prostheses in two, and bovine pericardial conduits in one patient. Useful long term results were obtained in three patients, but the bovine pericardial graft and one of the vein grafts failed within a few weeks.

Inferior vena caval replacement after resection of left renal tumor in canine model

An animal model simulating the necessity of replacing the inferior vena cava (IVC) with a prosthetic graft is described. Six dogs underwent replacement of the IVC with an expanded polytetrafluoroethylene (E-PTFE) graft using an interrupted-suture technique. Three dogs served as controls, undergoing resection and autograft of the native IVC. Distal side-to-side femoral arteriovenous fistulas were constructed in each case and allowed to remain for six weeks. Subcutaneous heparin and prophylactic antibiotics were administered in the early postoperative period. All grafts were patent at six months, indicating a potentially successful technique for reconstruction of the IVC involved in disease or trauma.

Venous prostheses: improved patency with external stents

A uniformly successful prosthesis for replacement in the venous system has not been developed. This study assesses the effect of external stents on the patency of polytetrafluoroethylene (PTFE) grafts in the infrarenal vena cava. Under general anesthesia, 21 mongrel dogs underwent midline laparotomy. The infrarenal vena cava was resected and replaced by a standard segment (8 cm X 10 mm) of stented PTFE (12 dogs) and nonstented PTFE (9 dogs). Patency was assessed by contrast venography and the results compared between the two groups. The 7-, 30-, and 90-day patency was 12/12, 10/12, and 9/12, respectively, for stented PTFE and 6/9, 2/9, and 2/9, respectively, for nonstented PTFE. The patency of externally stented PTFE at 30 and 90 days was significantly better than grafts fashioned from PTFE alone (P less than 0.05 by chi-square analysis). These data demonstrate that external stenting improves the early patency of PTFE prostheses in the infrarenal vena cava. Consideration should be given to the clinical use of externally stented PTFE when prosthetic replacement in the venous system is required.

Veno-venous allografts: patency, subendothelial proliferation, and the role of platelet-active agents

Patency and histology of 81 vein allografts and 10 autografts in the canine femoral venous system were compared and the effect of platelet active agents in altering patency rates and subendothelial proliferation in allografts was examined. It was found that allografts thrombose at a predictable interval after operation (18 +/- 7 days) and have significantly worse survival than autografts (P less than 0.001). Platelet-active agents did not alter allograft patency rate of the incidence of subendothelial proliferation in this model.

Surgical treatment of acute superior vena caval syndrome. A report of two cases

The syndrome caused by the acute obstruction of the superior vena cava with central nervous system symptoms as well as with symptoms related to the oedema of the upper respiratory tract is often very severe and fatal to the patient. Conservative treatment is usually of no help, and consequently the palliative reconstruction of the superior vena cava may be indicated. Two cases of acute superior vena caval syndrome with reconstruction of the superior vena cava are presented. In the first case, when a malignant mediastinal tumour (Hodgkin's) was removed, a segment of the superior vena cava and the anonymous vein had to be removed. Following this operation acute superior vena caval syndrome developed and another operation was performed in which the superior vena cava was reconstructed with a Dacron prosthesis. Radiological examination of the superior vena cava 28 months postoperatively showed the prosthesis patent and the patient was free from symptoms. 51 months after the operation the patient was still asymptomatic. In the second case the obstruction of the superior vena cava was caused by anaplastic carcinoma of the upper lobe of the right lung. The acutely obstructed superior vena cava was reconstructed with a Dacron prosthesis. 9 months postoperatively the superior vena caval syndrome recurred and two months later the patient died of lung cancer. In both cases good palliation of the obstruction of the superior vena cava was obtained.