Coronary artery bypass with freeze-preserved saphenous vein allografts

The Management of Aneurysmal Degeneration of Lower Extremity Cryopreserved Saphenous Vein Bypass Grafts

BACKGROUND

The use of cryopreserved saphenous veins (CSVs) for the treatment of lower extremity peripheral arterial disease is an attractive option when there is no available autogenous vein. Prior studies found CSVs are at risk for aneurysmal degeneration requiring reoperation. As the management of these complications and patient outcomes is not well described, the objective of this case series is to describe the open and endovascular management of degenerative CSVs at a tertiary community center.

METHODS

All CSVs implanted for lower extremity bypass at our institution between 2001 and 2021 were retrospectively reviewed. All CSVs with evidence of aneurysmal change were included in this study. CSVs with evidence of active infection were excluded. The decision to intervene was left to the discretion of the operating surgeon. Demographic data, indications for the index operation, and details about subsequent interventions for degenerative CSVs were recorded. Study end points included limb salvage and continued patency. Demographic data, indications for the index operation, and details about subsequent interventions for degenerative CSVs were recorded.

RESULTS

Seventeen bypasses were identified to have aneurysmal degeneration in 13 patients in the absence of infection between 2001 and 2021. Nine of the 13 patients were male, and the average age and body mass index during the index procedure were 72 and 28, respectively. Indications for the index bypass included acute limb ischemia (9), popliteal aneurysm (2), and chronic limb threatening ischemia with Rutherford's class IV (5) and V (1). The mean time between the index procedure and first graft revision due to aneurysmal changes was 4 years. Most of the aneurysms did not occur at the site of anastomosis with 13 occurring in the body of the graft. Thirteen grafts were managed with open surgery and 3 were managed with endovascular techniques. All endovascular repairs were managed via covered stenting. Patients were followed for an average duration of 7 years from the initial bypass and 2 years from their last aneurysmal repair. Limb salvage in this cohort was 87% with 2 limbs requiring amputation, all of whom underwent open reconstruction. The mortality rate in this series was 54% and no patients died due to complications from their graft. Continued patency on Kaplan Meier survival curve analysis was 79% at 6 months, 65% at 1 year, 54% at 3 years, and 27% at 5 years.

CONCLUSIONS

In our experience, aneurysmal degeneration of CSV grafts was mostly managed with standard open surgical techniques, although endovascular therapy also proved acceptable. Limb salvage rates and continued patency of repair at 1 year in this cohort were acceptable. This case series highlights the importance of diligent surveillance for patients with CSVs.

Vascular allografts for clinical application in Europe: assessment of 30 years of experience with vascular tissue banking in Brussels

Vascular tissue banking has been carried out in Brussels for over 30 years in compliance with EU and Swiss tissue banking regulations. A total of 2.765 vascular tissue donations were performed in Belgian, French, Netherlands and Suisse transplant centres: 547(20%), 1.013(37%) and 1.205(43%) during the first, second and third periods, respectively. 85% and 18% increase in donations during the second and third decades compared to previous one, were remarkable. Of the 7.066 evaluated vascular tissues, 2.407(227, 921 and 1.259) were discarded (34.1%), whereas 4.659(523, 1.861 and 2.275) accepted (65.9%) during the respective period. Of the 92 donated veins, 44(47.8%) were discarded and 48(52.2%) accepted. Allografts available for clinical application were stored in vapours of liquid nitrogen. A total of 4.636 allografts were delivered and transplanted for cases of infection (58%), critical limb ischaemia (16%) and congenital cardiac surgery (15%). Thirty veins were implanted. The progressive increases in donations of 20%, 37% and 43% and in transplantations of 20.8%, 34.6% and 45% during the first, second and third periods, respectively, were remarkable. Complications were reported after transplantation and these included acute rejection of two femoral arteries one month after transplantation. We conclude that the donation and transplantation of cryopreserved vascular allografts was stable with a progressive increase over time. Allografts were used predominantly for the treatment of infection, limb salvage for critical ischaemia and for neonates and infants with congenital cardiac malformation. Immune related rejection was observed. This should be a subject of future investigation.

Nonautologous Grafts in Coronary Artery Bypass Surgery: A Systematic Review

BACKGROUND

Suitable autologous conduits may be lacking when performing coronary artery bypass grafting. The aim of this review is to determine the status of nonautologous grafts in coronary artery bypass grafting.

METHODS

We conducted a literature search on MEDLINE All, Embase Classic, and Embase through Ovid from 1960 to April 2020.

RESULTS

Of the 1579 records identified, 21 studies were included in the review. The following grafts were assessed for patency: 109 homologous saphenous veins (patency rates ranged from 66.7% at a median follow-up of 8.5 months to 0% at 6-12 months and 7-18 months, respectively), 29 expanded polytetrafluoroethylene grafts (from 80% at a median follow-up of 5 months to 14.3% at 45 months), 12 human umbilical veins (50% at a median follow-up of 6 months), 50 Bioflow bovine internal mammary arteries (from 15.8% to 0% at a mean follow-up of 9.5 months and 19 months, respectively), 39 Perma-Flow grafts (80% and 76.9% at 1-3 months and 12 months, respectively), 20 No-React bovine internal mammary arteries (57.1% at a median follow-up of 28 months and 23.1% at a mean follow-up of 7 months), 40 autologous venous endothelial cell-seeded expanded polytetrafluoroethylene grafts (94.7% and 81% at a mean follow-up of 27 months and 60 months, respectively), and 12 autologous venous endothelial cell-seeded cryopreserved homologous veins (83.3% at a mean follow-up of 8.5 months).

CONCLUSIONS

The goal of an alternative conduit with patency and attributes that match those of autografts remains elusive. Autologous endothelial cell-seeded synthetic grafts have demonstrated promising results but require further investigation.

Biologic Scaffolds

Biologic scaffold materials composed of allogeneic or xenogeneic extracellular matrix are commonly used for the repair and functional reconstruction of injured and missing tissues. These naturally occurring bioscaffolds are manufactured by the removal of the cellular content from source tissues while preserving the structural and functional molecular units of the remaining extracellular matrix (ECM). The mechanisms by which these bioscaffolds facilitate constructive remodeling and favorable clinical outcomes include release or creation of effector molecules that recruit endogenous stem/progenitor cells to the site of scaffold placement and modulation of the innate immune response, specifically the activation of an anti-inflammatory macrophage phenotype. The methods by which ECM biologic scaffolds are prepared, the current understanding of in vivo scaffold remodeling, and the associated clinical outcomes are discussed in this article.

Smooth Muscle Function in Short- and Long-term Stored Cryopreserved Veins

There is considerable interest in banking of allograft veins for vascular recon struction procedures in patients for whom there are no suitable autologous or prosthetic vessels available. A major obstacle to vein banking has been posed by the lack of long-term storage studies and by a prior report indicating that veins deteriorated rapidly during liquid nitrogen storage. This study was, there fore, initiated to determine the effects of long-term liquid nitrogen storage on tissue viability. Viability was assessed by measurement of smooth muscle func tion in fresh, short-term (one to twenty-eight days), and long-term (> two years) cryopreserved canine saphenous veins. There were no significant differences in the median effective doses of norepinephrine, serotonin, and KCL for genera tion of isometric force by vein rings from short- and long-term stored groups. Similarly, the maximum forces generated by long-term-stored cryopreserved veins in response to each reagent were the same as in short-term-stored veins. These results demonstrate that vein viability is maintained in cryopreserved banked veins.

Clinical Experiences with the Stabilized Human Umbilical Vein in Coronary Bypass Surgery

Nine patients received 16 aortocoronary bypass grafts utilizing the umbil ical vein. A 4-mm internal diameter Dardik Biograft (Meadox Laboratories, Oakland, NJ) was used in all cases. Eight right coronary arteries, five circumflex, two anterior descending, and one diagonal artery were bypassed. There were no surgical deaths or perioperative myocardial infarctions. Clin ically, all patients are doing well 1 to 16 months postoperatively. Technical aspects of using these grafts are described. In patients lacking satisfactory saphenous veins, the umbilical vein can be used for the aortocoronary position. Continued long-term clinical evaluation is necessary.

The histo-blood group ABO system and tissue transplantation

In general, one might expect that ABO incompatibility of donor and recipient would be important to some degree if viability of the transplanted allograft is important for graft incorporation and function. This is true for some recipients of organs. However, ABO incompatibility appears to play a minor role, if any, in the clinical success of viable cornea and viable skin allografts. Even though A and B antigens may be present on the transplanted tissue, other factors that can contribute include the strength of the immune response, the avidity of the antibody, and the dose of the antigen presented, which may vary from donor to donor. Although A and B antigens are present on endothelium, the use of ABO-incompatible heart valves is successful, as they carry out their mechanical function by using the strength of the connective tissue rather than the viability of the donor endothelium. The presence, immunogenicity, and significance of A and B antigens in human vessel transplants have not been well studied. With the more commonly transplanted tissue, such as bone and tendon, posttransplant success does not depend on cellular viability or ABO compatibility.

Patency of cryopreserved saphenous vein grafts as conduits for coronary artery bypass surgery

STUDY OBJECTIVE

To determine the angiographic patency of cryopreserved saphenous vein grafts used as conduits during coronary artery bypass surgery and whether this is affected by postoperative immunosuppressive therapy.

DESIGN AND SETTING

A retrospective review of medical records and coronary angiograms of patients at a university hospital.

PATIENTS

Eleven patients undergoing 12 coronary artery bypass operations during which a total of 26 distal coronary anastomoses were created using cryopreserved vein grafts.

MEASUREMENTS

Eight postoperative coronary angiograms were performed in 10 patients surviving longer than 1 week. All angiograms were performed on the basis of symptoms of suspected myocardial ischemia. Angiographic results, postoperative anticoagulation, and therapy with immunosuppressive agents were analyzed.

RESULTS

Seventeen cryopreserved vein grafts were studied; one (6%) was patent, 12 (71%) were occluded, and 4 (23%) were stenosed. In patients treated with azathioprine, seven of the eight cryopreserved vein grafts were occluded. In patients not receiving immunosuppression, five were occluded, three were stenosed, and one was patent. All internal mammary grafts were widely patent.

CONCLUSION

Cryopreserved vein grafts have a poor angiographic patency which did not appear to be affected by immunosuppressive therapy with azathioprine. The use of this graft should be restricted and alternative arterial conduits utilized.

Vascular prostheses for aortocoronary bypass grafting: a review

Alternative conduits must be chosen when autologous grafts are not available for coronary artery bypass grafting (CABG). Viable grafts do not always have perfect characteristics for CABG, and homologous venous conduits have been used with unsatisfactory results. Many small caliber vascular grafts used for coronary bypass conduits have been developed in the past, but most of them have failed except in rare instances. In this paper the current problems in available conduits, new technologies for improvement, animal models, and possibilities for the future for CABG conduits are discussed.

Vein graft factors in the outcome of femorodistal bypass

Various vein factors affect the outcome of femorodistal bypass using vein in the treatment of lower limb ischaemia. In this review, the effect of factors such as vein size, compliance and morphology are discussed.

Cryopreserved arterial homografts: preliminary study

The use of arterial or venous allografts for vascular reconstruction was first reported in 1951, but long-term results have been disappointing. Rejection and inappropriate methods of preservation are the main reasons for failure. A successful solution to this problem could be achieved by programmed cryopreservation with cryoprotectant. Our study had two aims: to define the biomechanical properties of cryopreserved arterial allografts and to study their histologic appearance. Arteries were removed as part of a protocol for multiorgan harvesting for transplantation. Cryopreservation was performed within the first 24 hours after harvesting. Programmed cryopreservation with 15% dimethyl sulfoxide (cryoprotectant) was used. Mechanical testing was done immediately after thawing. Two groups were tested: a control group of fresh aortas and a group of cryopreserved aortas. Axial and circumferential strips were tested. High strain modulus and stress and strain characteristics were calculated for each strip. There was no statistically significant difference between the mechanical properties of fresh and cryopreserved human descending thoracic aortas. Biochemical tests were performed in the preservative solution at 1 and 7 days in both groups. There was no statistically significant difference between the two groups at day 1 or day 7 (p > 0.05). Histologic studies before and after arterial cryopreservation included standard and electron microscopy and showed that arteries had normal structure after cryopreservation. These results confirm that programmed cryopreservation with cryoprotectant does not alter the molecular or geometric configuration of collagen or elastic fibers. Endothelial cells were still present, however, their viability and function were not assessed.(ABSTRACT TRUNCATED AT 250 WORDS)

Cryopreserved allograft veins as alternative coronary artery bypass conduits: early phase results

Traditional autologous conduits are sometimes unavailable or unsuitable to permit total revascularization during coronary artery bypass grafting. In these patients the results of using nonautologous alternative conduits has been disappointing. Encouraged by the excellent long-term results seen with cryopreserved allograft valves, a clinical protocol was developed to evaluate the use of a commercially cryopreserved allograft saphenous vein (CPV). Our protocol consisted of using CPV when left internal mammary arteries and autologous saphenous vein grafts were unavailable or unsuitable for complete revascularization. Blood group (ABO) typed CPVs were thawed and implanted as required using standard surgical techniques. From December 1989 through June 1991, 19 of 1,602 patients who underwent coronary revascularization had CPVs implanted (1.2%). There were no operative deaths. An attempt was made to evaluate the patency of all grafts with coronary arteriography or ultrafast computed tomographic scans. Fourteen patients were available for patency evaluation. Patency rate in the 14 patients studied at a mean of 7 +/- 2 months (range, 2 to 16 months) were: internal mammary artery, 93% (14/15); saphenous vein graft, 80% (4/5); and CPV, 41% (7/17). The patency of the CPV was significantly less than the patency rate for the saphenous vein and internal mammary artery (p = 0.004). We conclude that the short-term patency rate of CPVs is inferior to that of autologous vessels. Due to its poor patency, we recommend that CPV should only be used when no other autologous conduit is available.

Cryopreserved vein transplantation

There have been numerous attempts to develop prosthetic conduits or utilize allograft saphenous veins for arterial bypass. This article summarizes our experimental and clinical experience with cryopreserved allograft saphenous veins. During these studies, particular attention was paid to vein donor postmortem ischemia time, vein procurement technique, and tissue storage methods. Experimental cryopreserved autograft studies demonstrated that cryopreservation of the veins does not alter subsequent graft patency, the arterialization process, blood flow, or platelet deposition in vein grafts. Endothelium-derived relaxing and contractile factors are produced by the endothelium of explanted cryopreserved autografts, and smooth muscle contractions and relaxations can be induced. In experimental cryopreserved allografts, the endothelium appears to be removed by an immune response during the first 10 days after transplantation, fibrin deposition is minimal, and re-endothelialization occurs over 6-9 months. Early clinical results using cryopreserved allograft saphenous veins are encouraging with 1-year patency rates of 79% for peripheral grafts and 86% for coronary bypass grafts.

Immunosuppressive treatment of venous allografts

In order to evaluate whether temporary immunosuppressive therapy is able to improve the results obtained with viable venous allografts and achieve better results than with synthetic grafts, 142 arterial reconstructions were performed in mongrel dogs bypassing their ligated femoral arteries. Histological as well as immunological studies were performed and patency determined by weekly palpation and regular angiography. The 6-month cumulative patency rates were: Group I: synthetic grafts (a) Dacron: 48%, (b) plasma-TFE: 53%. Group II: fresh grafts (a) autografts: 100%, (b) allografts: 37%, (c) allografts treated with cyclosporin 4 mg kg-1 daily for 1 month: 74% (100% after 1 month). Group III: grafts preserved in Hanks' solution with 15% DMSO at -160 degrees C for 1 month (a) autografts: 77%, (b) allografts: 35%, (c) allografts treated with methylprednisolone 1 mg kg-1 daily: 38%, (e) allografts treated with cyclosporin and methylprednisolone: 83%. Group IV: human saphenous veins implanted as xenografts and treated with cyclosporin and methylprednisolone: 18%. Immunosuppressive therapy with cyclosporin seems to be able to prevent early thromboses due to rejection seen after implantation of viable fresh or cryopreserved venous allografts, and the results are significantly better than those obtained with synthetic grafts. Tissue matching might further improve these results. This study suggests that cryopreserved venous allografts could be used for the creation of a vein-bank and their use, in combination with tissue typing and temporary immunosuppressive therapy may be warranted for arterial reconstructions when autologous saphenous vein is not available.

Freeze-dried microarterial replacement allografts in rabbits

Microvascular techniques offer important alternatives for reconstructive head and neck surgery. To test the viability of freeze-dried allografts, a pilot experimental study was performed using the rabbit model. Freeze-dried preserved arterial allografts were implanted into femoral artery defects in eight subjects. After 6 weeks, all grafts were harvested and prepared for histological and electron microscopic analysis. Immediate patency was 100%. One subject was excluded on the third postoperative day. Of the seven remaining grafts, three (43%) were patent at 6 weeks. These results are comparable to previous data obtained using freeze-dried arterial allografts in the same animal model. Although further investigation is required, this pilot study suggests possible future application of cryopreserved vascular micrografts.

Vein to artery allografts: experimental evidence of immunological sensitivity in rats

Vein allografts were studied in rats using the major histocompatibility complex-incompatible DA (RTIa) and LEW (RTI1) inbred strains. Allografts from DA rats were inserted in to 22 LEW hosts, and vice versa, by interposing a 5 mm segment of donor iliolumbar vein into a defect in the host's iliac artery (1 mm in diameter), using microsurgical techniques. Grafts were left in situ for 6 weeks and were then tested for evidence of sensitization by the insertion of an allogeneic fetal heart from the donor strain into the host's foot pad. The fetal heart beat was recorded with an ECG and the time of rejection determined by the cessation of ECG activity. As controls, allogeneic donor fetal hearts were implanted into 40 host rates (20 of each strain) which had not previously received a donor vein allograft. These were monitored by ECG, as above. Control LEW host rats rejected DA fetal hearts in a mean time of 8.45 days. Control DA hosts rejected LEW fetal hearts in 8.70 days. DA hosts with LEW vein allografts did not reject donor fetal hearts significantly sooner (mean 8.33 days) than the controls. However, LEW host rats with allografted DA veins rejected subsequent DA fetal hearts in 7.18 days, which was significantly sooner than in controls (8.45 days). These data provide evidence of sensitization of the rejection response by vein allografts.

Cryopreserved homologous saphenous vein: early and late patency in coronary artery bypass surgical procedures

Autologous saphenous vein has proved to be a satisfactory conduit for use in coronary artery bypass grafting. Unfortunately, it is not always available, and substitute material must sometimes be used. When satisfactory autologous veins were not available and the internal mammary arteries were unsuitable, cryopreserved homologous saphenous veins were used in 28 patients. A total of 76 grafts were constructed. Cryopreserved homologous veins were used for 61 grafts, autologous saphenous veins for 11 grafts, and the internal mammary artery for 2 grafts. Coronary angiography was performed 8 to 12 days postoperatively in 16 patients. Of the 31 homografts studied, 8 were occluded (26%), 3 were stenotic (9%), and 20 were normal (65%). The one internal mammary artery and six autologous veins studied were all patent. Six patients underwent late catheterization 6 to 12 months postoperatively. Thirteen homografts were studied at late catheterization: 11 were occluded, 1 was severely stenotic, and 1 was mildly stenotic. At late catheterization, the one internal mammary artery studied was patent, and the one autologous saphenous vein was 95% occluded. Results of both early and late catheterization performed on 18 patients demonstrated that of the 35 homografts studied, 17 (49%) were occluded, 3 (9%) had greater than 70% stenosis, 1 (3%) had mild disease, and 14 (40%) were free of disease. One year follow-up data obtained on 26 patients revealed that 4 patients (15%) died of cardiac causes, 2 patients (8%) died of noncardiac causes, 11 patients (42%) have recurrent angina, and 9 (35%) are asymptomatic. It is concluded that use of cryopreserved homologous saphenous veins for coronary artery bypass grafting should be avoided if at all possible.

Upper extremity vein graft for aortocoronary bypass

Twenty-four autologous vein grafts taken from the upper extremities were used in 13 patients undergoing aortocoronary bypass procedures. All of these patients had had previous bilateral saphenous vein stripping. Clinical follow-up between 3 months and 6 1/2 years is reported. Ten patients were recatheterized. There was neither operative mortality nor appreciable morbidity. All the patients are alive and well at the present time. Eleven out of 13 were in New York Heart Association (NYHA) Class I 3 months after operation. Nine patent grafts out of 10 were seen during recatheterization in 6 patients studied less than 9 months after operation. In a subgroup of 5 patients followed for more than 1 year, 2 are now in NYHA Functional Class I, 2 in Class II, and 1 in Class III. Graft patency had been determined in 4 of these patients. Five grafts out of 8 were patent, 2 of them with gross abnormalities. In conclusion, we have some reservations about the long-term fate of these grafts.

The effects of preservation on microvascular vein grafts in rats

Segments 15 mm in length were excised from the femoral veins of rats and preserved by refrigeration at 4 C in lactated Ringer's solution for periods up to 21 days. The findings show that veins can be preserved for up to seven days and successfully grafted to recipients. Although there was some success in preserving vein segments for more than seven days, a high rate of thrombosis occurred after implantation in the recipients. It is generally accepted that damaged endothelium causes thrombosis. The light and electron microscopic observations in this study, however, suggest that the condition of the endothelium may not be the only important factor in the patency of small vessels. A thickened and prominent elastic lamina may also play a role in keeping the lumen open.

Aortocoronary bypass with homologous saphenous vein: long-term results

Between February 1973, and February, 1979, 27 homologous saphenous veins were used in 20 patients (mean age, 54 years). Seven fresh grafts were used less than 24 hours after severance. They were kept at a temperature of 4 degrees C in saline solution containing penicillin. Twenty cryopreserved grafts were used within a period of eight days to 2 months from severance. They were preserved in glycerol at a temperature of -40 degrees C. One patient (5%) died postoperatively. A perioperative myocardial infarction developed in 3 patients (15%). Average follow-up is 27 months. No late mortality was registered. Fifteen patients are free from symptoms, and 3 patients have residual angina with exercise. Control angiograms were made in 13 patients 1 to 68 months after operation; 17 homografts were seen. Early occlusion of 1 graft and late occlusion of 8 grafts were registered. The poor late patency rate does not seem to be related to either histocompatibility or technical conditions. Conversely, microscopic examination of several cryopreserved grafts showed that the mode of preservation resulted in deterioration of intimal and medial tissues of the vein. Therefore, it appears to us that the use of homologous saphenous veins should be avoided for coronary bypass.

The short saphenous vein: an alternative to the long saphenous vein for aortocoronary bypass

The long saphenous vein and internal mammary artery are considered at present to be the best grafts available for coronary artery bypass. Patients who have had bilateral long saphenous vein stripping and who require multiple aortocoronary bypass grafts present a challenge to the cardiac surgeon. The short saphenous vein appears to be a suitable alterative.