Bovine internal mammary artery as a conduit for coronary revascularization: long-term results

Photooxidation and Pentagalloyl Glucose Cross-Linking Improves the Performance of Decellularized Small-Diameter Vascular Xenograft In Vivo

Small-diameter vascular grafts have a significant need in peripheral vascular surgery and procedures of coronary artery bypass graft (CABG); however, autografts are not always available, synthetic grafts perform poorly, and allografts and xenografts dilate, calcify, and induce inflammation after implantation. We hypothesized that cross-linking of decellularized xenogeneic vascular grafts would improve the mechanical properties and biocompatibility and reduce inflammation, degradation, and calcification in vivo. To test this hypothesis, the bovine internal mammary artery (BIMA) was decellularized by detergents and ribozymes with sonication and perfusion. Photooxidation and pentagalloyl glucose (PGG) were used to cross-link the collagen and elastin fibers of decellularized xenografts. Modified grafts’ characteristics and biocompatibility were studied in vitro and in vivo; the grafts were implanted as transposition grafts in the subcutaneous of rats and the abdominal aorta of rabbits. The decellularized grafts were cross-linked by photooxidation and PGG, which improved the grafts’ biomechanical properties and biocompatibility, prevented elastic fibers from early degradation, and reduced inflammation and calcification in vivo. Short-term aortic implants in the rabbits showed collagen regeneration and differentiation of host smooth muscle cells. No occlusion and stenosis occurred due to remodeling and stabilization of the neointima. A good patency rate (100%) was maintained. Notably, implantation of non-treated grafts exhibited marked thrombosis, an inflammatory response, calcification, and elastin degeneration. Thus, photooxidation and PGG cross-linking are potential tools for improving grafts’ biological performance within decellularized small-diameter vascular xenografts.

Electrospun nanofiber scaffold for vascular tissue engineering

Due to the prevalence of cardiovascular diseases, there is a large need for small diameter vascular grafts that cannot be fulfilled using autologous vessels. Although medium to large diameter synthetic vessels are in use, no suitable small diameter vascular graft has been developed due to the unique dynamic environment that exists in small vessels. To achieve long term patency, a successful tissue engineered vascular graft would need to closely match the mechanical properties of native tissue, be non-thrombotic and non-immunogenic, and elicit the proper healing response and undergo remodeling to incorporate into the native vasculature. Electrospinning presents a promising approach to the development of a suitable tissue engineered vascular graft. This review provides a comprehensive overview of the different polymers, techniques, and functionalization approaches that have been used to develop an electrospun tissue engineered vascular graft.

Review: Tissue Engineering of Small-Diameter Vascular Grafts and Their In Vivo Evaluation in Large Animals and Humans

To date, a wide range of materials, from synthetic to natural or a mixture of these, has been explored, modified, and examined as small-diameter tissue-engineered vascular grafts (SD-TEVGs) for tissue regeneration either in vitro or in vivo. However, very limited success has been achieved due to mechanical failure, thrombogenicity or intimal hyperplasia, and improvements of the SD-TEVG design are thus required. Here, in vivo studies investigating novel and relative long (10 times of the inner diameter) SD-TEVGs in large animal models and humans are identified and discussed, with emphasis on graft outcome based on model- and graft-related conditions. Only a few types of synthetic polymer-based SD-TEVGs have been evaluated in large-animal models and reflect limited success. However, some polymers, such as polycaprolactone (PCL), show favorable biocompatibility and potential to be further modified and improved in the form of hybrid grafts. Natural polymer- and cell-secreted extracellular matrix (ECM)-based SD-TEVGs tested in large animals still fail due to a weak strength or thrombogenicity. Similarly, native ECM-based SD-TEVGs and in-vitro-developed hybrid SD-TEVGs that contain xenogeneic molecules or matrix seem related to a harmful graft outcome. In contrast, allogeneic native ECM-based SD-TEVGs, in-vitro-developed hybrid SD-TEVGs with allogeneic banked human cells or isolated autologous stem cells, and in-body tissue architecture (IBTA)-based SD-TEVGs seem to be promising for the future, since they are suitable in dimension, mechanical strength, biocompatibility, and availability.

Non-Autologous Grafts in Coronary Artery Bypass Surgery: A Systematic Review

BACKGROUND

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

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 and 7-18 months, respectively), 29 expanded polytetrafluoroethylene (ePTFE) 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 and 19 months, respectively), 39 Perma-Flow grafts (80% and 76.9% at 1-3 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 ePTFE grafts (94.7% and 81% at a mean follow-up of 27 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.

How I choose conduits and configure grafts for my patients-rationales and practices

Coronary artery bypass grafting (CABG) continues to be an effective therapy for many patients with lasting long-term durability and consistent outcomes, despite the development of percutaneous revascularization. The long-term outcome for surgical revascularization depends on multiple variables, including the choice of conduits. However, the choice of coronary conduits has been studied and debated for decades now. In this review article, we examined the current evidences and described our choice on coronary conduits and grafting strategies at our medical center.

64-slice computed tomography of bovine internal mammary artery coronary grafts

In cases where conventional aortocoronary grafts cannot be used, No-React bovine internal mammary artery is a possible alternative. The aim of this study was to assess the patency and clinical performance of bovine internal mammary artery as a coronary bypass conduit, using 64-slice computed tomography coronary angiography. Eleven patients (mean age, 68.2 + or - 5.9 years) received 11 bovine grafts between 2002 and 2006. Eight of these patients were alive after a mean follow-up of 29.4 + or - 16.3 months. Their mean additive EuroSCORE was 6.5 + or - 3.2. The mean number of distal anastomoses was 2.5 + or - 0.5. Six grafts were anastomosed to the right coronary artery, 2 to the left anterior descending artery, and 3 to the circumflex artery. All 11 bovine grafts were found to be occluded after 14.1 + or - 3.6 months. This demonstrates very poor results with the bovine coronary graft, thus we do not recommend its use, and we suggest considering an hybrid approach in selected cases.

Endothelial cell-seeded bovine internal mammary artery for complete revascularization

We present a 79-year-old woman with coronary heart disease who underwent complete revascularization by using a No-React bovine internal mammary artery seeded with autologous endothelial cells. Her postoperative course was uneventful, and the patient was recently in New York Heart Association functional class I. Multislice computed tomography imaging showed patent grafts at 20 months of follow-up.

Development and evaluation of a novel decellularized vascular xenograft

Although autogenous saphenous vein remains the standard for coronary and infrapopliteal bypass, many patients do not have a suitable vein. Attempts at developing a small-caliber vascular graft have failed largely due to occlusion, neointimal hyperplasia, or aneurismal degradation. We have designed and characterized a novel small-caliber vascular xenograft that may overcome these failure modes. To reduce immune reactions, porcine common carotid arteries were decellularized by enzymatic and detergent treatments. Histology and electron microscopic examination showed complete removal of cellular components while the extracellular matrix structure remained intact. To reduce thrombogeneity, decellularized vascular grafts were covalently linked with heparin. The efficiency of heparin linkage was demonstrated with toluidine blue staining and the antithrombogeneity of the heparin-treated grafts was demonstrated with a clot time test. Mechanical testing of the graft was performed. Decellularized-heparin-treated grafts were similar in compliance to fresh vessels and burst testing showed grafts to withstand pressures exceeding 10 times physiologic blood pressure. There was no difference in suture retention strength between fresh vessels and decellularized-heparin-treated grafts. Decellularized, heparinized grafts were implanted in dogs as carotid artery bypass grafts and showed smooth muscle cells densely populating the wall, and endothelial cells lining the lumen by two months. This study provides a new strategy to develop a small-caliber vascular graft with excellent mechanical properties, antithrombogeneity, and tissue compatibility.

Clinical experience with autologous endothelial cell-seeded polytetrafluoroethylene coronary artery bypass grafts

OBJECTIVE

Autologous endothelial cell seeding was used to improve the patency of 4-mm polytetrafluoroethylene vascular prostheses.

METHODS

Since 1995, 14 patients with coronary artery disease received 21 autologous endothelial cell-seeded polytetrafluoroethylene vascular bypass grafts for coronary artery revascularization. The polytetrafluoroethylene grafts were seeded with the endothelial cells in a multiple step procedure, including cell culture techniques before coronary bypass operation. With the use of extracorporal circulation and cardioplegic arrest, a bypass operation was performed by means of conventional surgical techniques.

RESULTS

After a mean postoperative follow-up of 27.7 months (range, 7.5-48 months), the graft patency rate is 90.5%. Follow-up angiograms of the aorta-coronary polytetrafluoroethylene bypass grafts showed patent bypasses in all cases except two. Angiograms of all 19 patent endothelial cell-seeded polytetrafluoroethylene bypass grafts showed a smooth luminal borderline without stenotic regions. The percutaneous transluminal angioscopic evaluation showed a glossy white and smooth endoluminal graft surface without any fibrin, platelet, or erythrocyte deposits. Intravascular ultrasonographic examinations confirmed the results.

CONCLUSION

Patency of autologous endothelial cell-seeded 4-mm polytetrafluoroethylene vascular prostheses as coronary artery bypass grafts was much better than that of unseeded polytetrafluoroethylene grafts. Further evaluations and a larger population of patients will prove whether the encouraging patency will last.

Coronary artery bypass grafting with an expanded polytetrafluoroethylene graft

BACKGROUND

We report our experience with the Perma-Flow aortocoronary-right heart graft in 15 patients in whom autologous conduits were not available.

METHODS

Fifteen patients received 39 coronary anastomoses--10 to left anterior descending coronary artery branches, 15 to circumflex coronary artery branches, and 14 to branches of the right coronary artery. Early angiography was done in 11 patients.

RESULTS

One patient died on postoperative day 17 of multiorgan failure. The graft was patent at postmortem examination. Of 30 coronary anastomoses at risk, 24 were patent. Three connections to the left anterior descending system were occluded in patients with an additional internal mammary artery graft to the same coronary system, and three connections to the circumflex system were occluded in patients with a history of major posterior infarction. Three of five distal anastomoses to the right atrial appendage were occluded, whereas all six connections to the superior vena cava were patent. None of the patients had shown recurrent angina at a mean follow-up of 10.9 months (range, 2-39 months).

CONCLUSIONS

The synthetic Perma-Flow coronary graft appears to be a safe alternative in patients in whom arterial or venous conduits are not available. Competitive flow may lead to anastomotic occlusions. The appropriate site for the distal arteriovenous fistula seems to be the superior vena cava.

Evaluation of a porcine internal mammary artery (No-React II) as a small-diameter conduit

BACKGROUND

The patency of biologic small-diameter vascular grafts in the aortocoronary position is still unsatisfactory. Most of the studies suggest that xenografts are to be avoided as an aortocoronary bypass.

METHODS

The porcine internal mammary artery treated by the No-React II procedure was developed for use as an alternative coronary artery bypass conduit. The attempt of this study was to evaluate the patency and histologic changes of the porcine internal mammary artery in animals. Five calves underwent coronary artery bypass grafting with a porcine internal mammary artery graft to the right coronary artery. After euthanasia of the animals 103 days later, the samples of these grafts were studied morphologically for patency, structural changes, calcifications, and inflammatory and immunologic response.

RESULTS

One animal died during the procedure as result of acute thrombosis of the porcine internal mammary artery graft. In the other 4 animals all grafts became occluded. In the histologic sections of the grafts we noted multiple calcifications and a host-graft immunologic reaction (severe chronic rejection).

CONCLUSIONS

The present study demonstrates a very poor experience with the porcine internal mammary artery (No-React II) conduit. We do not recommend this prosthesis for clinical use in humans.

Coronary flow in a prosthetic aorto-coronary bypass graft: first report of Possis Perma-Flow graft physiology in a patient

The coronary physiology of a prosthetic Perma-Flow coronary bypass graft conduit is demonstrated in the first patient at 1-yr follow-up. Coronary blood flow velocity was measured in the body of the graft and into the side-to-side anastomosis to the first diagonal branch. This case report demonstrates the first information on the coronary and prosthetic graft flow in a patient with atherosclerotic coronary disease.

Physical properties of a porcine internal thoracic artery fixed with an epoxy compound

This study aimed to investigate the physical properties of a porcine internal thoracic artery fixed with an epoxy compound. Fresh and glutaraldehyde-fixed porcine arteries were used as controls. Both the epoxy-fixed and glutaraldehyde-fixed porcine arteries showed significant increases in fixation index and denaturation temperature as compared to the fresh one. Additionally, the resistance of porcine arteries against bacterial collagenase in vitro degradation increased significantly after cross-linking with the epoxy compound of glutaraldehyde. The reduction of the tensile strength of the epoxy-fixed artery after bacterial collagenase degradation was more severe than in its glutaraldehyde-fixed counterpart. Generally, with increasing pH, temperature or fixative concentration, the fixation indices and denaturation temperatures of the epoxy-fixed porcine arteries increased. The results obtained in this study may be used to optimize the fixation process for developing a small-diameter biological vascular graft fixed by an epoxy compound.

Conduit options in coronary artery bypass surgery

The choice of graft conduit is crucial to the success of coronary artery bypass grafting (CABG) because the patency of a coronary conduit is closely associated with an uneventful postoperative course and a better long-term patient survival. The standard conduits used for CABG are the greater saphenous vein (GSV) and the internal thoracic artery (ITA). An excellent substitute conduit for coronary bypass operations that can be taken "off the shelf" is certainly the dream of every practicing cardiac surgeon. However, virtually every synthetic and biologic alternative to arterial conduits or autologous fresh saphenous vein has proved disappointing. Fortunately, patients with absolutely no autologous conduit alternatives are uncommon. Circumstances exist, however, that often necessitate the use of alternative conduits such as young hyperlipemic patients, absent or unsuitable autologous ITAs and GSV as a result of previous myocardial revascularization, peripheral arterial reconstruction, and varicose vein ligation procedures. This review provides an update on the clinical work done with all coronary conduits available for myocardial surgical revascularization.

Clinical and invasive 7-month follow-up of a patient with a synthetic coronary graft

The PossisR polytetrafluoroethylene Permaflow is a synthetic coronary graft which incorporates a Venturi resistor and which is anastomosed to the superior vena cava. Multiple anastomoses to the coronary vessels can be established in sequence until the graft is finally connected to the aorta. This aortocaval fistula enables permanent flow within the synthetic graft. We present the post-operative clinical and invasive findings of a 69-year-old female patient with a PossisR coronary graft. Follow-up angiography 3 and 7 months post-operatively showed patency of both coronary anastomoses and sufficient run-off to the native vessel segments. The left-right shunt induced by the graft was hemodynamically insignificant. Left ventricular function had improved significantly. 30 MHz intravascular ultrasound of the proximal part of the PossisR graft did not show an extra inner layer at the luminal side of the synthetic graft wall, so that relevant intimal thickening could be excluded after an interval of 7 months post implantation. Using an intravascular imaging technique, focal atherosclerotic lesions or thrombotic graft wall alterations could also be ruled out.

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.

Bovine internal thoracic artery graft for myocardial revascularization: late results

From May 1988 to March 1990, the bovine internal thoracic artery (ITA) graft, 3 mm in diameter, was used for coronary artery bypass grafting in 29 patients with the approval of the Japanese Ministry of Health. Excluding three postoperative deaths and 6 patients who rejected postoperative angiography, 20 patients (13 men and 7 women; mean age, 62 years; range, 37 to 80 years) were followed up angiographically for up to 4 years. Sites of bovine ITA anastomosis were as follows: anterior descending, 4; circumflex, 5; and right coronary artery, 11. The mean bovine ITA graft blood flow measured by electromagnetic flowmeter was 75.2 mL/min (range, 40 to 150 mL/min). During the mean follow-up of 45 months (range, 30 to 52 months), 12 patients underwent postoperative angiography once, 6 patients twice, and 2 patients three times. It revealed 14 of 16 (88%) bovine ITA grafts were patent within 2 postoperative months. Three of 6 (50%) were patent at 3 to 12 months, of which 2 patent grafts required balloon angioplasty for distal anastomotic stenosis. In 7 patients restudied later than 1 year (20, 24, 25, 44, 48, 50, and 52 months), one of seven grafts (14%) was patent. There was stenosis (> or = 50%) at four distal and one proximal bovine ITA anastomotic sites, but no focal stenosis was found in the trunk at any period. There was one late death due to renal failure, one myocardial infarction, and one mild angina due to bovine ITA graft failure.(ABSTRACT TRUNCATED AT 250 WORDS)

First clinical use of the Possis synthetic coronary graft

The Possis polytetrafluoroethylene Permaflow coronary graft incorporates a Venturi resistor within the graft. Insertion is constructed by creating an anastomosis to the superior vena cava with subsequent anastomoses in sequence to coronary arteries requiring grafting. Finally, the graft is sewn to the aorta. The Venturi resistor controls flow through the aortocaval fistula, maintaining systemic pressure proximal, permitting systolic and diastolic flow to the grafted coronary arteries while maintaining constant flow through the graft. Animal studies demonstrated long-term patency. This graft was implanted in a patient with unstable angina pectoris and inadequate native conduit. Catheterization 6 weeks postoperative revealed patency of all anastomoses.