Microvascular grafts: effect of diameter discrepancy on patency rates

This study examined the effects of diameter discrepancy between interpositional vein grafts within a range of 0.25 to 2 mm. One hundred rats underwent isolation of a 10 mm segment of the femoral artery, from which a 4 mm segment was removed. Venous grafts measuring 8 +/- 2 mm were interposed. The rats were categorized by their graft to artery diameter ratios. Patency was assessed upon completion and 4-6 days postoperatively. All surgical specimens were submitted to the pathology department for microscopic evaluation. Results showed Group I: graft to artery ratio 1:1, patency rate 90% (18/20); Group II: ratio 0.75:1, patency rate 80% (16/20); Group III: ratio 0.5:1, patency rate 60% (12/20), Group IV: ratio 0.25:1, patency rate 20% (4/20); Group V: ratio 2:1, patency rate 60% (12/20). It is concluded that 1:1 venous graft to artery ratios are optimal. When this is impossible, diameter discrepancies should be at least 0.75:1 for acceptable patency rates to be attained in microvascular grafting.     

A comparison of femoral artery grafts in diabetic and nondiabetic patients

Results of 154 consecutive femoropopliteal saphenous bypass grafts in 140 patients are reported.     

Effect of stasis on the patency of microvenous grafts in avulsed rabbit femoral vessels

Seventy femoral arterial avulsions with interpositional microvenous graft repairs were performed in rabbits and were divided into three groups. In Group A clamps were reapplied for 15 minutes with an overall patency rate of 97% after 3 weeks. The overall patency rate in Group B with 30 minutes reclamping was 93% three weeks later. Group C without clamping served as Controls and a 100% patency rate was achieved. The position of the microclamps, static blood in the region of the anastomoses and in the microvenous grafts as well as the time of reclamping up to 30 minutes did not influence the patency rate in damaged vessels after sufficient resection of injured vessel walls. The results of this experiment suggest that if necessary clamps can be reapplied safely in the clinical situation for up to 30 minutes after microvenous grafts have been completed to enable the microsurgeon to perform further dissection in a bloodless field.     

Optimal patency rates obtained in coronary artery grafting with circular vein grafts.

Twenty-two patients underwent coronary artery grafting with a circular vein graft comprising four or five distal coronary anastomoses. Postoperative angiographic evaluation showed patency in 90 (95.7 percent) of the 94 coronary anastomoses fashioned in this manner. All four occlusions occurred in the one patient whose graft comprised five anastomoses and was occluded beyond the first anastomosis on the right coronary artery (RCA). Eleven of the 94 anastomoses were made onto arteries with limited runoff. Blod flow averaged 214 ml. per minute (range 130 to 320) in the main portion of the graft and 59 ml. per minute (range 35 to 100) in the most distal segment. Flow doubled (averaged 403 ml. per minute) in the 11 grafts injected with papaverine. The technique of circular vein grafting is described in detail and potential pitfalls are outlined. The reasons for the high early patency rate are believed to be the following: (1) high flow in the proximal segment of the graft insuring patency of said segment, (2) termination on the left anterior descending (LAD) coronary artery providing good distal flow and patency. (3) diamond-shaped side-to-side anastomoses (SSA's) preventing angulation of the graft at these crucial points, and (4) nearly equidistant anchoring at the site of the multiple anastomoses giving the graft a smooth, even contour.     

Rat femoral vein-to-vein grafts as a microvascular practice model: factors that influence patency

The rat femoral vein has become a standard model for microvascular anastomosis practice as well as for research investigations into various manipulative influences upon venous patency. Although vein grafts to the rat artery are the focus of many experimental studies, few reports have investigated vein-to-vein grafts. This study examines the short-term patency (1-3 days) of vein grafts interpositioned to the rat femoral vein. Several factors are studied for their ability to alter the patency rate. The results indicate that patency is difficult to achieve following the creation of a second serial anastomosis (construction of a vein-to-vein graft). Systemic heparin consistently improves patency rates, and trends toward increased patency are seen for reduction in longitudinal tension of the repaired vessel. It is also implied that a deeper understanding of venous hemodynamics and thrombotic events may lead to improved methodologies in the clinical applications of microvenous repairs. These results indicate that rat vein-to-vein grafts may provide a challenging microvascular training model, while introducing the novice microsurgeon to some of the complicating factors encountered with microvascular grafting.     

Y-grafts and sequential grafts in coronary bypass surgery: a critical evaluation of patency rates.

In a series of 584 patients undergoing coronary bypass, 425 patients received Y-grafts, sequential grafts, or a combination of the two. The saphenous veins from the legs frequently had Y- or double Y-branches suitable for bypasses. As many as 5 grafts have been served satisfactorily by a single proximal anastomosis. Simultaneous procedures included 45 left ventricular aneurysmectomies, 18 valve replacements, 7 carotid endarterectomies, repairs of a ventricular septal defect, an acute dissection, and coronary arteriovenous fistulas, with a total surgical mortality of 6 (1.4%). Restudy to determine graft patency was undertaken only in the 59 patients with unsatisfactory surgical results. These patients represent the worst 10% of the series in terms of surgical results. The patency rate for proximal anastomoses was 93%; Y-branchings, 93%; distal end-to-side anastomoses, 89%; and distal side-to-side anastomoses, 89%. Fifty-eight patients (98%) had at least 1 patient graft, and in 47 patients (80%) all anastomoses were patent up to six years after operation. Six patients underwent reoperation without any deaths.     

Prevention of aorta-coronary bypass graft occlusion. Beneficial effect of ticlopidine on early and late patency rates of venous coronary bypass grafts: a double-blind study

The efficacy of coronary bypass grafting obviously being linked to graft patency, it is compulsory to look for any innovation that could improve the patency rate. Ticlopidine, an antiplatelet drug, was tested against placebo in a double-blind trial: 173 patients (475 grafts) subjected to venous coronary artery bypass grafting were randomly treated with ticlopidine (250 mg twice daily) or placebo from the second postoperative day for 12 months. Graft patency was assessed by digital angiography on days 10 (99.4% of the patients), 180 (98.2%), and 360 (91.7%). The effect of treatment on platelet aggregation and bleeding time were measured concomitantly; a clear-cut effect was demonstrated at each interval. Intention-to-treat graft-by-graft analysis shows that ticlopidine significantly reduced the graft occlusion rate on day 10 (7.1% versus 13.4%, p less than 0.05), day 180 (15.0% versus 24.0%, p less than 0.02), and day 360 (15.9% versus 26.1%, p less than 0.01). Sequential grafts to the left anterior descending coronary artery, with side-to-side anastomosis to diagonal branch(es), are less frequently occluded than individual grafts. On the contrary, grafts to endarterectomized vessels occlude more frequently. Individual patient-by-patient analysis shows that patency of all grafts at each study time, is more frequent in the ticlopidine group. The difference is significant when one considers patients without sequential or endarterectomized grafts. The difference is also present at each study time: day 10 (84.4% versus 66.7%, p less than 0.05), day 180 (74.4% versus 52.3%, p less than 0.05) and day 360 (75.0% versus 52.5%, p less than 0.05). Results are even more impressive if one excludes from analysis the four patients in the ticlopidine group in whom administration of the drug was delayed. This supports previous suggestions that early therapy is necessary. These results show that graft occlusion occurs mainly in the first 6 postoperative months. The incidence of occlusion is significantly reduced by ticlopidine therapy.     

Improved long-term patency of infragenicular polytetrafluoroethylene grafts

This article reviews late graft patency and the incidence of postoperative complications in 75 infragenicular polytetrafluoroethylene bypass grafts (20 posterior tibial, 26 anterior tibial, and 29 peroneal). All patients received a heparin infusion after operation and were switched to warfarin before discharge to maintain coagulation parameters (prothrombin time and partial thromboplastin time) approximately twice that of control subjects. Primary procedures were done in 14 patients (19%), and the remaining patients had one or more previous procedures. Ninety-seven percent of patients had limb-threatening ischemia. Graft patency was confirmed by interval examinations and Doppler ankle pressure measurements. The mean follow-up was 36 months, and long-term graft patency (4 years) was determined by life-table analysis. The 2-year cumulative patency rate for this group was 45% and the 4-year patency rate was 37%. The latter is significantly better than the patency rates of 12% reported for similar untreated randomized grafts. Anticoagulation was subtherapeutic in 15 patients at the time of graft thrombosis, and if these were excluded, the 2- and 4-year patency rates were 58% and 50%, respectively. Hematomas requiring drainage occurred in 10 patients (13.3%) and six patients (8%) developed wound infections, but graft infection occurred in only two patients. Two patients (2.6%) developed late bleeding complications necessitating cessation of the warfarin. There was one fatal perioperative myocardial infarction (1.3%) and four late deaths, none of which were related to the warfarin therapy. Although the incidence of postoperative hematoma and wound infection was increased, late complications occurred infrequently.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparative review of early and intermediate patency rates of polytetrafluoroethylene and autogenous saphenous vein grafts for lower extremity ischemia

One hundred nine primary bypass operations were performed on 97 patients who had limb ischemia caused by arteriosclerosis obliterans, over a 32-month period starting in January, 1978. The majority of those procedures were done for rest pain or gangrenous changes. The greater saphenous vein was used whenever possible (44 of 109 procedures), and a polytetrafluoroethylene (Gore-Tex) prosthesis was used in 65 of 109 procedures. Average follow-up was 9.3 months. The cumulative patency rate in all vein grafts was 93.1% at 1 month and 73.4% after 31 months, whereas the cumulative patency rate for polytetrafluoroethylene was 83.3% at 1 month and 51% at 31 months. The difference is not statistically significant (0.10 less than P less than 0.25). In above-knee procedures for claudication, polytetrafluoroethylene performed identically to vein (P greater than 0.50), although vein appeared to perform better in above-knee procedures done for rest pain or necrosis. A limited number of below-knee revascularizations were performed, and although no conclusions of statistical significance can be drawn, cumulative patency of vein appeared to be better than polytetrafluoroethylene. For additional comparative analysis, this study was compared to a previous study in which Dacron was used in femoropopliteal arterial reconstructions. Patency rates in above-knee revascularizations appeared to be comparable in Dacron and polytetrafluoroethylene. Diabetes did not appear to alter age of onset of disease or patency rates, although smokers became symptomatic 10 years earlier than nonsmokers. Although the early and long-term results of arterial reconstructions in the ischemic extremity are known, the availability of new alternate arterial prostheses raises the question of the optimum material depending on the specific clinical circumstances.     

Long-term patency of aorto-coronary saphenous vein grafts]

One hundred eighty-two cases with 814 aorto-coronary saphenous vein grafts were studied according to coronary risk factors (smoking, hypertension, hyperlipidemia, diabetes mellitus, obesity and family history). The patency rates of all cases were as follows, early-term (within one year after operation): 92.3%, mid-term (within 5 years after operation) 80.7%, long-term (more than 5 years after operation): 66.0%. Coronary risk factors have great influence upon the mid- and long-term patency, especially upon the latter. The long-term patency rate of the grafts complicated with hyperlipidemia was 57.4% and that without hyperlipidemia was 81.8% (p less than 0.01). Hyperlipidemia, complicating 55.5% of all cases, was one of the most influential factors on the patency and also the most difficult one to be controlled. In the United States and Europe, many cases were complicated with hyperlipidemia, and it was considered that the poor patency of the saphenous vein grafts in those countries was due to this fact. Pathological studies revealed that hyperplasia of intima and media, characteristics of venosclerosis, appeared frequently in the saphenous vein grafts having more than three risk factors, and that the factors had effect not only upon arteries but also upon veins. So we conclude that saphenous vein grafts are the materials of good long-term patency, and that the control of the risk factors, particularly hyperlipidemia, is the key to improve the patency.     

Achieving better patency rates and neoendothelialization in 1-millimeter polytetrafluoroethylene grafts by varying fibril length and wall thickness.

This study evaluates the effects of different fibril lengths and wall thicknesses on patency and neoendothelialization in 1 mm inner diameter polytetrafluoroethylene (PTFE; Gore-Tex) grafts and highlights the importance of longer fibril lengths and matching wall thicknesses. Fibril lengths tested were 30, 60, and 90 microns. The grafts had a wall thickness ranging from 0.18 to 0.34 mm. Ninety-six grafts were implanted in the infrarenal aorta of Wistar rats. Grafts were harvested at various intervals and examined macroscopically, by light microscopy, and by scanning electron microscopy. Both the highest patency rates and the best grades of neoendothelialization were observed in the 90 microns fibril length grafts, while the lowest of both were seen in the 30 microns fibril length grafts. From this study we conclude that 90 microns fibril length PTFE can be considered a valid micrograft for bridging arterial defects in microvascular reconstructive procedures.     

Factors influencing patency of saphenous vein grafts.

To determine factors affecting saphenous vein graft patency, 218 grafts in 66 unselected patients were studied angiographically 1 year after operation. Fourteen variables were extracted from the angiograms, electrocardiograms, and intraoperative flow measurements to assess their predictive value. Preoperative coronary vessel diameter and degree of proximal stenosis measured angiographically correlated significantly with graft patency. Graft patency for vessels greater than 1.5 mm in diameter with greater than 70% stenosis was 93% (98 out of 105). Vessel size at operation and the presence of reactive hyperemia greater than 20 ml per minute also correlated significantly with graft patency. Reactive hyperemia increased significantly as the severity of the vessel stenosis proximal to the graft increased, thus suggesting a mechanism for the improved patency rate of grafts to more stenotic vessels. The patency rate of the end-to-side component of a continuity graft (left anterior descending coronary artery and diagonal or marginal artery in 1 graft) was 100% and of the side-to-side component, 77%. This study shows that the patency rate for saphenous vein grafts compares favorably with the reported patency for internal mammary grafts when critical factors such as vessel size (greater than 1.5 mm) and degree of stenosis (greater than 70%) are considered in bypass selection.     

Factors influencing patency of femoropopliteal artery bypass grafts

An analysis of 276 femoropopliteal bypass procedures performed in 264 patients at the Columbia-Presbyterian Medical Center over the past two decades showed a direct relationship of graft patency to preoperative popliteal artery runoff. Functional results were better than patency results. Sympathectomy and anticoagulation did not improve graft patency. The risk of amputation is outweighed by the benefits of restoration of blood flow to the ischemic extremity by a bypass procedure.     

Aspirin improves the patency rate of seeded vena cava grafts

The purpose of this study was to evaluate the effectiveness of aspirin (ASA) and porcine endothelial cell seeding in improving the patency rate of vena cava grafts. Thirty-nine dogs underwent infrarenal vena cava replacement by 10 cm lengths of 8 mm I.D. ringed polytetrafluoroethylene grafts. Thirty-one grafts were seeded with 1-1.5 x 10(6) porcine aortic endothelial cells while eight were not (GIII). Of the seeded group, 16 animals received no ASA (GI), while 15 others (GII) were given ASA (325 mg) daily starting two days preoperatively and continuing until sacrifice. Venograms were performed on the fourth postoperative day. Grafts were harvested 32 days after insertion and evaluated for patency rate and endothelialized surfaces. The 32-day patency rate was significantly higher for GII than for GI and III animals (67% vs. 13 and 25% respectively). Endothelialized surface was higher in GII than Gi and III (67% vs. 16% and 18% respectively). We conclude that endothelial cell seeding alone does not prevent graft closure and that a combination of ASA and cell seeding significantly increases the patency rate of vena cava grafts.