Further experience with the saphenous vein used in situ for arterial bypass

Intra-Operative Digital Angiography as a Control of the in Situ Saphenous Vein By-Pass Grafts

Forty-two patients undergoing in situ saphenous vein by-pass grafting procedures, in two patients bilaterally, were examined intra-operatively with digital subtraction angiography. In 19 (43%) of the examinations the graft and the anastomoses appeared adequate. In 8 cases (18%) significant abnormalities were found, including stenoses (11 %), deficient anastomoses (5%) and graft kinking (2%). Remaining arteriovenous fistulas were found in 17 patients (39%). In most cases immediate correction was possible avoiding later re-operation. At follow up 11 of the 44 grafts were occluded, 10 of these during the first five months and of these five during the first week.

Prognosis for Limb Loss in Patients with Chronic Critical Ischemia Considered Technically Inoperable

Of 427 patients with chronic critical ischemia of the lower extremity, admitted for infrapopliteal bypass surgery, 34 (8%) were considered technically inoperable : in 26 cases due to total occlusion of the runoff vessels and in 8 due to a poor runoff and no suitable vein. The symptoms were rest pain in 24 cases and gangrenous ulceration in 10. During a follow-up from eight to twenty-eight months 5 (15%) patients improved significantly and complained only of claudication. Three patients, suffering rest pain, were unchanged up to nine months, and 25 (74%) patients had a major amputation performed. The remaining patient died the day after admission. The mortality rate of these patients was significantly increased compared with that of the 393 patients who underwent infrapopliteal bypass surgery, who in turn had a higher mortality rate than that of an age- and sex-matched Danish population. Clinical judgment, together with ankle and toe pressure measurements, could not identify the group of patients who preserved their limb.

Interpositional substitution of free vas deferens segment autografts in rat: feasibility and potential implications

Background

Insufficient vas length for performing a tension-free vasovasostomy is a problem occasionally encountered by microsurgeons. Herein we evaluated utilization of a non-vascularized vas deferens autograft in a rat model.

Methods

Segments of isolated vas deferens, 2.5 cm in length, were used as bilateral autografts in 15 rats. Each autograft was implanted between the two transected ends of vas deferens using end-to-end anastomosis. Fertility, sperm motility, and graft survival was evaluated and compared with the control group.

Results

At the end of the 3 months, 9/15 (60%) rats were able to breed successfully and 24 (80%) vas grafts were patent and viable. Large granulomata developed at the proximal anastomosis sites in 6 (20%) autografts that failed. Unilateral minimal fluid leakage was observed in 6 (20%) of the proximal (testicular end) anastomosis sites in those rats that were able to breed. Histological evaluations demonstrated that graft survival was associated with mild to severe changes in the structure of the vas autograft. On semen analysis 76% of the sperms in the experimental group had forward motility compared to 78% in the control group (p > 0.05).

Conclusions

Vas autograft can successfully be performed in a rat model with ultimate breeding capability.

In Situ Saphenous Vein Bypass—Forty Years Later

In situ saphenous vein bypass, which was performed first by Rob in 1959, but introduced by Hall in 1962, has been widely applied as an alternative to the reversed bypass. Now, forty years later, it seems appropriate to review its current place and technique. Of the presumed original benefits of the in situ operation, it is now clear that the hemodynamic flow of converging (in situ) versus diverging vein (reversed) boundaries plus better vein/artery size match are the main advantages. It is now popular belief that the reversed saphenous vein graft to the popliteal artery has no significant hemodynamic disadvantage because the vein is of comparable diameter at the knee and in the groin. In contrast, vein bypass from the groin to the ankle strongly favors the in situ procedure because of the convergence of the walls of the vein below the knee and better vein/artery size match. The most controversial facet of the in situ operation has been the question of valvulotome is superior to lyse valves and whether to perform the operation open as originally described, or closed to avoid skin complications from a long groin to ankle incision. Preoperative vein mapping is advantageous for all saphenous vein conduit operations. For open leg in situ procedures, skin bridges and incisions made directly over the vein, directed by mapping, will minimize skin complications. Use of endoscopic in situ techniques is ideal but only with an experienced endoscopist. Valve lysis has improved but is still not foolproof.

Infrainguinal arterial reconstruction for claudication: is it worth the risk? An analysis of 409 procedures

PURPOSE

Infrainguinal reconstruction traditionally has been reserved for patients with limb-threatening ischemia. Surgery for debilitating claudication, however, has been discouraged as a result of the perceived fear of bypass graft failure, limb loss, and significant perioperative complications that may be worse than the natural history of the disease. In this study, the results of infrainguinal reconstructions for claudication performed during the past 10 years were evaluated for bypass graft patency, limb loss, and long-term survival rates.

METHODS

Data were collected and reviewed from the vascular registry, the office charts, and the hospital records for patients who underwent infrainguinal bypass grafting for claudication.

RESULTS

From 1987 to 1997, 409 infrainguinal reconstructions were performed for claudication (9% of all infrainguinal reconstructions in our unit). The patient population had the following demographics: 73% men, 28% with diabetes, 54% smokers, and an average age of 64 years (range, 24 to 91 years). Inflow was from the following arteries: iliac artery/graft, 10%; common femoral artery, 52%; superficial femoral artery, 19%; profunda femoris artery, 16%; and popliteal artery, 2%. The outflow vessels were the following arteries: 165 above-knee popliteal arteries (40%), 150 below-knee popliteal arteries (37%), and 94 tibial vessels (23%). The operative mortality rate was 0%, and one limb was lost in the series from distal embolization. The primary patency rates were 62%, 77%, and 86% for above-knee popliteal artery, below-knee popliteal artery, and tibial vessel reconstructions at 4 years, and the secondary patency rates were 64%, 81%, and 90%, respectively. Cumulative patient survival rates were 93% and 80% at 4 and 6 years as compared with 65% and 52%, respectively, for infrainguinal reconstructions performed for limb salvage.

CONCLUSION

Infrainguinal arterial reconstruction for disabling claudication is a safe and durable procedure in selected patients. These data indicate that concern for limb loss, death, and limited life span of the patients with this disease may not be warranted.

Venous allografts for infrainguinal vascular bypass

Between 1978 and 1993, 107 patients received venous allografts for infrainguinal revascularization because autogenous material was unavailable. These operations comprised 7.4% of 1442 reversed vein bypass procedures performed during the same period. Alloveins were harvested during varicose vein stripping and stored up to 10 days in saline solution containing heparin and antibiotics. Veins with or without minimal degenerative changes were used and when necessary segments were sutured end-to-end to obtain a convenient length. The patients comprised 95 men and 12 women of age range 44-87 years. All operations were performed for limb salvage (rest pain and gangrene); 40 femoropopliteal and 67 femorocrural bypasses were performed; 66 were primary reconstructions and 41 secondary reconstructions. The operative mortality rate was 3.7%. Early thrombosis occurred in 18 patients (16.8%), nine of whom were successfully reoperated upon. The cumulative patency rates for all bypass operations was 82.9%, 38.7% and 21.3% at 30 days, 3 and 5 years, respectively, the limb salvage rates being 84.8%, 48.0% and 29.2%, respectively. Allografts may have a place in lower-limb bypass surgery in the absence of veins, polytetrafluoroethylene or human umbilical vein.

Have the results of infrainguinal bypass improved with the widespread utilisation of postoperative surveillance?

OBJECTIVES

The objectives of this study were to assess the impact of Duplex surveillance on the results of infrainguinal vein grafts. A review has been performed comparing the outcome of vein grafts undergoing Duplex surveillance plus prophylactic treatment of stenoses to that of vein grafts followed clinically.

DESIGN, PATIENTS, AND METHODS

Only studies providing information on occlusion rates were included. Mortality and limb salvage rates were also analysed but were not available from all studies.

RESULTS

2680 surveillance and 3969 non-surveillance vein grafts were analysed. There was no significant difference between the two groups with respect to presence of critical ischaemia (p=0.3) and level of distal anastomosis (p>0.5). Surveillance identified 493 stenoses in 469 (19%) grafts, 397 (16%) grafts were treated by surgery (248; 62%) and angioplasty (149; 38%). Ninety-eight (26%) grafts developed recurrent stenoses. Total number of deaths, total number of occluded grafts and number of occlusions after 30 days were significantly greater for the non-surveillance group (p<0.001; p<0.001; p<0.01). Perioperative occlusion rates were not significantly different (p=0.1). Few surveillance studies reported limb salvage rates (6 of 17). The numbers of amputations were not significantly different between the two groups (p>0.5).

CONCLUSIONS

The patency of infrainguinal vein grafts would appear to be improved as a result of surveillance. However, no improvement in limb salvage has been demonstrated.

Infragenicular in situ vein bypass graft occlusion: a multivariate risk factor analysis

Early postoperative thrombosis and the later development of graft stenoses are the two major causes of vein bypass graft failure. The risk factors for both these outcomes were analysed in a multivariate analysis of 82 consecutive infragenicular in situ vein grafts. Twenty-four grafts failed within 30 days but eight were successfully revised. Technical errors accounted for six of the failures. A multivariate analysis revealed graft resistance > 1.4 peripheral resistance units (odds ratio 5.8, 95% C.I. 1.6-20) as the only independent risk factor for early graft failure. Eighteen grafts (27%) developed a stenosis most commonly in the distal third of the graft (46%). Poor quality, small diameter vein was the only independent risk factor for graft stenosis (odds ratio 7, 95% C.I. 1.5-34). Composite vein grafts, where narrowed and thickened vein had been replaced, had a significantly lower stenosis rate (difference in proportions 0.41, 95% C.I. 0.1-0.8, Mann-Whitney U test).

Infrainguinal vein graft stenosis

Although knowledge of the biological processes involved in the development of intimal hyperplasia has increased markedly in recent years, the precise aetiology of infrainguinal vein graft stenosis remains undetermined. Current therapy is therefore directed at treatment of the established lesion rather than its prevention. There seems little doubt, however, that recent advances in understanding of the vascular biology of normal and pathological saphenous vein will eventually lead to specific targeted therapy that will allow the prevention of vein graft stenosis.

The influence of harvesting technique on endothelial preservation in saphenous veins

To study optimal conditions of preparation of saphenous veins as coronary artery bypass grafts, segments of saphenous veins were obtained from 29 consecutive patients undergoing coronary artery bypass grafting. The saphenous vein segments were divided into three groups. In Group I, 10 saphenous vein segments were harvested using a "no-touch" technique without any other preparation aids. In Group II, 10 saphenous vein segments were removed while distended at 70-120 mm Hg with a balanced pH electrolyte solution at 37 degrees C. In Group III, consisting of 10 saphenous vein segments, nitroglycerin (1 microgram/ml) was added to the distending solution used in Group II. Samples of saphenous vein were assessed in a blind study using light and scanning electron microscopy to estimate endothelial cell preservation by the three harvest techniques. Saphenous veins receiving only a no-touch dissection technique without distention solution (Group I) revealed significantly better endothelial preservation (P less than 0.005). The administration of distention solution alone, or with nitroglycerin, to saphenous veins in situ using our operative technique during harvest does not appear to protect endothelial-integrity and may be harmful.

The effect of arteriovenous fistulas on in situ saphenous vein bypasses

Intraoperative identification and later development of arteriovenous fistulas were investigated prospectively in 70 in situ saphenous vein bypass procedures. Surveillance was performed by completion arteriography and intra- and postoperative continuous wave Doppler examination. The intraoperative Doppler examination identified 89% of those branches with sufficient flow to opacify the deep venous system on completion arteriogram. Half of the missed fistulas underwent spontaneous thrombosis, and in only one case did the arteriovenous fistula lead to hemodynamic symptoms demanding surgical closure of the fistula. Pursuing a policy of selectively ligating fistulas that only fill the deep venous system on completion arteriography led to an additional nine arteriovenous fistulas. Developed over an average follow-up of six months, four patients presented symptoms of edema and swelling and were relieved upon closure of the fistulas. The incidence of bypass thrombosis did not differ significantly among patients with remaining arteriovenous fistulas, patients who developed fistulas during follow-up, and patients who had no signs of arteriovenous fistulas. It seems justified to continue selective intraoperative ligation of arteriovenous fistulas based on continuous wave Doppler.

Results of infrainguinal revascularization with reversed vein conduits: a modern control series

To determine the outcome of infrainguinal reversed vein bypasses in the modern era, we reviewed the results of 120 consecutive reversed vein grafts performed from March, 1986 to March, 1990. Forty-nine bypasses were to tibial, peroneal, or pedal arteries, 46 grafts to the below-knee popliteal artery, and 25 grafts to the above-knee popliteal artery. Limb salvage was the indication for revascularization in 70% of patients. All grafts were followed with serial, duplex scan, peak-systolic graft flow velocity measurements every three months for one year and every six months thereafter. The primary life table patency rate at 36 months was 67.6% for the entire series; the secondary patency rate was 92.5%. The secondary patency rate reflects the impact of graft revisions resulting from the detection of failing grafts by duplex scanning. Patency rates of reversed vein grafts to the tibial arteries at 36 months (73.8% primary and 89.8% secondary) were equivalent to those performed to the popliteal artery. Our current patency rates with reversed vein grafts are comparable or superior to those reported for in-situ vein conduits and suggest that operative technique and meticulous follow-up are more important with respect to long-term graft durability than whether the vein is used in the in-situ or reversed configuration.

Nonreversed saphenous vein grafts for coronary artery bypass grafting

Between August 1985 and December 1988, valvotomized saphenous vein grafts were used in 365 patients undergoing coronary artery bypass grafting (CABG). In this operation, the femoral end of the vein is attached to the aorta and the pedal end is attached to the coronary artery. Vein diameters measured 8 +/- 2 mm at the femoral end, 4.5 +/- 1.2 mm at the knee level, and 3.5 +/- 1.3 mm at the ankle. Ratios between levels were as follows: knee to femoral end, 0.56, and ankle to femoral end, 0.43. The ratio of knee to femoral end was 0.42 in cases with vein midthigh bifurcation. There were 1,310 grafts implanted (3.6 per patient). In 341 patients, CABG alone was performed, and 24 patients had combined procedures: 11 had CABG with mitral valve replacement, 9 had CABG with aortic valve replacement, 2 had CABG with repair of postinfarct ventricular septal defect, and 2 had CABG with automatic defibrillator implantation. Follow-up (up to 3.5 years) was attained in 97% of patients. For various reasons, 34 patients had a second angiogram between 3 and 41 months postoperatively. Of 120 vein grafts, 108 (90%) were patent. At autopsy, 11 patients with 45 vein grafts had 43 patent and clean grafts and two thrombosed. Use of nonreversed saphenous vein for coronary bypass is recommended. It assures a large proximal anastomosis, natural vein bifurcations can be used with fewer proximal anastomoses, better vein-coronary artery size matching is obtained, and the patency rate is satisfactory.

The in situ bypass above the knee

The anatomical location of the saphenous vein in the distal thigh allows for construction of an in situ bypass to the above-knee popliteal artery. The authors have performed over 1400 in situ bypasses in the past 10 years. Forty-three of these have been to the above-knee popliteal artery. Thirty-three bypasses were performed for limb threatening ischemia, seven for disabling claudication and three for microemboli. Mean patient age was 67 years, 51% were males, 44% had diabetes mellitus, and 93% smoked. Grafts were followed from one to 108 months. The cumulative patency rate at two years was 90% and at four years 77%. Patency rates compare favorably to those of femoral-to-above-knee popliteal bypasses constructed using reversed saphenous vein or polytetrafluoroethylene. The authors found that the in situ femoral-to-above-knee popliteal bypass is a technically easy procedure requiring short operative times and has a low morbidity rate. In those select patients in whom a femoral-to-above-knee bypass is the procedure of choice the in situ bypass should be considered.

In situ tibial reconstruction. State-of-the-art or passing fancy

To further evaluate the efficacy of in situ saphenous vein bypass, the authors have reviewed their experience with in situ bypass. Between October 1981 and December 1985, 120 in situ saphenous vein bypass were performed; 81 were to infrapopliteal vessels. All procedures were performed for limb salvage. The mean patient age was 74 years, and 74% were men, 57% had diabetes mellitus, 92% were smokers, and 72% had hypertension and/or coronary artery disease. All patients were evaluated by preoperative noninvasive testing and biplanar angiography. All procedures were performed by the valve incision technique. The vein utilization rate was 91%. Grafts were routinely placed into isolated tibial segments and foot vessels without evidence of a patent pedal arch. Follow-up information was obtained at 3-month intervals. Patency and limb salvage data were calculated by life-table analysis. The cumulative patency rates were 98% at 1 month, 88% at 12 months, and 82% at 50 months. These data demonstrate that the in situ bypass maintains an excellent patency rate and provides durable limb salvage.

Real-time duplex ultrasound mapping of the greater saphenous vein before in situ infrainguinal revascularization

From November 1983 through September 1985, 102 greater saphenous veins (GSVs) were assessed and mapped by means of real-time duplex ultrasonic scanning before in situ infrainguinal revascularization. Each GSV was also visually assessed at operation. Eighty-five GSVs were successfully used for infrainguinal revascularization; duplex scanning correctly identified 82 of these GSVs as being acceptable for use in in situ bypass. Seventeen GSVs were unacceptable for in situ bypass; duplex scanning correctly identified 11 of these as being unacceptable. Duplex scanning provides anatomic information about the GSV, including size, patency, course, varicosities, double segments, and tributaries. This information permits the surgeon to perform infrainguinal revascularization expeditiously.

The success of in situ vein grafting: early results in comparison with the reversed vein technique

In a 6-year retrospective analysis of 341 consecutive femorodistal autogenous vein bypasses, results from 104 in situ veins (IS) were compared with 209 reversed veins (RV). The groups were comparable for age, sex, diabetes, indication for surgery and calf vessel run-off, but a significantly higher proportion of the in situ group had a lower distal anastomosis (16% IS, 6% RV, chi 2 = 7.1 P less than 0.01). Overall, operative mortality was 2% and early graft failure was similar in both groups (11% IS, 12% RV, P = NS). Cumulative graft patency rates were 74% IS, 79% RV at one year and 71% IS, 71% RV (P = NS) at three years. Cumulative limb survival rates were 81% IS, 85% RV at one year and 79% IS, 81% RV [P = NS) at 3 years. These results demonstrate that the in situ technique has been used in a wider variety of patients and yielded similar early and intermediate term results to reversed vein.

Arterial reconstruction at diverse sites using nonreversed autogenous vein. An application of venous valvulotomy

Improved instrumentation for venous valve extirpation has allowed rapid development of the in situ technique for femoral-tibial arterial reconstruction. Extension of this valvulotomy technique permits the expeditious construction of branched, nonreversed saphenous vein grafts for multiple vessel revascularization, and allows use of veins otherwise unsuitable in length for certain arterial bypass procedures. The nonreversed vein graft also appears to offer advantages over the reversed graft with regard to the size of the proximal and distal anastomoses when used as an aortorenal or iliorenal graft as well as in other anatomic locations. Over the past 30 months these techniques were used to implant 10 vein grafts at diverse sites in nine patients with initial success in all instances and one late graft failure.

The evolution of morphologic and biomechanical changes in reversed and in-situ vein grafts

A comparative study of experimental reversed (RV) and in-situ (INS) vein grafts with respect to the evolution of morphologic and compliance characteristics was done in a canine model. In addition, the compliance characteristics in a series of human INS vein grafts were recorded as a function of time after operation. At 6 months after implantation, all experimental grafts displayed well-developed intimal hyperplasia. There was no significant difference in either absolute intimal thickness (INS 0.133 +/- 0.09 mm vs. RV 0.085 +/- 0.06 mm; NS) nor in the percentage of the total wall thickness occupied by the intima when experimental INS grafts were compared with RV grafts after 6 months. Similarly, compliance values of INS and RV vein grafts were similar at all time intervals examined up to 6 months after operation. Thirty-three human INS vein grafts had a mean compliance value of 1.74 +/- 0.72 (percent radial changes per mmHg X 10(-2) at a median postoperative interval of 14 weeks. This value did not differ significantly from those measured in the INS vein grafts. Although all vein grafts examined retained their native viscoelastic properties, this study suggests that functioning human INS vein grafts are less compliant than previously suspected on the basis of prior ex-vivo and clinical studies of RV saphenous vein grafts. The purported clinical superiority of the INS vein graft cannot be explained on the basis of superior biomechanical performance or failure to develop intimal hyperplasia.

Valvular obstruction of blood flow through saphenous veins

To measure effects of vein valves upon blood flow through venous bypass conduits, 15 human saphenous veins (mean length 40.6 cm, 5.3 valves/vein) were perfused with normal saline at constant pressure (100 mm Hg). Flow through vein was measured before and after valve bisection. Vein valves were bisected using Leather's techniques. After valve bisection, flow in antegrade and retrograde directions was measured in seven veins. These data were analyzed using paired t tests. Antegrade flow through seven veins with intact valves averaged 317.1 cc/min. With valve bisection this increased significantly (P less than 0.001) to 474.3 cc/min. Retrograde flow through veins with valves bisected increased significantly (P less than 0.0001) to 428.3 cc/min. Eleven veins (mean length 42.2 cm, 5.6 valves/vein) perfused simulated capillary beds with banked blood using pulsatile flow (mean pressure 92 mm Hg). Flow, again, was measured before and after valve bisection. Data were analyzed using the paired t test. Antegrade flow increased from 124.4 cc/min in veins with valves intact to 142.5 cc/min once valves were bisected (P = 0.02). These data demonstrate that saphenous vein valves cause significant obstruction to blood flow under conditions similar to those in the arterial system. Bisection of vein valves significantly increases flow through vein. Improved patency of vein grafts using valve bisection techniques may be explained by increased blood flow alone.

In situ saphenous vein bypass for occlusive disease in the lower extremity

In situ saphenous vein bypass, using the new valve incision techniques, has shown great promise in the early clinical trials to date. This procedure allows disruption of the venous valves without removal of the vein from its bed, thus allowing preservation of the vasa vasorum and maintenance of the endothelial integrity of the veins. This has allowed an overall improvement in the patency rates of the lower extremity bypasses, particularly in the bypasses to the infrapopliteal position. Also, and perhaps most important, it has permitted the use of smaller veins, with a minimum diameter of 2 mm. This greatly increases the number of patients who can benefit from such a vein bypass since reversed vein bypasses previously have required veins to have a minimum diameter of 3.5 to 4 mm. Long-term follow-up of in situ bypasses is not yet available. However, if the encouraging preliminary results of these bypasses are substantiated on long-term follow-up, in situ saphenous vein bypass may well become recognized as the procedure of choice for lower extremity bypass.

Ankle bypass: should we go the distance?

This report reviewed the results of 47 distal arterial reconstructions to or below the level of the malleolus. The operations were performed by the techniques of popliteal-to-distal bypass (20 procedures) and in situ bypass (27 procedures). Seventy-five percent of patients had gangrene of ischemic ulceration, and all procedures were performed for limb salvage. Seventy-three percent of all patients were diabetic. The patency rates for popliteal-to-distal bypass with reversed saphenous vein were 92 percent at 24 months and 57 percent at 60 months, with a limb salvage rate of 70 percent at 60 months; the patency rates for popliteal-to-distal bypass with PTFE were 53 percent at 12 months and 0 at 36 months, with a limb salvage rate of 53 percent at 36 months; and the patency rate for in situ saphenous vein bypass was 96 percent at 24 months, with a limb salvage rate of 80 percent at 24 months. Early results are promising for ankle bypass using the techniques of popliteal-to-distal and in situ bypass.

Endothelial preservation in reversed and in situ autogenous vein grafts. A quantitative experimental study

The hypothesis that superior endothelial preservation occurs when in situ (as opposed to harvested and reversed) autogenous veins are used as arterial grafts was investigated in a canine model by quantitating endothelial loss as seen on scanning electron micrographs. In situ grafts were compared to atraumatically dissected, nondistended, reversed grafts and to grafts distended to 500 mmHg pressure. Two hours after arterial transplantation, endothelial denudation averaged 3.9 +/- 6.7% on in situ grafts, 18.6 +/- 5.9% on reversed grafts (p less than 0.01), and 35.3 +/- 5.4% on reversed and distended grafts (p less than 0.001). At 24 hours after grafting, a significant increase (p less than 0.01) in endothelial destruction on in situ grafts resulted in a smaller, yet still significant difference in endothelial preservation between in situ and reversed grafts (15.2 +/- 9.5% vs. 25.1 +/- 23.4%, p less than 0.05). Endothelial healing was largely accomplished at 2 weeks regardless of technique. No difference in endothelial fibrinolytic activity could be detected between in situ and gently handled, reversed grafts at 24 hours or 6 weeks after surgery. An obligatory, although modest, degree of endothelial destruction occurred on the undissected portion of in situ grafts as a consequence of exposure to arterial hemodynamics. However, in the immediate postoperative period, endothelial preservation on in situ grafts surpassed that seen in even the most gently handled reversed vein grafts.

Nonreversed and in situ vein grafts. Clinical and experimental observations

The in situ saphenous vein (ISSV) graft has shown promise in distal bypass. Although improved patency has been attributed to preservation of vasa vasorum, there is no direct evidence to support this hypothesis. Femorodistal bypass was done in 33 patients using ISSV grafts (21) or nonreversed saphenous vein (NRSV) grafts (12) during an 18-month period. The NRSV were completely removed from the vein bed but were otherwise prepared in an identical fashion to the ISSV. Immediate complications including incomplete valvulotomy (one), intimal laceration (one), persistent AV communication (two), and extrinsic graft compression (one) were identified and corrected. Two grafts of 2.5 mm diameter occluded acutely. There were no deaths. Of 30 patients discharged with a patent graft, there was one late occlusion (ISSV) at 10 months. No difference in patency between ISSV and NRSV grafts was noted during follow-up extending to 24 months. Overall limb salvage was 94%. In a canine model, 60 vein segments were interposed in the carotid artery using in situ, reversed, and nonreversed techniques. Ultrastructural studies 1, 2, 3, and 6 months after implantation reveal no differences in in situ and nonreversed grafts. New vasa vasorum were identified in NRSV within 1 month. Both ISSV and NRSV grafts demonstrate excellent patency and maintenance of smooth muscle cell architecture. Factors including reduced size disparity at the proximal and distal anastomoses, physiologic distension under arterial pressure, careful handling, and meticulous technique appear to be more important than the theoretic advantages of preserving vasa vasorum.

In situ saphenous vein bypass grafting. Experience in 34 extremities over a 2 year period

Over a 2 year period, 34 limbs were revascularized in 33 patients. The in situ saphenous vein technique was used. Improved instrumentation and patency rates have encouraged the use of this method. Eighteen patients were insulin-dependent diabetics. The indication for operation was limb salvage in 25 limbs (73 percent). No vein was considered too small to use. The origin of 25 of the grafts were femoral and 9, popliteal. The termination of 15 of the grafts were popliteal, 11 tibial or peroneal, and 8 pedal. Of 12 limbs considered to be the most difficult to treat due to diabetes and accompanying poor runoff, 4 had a patent pedal arch. Initial graft patency was achieved in 94 percent of the limbs. Overall graft patency was 73 percent; femoropopliteal patency was 86 percent; and combined femoral, tibial, peroneal, and pedal patency was 64 percent. Learning the in situ bypass technique is tedious. The low thrombogenicity of the graft provides a temptation to extend operative indications. Use of the saphenous vein in situ can result in superior revascularization of the leg.

Ultrastructural changes of venous autologous bypass grafts in rabbits: correlation of patency and development

Electron microscopic techniques were used to correlate the patency of venous autografts in rabbits with ultrastructural changes within a time range from 5 days to 6 months p.o. Early degenerative changes of the grafts include endothelial desquamation followed by fibrin deposition or platelet adhesion, mural edema and extensive medial and adventitial degeneration. The regeneration of the grafts is due to an early adventitial vascularization (10 days p.o.), which enables the surviving smooth muscle cells and fibrocytes to proliferate and to develop an arterial-like vessel. The organization of the 6-month-old graft is comparable to the carotid artery of the animal, but shows, in contrast, many features of a muscular artery.