Incidentally detected stenoses proximal to grafts originating below the common femoral artery: do they affect graft patency or warrant repair in asymptomatic patients?

Technical factors affecting autogenous vein graft failure: observations from a large multicenter trial

OBJECTIVE

The influence of operator-dependent variables on the outcomes of lower extremity bypass (LEB) surgery have primarily been reported in single-institution, retrospective studies. We utilized data from a prospective, multicenter trial to identify technical variables that were significantly associated with early and midterm results of autogenous LEB for limb salvage.

METHODS

The PREVENT III trial database includes 1404 North American patients with critical limb ischemia (CLI) who underwent LEB using excised autogenous vein. The study protocol excluded claudicants and in situ reconstructions. Technical factors analyzed included vein diameter, conduit type, graft length, vein orientation, location of proximal and distal anastomoses, and performance of completion imaging. Univariate analysis was used to determine the effect of these factors on 30 day and 1-year outcomes. Multivariate Cox regression models evaluated the influence of these factors while adjusting for age, sex, race, tobacco, diabetes, dialysis-dependency, previous index limb bypass, and study drug (edifoligide) administration. The primary outcomes were primary patency (PP), primary assisted patency (PAP), and secondary patency (SP) assessed by Kaplan-Meier method.

RESULTS

Univariate analysis revealed that vein diameter <3.5 mm and composite graft type were significantly associated with early (30 day) graft failure. At 1 year, multivariate analysis revealed that patency rates were negatively associated with diameter <3.5 mm (PP, PAP, SP), non-great saphenous vein (GSV) type (PP, SP), and graft lengths >50 cm (PP only). Limb salvage and survival at 1 year were not significantly impacted by technical variables. Employing a prespecified trial definition of high-risk conduits (diameter <3mm or nonsingle segment GSV; 24% of entire cohort) revealed that use of such conduits was associated with a 2.1-fold increased risk of 30 day graft failure (P < .05), as well as reduced PP, PAP, and SP at 1 year. Use of a high-risk conduit was also associated with an increased index length of stay (mean 9.37 vs 8.71 days, P = .03) and a greater number of reinterventions (mean 0.67 vs 0.42, P < .0001) over the ensuing year.

CONCLUSIONS

In this large, multicenter cohort of patients undergoing LEB for CLI, vein diameter and conduit type were the dominant technical determinants of early and late graft failure. High-risk conduits and longer grafts may benefit from aggressive postoperative graft surveillance.

Critical limb ischemia

Critical limb ischemia (CLI) is the most severe manifestation of peripheral artery disease (PAD). Without timely recognition, appropriate diagnosis, and revascularization, patients with CLI are at risk for amputation or potentially fatal complications. The past decade has seen substantial growth in endovascular CLI therapies and options now exist for treating long-segment lower-extremity arterial occlusive disease, but surgical bypass may yield more durable results. Patients who are younger, more active, and at low risk for surgery may have better outcomes with an operation. Surgical treatment is also indicated for failures of endovascular therapy, which may include early technical failures or later occlusion after placement of stents or other interventions.

Superficial femoral artery percutaneous intervention is an effective strategy to optimize inflow for distal origin bypass grafts

BACKGROUND

Iliac angioplasty in preparation for an infrainguinal bypass graft has been shown to be an effective strategy. We undertook this study to determine if superficial femoral artery (SFA) angioplasty offers durable inflow for distal origin grafts originating from the SFA or popliteal artery.

METHODS

All distal origin grafts performed at a single institution between 1988 and 2006, </=30 days of an ipsilateral SFA percutaneous intervention, were reviewed retrospectively. Patients were identified from a computerized vascular registry, and data were obtained by review of patient charts, angiograms, and duplex studies.

RESULTS

We identified 23 autogenous distal origin grafts procedures performed distal to an SFA intervention, of which 22 were performed for critical limb ischemia (96%). The SFA lesions intervened on (20 angioplasty alone, 3 angioplasty with stenting) included 11 TransAtlantic Inter-Society Consensus (TASC) A (48%), seven TASC B (30%), five TASC C (22%), and no TASC D (0%). Of the bypasses, five originated from the distal SFA, five originated from the above knee popliteal artery, and 13 originated from the below knee popliteal artery. A significant majority of the patients (87%) were diabetic. No deaths, amputations, or early graft failures occurred during the perioperative period. The mean duration of follow-up was 40.8 months. By life-table analysis, the primary patency rate was 58% at 5 years. The primary assisted patency rate was 69% at 5 years. Of the seven interventions required to maintain patency, only one targeted the SFA. None of the graft failures could be specifically attributed to disease progression of the SFA. The 5-year limb salvage rate was 70% and the survival rate was 65%.

CONCLUSIONS

Percutaneous SFA intervention in preparation for a distal origin graft is a useful and effective strategy in select patients. The durability appears comparable with distal origin grafts performed in the absence of an SFA intervention. This strategy provides a good option in the setting of both atherosclerotic SFA disease and limited autogenous conduit.

That Hemodynamics and Not Material Mismatch is of Primary Concern in Bypass Graft Failure: An Experimental Argument

The long term patency of end-to-side peripheral artery bypasses are low due to failure of the graft generally at the distal end of the bypass. Both material mismatch between the graft and the host artery and junction hemodynamics are cited as being major factors in disease formation at the junction. This study uses experimental methods to investigate the major differences in fluid dynamics and wall mechanics at the proximal and distal ends for rigid and compliant bypass grafts. Injection moulding was used to produce idealized transparent and compliant models of the graft/artery junction configuration. An ePTFE graft was then used to stiffen one of the models. These models were then investigated using two-dimensional video extensometry and one-dimensional laser Doppler anemometry to determine the junction deformations and fluid velocity profiles for the rigid and complaint graft anastomotic junctions. Junction strains were evaluated and generally found to be under 5% with a peak stain measured in the stiff graft model junction of 8.3% at 100mmHg applied pressure. Hemodynamic results were found to yield up to 40% difference in fluid velocities for the stiff/compliant comparison but up to 80% for the proximal/distal end comparisons. Similar strain conditions were assumed for the proximal and distal models while significant differences were noted in their associated hemodynamic changes. In contrasting the fluid dynamics and wall mechanics for the proximal and distal anastomoses, it is evident from the results of this study, that junction hemodynamics are the more variable factor.

Usefulness of autogenous bypass grafts originating distal to the groin

PURPOSE

Infrainguinal bypass grafting with a proximal anastomosis distal to the groin has been used increasingly to conserve available conduit and reduce wound morbidity and recovery time. The usefulness of the liberalized use of distal origin grafts (DOGs) is unknown.

METHODS

Consecutive autogenous DOG procedures that were performed between 1978 and 2000 were reviewed retrospectively with a computerized registry. Procedures performed as revisions to earlier infrainguinal bypass grafting procedures and for popliteal aneurysm were excluded.

RESULTS

In the 22-year study period, 249 autogenous DOG procedures were performed in 217 patients. Comparison of the 159 DOGs in patients with diabetes mellitus (+DM) with the 90 grafts in patients without diabetes mellitus (-DM) revealed more associated renal disease (33% vs 9%), preoperative foot necrosis (80% vs 52%), distal popliteal artery graft origins (49% vs 37%), and non-greater saphenous conduits used (30% vs 19%) among the +DM subgroup than the -DM subgroup (P <.05). The operative mortality rate was 2.0%, the major morbidity rate was 8.8%, the early graft failure rate was 6.4%, and the early amputation rate was 2.4%, with no differences related to diabetes mellitus. Follow-up was complete in 92% of patients in a mean interval of 27 months. At 5 years, cumulative primary graft patency rates were 62% overall, 73% for the +DM subgroup, and 45% for the -DM subgroup (P <.001). The overall limb salvage rate after DOG procedures for critical ischemia was 79%, and it was 84% for the +DM subgroup and 69% for the -DM subgroup (P <.04). The overall patient survival rate was 45%, with no difference related to diabetes mellitus.

CONCLUSION

Outcome after autogenous DOG revascularization is satisfactory overall. Graft patency and limb salvage after DOG for critical ischemia are significantly better among patients with diabetes mellitus than patients without diabetes mellitus, despite significantly more bypass grafting procedures performed for foot necrosis. DOG revascularization appears to be an appropriate preference for patients with diabetes mellitus with good inflow below the groin; it should be used less liberally among patients without diabetes mellitus.

Critical Limb Ischemia

Patients with critical limb ischemia (CLI) present with ischemic rest pain or with tissue loss. Tissue loss, in its mildest presentation, includes focal ischemic ulceration or nonhealing wounds. Gangrene is the manifestation of severe chronic ischemia. Without revascularization, patients with CLI are at risk for limb loss and for potentially fatal complications from the progression of gangrene and the development of sepsis. The best patient outcomes are achieved when the diagnosis and appropriate treatment for CLI are not delayed. Simple noninvasive tests, such as measurement of ankle-to-brachial indices or toe Doppler pressures, take only minutes to provide sufficient information to confirm the diagnosis of peripheral artery disease (PAD) and to document the severity of limb ischemia. Subsequent diagnostic imaging studies, such as arteriography, magnetic resonance angiography, or ultrasound duplex scanning, provide the detailed information needed to plan revascularization therapy. Balloon angioplasty and stenting work best for focal segments of narrowing or short occlusions of the iliac arteries, but endovascular treatments yield progressively poorer results with longer and more distal lesions. Long segments of occlusion, especially those distal to the common femoral artery, are best treated with surgical bypass. Pharmacotherapy and adjunctive therapies, such as topical therapies or hyperbaric oxygen treatment, may have a limited role in patients in whom revascularization procedures have failed or for those in whom revascularization is not technically possible--particularly when amputation is the only alternative. Prostanoids are the best-studied class of drugs for such applications, but their use is still investigational in the United States. Though other medical approaches, such as use of other vasoactive agents, drugs that treat claudication, or gene-induced angiogenesis may prove useful, they do not yet have demonstrated roles in the treatment of patients with CLI.