The Role of Open Bypass Surgery for Limb Salvage in Patients With Diabetes

Index: WOUNDS 2011;23(12):364–368

  Abstract: The pathogenesis of foot ulceration in patients with diabetes involves the interplay of neuropathy, vasculopathy, and immune dysfunction. Autonomic neuropathy results in loss of pain sensation, decreased sweating, and the development of brittle skin, which predisposes these patients to foot trauma. As a result, the traumatized tissue progresses to necrosis and subsequent ulceration. Once an ulcer is present, the vascular supply to the foot plays an integral role in healing. Foot ischemia in patients with diabetes may be attributed to atherosclerotic macrovascular disease and additional microcirculatory dysfunction. The following report will review the role of open bypass surgery addressing macrovascular problems for limb salvage.

Diagnostic Evaluation

  Patients with limb-threatening critical limb ischemia (CLI) present with nonhealing ulcers and associated tissue necrosis, gangrene, or infection. Evaluation of the extent of tissue loss and relationship with pressure bearing surfaces should be performed. Lower extremity segmental Doppler studies are helpful in determining severity of ischemia. Moderate ischemia is associated with ankle brachial indices (ABI) 0.5–0.9 and severe ischemia with ABI < 0.5. Doppler studies can be inaccurate in patients with diabetes because of noncompressible vessels due to calcified arterial walls, and as a result ABIs can be falsely elevated. Alternatively, pulse volume recording, toe pressures, and transcutaneous oxygen measurements may be utilized. Diagnostic contrast arteriography is typically performed for more accurate evaluation of occlusive disease pattern and for operative planning. While aortoiliac and femoropopliteal levels can have evidence of occlusive disease, patients with diabetes often exhibit tibioperoneal arterial occlusive disease with sparing of the pedal level. Particular attention is paid to both the inflow and outflow target arteries, both of which should be free of occlusive disease above and below intended bypass with continuous patent distal flow to the foot. Ultrasound mapping of potential venous conduits in bilateral lower extremities (great and small saphenous vein) and upper extremities (cephalic and basilic veins) provides information about conduit availability and suitability of operative bypass.

Management Strategies

  Generally, surgical intervention is recommended for patients with diabetes and CLI from occlusive disease. While endovascular options for treating occlusive disease have expanded in recent years and are best for patients of advanced age, higher medical risk profile, and less severe occlusive disease, operative bypass is preferred, if risk permissible, and for more extensive occlusive disease patterns. The advantages of operative bypass over endovascular approaches is that it is not limited by the extent of occlusion or length of diseased segment, and in the long run has more extended durability, especially for distal tibial occlusive disease patterns more often seen in patients with diabetes.   Revascularization procedures must be tailored to the individual patient based on anatomy, particularly the inflow and outflow, as defined by the preoperative angiography. For patients with multilevel disease, multilevel reconstruction at the aortoiliac and infrainguinal levels may be needed. Infrainguinal bypass procedures need to arise from a patent and uncompromised inflow artery. The quality of the outflow artery is an equally important determinant of patency and a distal vessel of the best quality should be used for distal target. Conduit is also critical with the vein having better long-term patency than prosthetic for infrainguinal revascularization. Over the short term, polytetrafluoroethylene (PTFE) has delivered nearly equivalent results in the above knee position, although for below knee or infrapopliteal bypass, long-term patency of synthetic conduit remains dismal.   Patients with ischemic tissue loss and superimposed infection who have a salvageable foot should have the infection controlled prior to revascularization. Broad-spectrum antibiotics in concert with debridement and partial foot amputation may be required. Bypass may be performed once cellulitis, lymphangitis, and edema have improved.   Surgical lower extremity revascularization is not recommended, and primary amputation may be preferred for patients with severe dementia or organic brain syndromes, nonambulatory status, severe flexion contractures of the knee or hip, terminal cancer with short life expectancy, or an unsalvageable foot due to extensive necrosis from ischemia or infection.

Outcomes

  While there is some debate regarding an endovascular approach versus operative bypass, for patients with CLI from more severe infrainguinal and infrapopliteal occlusive disease, bypass is generally preferred. In one of the few randomized studies comparing angioplasty and bypass, the BASIL¹ investigators showed that 1) angioplasty was associated with a significantly higher early failure rate than bypass with most angioplasty patients ultimately requiring surgery; 2) for patients undergoing angioplasty first, bypass outcomes after failed angioplasty were significantly worse than for bypass performed as a first revascularization attempt; 3) although there was no difference in amputation-free or overall survival between the two strategies, for those patients who survived for at least 2 years after randomization, a bypass first revascularization strategy was associated with a significant increase in overall survival and a trend toward improved amputation-free survival.   Several other nonrandomized studies evaluating operative bypass for CLI show reasonable long-term patency, limb salvage, and survival potential, although results are more tempered in patients with diabetes compared to nondiabetics. Taylor et al² performed a retrospective analysis of 331 consecutive bypasses in which the definition of clinical success after surgical bypass for tissue loss incorporated wound healing in addition to graft patency and limb salvage. The overall clinical success of surgical bypass for CLI was 44%. Risk factors associated with clinical failure included impaired ambulation at the time of presentation, end-stage renal disease, gangrene, need for infrainguinal bypass, and hyperlipidemia. Tannenbaum et al³ reviewed results from more than 1000 bypasses to the dorsalis pedis artery. Perioperative mortality was 0.9%, and the popliteal artery was the inflow vessel in 53.2% of patients. At 5 years, primary patency was 56.8%, secondary patency 62.7%, and limb salvage 78.2%. A retrospective review by Berceli et al⁴ of 517 pedal bypasses for critical foot ischemia manifested by gangrene or nonhealing ulceration resulted in 5-year patency rates between 55% and 60% with secondary patency rates between 60% and 70%. In the diabetic population, the dorsalis pedis artery is typically spared of atherosclerotic occlusive disease. This study yielded healing rates close to 90% for heel ulcerations with an average time to healing of 20 weeks and greater than 85% 5-year limb salvage rate for forefoot and heel tissue loss. Additionally, graft patency and wound healing were not dependent upon an intact pedal arch.   Graft patency remains an objective measure of technical success as opposed to clinically-based patient outcomes. Simons et al⁵ performed a prospective study utilizing the Vascular Study Group of Northern New England⁶ (VSGNNE) to identify those patients who underwent elective infrainguinal lower extremity bypass for critical limb ischemia. They noted that 10% (79 of 788) of patients with a patent graft did not improve clinically at 1 year, 2.7% (21) of patients ultimately undergoing major amputation, and 7.4% (58) with continued rest pain or tissue loss. Multivariable analysis was performed to identify predictors of clinical failure, which included dialysis dependence (odds radio 3.74) and preoperative inability to ambulate independently (odds ratio 2.17).   Unlike forefoot tissue loss, ulceration confined to the heel often fails to heal despite palpable pedal pulse at the ankle and local wound care. Treiman et al⁷ outlined an approach to the management of ischemic heel ulcerations. This group performed a retrospective study, treating 91 patients with nonhealing heel wounds with a mean preoperative ABI of 0.51. Eighty-one patients underwent infrainguinal bypass, resulting in a mean ABI improvement of 0.40. Wounds healed within 6 months in 73% (66) of patients. Graft occlusion in six patients occurred within 6 months of open revascularization, suggesting that short-term graft patency did not promote limb salvage. Those 28 patients with renal failure and diabetes identified in this study did demonstrate wound healing, supporting the notion of offering arterial reconstruction to this subset of patients if they are willing to commit to close surveillance and/or follow up. Variables that predicted wound healing were normal renal function, patent posterior tibial artery past the ankle, palpable pedal pulse, and the number of patent tibial arteries to the ankle post-intervention.   Restoring pulsatile blood flow to the foot is one of the tenets of treatment of forefoot ulceration/gangrene. Direct revascularization of the hindfoot via posterior tibial artery is often limited due to tibial atherosclerosis in the diabetic population. As a result, restoration of blood flow to the foot via the dorsal circulation usually occurs through collateral pathways. However, based on the concept of the “angiosome,” a three-dimensional vascular territory supplied by specific arteries and drained by specific veins, angiosome directed revascularization when possible might be preferable. Neville et al8 performed a retrospective analysis of angiosome-based revascularization, citing associated successful healing and limb salvage, as well as lower amputation rates.

Evidence-based Recommendations

  Overall aggregate patency, limb salvage, and survival results for operative bypass as reported in a recent review of basic data related to surgical infrainguinal revascularization and as summarized in the Trans-Atlantic Inter-Society Consensus Document on Management of Peripheral Arterial Disease (TASC II)⁹ are shown in Table 1 and Table 2, respectively. A summary of the current evidence based guidelines adapted from TASC II pertaining to diabetics and nondiabetics with CLI who require open bypass surgery are as follows:     • Multidisciplinary Approach: Patients with CLI should be referred to a vascular specialist early in the course of their disease to plan for revascularization options [Grade C]. A multidisciplinary approach is optimal for treatment of CLI to control pain, cardiovascular risk factors, and other co-morbid disease [Grade C]. Patients with CLI who develop foot ulceration require multidisciplinary care to avoid limb loss [Grade C].     • Diagnostic Evaluation: CLI is a clinical diagnosis but should be supported by objective tests [Grade C]. All patients with ischemic rest pain symptoms or pedal ulcers should be evaluated for CLI [Grade B]. All patients with diabetes with ulceration should be evaluated for PAD using objective testing [Grade C].     • Revascularization Strategy: Revascularization is the optimal treatment for patients with CLI [Grade B]. In a situation where endovascular revascularization and open repair/bypass of a specific lesion causing symptoms of peripheral arterial disease give equivalent short-term and long-term symptomatic improvement, endovascular techniques should be used first [Grade B].     • Open Bypass Surgery: For femorodistal bypass, any artery, regardless of level may serve as an inflow artery for a distal bypass provided flow to that artery and the origin of the graft are not compromised [Grade C]. In a femoral tibial bypass, the least diseased distal artery with the best continuous run-off to the ankle/foot should be used for outflow regardless of location, provided there is adequate length of suitable vein [Grade C]. An adequate long segment of great saphenous vein is the optimal conduit in femoral below-knee popliteal and distal bypass [Grade C]. In its absence, another good quality vein, if available, should be used over synthetic graft options [Grade C].     • Postoperative Management: Antiplatelet therapy should be started preoperatively and continued as adjuvant pharmacotherapy after an endovascular or surgical procedure [Grade A]. Unless subsequently contraindicated, this should be continued indefinitely [Grade A]. All patients undergoing bypass graft placement should be entered into a clinical surveillance program, performed in the immediate postoperative period and at regular intervals (usually every 6 months) for at least 2 years [Grade C].

Conclusion

  Limb salvage involves a complex interplay between neuropathy, vasculopathy, and immune system modulation. The restoration of blood flow often promotes wound healing by relieving limb ischemia. Through careful preoperative planning, the vascular surgeon is able to reroute blood flow to where it is needed, accounting for arterial inflow, outflow, and the suitability of appropriate conduit. Despite the best efforts to prevent limb loss through open distal revascularization, there exists a subset of patients who still necessitate subsequent major amputation.

References

1. BASIL Investigators. Final Results of the BASIL Trial (Bypass Versus Angioplasty in Severe Ischaemia of the Leg). J Vasc Surg. 2010;51(5 Suppl):S1–S76. 2. Taylor SM, Cull DL, Kalbaugh CA, et al. Critical analysis of clinical success after surgical bypass for lower-extremity ischemic tissue loss using a standardized definition combining multiple parameters: A new paradigm of outcomes assessment. J Am Coll Surg. 2007;204:831–839. 3. Tannenbaum GA, Pomposelli FB Jr, Marcaccio EJ, et al. Safety of vein bypass grafting to the dorsal pedal artery in diabetic patients with foot infections. J Vasc Surg. 1992;15(6):982–988. 4. Berceli SA, Chan AK, Pomposelli FB Jr, et al. Efficacy of dorsal pedal artery bypass in limb salvage for ischemic heel ulcers. J Vasc Surg. 1999;30:499–508. 5. Simons JP, Goodney PP, Nolan BW, et al. Failure to achieve clinical improvement despite graft patency in patients undergoing infrainguinal lower extremity bypass for critical limb ischemia. J Vasc Surg. 2010;51:1419–1424. 6. Goodney PP, Nolan BW, Schanzer A, et al. Factors associated with amputation or graft occlusion one year after lower extremity bypass in northern New England. Ann Vasc Surg. 2010;24:57–68. 7. Treiman GS, Oderich GSC, Ashrafi A, Schneider PA. Management of ischemic heel ulceration and gangrene: An evaluation of factors associated with successful healing. J Vasc Surg. 2000;31:1110–1118. 8. Neville RF, Attinger CE, Bulan EJ, Ducic I, Thomassen M, Sidawy AN. Revascularization of a specific angiosome for limb salvage: does the target artery matter? Ann Vasc Surg. 2009;23:367–373. 9. Norgren L, Hiatt WR, Dormandy JA, et al. Inter-Society Consensus for the Management of Peripheral Arterial Disease (TASC II). J Vasc Surg. 2007;45(Suppl):S5–67. 10. Ziegler KR, Muto A, Eghbalieh SD, Dardik A. Basic data related to surgical infrainguinal revascularization procedures: a twenty year review. Ann Vasc Surg. 2011;25:413–422.

Additional Reading

Davies MG. Diabetic foot. SVS comprehensive vascular review course. September 9–10, 2011. Intercontinental Chicago O’Hare. Hirsch AT, Haskal ZJ, Hertzer NR, et al. ACC/AHA 2005 guidelines for the management of patients with peripheral arterial disease (lower extremity, renal, mesenteric, and abdominal aortic): executive summary a collaborative report from the American Association for Vascular Surgery/Society for Vascular Surgery, Society for Cardiovascular Angiography and Interventions, Society for Vascular Medicine and Biology, Society of Interventional Radiology, and the ACC/AHA Task Force on Practice Guidelines (Writing Committee to Develop Guidelines for the Management of Patients With Peripheral Arterial Disease) endorsed by the American Association of Cardiovascular and Pulmonary Rehabilitation; National Heart, Lung, and Blood Institute; Society for Vascular Nursing; TransAtlantic Inter-Society Consensus; and Vascular Disease Foundation. J Am Coll Cardiol. 2006;47(6):1239–1312. Dr. Yamaguchi is from the Fellow, Vascular Surgery, University of Alabama at Birmingham, Section of Vascular Surgery and Endovascular Therapy. Dr. Passman is Professor of Surgery, University of Alabama at Birmingham, Section of Vascular Surgery and Endovascular Therapy. Address correspondence to: Marc A. Passman, MD University of Alabama at Birmingham Section of Vascular Surgery and Endovascular Therapy BDB 503 1808 7th Avenue South Birmingham, AL 35294-0012 205-934-2003 Marc.Passman@ccc.uab.edu