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Pedal Revascularization: Extending the Limits of Endovascular or Surgical Means to Prevent Amputation
Over 200 million people have peripheral arterial disease (PAD), which has an annual incidence of 2.4% worldwide.1 Additionally, approximately 10% of the United States population has PAD, including more than 30% of individuals aged more than 65 years.2 Although the majority of people with PAD are asymptomatic, 30% to 40% present with claudication.3 The prevalence of critical limb ischemia (CLI) is estimated at 1% to 3% of patients with PAD.4,5
CLI is limb-threatening ischemia. Four-year survival rates have been reported at 46% and freedom from major amputation at 87%.6 Reported high morbidity and mortality rates of up to 60% support the need for timely and aggressive intervention both to impact longevity and prevent amputation.7,8 Current management of CLI includes risk factor modification, medical therapy, and revascularization. While bypass surgery has classically been used as the initial mode of revascularization, endovascular techniques for CLI, often involving the tibial arteries, continue to develop. In the event that a patient’s disease involves diffuse and multivessel tibial and pedal arteries, aggressive attempts at pedal surgical reconstruction or angioplasty should be considered.
Case Report
A 61-year-old man presented with left lower extremity ischemic rest pain and forefoot gangrene. His past medical history was significant for hypertension, hyperlipidemia, poorly controlled type 2 diabetes mellitus (HbA1c 9), diabetic neuropathy, chronic kidney disease (baseline creatinine 1.2), and coronary artery disease status post coronary artery bypass. He denied any history of smoking or illicit drug use. On physical examination, the patient was found to have ischemic changes of the forefoot with multiple wounds on the first, second, and fourth toes (Figure 1). There were no obvious signs of infection. Vascular examination revealed palpable femoral and popliteal pulses, but he had non-palpable pedal pulses (posterior tibialis [PT] and dorsalis pedis [DP]). The patient had a past history of multiple unsuccessful attempts at endovascular therapy via an antegrade approach.
Noninvasive studies in the vascular laboratory demonstrated triphasic popliteal waveforms, monophasic waveforms at the PT and DP with diminished toe pressures, and severely dampened arterial waveforms at the digital level. Ankle-brachial index/toe-brachial index (ABI/TBI) was 1.18/0.7 on the right and 0.99/0 on the left. Combination CO2 and contrast arteriography revealed severe pedal arterial disease that was not amenable to retrograde pedal access or bypass surgery (Figure 2). Arterial anatomy was patent to the popliteal level with PT and peroneal arterial caliber greatly diminished beyond the trifurcation. Both arteries were occluded at the mid-calf level with minimal plantaris pedis collateralization. The distal anterior tibial (AT) artery was occluded at the ankle level with reconstitution of a segment of the DP and the first tarsal branch. In order to perfuse the forefoot, an AT thrombo-endarterectomy with patch angioplasty and an end-to-end AT tibial reconstruction from the DP segment to the AT tarsal branch at the metatarsal level was performed (Figure 3). This resulted in a palpable DP pulse.
The patient was discharged with a palpable AT pulse, and a biphasic signal at the DP and retrograde at the PT level. At 2-week follow-up, the patient was doing well with minimal pain, a pulse at the AT level, and a biphasic Doppler signal in the DP at the dorsum of the foot. The foot was warm and well perfused, and incision sites were well approximated with healing at the digital level (Figure 4). At the 3-month postoperative visit, the AT pulse was present with relief of rest pain and nearly complete healing, with a small ulceration remaining on the second digit.
Discussion
The pathogenesis of CLI involves severe arterial occlusive disease such that perfusion is unable to keep up with the basal tissue oxygen demand, ie, the amount of oxygen required for optimal tissue function.9 Originally defined as chronic ischemia representing a major threat to the limb in patients without diabetes, CLI has been described by various schemes: Rutherford classification, TASC II consensus document, and the WIFI grading system. Defining characteristics include ABI < 0.3, ankle pressures < 50 mm Hg, toe pressures < 30 mm Hg, PVR < 4-5 mm, and TcO2 < 20-40 mmHg. The clinical presentation includes rest pain (Rutherford class IV), poorly healing wounds, and subsequent tissue loss (Rutherford class V) or gangrene (Rutherford class VI).3 Although CLI accounts for only 3% of patients with PAD, up to 40% of patients with CLI can eventually require amputation, with over 150,000 cases annually associated with increased cost, mortality, and reduction in quality of life.6,10 Approximately 25% of CLI patients die within a year of the initial diagnosis.6,7 Efforts dedicated to preventing mortality and limb loss focus on a multidisciplinary approach, including optimizing cardiovascular risk factors and aggressive revascularization to improve wound healing and prevent major amputation, thereby improving or maintaining quality of life and increasing survival rates.11 Advancing methods of revascularization integral to this effort push what have been prior limits to involve pedal revascularization.
Endovascular therapy as the primary or initial mode of revascularization for symptomatic PAD is accepted. However, there is little prospective, randomized data comparing the efficacy of endovascular and surgical revascularization.12 Comparable 3-year limb salvage rates (82.4%) using percutaneous transluminal angioplasty (PTA) as the primary treatment modality versus bypass surgery (82.3%) have been reported.13,14 Of note, the endovascular approach had lower rates of primary and secondary patency.13 Despite this trend towards “endovascular first,” the choice of therapy is often on a case-by-case basis with operator judgment and skill as a major factor.15 Patients with many comorbidities, increasing frailty, and a limited life expectancy may be considered more likely to tolerate endovascular revascularization rather than surgical reconstruction.11 In contrast, more robust patients may benefit from the reported “long-term durability” of surgical repair.11 Increasingly, there are patients who may benefit from a hybrid procedure combining a limited surgical reconstruction with endovascular intervention, especially those patients with multilevel disease with femoral bifurcation involvement.11 Hybrid procedures increase the likelihood of complete revascularization with the added benefit of decreased morbidity given the decrease in magnitude of the surgical portion of the procedure to achieve complete revascularization with a reduction in risk of perioperative complications.11 As such, hybrid therapy may be appropriate in patients with increased frailty.16
Primary strategies for revascularization in CLI are “complete” and “direct” revascularization. In complete revascularization, the goal is to restore maximal perfusion by revascularization of as many tibial arteries as possible. The rationale is that wound healing is a blood-flow–dependent phenomenon such that the greater the flow, the more enhanced the healing capabilities of the tissue. In a retrospective analysis of 1268 patients with CLI by Peregrin and colleagues, there was a direct positive correlation between the number of tibial arteries with restored patency and limb salvage rates.16 Direct revascularization is based on the angiosome concept, coined in 1987 by Taylor and Palmer.15 The lower leg and foot are divided into 6 angiosomes based on the anterior tibial, posterior tibial, and peroneal arteries.17,18 Direct revascularization of the angiosome in which the wound is located is a factor in more rapid and complete healing.19 In a meta-analysis comparing angiosome-direct versus angiosome-indirect revascularization, a 60% relative reduction of major amputation was observed.20 Interestingly, a study by Varela and colleagues demonstrated similar rates of healing and limb salvage when direct revascularization was compared to indirect revascularization with documented collateral pedal branches supplying the wound.21 Angiosome revascularization may be especially pertinent to treat diabetic and end-stage renal disease patients with CLI.22
Among patients with CLI, the most difficult to treat are those with severe infrapopliteal or below-the-knee (BTK) arterial occlusive disease, and increasingly, patients with pedal disease. Pedal bypass has been well recognized in the past. Vein bypass to the DP or plantar branches of the posterior tibial artery have met with good success.23,24 In a retrospective study of over 1000 cases of DP bypasses, primary patency rates were reported at up to 56.8%.23 In the same study, saphenous vein grafts had the best outcomes with secondary patency rates of 67.6%.23 Similar patency rates (primary patency rates of 67% at 1 year) were reported in a retrospective study of patients undergoing inframalleolar bypass to plantar artery branches.24 However, limb preservation practices increasingly face the clinical challenge of patients with significant infra-malleoli pedal disease, the so-called “desert foot.” These cases present the challenge of extensive pedal artery disease with no obvious target for distal bypass revascularization, and difficulty with standard endovascular techniques. In order to establish perfusion for limb preservation, aggressive bypass and endovascular techniques are required.
Antegrade femoral access is the conventional percutaneous approach for endovascular therapy of below-the-ankle (BTA) and BTK lesions.25 This is complemented with balloon angioplasty, which has become the primary mode of endovascular treatment for pedal revascularization, with stent deployment and drug elution technology rarely used.26 Unfortunately, studies have shown that the standard antegrade approach fails in up to 20% of patients. As such, endovascular innovations such as retrograde pedal access and pedal-plantar loop revascularization with the possible use of transcollateral revascularization have been developed. The pedal-plantar loop technique aims to revascularize both the dorsal and plantar circulations of the foot by creating a track through the plantar arch. By doing so, this technique is able to achieve complete BTA and BTK revascularization despite there being only one patent calf artery, or when there are failed attempts at revascularizing occluded calf vessels through an antegrade approach.26 According to Palena and colleagues, combining pedal-plantar loop technique with retrograde access and an antegrade ipsilateral common femoral artery approach will optimize revascularization, thereby optimizing wound healing.27 In fact, the aforementioned novel percutaneous approaches have shown increased success rates of up to 85%.28,29
In this case, an attempt at pedal endovascular recanalization was unsuccessful, and although autologous bypass grafts and prosthetic grafts with a distal vein patch have been reported, our patient lacked a suitable target artery for either bypass choice.30 Localization of atherosclerotic disease in multiple major and minor pedal arteries in this diabetic patient necessitated an alternative method at revascularization. Pedal artery thrombo-endarterectomy with autogenous patch angioplasty to perfuse the segmental DP and tarsal branch may not have significant follow-up data available, but the short-term results in this case have been effective to date. Given the novelty of this treatment, we cannot make definitive conclusions as to its long-term efficacy.
Conclusion
In the case presented herein, we demonstrated the use of an autologous vein for arterial reconstruction. Our case is unique in that rather than opting for amputation in a patient with CLI not amenable to open bypass surgery or endovascular therapy, we devised a novel open surgical approach to revascularize the pedal arteries by creating a long segment vein patch on a heavily diseased AT artery. While further follow-up examination is still needed, given the improved vascular examination and decreased ischemic rest pain on 3-month follow-up post-revascularization, this method shows promise as an alternative treatment in patients presenting with BTK CLI.
Disclosure: All authors have completed ICJME disclosure forms. Dr Neville discloses that Gore Medical has provided grant support to the Inova Heart and Vascular Institute (IHVI) Scientific Advisory Board. Gi-Ann Acosta has nothing to disclose.
Manuscript submitted on May 2, 2019; accepted on May 9, 2019.
Address for correspondence: Richard Neville, MD; Inova Heart and Vascular Institute;, Falls Church, Virginia. Email: Richard.Neville@inova.org
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