Up to 50% of those with either type 1 or type 2 diabetes develop PAD within 10 years of their diabetes diagnosis. Due to the common occurrence of PAD in those with diabetes and co-existing diseases, often these patients are not ideal candidates for surgical intervention. Studies have shown amputation rates for those with diabetes to be 5 times higher in comparison to non-diabetics (21.8/1000/year vs. 3.9/1000/year) with 10-20% of diabetics with foot infections eventually requiring an amputation. CLI often causes diminished quality of life in those affected due to the high prevalence of co-existing cardiac diseases among these patients. If successfully treated with limb salvage or amputation, the mortality rate at one year for these patients is still as high as 25%, which is similar to the mortality rate seen in patients suffering from coronary artery disease and myocardial infarction. Given the grave prognosis associated with CLI, particularly in the diabetic population, aggressive intervention with revascularization is often pursued and will be the focus of the subsequent sections in this review as outcomes and recommendations in utilizing various revascularization procedures in the diabetic population will be discussed.
Definition of Peripheral Arterial Disease
Peripheral arterial disease (PAD) is a major health problem which is estimated to affect over 200 million people worldwide. PAD increases the likelihood of coronary artery disease, myocardial infarction, and death. The pathogenesis of atherosclerosis in the peripheral arterial beds is known to be similar to that in the coronary circulation. The disease begins in the endothelium, where monocytes and T-lymphocytes adhere and migrate into the intima. This is followed by lipid accumulation in the macrophages and smooth muscle cells. These cells become foam cells and elaborate matrix. Ultimately, the cells may die, leaving a lipid core with a fibrous cap. The lesion may undergo remodelling, and superficial lesions may ulcerate. This may be followed by thrombosis and distal embolization. The progression of atherosclerosis in the lower limb can result in various symptoms. The most common symptom is intermittent claudication, which is defined as pain or cramping in the calves, thighs, or buttocks that occurs during exercise and is relieved by rest. This is a marker for increased cardiovascular mortality, myocardial infarction, and stroke. People with PAD often suffer from an impaired quality of life due to functional impairment caused by leg pain. Pain at rest and ulceration of the lower limb are further symptoms of severe PAD. Ischemia can reach such an advanced stage that the limb is threatened and there is a possibility of amputation. In the UK, a total of 12,750 primary major amputations were performed in 2005-6, and 80% of these are due to PAD. This is despite the fact that 90% of the people with limb loss due to PAD will have had symptoms that would have benefited from revascularization.
Importance of Surgical Options and Considerations
Peripheral artery disease (PAD) in the lower extremities is the result of systemic atherosclerosis, in which there is an abnormal gait or interruption of the blood flow to the arteries located above the aortic arch. A patient with PAD may experience a range of debilitating symptoms, from mild discomfort to a debilitating limb ulceration or gangrene. The natural history of the disease is unpredictable, although 60-70% of patients will remain stable or improve, while 10-15% will progress to critical limb ischemia, which is associated with a high mortality rate and limb loss. A further 10-15% of patients with PAD will experience intermittent claudication, with only 1-2% requiring major limb amputation. Generally, patients with PAD have a much higher mortality rate than the general population, and in those patients with associated cardiovascular disease, the risk may be as high as 15% in 2 years. Due to the systemic nature of atherosclerosis, these patients are often at risk from other cardiovascular events, such as heart attack and stroke. The effect that PAD has on the quality of life of patients is often underestimated and is relatively greater in those who have more severe symptoms and those with multiple comorbidities. Therefore, it is important to consider the implications of surgical options in the management of PAD and the effect they have on clinical outcome and prognosis.
Surgical Options for Peripheral Arterial Disease
Surgical management becomes a treatment option when lifestyle-limiting claudication problems persist despite good medical therapy or when critical limb ischemia is present. Over the last 20 years, there have been major advances in the less invasive methods of angioplasty and endovascular stenting. Conventional open surgery still remains the gold standard for infra-inguinal revascularizations, and in particular cases, may be the only option. The decision on when to choose angioplasty, stenting, or bypass surgery is complex and requires careful consideration of many factors, including lesion characteristics, co-morbidities, life expectancy, and patient preference. Clear discussion with the patient is necessary to establish realistic treatment goals and to balance the risk of the intervention against the potential long-term benefits. Randomized controlled trials comparing the various methods of revascularization have been limited and have typically focused on short-term symptom relief. A recent meta-analysis of the available evidence compared angioplasty, stenting, and bypass surgery for symptomatic PAD and found that there were no significant differences in amputation-free survival rates between surgical and endovascular techniques. However, surgery was associated with a lower risk of repeat revascularization. Clouband et al discuss a proposed algorithm on revascularization strategy, which aims to direct treatment based on the lesion that would benefit invasive treatment, limiting the invasiveness of the method, and leaving all open surgical options as the last resort. He reasons that with this approach and considering the increasing life expectancy in these patients, there will be more cases of restenosis needing repeat revascularization if open surgery is avoided. This is particularly true in cases of chronic total occlusions where poor results have been seen with endovascular treatment.
Angioplasty and Stenting
Today, with the refusal of proving its superiority over more conservative forms of management, has instead evolved to become an alternative to balloon angioplasty for lesions not appropriate for PTA. Rather than a means of providing the mechanical dilation of atherosclerotic lumens, stent implantation has become a strategy for providing long-term suppression of arterial recoil and for embolization reduction. Consequently, the role of stent implantation in treating PAD has been focused upon lesions causing critical limb ischemia. Because PTA and stent implantation are void of the physiologic insult and invasiveness of surgery, there has been an attempt to evaluate the potential benefit of revascularization in a high-risk population of patients in whom limb threat can often times be palliated. Patients with poor life expectancy or severe medical comorbidities that evoke a prohibitive surgical risk have been subject to limb amputation or medical management despite a heavily ischemic limb. A necessary effort should be made to improve the quality of life in these patients as they often have a disease-free coronary and carotid vasculature. Randomized comparisons of PTA and stent implantation versus surgical bypass for limb threat in high surgical risk patients are lacking, but attempts to do so will be indicative of the overall value of limb revascularization in this particular patient population.
Bypass Surgery
Postoperative Management and Results With rapid advances in perioperative management of myocardial and renal disease, there has been a trend toward performing arterial surgery in the patient populations that have these coexistent disease states. Preoperative and intraoperative revascularization of critical limb ischemia improves rest pain and ulcer healing in 90-95% of patients. Unfortunately, especially with femoropopliteal and infrapopliteal bypass surgery, only 50-70% of patients have durable graft patency and limb salvage at 5 years. These results are influenced by the progressive nature of atherosclerosis and increased complexity of arterial lesions in aged patients, who comprise the majority of the peripheral artery disease population. Improvements in surgical techniques and adjunctive medical therapy promise enhanced results for arterial revascularization in the future.
Surgical Technique With the patient under general or regional anesthesia, arteriotomy is performed and the plaque in the occluded arterial segment is either distally extruded or an embolectomy catheter may be used to extract it. Aortoiliac and iliofemoral lesions may be treated with endarterectomy and simple closure of the arteriotomy site. Because femoropopliteal and infrapopliteal endarterectomy has unfavorable long-term results, it is generally followed by placement of a vein or prosthetic bypass graft. Especially in smaller arteries, endarterectomy may improve long-term patency by removing intimal plaque that would be traversed by a prosthetic or vein graft.
Technique Overview Aortoiliac and aortofemoral bypass surgery provide effective relief of ischemic rest pain and healing of ischemic ulcers for patients with debilitating claudication that is not relieved by conservative measures. By contrast, femoropopliteal and infrapopliteal bypass surgery have less promising long-term results but are indicated for limb salvage in patients who have no other option. Preoperative imaging with arteriography or noninvasive vascular testing is used to define the anatomy and location of arterial occlusive disease that may be amenable to surgical intervention. Aortoiliac lesions are accessed through a midline or a paramedian skin incision and a retroperitoneal exposure of the aorta and iliac arteries. Iliofemoral lesions may be approached through a lower abdominal transperitoneal exposure. Femoral and popliteal lesions are accessed through a variety of groin, thigh, or knee incisions according to the preference of the surgeon and location of the lesion. The potential for vein harvest, especially the great saphenous vein, may be considered in planning the location of the skin incision and the subsequent limb position. Various autologous vein and prosthetic conduit configurations may be used to bypass arterial lesions depending on the anatomic location and the preference of the surgeon.
Endarterectomy
Carotid endarterectomy (CEA) is a procedure to treat carotid artery disease. The carotid arteries are the main blood vessels that carry oxygen-rich blood to the brain. In CEA, a surgeon makes a cut (incision) on the neck to open the carotid artery and remove the plaque.
Endarterectomy is a way to remove the plaque and reduce your risk of a heart attack or stroke.
Endarterectomy is a surgical procedure to remove plaque from the inside of an artery. Plaque is made up of fat, cholesterol, calcium, and other substances found in the blood. Over time, plaque can harden or rupture (break open). Hardened plaque narrows the artery and reduces the flow of oxygen-rich blood to your organs and other parts of your body. If the plaque ruptures, a blood clot can form on its surface. A clot can mostly or completely block blood flow through an artery.
Considerations for Surgical Treatment
Surgery is an attractive option for any patient with symptoms severe enough to affect quality of life who has not responded to or is not a candidate for other treatments. However, the potential benefits of surgical revascularization must be carefully weighed against the potential increase in procedural risk for the individual patient, given that even contemporary open bypass techniques have a higher associated morbidity and mortality than endovascular procedures. The decision to proceed with revascularization, as well as the specific operation chosen, will thus depend on the skill and experience of the surgical and anesthesia team, coupled with a comprehensive assessment of the patient’s risk and estimated longevity. Patient selection, in turn, is influenced by the expected patency and durability of the revascularization procedure, with patients expected to live less than 2 years often better served by palliative medical therapy. Considerations for surgical treatment should also involve an assessment of the availability of suitable vein or prosthetic material specific to humans and animal models, as well as the local expertise and facilities.
Patient Selection Criteria
In patients with severe functional impairment or limb-threatening ischemia, bypass grafting is associated with an 80-90% limb salvage rate and provides the best long-term results. Those with focal iliac disease and limited life expectancy may be best served with an aortoiliac procedure, as the short-term and long-term mortality rates are significantly higher when compared to those undergoing femoropopliteal bypass. In patients requiring amputation, those receiving major amputations have a 5-year mortality rate of 39%/13.4, and the decision to perform a bypass prior to amputation must be carefully made.
Peripheral arterial disease affects a large number of individuals, and most are able to be treated non-operatively. When considering surgical treatment, patients must be carefully selected in order to minimize potential risks and streamline the postoperative recovery period. When compared to claudicants, patients with severe claudication and critical limb ischemia have improved results with revascularization.
3.1 Simple Sentence Structures
Preoperative Assessment and Preparation
Assessment of cardiac and pulmonary conditions is critical in determining a surgical candidate’s risk for a procedure. Patients with severe congestive heart failure are extremely high-risk surgical candidates, and attempts should be made to optimize medical management or consider alternative therapies. While it is clear that patients with ischemic rest pain or tissue loss receive significant benefit from revascularization procedures, the management of patients with claudication is not as straightforward. For the most part, the goal of intervention in claudicants is to improve quality of life by minimizing symptoms. However, in cases where iliac disease is severe and functionally limits a patient’s lifestyle, an attempt at revascularization may be of benefit. Also, patients with aortoiliac disease and concomitant coronary artery disease are best served by initial revascularization with the intent to ultimately relieve symptoms of claudication and improve cardiovascular functional status. Finally, patients with claudication resulting from iliac stenosis and poor quality of life due to bilateral gluteal and thigh claudication are logical candidates for intervention. In general, catheter-based angiography is indicated to confirm the presence of iliac disease and determine its anatomic distribution. High-risk patients with multiple co-morbid conditions are often best served by angiography and possible intervention during the same hospitalization to minimize the risk of an invasive procedure at a later date.
Potential Complications and Risks
Randomized controlled trials comparing revascularization with medical management have generally not shown any improvement in quality of life outcomes for patients with claudication. This is likely to be related to the previously mentioned issues of patient selection and the high prevalence of coexistent medical conditions. Potential complications can be separated into those specific to the revascularization procedure being undertaken and those related to the possibility of disease progression during the natural history of the patient’s arterial occlusive disease.
In general terms, the higher the operative risk, the greater the potential benefits of surgical revascularization. A patient who is unfit for surgery due to coexistent medical conditions may be a candidate for endovascular intervention because of its lower associated morbidity and mortality. An estimated operative risk should be made using clinical judgment and the patient’s coexistent morbidity. This can then be compared with the expected benefit of surgery. Informed decision making in this way may avoid subjecting patients to procedures from which they are unlikely to benefit.
Potential complications and risks are important to consider before embarking on any surgical procedure. For peripheral vascular surgery, these considerations are even more important because the majority of the patients are elderly and have multi-system dysfunction. The risks of surgery must be carefully weighed against the potential benefits. A patient with lifestyle-limiting claudication may not be a good candidate for surgery, whereas a patient with limb-threatening ischemia may be prepared to take high risks for a chance of cure. This decision should be made jointly between the patient and the vascular surgeon after carefully considering the potential benefits of surgery and the likely risks.
Postoperative Care and Rehabilitation
This is a vital step in the surgical process. Patients and family cannot be educated enough about the importance of compliance in this phase. Although patients may feel better after surgery, the reality is that full recovery takes time and needs persistence and patience in continuing through the care plan. In general, the postoperative goal for claudicants is to return to their prior level of function. This can only be accomplished with aggressive management of cardiac risk factors and diligent wound care. Claudicants who underwent limb bypass need consistent wound care with evaluation of wound healing. This may involve specialist care with a wound clinic to ensure that the wounds do not progress to limb-threatening ischemia. These wounds are often subtle, below the ankle, and may be missed by the patient. To ensure proper wound care, a team approach with the surgeon, nurse, and family can ensure success. Evaluation of wound status with surveillance studies will ensure early intervention if problems arise. High-quality wound care can ensure the wounds heal and the patient is symptom-free. This phase is also the time to aggressively manage cardiac risk factors. Control of diabetes, hypertension, and hyperlipidemia are all important to prevent recurrence of symptoms. The cornerstone of medical therapy of PAD is exercise and cilostazol. Although it may be difficult for patients to exercise initially, encouragement and social support will help the patient maintain independence and decrease symptoms. Compliance with this step can assure long-term relief of claudication.
Conclusion
The decision regarding which surgical intervention to choose in the management of PAD is complex and must be individualized to each patient. For the patient with lifestyle-limiting claudication, those at increased risk for standard revascularization, and those with lesions not conducive to angioplasty, endarterectomy is a viable option. It provides excellent symptomatic relief, has acceptable morbidity and mortality rates, and is cost effective. As the technology and expertise in the endovascular field continues to advance, stenting and angioplasty will likely play an even larger role in the management of PAD. The use of distal embolic protection devices during angioplasty and a better understanding of lesion characteristics that predict restenosis will improve the outcomes of these procedures. Patients with short segment lesions and those at high surgical risk are excellent candidates for angioplasty, and those with common femoral or iliac stenosis who are good surgical candidates are better suited for stenting. Although there currently is general lack of consensus on the best medical therapy to accompany these procedures, patients with extensive occlusive disease and those with critical limb ischemia are at high risk for limb loss and may benefit most from bypass surgery. This option provides the best chance for limb salvage and is underutilized in this high-risk population. Overall, a careful consideration of the risks and benefits of each procedure in the context of the individual patient is essential.