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![[SYMPOSIUM]](../../../graphics/sym_logo.gif){kind=logo} Current trends in peripheral vascular surgeryWhen is surgical intervention the best option?Michael E. Gorton, MD VOL 106 / NO 3 / SEPTEMBER 1999 / POSTGRADUATE MEDICINE
CME learning objectives
This is the third of three articles on peripheral vascular disease Preview: Vascular surgery continues to evolve as technology uncovers new insights into the causes and treatment of arterial, venous, and lymphatic diseases. Even with all the advances of the past decade, traditional surgical procedures still play a role in improving the quality of life and saving the limbs of many patients. But when and for whom is operative intervention appropriate? In this article, Dr Gorton highlights recent advances and discusses how they affect current surgical practice. Surgical correction of peripheral vascular defects is safe and effective for many patients in whom less invasive procedures are not adequate. Success rates have improved steadily over the years, and surgery can benefit even many of the oldest and sickest patients. Early detection, which often falls to the primary care physician, is the key to successful outcome for problems ranging from aneurysm to various occlusive arterial and venous diseases. AneurysmsAn aneurysm, the most common lethal peripheral vascular abnormality, is an artery whose diameter is 1.5 times normal. Once an aneurysm develops, it almost always continues to enlarge. The annual rate of growth averages 0.5 cm, but this varies widely. The underlying cause is not completely understood, but a congenitally abnormal matrix within the arterial wall is probably involved. Coexisting medical conditions, such as diastolic hypertension and chronic obstructive pulmonary disease (COPD), are known risk factors, and some reports suggest a hereditary link (1-3). However, these factors are weak predictors of aneurysm, which tends to occur at random. The most worrisome aspect of aneurysms is their relative silence until they rapidly expand or rupture. Most aneurysms are discovered incidentally during other examinations, which reinforces the importance of the routine abdominal examination. The obvious question is, When and in whom is screening appropriate (4,5)? In an ideal world, everyone over age 50 would have annual abdominal ultrasound examination. This is the most cost-effective screening tool available, and its sensitivity is 98% to 99% (6). Since routine examinations are not practical, my personal bias is to screen patients who are over age 50 and whose health and body shape preclude a good abdominal physical examination, especially those with COPD or diastolic hypertension. Once an aneurysm is discovered, many factors affect the course of treatment. The natural history of untreated abdominal aneurysms results in a linear annual increase in rupture (figure 1: not shown) (7). The risk of rupture at 5 cm is about 10% per year, and most authorities agree that unless a patient is at extremely high operative risk, surgical intervention is warranted. We believe that most patients who are living independently should be offered resection for an aneurysm that measures 5 cm or larger. In a series of 574 aneurysms resected during the last 25 years at Mid-America Heart Institute, the mortality rate was 1.6% overall but 0.4% for patients operated on after 1986 (8). This is one of the lowest mortality rates reported to date and is particularly striking because the patients were relatively old and often had age-related comorbidities. Only a handful of patients in the series were denied resection. We attributed the low operative mortality to rigorous preoperative cardiac evaluation.
Evaluating the risks Aneurysms involving the iliac arteries are also likely to rupture. The common and external iliac arteries are normally 1 to 1.5 cm in diameter. Therefore, enlargement to a diameter of 2 to 2.5 cm warrants further investigation. Aneurysmal changes in the internal iliac and visceral arteries are rare but require immediate repair (10,11). Peripheral aneurysms involving the femoral or popliteal regions behave differently than intraabdominal aneurysms. Peripheral lesions rarely rupture but are often associated with the risk of laminated thrombus and thromboemboli. These aneurysms require aggressive surgical intervention. Generally the artery is ligated, and a bypass graft is placed around the aneurysm (figure 2: not shown).
Preoperative considerations If the patient has coexisting severe hypertension and renal artery stenosis, a concomitant renal artery bypass is performed. Bypass of a high-grade asymptomatic renal artery stenosis preserves renal function and helps control blood pressure (12). Because renal artery bypass can be accomplished without increasing the operative risk, I prefer to perform a bypass on those arteries with stenosis of greater than 90%. If there is evidence of severe aortoiliac occlusive disease, the aortic graft is extended to the femoral arteries. Careful history taking and physical examination are essential before operation, and major comorbidities must be carefully assessed. The leading cause of perioperative mortality is myocardial infarction. Most of the patients in our practice have preexisting coronary artery disease and have undergone evaluation by a cardiologist. Most have also had a radionuclide cardiac stress test. Among 511 patients undergoing resection in our practice, only 2 (0.4%) had a perioperative myocardial infarction. This is one of the lowest incidences reported to date, and we believe it reflects our aggressive preoperative posture. Current recommendations for the general population support cardiac screening, thorough history taking and physical examination, and electrocardiographic evaluation. Although severe COPD is a significant risk factor, we have operated on patients whose forced expiratory volume in 1 second was 700 to 800 mL but had no major sequelae. Our experience suggests that surgery is contraindicated in only a few patients. Arteriosclerosis obliteransArteriosclerosis obliterans of the lower extremities is a major cause of morbidity and mortality, especially in patients with diabetes. These lesions usually occur in one of three regions: the aortoiliac distribution, the superficial femoral distribution, or the tibial arteries. However, patients with advanced disease often have involvement in all three areas.
Aortoiliac occlusive disease The preoperative workup is similar to the aneurysm evaluation, except that aortography with runoff is needed to define the extent of the disease. Improved noninvasive imaging techniques, including vascular ultrasound with Doppler and color flow or magnetic resonance angiography, are eliminating the need for iodinated dyes that potentially contribute to renal failure (13). Aortobifemoral bypass with a prosthetic graft has been the traditional treatment of choice for aortoiliac occlusive disease since the 1960s. The operative morbidity and mortality are in the 2% range, and long-term patency exceeds 90%. For patients who have already had multiple abdominal operations, thoracic-to-aorta-to-bifemoral bypass is an option that has the same risks and long-term benefits (14). An excellent alternative for high-risk patients and those who have had multiple abdominal procedures is an extra-anatomic axillobifemoral bypass (15). This avoids the need for a major abdominal operation and has a 5-year patency rate that approaches 80%. Recently, endovascular techniques involving angioplasty and stent placement have offered a potentially less invasive alternative. However, more information is needed before they become the "standard of care." Surgery will always be indicated for some patients, including those with long-standing chronic occlusions, stent restenosis, and the complications from endovascular procedures.
Superficial femoral occlusive disease Angiography usually shows occlusion of the superficial artery at its origin, with reconstitution of the popliteal artery either above or below the knee. If the disease is limited to the superficial femoral artery or only one arterial segment, the likelihood of tissue loss is low and nonoperative treatment is appropriate. If life-limiting claudication persists or if pain occurs at rest, more aggressive intervention is warranted. Short areas of disease are readily treated with endovascular techniques. If the lesion is long or chronically occluded, surgical bypass is needed. Artificial grafts provide excellent long-term patency for bypasses to the above-knee popliteal artery. However, nonautogenous bypass grafts to the below-knee vessels have poor long-term patency. The greater saphenous vein is preferred for below-knee procedures.
Tibial artery disease Noninvasive imaging reveals nonpulsatile monophasic Doppler signals in the foot. The ankle- brachial index is typically less than 0.4 before rest pain develops, and any value less than 0.3 almost always results in ischemic tissue loss. Anatomic definition is often difficult because of the slow flow in the tiny vessels. Therefore, delayed angiographic runoff films are required. Magnetic resonance angiographic techniques help delineate small distal vessels and avoid the complications associated with use of iodinated dye. The risk of limb loss is low for patients with claudication alone, but failure of an arterial bypass could result in thrombosis of the vessel above or below the graft and could lead to a nonviable extremity. Therefore, we generally reserve below-knee bypasses for patients with pain at rest and impending tissue or limb loss. Endovascular techniques have limited usefulness in this region, and surgical bypass is generally required. Reversed saphenous bypass, developed in the 1940s, remains the mainstay for bypassing infrageniculate arterial segments. Bypass can successfully be carried out to a single tibial vessel and can reach the dorsum of the foot and distal posterior tibial artery. Isolated peroneal artery bypass, albeit not as successful as procedures using the anterior or posterior tibial vessels, can save a threatened limb (16,17). Leaving the greater saphenous vein in situ and using a valvulotome for valve disruption may have advantages because of better distal size match. This procedure has been used successfully by many surgeons (18). Endoscopic harvesting of saphenous veins is being attempted to avoid the long surgical scars and poor healing associated with removal. However, patients with end-stage peripheral vascular disease often have coexisting disease in the coronary vessels and eventually require coronary bypass surgery as well. The greater saphenous vein then becomes a precious commodity. Alternative conduits include the lesser saphenous vein, arm veins, and cryopreserved human allografts. Unfortunately, these tend to be of poorer quality than the saphenous vein, and long-term results are marginal. As we begin to use more "arterial" grafts in the coronary distribution, the battle between the heart and legs for vein utilization may become less of an issue. Upper extremity diseaseAtherosclerotic disease involving the arms is almost always limited to the larger proximal vessels and rarely involves the brachial, radial, or ulnar arteries. Most people tolerate stenosis or occlusion of the subclavian artery on either side because of the rich supply of collateral vessels around the shoulder. Although these patients may have no symptoms, they can have a large discrepancy in blood pressure between the right and left arms. Therefore, it is always prudent to measure the blood pressure in both arms. Some patients may have symptoms of claudication in the hand and forearm after repetitive motions, but it is exceedingly unusual for ulcerative or gangrenous changes to occur. If the symptoms interfere with quality of life, surgical bypass from the carotid to the subclavian artery can be performed (figure 3: not shown) (19). Deep venous thrombosisLife-threatening rupture, bleeding, or ischemic complications are rare in the venous and lymphatic systems because of their low pressure and redundancy. However, pathologic changes can cause significant morbidity and emotional distress. Deep venous thrombosis (DVT) is perhaps the most dangerous problem, and great care should be taken to prevent it, especially in high-risk situations (eg, perioperative state). Recent evidence suggests that patients at risk are undertreated. Instead of discontinuing prophylaxis for DVT when high-risk patients leave the hospital, it may be prudent to continue anticoagulation medication for 4 weeks after discharge (20). Once DVT has developed, the first steps are to halt the process and dissolve the clot, then take measures to prevent recurrence. If the clot is limited to the deep veins of the leg and is immobile, as evidenced by venous duplex imaging, anticoagulation is indicated, first with intravenous heparin sodium and then with oral warfarin sodium (Coumadin). Subcutaneous injection of low-molecular-weight heparin daily, with conversion to warfarin, is as efficacious as intravenous heparin and may allow outpatient treatment of uncomplicated DVT (21). Patients with DVT have a 30% to 40% risk of recurrence later in life and should be made aware of this risk. Oral anticoagulation should be continued for at least 3 months and perhaps should be extended 6 months or longer. Proximal superficial vein thrombosis can progress to DVT in more than 10% of patients and should be treated like DVT (22). Distal superficial vein thrombosis (ie, below the knee) can be observed with serial duplex imaging and treated if necessary. Extensive involvement of the femoral or pelvic veins, with or without involvement of the inferior vena cava, warrants more aggressive treatment, especially if duplex ultrasound shows that the clot is mobile. Systemic or direct intravenous thrombolysis with tissue plasminogen activator or urokinase (Abbokinase) is being used with increasing frequency. If pulmonary emboli develop despite the use of anticoagulants or if a large, highly mobile clot is evident, an intracaval filter is inserted via a percutaneous route.
Postphlebitic syndrome Once the disease has progressed to this point, the mainstay of treatment is compression stockings and leg elevation. Nonelastic compression stockings seem to be as effective as elastic stockings and are more likely to be worn by the patient (23). Regardless of the type, compression stockings definitely decrease long-term sequelae. New techniques that transpose venous valves from the brachial region to the femoral veins may reduce the severity of postphlebitic syndrome. Another option is iliac vein-to-vena cava bypass if the iliac veins are occluded. However, both of these techniques are experimental, and long-term data are not available. Aggressive thrombolysis has been tried to prevent long-term sequelae in patients with uncomplicated DVT but has not proved to have any significant benefit. Such therapy must be weighed against the risk of major hemorrhage. Varicose veinsAn article on vascular surgery would not be complete without a discussion of the troublesome issue of varicose veins. These range from unsightly spider veins to the bothersome swollen and serpiginous varicosities that engulf the legs. They are a consistent cause for concern among patients. However, because varicosities are not life-threatening, they are treated electively. Cosmetic considerations aside, medical indications for removal of simple purple blemishes on the legs are virtually nonexistent. However, large, undulated, and distended varicosities of the greater and lesser saphenous systems can cause heaviness and significant discomfort in the leg. In these cases, it is reasonable to provide symptomatic relief by using multiple small incisions to ligate and remove the veins. Eversion vein stripping of the entire greater saphenous vein is seldom performed today, and most vascular surgeons plead with patients and physicians alike to preserve the vein if at all possible. Too often we see patients who need a vein for bypass, only to find that the vein was stripped in the past for cosmetic reasons. SummarySurgery continues to play an important role in the management of peripheral vascular disease. Revascularization procedures provide excellent outcomes for many patients at risk for loss of a limb or seriously impaired quality of life. Although endovascular techniques are now being used for managing many vascular problems, the traditional surgical approaches still offer well-documented benefits. References
Dr Gorton is clinical associate professor of cardiothoracic surgery, University of Missouri-Kansas City School of Medicine, and cardiothoracic surgeon, Mid-America Heart Institute, St Luke's Hospital, Kansas City, Missouri. Correspondence: Michael E. Gorton, MD, Mid-America Heart Institute, St Luke's Hospital, 4320 Wornall Rd, Suite 50-II, Kansas City, MO 64111. E-mail: ravencrest@kansascity.com.
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