Arteriosclerosis obliterans (ASO) is a systemic disease that primarily affects large and medium-sized arteries. When it involves the abdominal aorta and its distal main arteries, it can lead to chronic ischemia in the lower limbs. It is more common in males, typically occurring at an age over 45, with an increasing incidence. Patients often have concurrent atherosclerotic lesions in other vascular regions.
Etiology and Pathology
The exact cause is not fully understood. High-risk factors include hyperlipidemia, hypertension, smoking, diabetes mellitus, and obesity. The main pathological changes include the presence of atherosclerotic plaques in the intima and degeneration or calcification of the medial layer, with or without secondary thrombosis. These changes ultimately result in luminal narrowing or complete occlusion. Embolization of distal arteries may occur due to the detachment of thrombi or plaques.
Clinical Manifestations
The severity of symptoms depends on the disease progression, the degree of arterial stenosis, and collateral compensation in the lower limbs. Early symptoms include cold sensation and pallor of the affected limb, progressing to intermittent claudication. When the lesion is localized in the aortoiliac arteries, pain may occur in the buttocks, hips, or thighs, potentially accompanied by impotence. When the femoropopliteal arteries are affected, the pain is more commonly felt in the calf muscles.
In advanced stages, affected limbs may exhibit a markedly reduced temperature and appear pale or cyanotic. Rest pain occurs, and ischemic ulcers or gangrene may develop in the distal extremities. Pulses in the femoral, popliteal, posterior tibial, and dorsalis pedis arteries may be diminished or absent in the affected limb.
Diagnostic Assessments
As a systemic disease, comprehensive evaluations are necessary, including lipid profiling and assessments of cardiac, cerebrovascular, renal, and fundoscopic conditions. The following tests aid in diagnosis and disease evaluation:
General Examination
Palpation and auscultation of the arteries in the extremities and neck, recording intermittent claudication time and distance, comparison of skin temperature differences between corresponding areas in both limbs, and the Buerger test for limb elevation.
Specialized Tests
Doppler Ultrasound
This evaluates wall thickness, degree of stenosis, and the presence of mural thrombi, while measuring blood flow velocity. A pressure comparison between different segments of the same limb or corresponding segments in both limbs showing a difference of more than 20–30 mmHg indicates arterial occlusive changes in the side with reduced pressure.
The ankle-brachial index (ABI), calculated as the ratio of ankle artery pressure to the higher brachial artery pressure, is also used. The normal range is 0.9–1.3; values <0.9 indicate arterial ischemia, and values <0.4 suggest severe ischemia. In patients with severe arterial calcification, ABI values may be unreliable.
Angiography (DSA, MRA, and CTA)
This identifies the site, extent, and distal runoff of arterial stenosis or occlusion, as well as collateral circulation. These findings confirm the diagnosis and guide treatment planning.
Diagnosis and Classification
For individuals over 45 with clinical manifestations of chronic limb ischemia, ASO should be considered. The diagnosis can be established based on positive findings from the aforementioned examinations, especially evidence of stenosis or occlusion primarily involving large and medium-sized arteries. Disease severity can be classified using the Rutherford Classification:
- Grade 1: Mild intermittent claudication with a maximum walking distance >500 meters.
- Grade 2: Moderate intermittent claudication with a maximum walking distance of 300–500 meters.
- Grade 3: Severe intermittent claudication with a maximum walking distance <300 meters.
- Grade 4: Rest pain, characterized by persistent, severe lower limb pain even at rest, worsening at night.
- Grade 5: Minor tissue loss or active ulcers.
- Grade 6: Extensive tissue ulcers or gangrene.
The diagnosis requires exclusion of non-vascular causes such as lumbar spinal stenosis, herniated discs, sciatica, polyneuritis, or bone and joint diseases in the lower limbs. Differential diagnosis with the following arterial diseases is also necessary:
- Thromboangiitis Obliterans: Common in young adults and characterized by segmental occlusion of middle and small arteries, often with a history of migratory superficial thrombophlebitis, and typically without coronary artery disease, hypertension, hyperlipidemia, or diabetes mellitus.
- Takayasu Arteritis: Predominantly affects young females, involving the aorta and its proximal branches, often presenting with elevated erythrocyte sedimentation rate and abnormal immune markers during the active phase.
- Diabetic Foot: Characterized by diabetes mellitus with concurrent vascular complications involving multiple organ systems. Infection often leads to diabetic ulcers or gangrene, commonly in high-pressure areas such as the toe pads, heel, and other weight-bearing regions of the foot, with ulcers that can extend into deeper tissues such as tendons and bones.
Treatment
Non-Surgical Treatment
The primary goals are to lower lipid levels, stabilize arterial plaques, improve hypercoagulable states, dilate blood vessels, and promote collateral circulation. Methods include weight management, smoking cessation, and moderate exercise. Antiplatelet aggregation and vasodilator drugs such as aspirin and alprostadil may be used. Hyperbaric oxygen therapy can increase oxygen levels in the blood, enhance oxygen diffusion in the limbs, and alleviate tissue hypoxia.
Surgical Treatment
The objective is to restore arterial blood flow through surgical or endovascular methods.
Percutaneous Transluminal Angioplasty (PTA)
This procedure involves introducing a balloon catheter via percutaneous puncture to the stenotic artery segment. Balloon inflation under appropriate pressure expands the narrowed lumen and restores blood flow. Metal stents prevent elastic vessel recoil and maintain lumen patency. Drug-coated balloons that release paclitaxel at the lesion site can inhibit intimal hyperplasia and improve long-term patency. Endovascular treatment has shown favorable short-term outcomes for salvaging limbs in cases of single or multiple stenotic or occlusive lesions in the iliac, femoral, and distal main arteries. However, long-term issues such as elastic recoil and in-stent restenosis may occur, resulting in recurrence of symptoms.
Endarterectomy
This procedure removes the thickened intima, atherosclerotic plaques, and secondary thrombi from the affected artery segment. It is primarily suitable for short-segment lesions of the common femoral artery.
Bypass Grafting
Autologous veins or synthetic grafts are used to create a bypass between the proximal and distal ends of the occluded segment. When performing bypass surgery, a clear arterial inflow and outflow pathway is essential. The anastomoses should be sufficiently large and located as far as possible from atherosclerotic lesions. For limited atherosclerotic plaques, endarterectomy may first be performed to create suitable conditions for the anastomosis.
Wound Management
For wounds with dry gangrene, disinfection and bandaging are required to prevent secondary infections. Infected wounds may be managed with wet dressings. In cases where tissue necrosis is clearly demarcated or when severe infection leads to toxemia, amputation (of the toes or fingers) may be necessary. The appropriate use of antibiotics is essential.