I. Disease Overview
Arteriosclerosis obliterans is a disease in which atherosclerotic lesions involve the peripheral arteries and cause chronic occlusion. It is most commonly seen in large and medium-sized arteries in the lower part of the abdominal aorta. The disease is characterized by atherosclerotic plaques and their internal bleeding or rupture, leading to secondary thrombosis and progressive luminal narrowing or occlusion, resulting in clinical manifestations such as ischemia of the affected limb.
The disease is mostly seen in the elderly, the age of onset is mostly between 50 and 70 years old, more men than women, women only account for 8% to 10%. The disease occurs 11 times more frequently in diabetic patients than in non-diabetic patients, and it develops at an earlier age and is more likely to affect smaller caliber and more distal parts of the artery. About 35% of patients have hypertension.
Etiology and pathology
This disease is a part of systemic atherosclerosis, and its etiology and pathogenesis have not been fully elucidated. Many factors are involved, but it is well documented that disorders of lipid metabolism, alterations in hemodynamics, dysfunction of the arterial wall, and disorders of the coagulation and fibrinolytic systems are important factors (see “Atherosclerosis”). Changes in the stress, tension, and pressure of blood flow in certain vascular regions are the basis for the pathogenesis of the disease.
The persistent pressure of turbulent and eddy flow at the diagonal of a vessel branch or bifurcation can lead to endothelial cell damage and proliferation, so that segmental lesions are often seen at the bifurcation of the common carotid artery from the internal carotid artery and the aorta from the iliac artery; in the standing position, higher blood pressure in the lower body may account for more involvement of the lower extremities than the upper extremities.
Occlusive atherosclerosis is more common in the lower abdominal aorta, iliac artery and femoral artery, and less commonly in the upper extremity arteries, occasionally in the proximal subclavian and ulnar arteries. In some elderly patients or those with diabetes mellitus, lesions may first occur in smaller arteries, such as the anterior and posterior tibial arteries. Later in the course of the disease, the artery often becomes dilated, stiffened, striated, or irregularly twisted.
See “Atherosclerosis” for changes in the arterial wall. Rarely, the artery may become dilated and form an aneurysm.
The degree of ischemia in the affected limb depends on the site, degree, and extent of the arterial occlusion, the rate at which the occlusion occurs, and the degree of compensation for the establishment of collateral circulation. In occlusion of the arterial circulation in the arm, because of the rich network of collateral branches in the neck, scapular girdle and elbow may be sufficient to prevent ischemic symptoms. Symptoms in the arm are usually caused by obstructive lesions of the subclavian and cephalic brachial arteries close to the aortic arch.
Stenoses of less than 75% usually do not affect blood flow to the limb at rest, and stenoses of ≥60% occur during exercise before limb ischemia occurs. Ischemia of the affected limb tissue is followed by skin atrophy and thinning, loss of subcutaneous fat replaced by fibrous, connective tissue, bone sparing, muscle atrophy, and ischemic neuritis. Gangrene can develop later, often starting at the end of the affected limb and can be confined to the toes or extend to the foot or lower leg, but rarely beyond the knee joint. Patients with diabetes are susceptible to gangrene and infection of the tissues.
III. Symptoms
The symptoms of this disease are mainly due to localized blood supply deficiency to the limb caused by arterial stenosis or occlusion. The earliest symptoms are coldness, numbness and intermittent claudication of the affected limb. If occlusion occurs in the lower abdominal aorta or iliac artery, there is soreness, weakness and pain throughout the buttocks and lower extremities when walking, and there may be manifestations of impotence of vascular origin; if symptoms occur in the lower legs, there may be occlusion of the femoral or N artery; if symptoms involve the foot or toe, there may be occlusion of the artery as low as the ankle. Arteriosclerosis of the upper extremities may also manifest as intermittent claudication of the upper extremities; tinnitus, vertigo, dysarthria, diplopia, bilateral blurred vision, unilateral or bilateral sensory loss, and even fainting due to “cerebral steal syndrome”.
As the disease progresses, the degree of ischemia increases and persistent resting pain in the lower extremities develops, often aggravated in the elevated position of the limb and relieved in the drooping position, and the pain is more intense at night. The affected limb has pale skin, decreased temperature, decreased sensation, thinning of the skin, loss of sweat hair, muscle atrophy, thickened and deformed toenails, and sparse bone. Later, dry gangrene and ulcers of the toes, feet or lower legs may develop. Diabetic patients often have wet gangrene and secondary infection.
Arterial pulsations in the affected limb are weak or absent, and blood pressure is reduced or undetectable; the difference in blood pressure between the two arms may be ≥2.67 kPa (20 mmHg) in upper limb lesions. If the artery of the affected limb is partially obstructed, a systolic blowing murmur of the vessel can be heard in the narrowed arterial region, which often indicates a ≥70% reduction in the lumen; rarely, an aneurysm can be detected, mostly in the femoral artery below the N fossa or inguinal ligament.
The color of the affected limb changes, especially the foot and toes are pale when elevated and flushed and purple when lowered, suggesting arterial ischemia at the microcirculatory level; the skin temperature of the two limbs is different, with the affected foot becoming cooler and colder; the “congested knee sign”: in the case of obstruction of the distal superficial femoral artery or the proximal and middle segments of the N artery, the affected knee is warmer than the healthy side, and the temperature difference between the two knees can be 2-5° F. This sign indicates the presence of periprosthetic collateral circulation from the deep femoral artery.
Both lower extremities may be involved at the same time, often with clinical manifestations of hypertension, diabetes mellitus or other internal organs such as brain, heart, kidney, mesentery and other atherosclerosis.
IV. Laboratory examination
(A) General examination including lipid and blood sugar measurement, electrocardiogram and exercise test, etc.
(B) Walking test Ask the patient to step in place at a certain speed for a specified period of time until the symptoms of claudication appear. According to the location and time of muscle pain, fatigue and tightness, the location and severity of the lesion can be initially indicated.
(C) affected limb elevation and drop test In a warm room, elevate the limb above the horizontal position for 1 to 2 minutes to observe the skin color of the plantar surface of the foot. The bottom of the foot remains pink in normal people; when the affected limb has insufficient lateral circulation, the bottom of the foot is pale; if it turns pale after exercise, it means that the lesion is not too serious. Then make the affected limb droop, observe the dorsal foot vein filling time and foot reddening time. In normal people, the filling time of veins is <20s and the reddening time is <10s. Generally, it is considered that the reddening time of the limb does not recover within 15s as moderate ischemia, does not recover within 30 seconds as obvious ischemia, and does not recover within 60 seconds as severe ischemia.
(iv) Capillary filling time The color recovers immediately after compression of the nail bed or the soft tissue on the metatarsal side of the toe (palmar side of the finger) when normal, and should be considered as having ischemia if the color recovers >2s. The color recovery time of the affected limb is significantly longer.
(E) Ultrasonic vascular examination.
①Manometry: ankle/brachial index <1 in the affected limb, <0.4 suggests significant ischemia in the affected limb. If the symptoms of the affected limb are typical and the blood pressure of the foot is close to the blood pressure of the arm, the blood pressure should be measured after the exercise of the affected limb. In normal individuals, blood pressure may decrease slightly for about 30 seconds after exercise and then rise to slightly higher than before exercise. However, in those with arterial obstruction or stenosis, the blood pressure of the affected limb decreases after exercise and only gradually returns to the pre-exercise level after 5 minutes. If the ankle systolic pressure is below 8kPa (60mmHg), it suggests that the limb is significantly ischemic; if it is below 4kPa (30mmHg), it is severely ischemic and the affected limb will soon develop resting pain and ischemic ulceration or gangrene of the limb.
(ii) Color ultrasound Doppler examination: the degree of stenosis and the lesion status of atheromatous plaque can be detected directly.
(vi) Impedance volumetric tracings This method is valuable in identifying normal, intermittent claudication from resting painful limbs. In particular, peak arterial blood flow [ml/(s・100 ml tissue)] was measured during reactive congestion in the lower extremities, 24.8±1.6 in normal subjects, 10.5±1.3 in those with intermittent claudication, and 5.3±0.5 in those with resting pain.
(vii) Transcutaneous tissue oxygen tension measurement (PtcO2) This method is used to understand tissue blood perfusion by measuring local oxygen release. PtCO2 values in normal subjects are 8.07-9.95 kPa (60.7±7.48 mmHg), increasing by an average of 1.33 kPa (10 mmHg) in the standing position, then increasing by another 0.53 kPa (4 mmHg) during exercise, and then slowly decreasing and returning to the resting level after 10 minutes. PtcO2 values were close to normal at rest in those with intermittent claudication, but decreased significantly after exercise. PtcO2 before exercise in those with resting pain was only 5.83-6.01kPa (4.38±4.52mmHg).
(H) X-ray examination
1. Plain film examination of the affected limb may reveal irregular calcified spots at the arteries, which often suggest the site of occlusive lesions. If a diffuse and uniform thin layer of calcification is seen on the artery, or the edge of the artery shows a dentate calcification shadow, it is suggestive of calcification in the middle layer of the artery. Ankle or foot radiographs may show the presence of bone sparing. The presence or absence of bone atrophy, osteomyelitis or joint destruction can be determined for those with ulcers or gangrene.
2.Arteriography can reveal the site, extent and degree of obstruction of the arteries in the affected limb, as well as the establishment of collateral circulation.
3.Magnetic resonance can image carotid intimal plaque and larger arterial branches in the abdominal cavity, and can especially identify the patency of the entrapped aneurysm and graft vessels.
V. Diagnosis and differentiation
Men, over 50 years old, with chronic ischemic symptoms of lower or upper extremities and diminished or absent arterial pulsation; with clinical manifestations of atherosclerosis in hypertension, hyperlipidemia, diabetes mellitus and/or other internal organs such as brain, heart and kidney; and X-ray films showing patchy calcified shadows within the arterial wall should suspect the possibility of this disease. Arteriography can confirm the diagnosis.
The disease should be differentiated from other chronic arterial occlusive lesions, including thrombo-occlusive vasculitis, polyarteritis and polyarteritis nodosa.
VI. Treatment
(a) General treatment: limit physical activity, bed rest should be kept in a slightly drooping position with the affected limb 20° to 30° below the horizontal plane and avoid direct heat; quit smoking (smoking can lead to vasospasm); regular exercise should be made: patients should walk under guidance to the distance that causes claudication pain, however, stop walking and rest until the symptoms are relieved. Then, re-walk for about 20 to 30 minutes of exercise. Exercise increases the collateral circulation and enhances the function of muscle groups; treat hyperlipidemia and control diabetes; keep the skin of the affected limb clean, dry and soft, and prevent it from freezing and trauma; if the affected limb has infection or trauma it should be treated quickly.
(B) vasodilators: it is debated whether such drugs are effective in this disease. In some cases, the ischemic damage is aggravated by lowering the arterial pressure and reducing the collateral blood flow or shifting the blood flow to the healthy area proximal to the lesion, resulting in lower perfusion pressure in the distal affected limb. When it must be applied, refer to the section on “thrombo-occlusive vasculitis”. Recently, it has been proposed that oral administration of pentoxifylline, 400 mg three times a day, can prolong the movement time of the affected limb and increase the deformability of red blood cells and reduce blood viscosity.
(C) Anti-platelet aggregation drugs: refer to the section of “polyarteritis major”.
(iv) Anticoagulation therapy: Generally used after bypass surgery or PTA surgery, usually treated with warfarin, its usage and dosage refer to the section of “coronary artery atherosclerotic heart disease”.
(E) Plasma exchange therapy: see “Raynaud’s syndrome”.
(f) Surgery: In view of the segmental nature of the lesion and the fact that it mostly occurs in large and medium-sized arteries, about 80% of patients can be treated surgically. Surgery is indicated for patients with severe resting pain, progressive increase in symptoms, and the possibility of ulceration or gangrene. Lumbar sympathectomy can be used as an adjunctive surgical treatment to increase blood flow to the skin of the affected limb and promote healing of the skin ulcer. Most of them use artificial vessels or autologous saphenous vein bypass grafting, or endarterectomy to unblock the arterial blood flow to the affected limb.
(vii) Traditional Chinese medicine ointment: For dry gangrene and ulcers of the toe, foot or lower leg that can arise in the later stages, the application of traditional Chinese medicine ointment is very important. Commonly used Puji ulcer cream, with live blood block, anti-inflammatory and hemostatic, remove rot and produce new, grow skin, prevent deepening of the wound, promote wound healing effect, before using saline cotton ball wipe clean ulcer wound, get rid of necrotic decay tissue, then spread the ulcer cream on gauze dressing about 2 mm thick, dressing cover paste on the wound, adhesive tape strip fixed, change medicine once every 1 day. With clinical medication, better results can be achieved.
(H) Interventional treatment: It is mainly applied to those with relatively short stenotic segments and vessels not yet completely blocked. The main methods are percutaneous balloon dilatation angioplasty, percutaneous endoluminal rotation or rotation grinding. Interventional treatment is simple, has a low disability rate, is inexpensive, has a high success rate, and can be used repeatedly. The dilated vessels have a good long-term patency rate, but the restenosis rate is still as high as 20% to 30% within 1 year due to thrombosis, intimal and mesangial hyperplasia.
VII. Prognosis prevention
Prevention of atherosclerosis (see “Atherosclerosis”) and avoidance of vasoconstrictive drugs are the main concerns. The affected limb should be protected from cold, but do not bake or sunbathe; do not sit with legs crossed, keep the skin of the affected limb clean and dry; cut the toenail in time, but do not cut too close to the skin; do not wear too tight shoes and socks, and do not walk barefoot; treat corns and calluses in time to avoid injury, and self-examine the affected foot every week for cracks and wounds, and treat them with local medication in time.