- Atherosclerosis obliterans (ASO), especially of the lower extremities, is associated with spectrum of cutaneous findings of slowly progressive ischemic changes.
- Symptoms range from intermittent claudication with exertional muscle pain and fatigue to limb ischemia with rest pain and tissue damage and acute ischemia.
- Cutaneous findings range from dry skin, hair loss, onychodystrophy, gangrene, and ulceration.
- Atheroembolism is the phenomenon of dislodgment of atheromatous debris from a proximal affected artery or aneurysm with centrifugal microembolization and resultant acute ischemic and infarctive cutaneous lesions.
- More common with advanced age and invasive procedures.
- Manifestations are blue or discolored toes (“blue toe”), livedo reticularis, and gangrene.
Atherosclerosis is the cause of 90% of arterial disease in developed countries, affecting 5% of men >50 years; 10% (20% of diabetics) of all men with atherosclerosis develop critical limb ischemia.
Risk Factors for Atherosclerosis
Cigarette smoking, hyperlipidemia, low high-density lipoprotein (HDL), high low-density lipoprotein (LDL), high cholesterol, hypertension, diabetes mellitus, hyperinsulinemia, abdominal obesity, family history of premature ischemic heart disease, personal history of cerebrovascular disease or occlusive peripheral vascular disease.
Diabetes Mellitus and Lower Leg Ischemia
Gangrene of lower extremities is estimated to be up to 150 times more frequent in diabetic than in nondiabetic individuals, most often occurring in those who smoke.
Atherosclerosis is the most common cause of arterial insufficiency and may be generalized or localized to the coronary arteries, aortic arch vessels to the head and neck, or those supplying the lower extremities, i.e., femoral, popliteal, anterior and posterior tibial arteries. Atheromatous narrowing of arteries supplying the upper extremities is much less common. Atheromatous deposits and thromboses occur commonly in the femoral artery in Hunter canal and in the popliteal artery just above the knee joint. The posterior tibial artery is most often occluded where it rounds the internal malleolus, the anterior tibial artery where it is superficial and becomes the dorsalis pedis artery. Atheromatous material in the abdominal or iliac arteries can also diminish blood flow to the lower extremities as well as break off and embolize downstream to the lower extremities (atheroembolization). Detection of atherosclerosis is often delayed until an ischemic event occurs, related to critical decrease in blood flow.
In addition to large-vessel arterial obstruction, individuals with diabetes mellitus often have microvasculopathy associated with endothelial cell proliferation and basement membrane thickening of arterioles, venules, and capillaries (see Section 15, Diabetic Dermopathy).
Multiple small deposits of fibrin, platelet, and cholesterol debris embolize from proximal atherosclerotic lesions or aneurysmal sites. Occurs spontaneously or after intravascular surgery or procedures such as arteriography, fibrinolysis, or anticoagulation. Emboli tend to lodge in small vessels of skin and muscle and usually do not occlude large vessels.
Atherosclerosis of Lower Extremity Arteries
Pain on exercise, i.e., intermittent claudication. With progressive arterial insufficiency, pain and/or paresthesias at rest occur in leg and/or foot, especially at night. Individuals with arterial insufficiency of the lower extremities often have symptoms of ischemic heart disease (coronary artery disease or arteriosclerotic heart disease), diabetes mellitus.
Acute pain and tenderness at site of embolization. “Blue toe,” “purple toe” syndrome: peripheral ischemia, livedo reticularis of sudden onset may be accompanied by embolization to kidney, pancreas, muscle, etc.
General findings associated with ischemia include pallor, cyanosis, livedoid vascular pattern (Fig. 16-1), loss of hair on affected limb. Earliest infarctive changes include well-demarcated maplike areas of epidermal necrosis. Later, dry black gangrene may occur over the infarcted skin (purple cyanosis → white pallor → black gangrene) (Fig. 16-2). Shedding of slough leads to well-demarcated ulcers in which underlying structures such as tendons can be seen.
Atherosclerosis obliterans, early The great toe shows pallor and there is mottled, livedoid erythema on the tip of the toe. In this 68-year-old diabetic man, the iliac artery was occluded.
Atherosclerosis obliterans A. There is pallor of the forefoot and mottled erythema distally with incipient gangrene on the great toe and the second digit. This is a female diabetic with partial occlusion of the femoral artery. The patient was a smoker. B. More advanced gangrene of the second to the fifth toe, the great toe is ebony white and will also turn black.
Pulse of large vessels usually diminished or absent. In diabetics with mainly microangiopathy, gangrene may occur in the setting of adequate pulses. Temperature of foot: cool to cold.
With significant reduction in arterial blood flow, limb elevation causes pallor (best noted on plantar foot); dependency causes delayed and exaggerated hyperemia. Auscultation over stenotic arteries reveals bruits.
Ischemic ulcers are painful; in diabetics with neuropathy and ischemic ulcers, pain may be minimal or absent.
Ischemic ulcers may first appear between toes at sites of pressure and beginning on fissures on plantar heel. Dry gangrene of feet, starting at the toes or at ...