Wednesday, May 3, 2017

Arterial occlusive disease

With arterial occlusive disease, the obstruction or narrowing of the lumen of the aorta and its major branches causes an interruption of blood flow, usually to the legs and feet. Arterial occlusive disease may affect the carotid, vertebral, innominate, subclavian, mesenteric, or celiac artery. Occlusions, which may be acute or chronic, often cause severe ischemia, skin ulceration, and gangrene.
Arterial occlusive disease is more common in males than in females. The prognosis depends on the location of the occlusion, the development of collateral circulation to counteract reduced blood flow and, if the patient has acute disease, the time elapsed between occlusion and its removal.
Arterial occlusive disease is a common complication of atherosclerosis. The occlusive mechanism may be endogenous, due to embolus formation or thrombosis, or exogenous, due to trauma or fracture. Predisposing factors include smoking; aging; conditions such as hypertension, hyperlipidemia, and diabetes; and a family history of vascular disorders, myocardial infarction, or stroke.
Signs and symptoms
Evidence of this disease varies widely, according to the occlusion site. (see table at the end of the article)

With arterial occlusive disease, the diagnosis is usually based on patient history and physical examination.
Pertinent supportive diagnostic tests include the following:
  • Arteriography demonstrates the type (thrombus or embolus), location, and degree of obstruction and collateral circulation. Arteriography is particularly useful in patients with chronic disease or for evaluating candidates for reconstructive surgery.
  • Doppler ultrasonography and plethysmography are noninvasive tests that, in acute disease, show decreased blood flow distal to the occlusion.
  • Ophthalmodynamometry helps determine the degree of obstruction in the internal carotid artery by comparing ophthalmic artery pressure with brachial artery pressure on the affected side. A more than 20% difference between pressures suggests insufficiency.
  • EEG and a computed tomography scan may be necessary to rule out brain lesions.
Effective treatment depends on the cause, location, and size of the obstruction. The goal of medical management is to impede progression of peripheral arterial occlusive disease. 

For mild chronic disease, supportive measures include elimination of smoking, control of hypertension, and initiation of a walking program. 

For carotid artery occlusion, antiplatelet therapy may begin with aspirin. 

For intermittent claudication of chronic occlusive disease, pentoxifylline may improve blood flow through the capillaries, particularly in patients who are poor candidates for surgery. Exercise also plays a vital role in treatment for claudication.
Acute arterial occlusive disease usually requires surgery to restore circulation to the affected area.
Possible procedures include the following:
Embolectomy— A balloon-tipped catheter is used to remove thrombotic material from the artery. Embolectomy is used mainly for mesenteric, femoral, or popliteal artery occlusion.
Thromboendarterectomy—The occluded artery is opened and the obstructing thrombus and the medial layer of the arterial wall removed. This procedure is usually performed after angiography and is commonly used with autogenous vein or Dacron bypass surgery (femoral-popliteal or aortofemoral).
Patch grafting— This procedure involves removal of the thrombosed arterial segment and replacement with an autogenous vein or Dacron graft.
Bypass graft— Blood flow is diverted through an anastomosed autogenous or Dacron graft past the thrombosed segment.
Thrombolytic therapy— Any clot around or in the plaque is lysed by urokinase, streptokinase, or alteplase.
Atherectomy— Plaque is excised using a drill or slicing mechanism.
Balloon angioplasty— The obstruction is compressed using balloon inflation.
Laser angioplasty— Excision and hot-tip lasers are used to vaporize the obstruction.
Stents— A mesh of wires that stretch and mold to the arterial wall are inserted to prevent reocclusion.
Combined therapy— Any of the above treatments are used concomitantly.
Lumbar sympathectomy— The procedure is an adjunct to surgery, depending on the condition of the sympathetic nervous system.
Amputation becomes necessary with failure of arterial reconstructive surgery or with the development of gangrene, persistent infection, or intractable pain.
Other treatments include heparin to prevent embolus formation (for embolic occlusion) and bowel resection after restoration of blood flow (for mesenteric artery occlusion)

Clinical features of arterial occlusive disease
Site Of OcclusionSigns and symptoms
Aortic bifurcation (saddle block occlusion, an emergency associated with cardiac embolization)Sensory and motor deficits (muscle weakness, numbness, paresthesia, paralysis) and signs of ischemia (sudden pain; cold, pale legs with decreased or absent peripheral pulses) in both legs
Carotid arterial system
  • Internal carotid arteries
  • External carotid arteries
Neurologic dysfunction (transient ischemic attacks [TIAs] due to reduced cerebral circulation produce unilateral sensory or motor dysfunction [transient monocular blindness, hemiparesis], possible aphasia or dysarthria, confusion, decreased mentation, and headache; these recurrent clinical features usually last 5 to 10 minutes but may persist up to 24 hours and may herald a stroke); absent or decreased pulsation with an auscultatory bruit over the affected vessels
Femoral and popliteal arteries
(associated with aneurysm formation)
Intermittent claudication of the calves on exertion; ischemic pain in feet; pretrophic pain (heralds necrosis and ulceration); leg pallor and coolness; blanching of feet on elevation; gangrene; no palpable pulses in ankles and feet
Iliac artery
(Leriche’s syndrome)
Intermittent claudication of lower back, buttocks, and thighs relieved by rest; absent or reduced femoral or distal pulses; possible bruit over femoral arteries; impotence
Brachiocephalic artery
Neurologic dysfunction (signs and symptoms of vertebrobasilar occlusion); indications of ischemia (claudication) of right arm; possible bruit over right side of neck
Mesenteric artery
  • Superior (most commonly affected)
  • Celiac axis
  • Inferior
Bowel ischemia, infarct necrosis, and gangrene; sudden, acute abdominal pain; nausea and vomiting; diarrhea; leukocytosis; and shock due to massive intraluminal fluid and plasma loss
Subclavian arterySubclavian steal syndrome (characterized by the backflow of blood from the brain through the vertebral artery on the same side as the occlusion, into the subclavian artery distal to the occlusion); clinical effects of vertebrobasilar occlusion and exercise-induced arm claudication; possible gangrene, usually limited to the digits
Vertebrobasilar system
  • Vertebral arteries
  • Basilar arteries
Neurologic dysfunction (TIAs of brain stem and cerebellum produce binocular visual disturbances, vertigo, dysarthria, and “drop attacks” [falling down without loss of consciousness]); less common than carotid TIA

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