Arterial embolism


Arterial embolism is a sudden interruption of blood flow to an organ or body part due to an embolus adhering to the wall of an artery blocking the flow of blood, the major type of embolus being a blood clot. Sometimes, pulmonary embolism is classified as arterial embolism as well, in the sense that the clot follows the pulmonary artery carrying deoxygenated blood away from the heart. However, pulmonary embolism is generally classified as a form of venous embolism, because the embolus forms in veins. Arterial embolism is the major cause of infarction.

Signs and symptoms

Symptoms may begin quickly or slowly depending on the size of the embolus and how much it blocks the blood flow. Symptoms of embolisation in an organ vary with the organ involved but commonly include:
Later symptoms are closely related to infarction of the affected tissue. This may cause permanently decreased organ function.
For example, symptoms of myocardial infarction mainly include chest pain, dyspnea, diaphoresis, weakness, light-headedness, nausea, vomiting, and palpitations.
Symptoms of limb infarction include coldness, decreased or no pulse beyond the site of blockage, pain, muscle spasm, numbness and tingling, pallor and muscle weakness, possibly to the grade of paralysis in the affected limb.

Commonly occluded sites

Arterial emboli often occur in the legs and feet. Some may occur in the brain, causing a stroke, or in the heart, causing a heart attack. Less common sites include the kidneys, intestines, and eyes.

Risk factors

Risk factors for thromboembolism, the major cause of arterial embolism, include disturbed blood flow, injury or damage to an artery wall, and hypercoagulability. Mitral stenosis poses a high risk of forming emboli which may travel to the brain and cause stroke. Endocarditis increases the risk for thromboembolism, by a mixture of the factors above.
Atherosclerosis in the aorta and other large blood vessels is a common risk factor, both for thromboembolism and cholesterol embolism. The legs and feet are major impact sites for these types. Thus, risk factors for atherosclerosis are risk factors for arterial embolisation as well:
Other important risk factors for arterial embolism include:
A septal defect of the heart makes it possible for paradoxical embolization, which happens when a clot in a vein enters the right side of the heart and passes through a hole into the left side. The clot can then move to an artery and cause arterial embolisation.

Pathophysiology

An arterial embolism is caused by one or more emboli getting stuck in an artery and blocking blood flow, causing ischemia, possibly resulting in infarction with tissue death. Individuals with arterial thrombosis or embolism often develop collateral circulation to compensate for the loss of arterial flow. However, it takes time for sufficient collateral circulation to develop, making affected areas more vulnerable for sudden occlusion by embolisation than for e.g. gradual occlusion as in atherosclerosis.

Materials

Arterial embolisms can consist of various materials, including:
In contrast, amniotic fluid embolism almost exclusively affects the venous side.

Diagnosis

In addition to evaluating the symptoms above, the health care provider may find decreased or no blood pressure in the arm or leg.
Tests to determine any underlying cause for thrombosis or embolism and to confirm presence of the obstruction may include:
Prevention of atherosclerosis, which is a major risk factor of arterial embolism, can be performed e.g. by dieting, physical exercise and smoking cessation.
In case of high risk for developing thromboembolism, antithrombotic medication such as warfarin or coumadin may be taken prophylactically. Antiplatelet drugs may also be needed.

Treatment

Treatment is aimed at controlling symptoms and improving the interrupted blood flow to the affected area of the body.
Medications include:
Appropriate drug treatments successfully produces thrombolysis and removal of the clot in 50% to 80% of all cases.
Antithrombotic agents may be administered directly onto the clot in the vessel using a flexible catheter. Intra-arterial thrombolysis reduces thromboembolic occlusion by 95% in 50% of cases, and restores adequate blood flow in 50% to 80% of cases.
Surgical procedures include:
If extensive necrosis and gangrene has set in an arm or leg, the limb may have to be amputated. Limb amputation is in itself usually remarkably well tolerated, but is associated with a substantial mortality, primarily because of the severity of the diseases in patients where it is indicated.

Prognosis

How well a patient does depends on the location of the clot and to what extent the clot has blocked blood flow. Arterial embolism can be serious if not treated promptly.
Without treatment, it has a 25% to 30% mortality rate. The affected area can be permanently damaged, and up to approximately 25% of cases require amputation of an affected extremity.
Arterial emboli may recur even after successful treatment.

Complications

Possible complications of arterial embolism depend on the site of the obstruction:
In the United States, approximately 550,000 people die each year from heart-related arterial embolism and thrombosis. Approximately 250,000 of these individuals are female, and approximately 100,000 of all these deaths are considered premature, that is, prior to the age of average life expectancy.