The pulmonary embolism represents the obstruction of the pulmonary arteries. Once the artery is obstructed, usually by one or more emboli, the blood oxygen level decreases and the pulmonary pressure increases.
Pulmonary embolism caused by large thrombus can cause sudden death, usually within 30 minutes of the onset of symptoms. Smaller thrombi can cause irreversible damage to the heart and lungs.
Pulmonary embolism – Causes
Pulmonary embolism is caused by the obstruction of the pulmonary arteries. The main cause of this obstruction is represented an embolus that forms in a deep vein of the lower limbs and circulates to the lung, where it remains stuck in the lower lung artery.
Over 95% of emboli causing pulmonary embolism are formed proximally, in the deep veins of the legs (thigh). Emboli can also be collected from the deep veins of the legs – distally – (from the calf and foot), but also from the deep veins of the pelvis or upper limbs. However, only 20% of emboli from the thigh grow in size, detach and move towards the proximal areas.
Rarely, embolisms form in superficial veins, but they are rare causes of pulmonary embolism.
In exceptional cases, pulmonary embolism can be caused by other substances than thrombi:
– Tumors resulting from the rapid growth of cancer cells
– Gaseous embolism (air bubbles in the blood resulting from traumatic or surgical manoeuvres)
– Amniotic fluid resulting from a normal delivery or complicated (exceptional)
– Infectious material
– Fat that can get into the bloodstream as a result of fractures, surgery, trauma, burns or other conditions
– Foreign substances such as catheter needles (which can break during an operation), mercury, iodine, cotton.
Pulmonary embolism – Risk Factors
The presence of a thrombus in the deep veins of the legs and the existence of a history of an episode of pulmonary embolism are the most important risk factors for pulmonary embolism.
Thrombi develop especially when the blood flow is not normal. Decreased blood flow velocity may be due to:
– Prolonged bed rest: after surgery, trauma or serious diseases
– Stay in the chair for a long period of time, as in the case of long trips by plane
– Lower limb paralysis, because the legs cannot be moved without help.
Some people have a condition in which blood coagulates too fast or too easy. These people are likely to develop high blood clots that break and travel to the lungs.
Conditions that may enhance thrombus formation are:
– Hereditary factors (inherited): some people inherit the tendency of developing hypercoagulability which can lead to pulmonary embolism
– Severe infections
– The use of oral contraceptives or other medications containing estrogen or estrogen-like hormones (similar in structure and function of estrogen)
Trauma in the walls of blood vessels
Differential Diagnosis of Pulmonary embolism
The following heart disease can often be mistaken for pulmonary embolism:
– Heart failure or pulmonary edema
– Cardiac arrhythmia (irregular heartbeat)
Other lung disease can be confused with pulmonary embolism:
– Pleural effusion
– Chronic Obstructive Pulmonary Disease
– Pneumothorax (accumulation of air in the pleural cavity with partial or total collapse of the lung).
And other conditions can be confused with thromboembolism:
– Dissecting aneurysm of the aorta
– Hyperventilation (excessive ventilation)
– Panic attacks.
Pulmonary embolism may be suspected whenever there is a syncope (fainting) without an obvious cause.
Pulmonary embolism Investigations
Diagnosing pulmonary embolism is difficult because symptoms can be attributed to other causes such as heart attack or panic attack.
Correct diagnosis is based on a well-documented history to exclude other diseases.
The doctor should be informed about symptoms and other risk factors such as family history and hypercoagulability or recent surgery. This information, combined with a good physical exam performed, could lead to finding the best solutions for diagnosing deep vein thrombosis or pulmonary embolism.
Tests which are performed if the patient accuses breathlessness (dyspnea) or chest pain are:
– Chest radiography: its outcome eliminates suspicion of dilatative cardiomyopathy or lung injury, leading to perform other exams
– Electrocardiogram (ECG) follows the electrical activity of the heart and may exclude a possible heart attack
– Measurement of blood gases: rapid decrease of oxygen levels may suggest a pulmonary embolism.
The results of these initial tests can rule out other causes such as heart attack and pneumonia.
The following tests are made:
– Measurement of D-dimer: this is a test that measures a substance that is released when the thrombus detaches; usually in patients with pulmonary embolism, the D-dimer level is high
– Pulmonary perfusion scintigraphy: This test detects abnormal blood flow to the lungs after the intravenous injection of a radioactive tracer and the inspiration of a gas
– Pulmonary angiogram: is the safest way to diagnose a pulmonary embolism; it is not available in smaller hospitals and is more invasive than other diagnostic methods
– Echocardiogram: This test detects abnormalities of the right ventricle in size and function, which may occur due to pulmonary embolism
– Doppler ultrasound: using reflection waves to determine the presence of a clot in a vein in your leg
– Magnetic resonance imaging (MRI) may be useful in detecting thrombi in the deep veins and lungs.
Treatment of Pulmonary embolism
Treatment – General
The treatment of pulmonary embolism is based on preventing future episodes using anticoagulant drugs. It prevents the existing thrombi to grow in size and the appearance of new ones.
If the symptoms are severe and life threatening, the patient requires immediate and aggressive treatment. Aggressive treatment may include thrombolytic agents that can dissolve a clot quickly but can also increase the risk of severe bleeding. Another option for severe cases is surgical removal of the thrombus, surgery called embolectomy, but this procedure is performed only in some large hospitals.
Some people may benefit from the introduction of a filter in the vena cava. It can prevent thrombi from reaching the lungs. Filter is used when anticoagulants are not an option, when thrombi are formed despite the existence of anticoagulant therapy or when there is an increased risk of death if there is a new episode of embolism.
Outpatient treatment (at home)
It is not recommended that the treatment of pulmonary embolism begin at home. However, it is important to prevent thrombus formation and other deep vein thrombosis, as they can lead to recurrent pulmonary embolism.
Measures that decrease the risk of deep vein thrombosis are:
– Exercise: it can maintain good blood circulation by bringing tip toes closer to the head, so that the legs would be stretched, then relax and repeat; This exercise is important to perform especially when seated for a long period of time (eg during long journeys by car or plane)
– Mobilization as early as possible after surgery or illness requiring prolonged bed rest is very important; if it is not possible, mobilization exercises should be performed as described above for calves every hour, to help circulate blood
-quitting smoking: this is especially important for people who are taking estrogen (such as oral contraceptives)
– Use of elastic stockings to prevent deep vein thrombosis in individuals who are at risk.
Drug treatment can prevent recurrent episodes of pulmonary embolism by preventing clots from forming and the enlargement of existing ones.
Anticoagulant drugs: are prescribed when the pulmonary embolism is diagnosed or strongly suspected. Normally, after the occurrence of injuries that cause bleeding, the body sends signals which result in the formation of a thrombus on site.
The thrombus dissolves as the wound heals. A person with coagulopathy (clotting disease) shows an imbalance between the production and the dissolving of the thrombi. Anticoagulants prevent the production of proteins needed for the blood to clot. Although anticoagulants may prevent the formation of new thrombi and their increase, they can not dissolve already formed thrombi.
Heparin and warfarin are the main anticoagulants used to treat pulmonary embolism.
Heparin is an anticoagulant which is administered intravenously. It has an immediate effect on the body’s clotting system. Oral anticoagulants (warfarin) require a longer time to achieve therapeutic levels.
In the initial treatment using low molecular weight heparin is preferred, as may be administered once or twice daily and can be administered at home so that patients can leave the hospital earlier. No blood tests are needed to monitor the effect of this type of heparin.
Unfractionated heparin is another form that you can use. This should be continuously administered intravenously. Frequent blood tests are needed (every 6 hours) to monitor the anticoagulant effect of this medicine.
Recent studies have shown that small molecule heparin (lower molecular weight) can be as effective as the unfractionated for the majority of people with pulmonary embolism.
However, it is uncertain whether small molecule heparin is a good choice for proper treatment of massive pulmonary embolism. Many doctors prefer the use of unfractionated heparin in the treatment of severe cases.
Both forms of heparin can cause severe bleeding in some people. The risk of bleeding is approximately equal for both types of heparin. However, in case of hemorrhage, unfractionated heparin administration can be switched off while the small molecule continues to act.
Warfarin is an anticoagulant in the form of tablets. Its administration begins during the treatment with heparin as several days are needed until it reaches therapeutic concentrations. When warfarin levels reached optimum levels, the heparin is discontinued and it is continued the warfarin treatment only.
Studies have shown that the therapy with both heparin and warfarin reduces mortality from pulmonary embolism. Typically, warfarin is administered in high doses for at least 3-6 weeks or longer, in order to minimize the risk of new thrombi. Treatment with anticoagulants can stretch over the entire lifetime if the risk of developing a new episode of pulmonary embolism is high. Your doctor can decide whether long-term treatment with low doses of warfarin is recommended after initial treatment.
For people at risk, such as cancer, anticoagulant treatment continues until the risk factor disappears. For those with inherited bleeding disorders, history of recurrent deep vein thrombosis or pulmonary embolism, there is a possibility of recommending anticoagulant treatment for life.
Because warfarin may increase the risk of birth defects, it is not recommended for pregnant women. A few days after birth, the woman can move from the treatment with heparin to the one with warfarin..
Thrombolytic drugs are not commonly used in the treatment of pulmonary embolism. Although they quickly dissolve thrombi, thrombolytics significantly increase the risk of bleeding. They are used occasionally to treat life-threatening pulmonary embolism.
Once the diagnosis of pulmonary embolism, the doctor sets:
– If anticoagulant treatment is necessary
– The duration of treatment with anticoagulants.
Normally, in case of a recent stroke, recent surgery or an active internal bleeding, the use of thrombolytics is not recommended. A vena cava filter may help reduce the risk of a new episode of pulmonary embolism.
Tips for people who are taking warfarin
– Regular blood tests to check if the product is in optimal dose
– Diet must be balanced: not to suddenly reduce the intake of products with a high content of vitamin K: broccoli, Brussels sprouts, cabbage, asparagus, lettuce, spinach and some fruit juices; is very important to regularly consume foods with high content of vitamin K
– Avoid excessive alcohol consumption: chronic consumption can damage the liver and thus it enhances the effects of warfarin
– Smoking is prohibited
– Avoiding high-risk activities such as skiing, football or other sports that require physical contact (for those who are taking warfarin one wound can lead to an excessive bleeding)
– Wearing the seatbelt.
Prevention minor bleeding during anticoagulant therapy is important.
These items may be necessary to reduce the risk of bleeding:
– Electric shaving machine
– Toothbrush with soft bristles
– Protective clothing: gloves and shoes
– Slip mat for bath or shower.
The surgical removal of thrombi is called embolectomy. This treatment method is rarely used in case of pulmonary embolism. It is considered that the trombi in the main pulmonary artery are very large and extremely dangerous and cause serious symptoms. Embolectomy may also be an option for those whose condition is stable but they show clinical signs of significant reduction of the blood flow in the pulmonary artery.
Surgical treatment increases the risk of new thrombi that can cause another episode of pulmonary embolism.
Some people cannot follow anticoagulant therapy or continue to produce other thrombus despite medical treatment. If neither drugs nor surgery can be used, there are other methods for the prevention of pulmonary embolism, one of which is the use of vena cava filters.
You can enter a filter in the vena cava, the vein that crosses the abdomen and brings all the blood back to the heart. This filter can prevent thrombi in the veins of the lower limbs and pelvis to reach the lungs, and they are permanent or removable.
Studies show that these filters help prevent pulmonary embolism but are more effective when used in combination with anticoagulants.
Complications of pulmonary embolism may include:
– Sudden death
– Cardiac arrhythmia (irregular heartbeat)
– Pulmonary infarction
– Pleural effusion (fluid accumulation increased between the two foils of the pleura)
– Paradoxical embolism
– Myocardial infarction.
An aggressive attitude will be taken into account in case of a pulmonary embolism which is considered life-threatening for the patient. Deaths from pulmonary embolism usually occur within 30 minutes of the onset of symptoms.
Prevention of Pulmonary embolism
Daily use of anticoagulants may be useful in preventing recurrence of pulmonary embolism by preventing the formation of new clots and stopping the development of the existing ones.
Recent studies have shown that the risk of a new thrombus is higher during the initial 4-6 weeks after an episode of pulmonary embolism. This risk decreases over time.
However, the risk remains significant for months and even years, depending on the cause that triggered pulmonary embolism. People with recurrent thrombi and / or pulmonary embolism may need to take anticoagulation therapy for life. Anticoagulant drugs are frequently given to people who are going to undergo surgery to the legs, abdomen or pelvis.
Other preventive methods may be used:
– Early mobilization after surgical interventions
– Use of compression stockings (elastic) for the prevention of venous thrombosis for people at risk
– Administration of small amounts of aspirin before a long journey by plane or car.
Aspirin can reduce the risk of thrombus but it is not suitable for treating pulmonary embolism.