Pulmonary embolism is relatively frequent and often a life-threatening situation. From the diagnostic point of view it can be a big problem as the symptoms may be quite vague and it is very easy to misdiagnose the patient.
Pulmonary embolism occurs when a certain portion of pulmonary arteries get obstructed by blood clots. These blood clots come from other veins of the body. Usually it is the deep vein thrombosis of the lower extremities, but the blood clot can occur in practically any vein of the body. It is necessary to differentiate two terms – the thrombus and embolus. Thrombus is a blood clot in the location of its occurrence. When a part of the thrombus tears away and travels to another blood vessel (which it obstructs), we refer it to as the embolus.
And why does the thrombosis occur? It can happen even in a healthy person without a clear reason, but usually it is caused by combination of different risk factors (high age, pregnancy, hormonal contraception, Factor V Leiden and other disorders of the blood coagulation system, hyperhomocysteinemia, postoperative conditions, dehydration and prolonged immobility of the lower extremities. Increased risk of thrombosis and embolism is during long air travel. For a more complete overview, visit the text about the deep vein thrombosis.
The symptoms depend on extent of the affected lung tissue and on how quickly the process occurred. Small pulmonary embolism may be totally asymptomatic. A rapid and extensive obstruction of the pulmonary circulation means a sudden overload of the right heart ventricle, which must pump against significantly increased resistance. The symptoms may include sudden chest pain and shortness of breath, acute heart failure, unconsciousness and death.
Less extensive and rapid pulmonary embolism usually causes similar symptoms, but without the cardiovascular and heart failure. The affected person suffers from a sudden chest pain, pain between the shoulder blades, dry cough and shortness of breath and sometimes he or she coughs up blood. The chest pain may worsen during inspiration and thus mimic the pleurisy.
Gradual successive pulmonary embolism occurs due to a slow and chronic embolisation from a peripheral thrombosis. The pulmonary vessels are slowly clogged, but the lung has adequate capacity and time to adapt. Therefore, the above-mentioned symptoms occur gradually and the most important complaint of the patient is the increasing shortness of breath during physical activity.
The suspicion may arise from the clinical symptoms and presence of any of the mentioned risk factors. In blood tests, it is helpful to evaluate the serum level of D-dimers. The D-dimers are substances that are formed during blood clot formation and their levels significantly increase in thrombosis and pulmonary embolism. Ultrasound of the veins of the lower extremities may confirm the presence and extent of deep vein thrombosis. Certain findings can be found in the ECG curve, but they are not specific and usually they are present only in case of an extensive embolism. However, all the previously mentioned methods are only indirect. When we want to confirm the embolism, it is necessary to perform a lung examination, either the lung scintigraphy or CT angiography.
The prevention includes preventive application of anticoagulation drugs (especially the low-molecular-weight-heparins) to patients with deep vein thrombosis or with high risk of thrombosis development. Part of the prevention is also a responsible prescription of hormonal contraception to teenage girls, when the doctor should be vary cautious in girls with increased risk of thrombosis (smokers, frequent occurrence of thrombosis in the family, already confirmed Leiden mutation, etc.).
The pulmonary embolism in a patient with known extensive deep vein thrombosis is also preventable by an endovascular intervention with placing the so-called caval filter into the inferior vena cava. The filter allows the blood to flow freely, but its stops any blood clots.
The treatment of the majority of cases includes administration of anticoagulation drugs in therapeutic doses (heparin, LMWH, warfarin, etc.). The anticoagulation therapy usually lasts for about a year, but in certain very risky patients it may become life long. Acute pulmonary embolism, which directly threatens the life of the patient, may be treated by using special medications that directly dissolve the emboli. However, these drugs have a high risk of hemorrhage including bleeding into internal organs.