Venous thromboembolism (VTE):

A pulmonary embolism, or PE, occurs when an embolus, which is a small mass that could be a blood clot, a piece of plaque, fat or air, becomes lodged in the pulmonary artery and obstructs the pulmonary circulation. Most often the embolus is a blood clot associated with deep vein thrombosis, or DVT, which is when a clot forms in a large vein, usually in the leg or pelvis. The clot becomes a venous thromboembolism, or VTE, when it breaks off and travels up the inferior vena cava to the right atrium, into the right ventricle, and finally into the pulmonary artery. This causes decreased blood flow to the lung tissue and impaired oxygenation.

Factors that increase the risk of a pulmonary embolism are summarized in Virchow’s triad, which include slowed blood flow, or venous stasis, hypercoagulation, meaning the blood is more likely to form clots, and damage to the endothelial lining of a blood vessel. Venous stasis can occur because of prolonged immobility like during a severe illness or after surgery, when an enlarged uterus compresses the nearby veins during pregnancy, or due to long-haul travel. Hypercoagulability can be caused by clotting disorders, use of oral contraceptives, smoking, and it occurs normally during pregnancy.  And lastly, damage to the endothelial cell lining of a blood vessel can be the result of trauma or surgery. 

Signs and symptoms of a VTE depend on the size and location of pulmonary artery blockage. Even a small blockage impairs blood from getting into the lungs to pick up oxygen. Impaired oxygenation may cause a sudden onset of dyspnea, cough, tachypnea and chest pain that is described as pleuritic, meaning a sharp pain felt when inhaling and exhaling.  The client may become disoriented and anxious from the hypoxemia, or they may report a feeling of apprehension and impending doom. As inflammation sets in, fluid buildup causes crackles which can be heard upon auscultation. Further deprivation of oxygen from the lung tissue leads to infarction of the lung tissue, which may result in hemoptysis. Complications from a VTE can include pulmonary hypertension, right ventricular failure, shock and sudden death.

Diagnostics used to identify a VTE include computed tomography pulmonary angiogram, or CTPA, where a dye is injected into the blood vessels to locate the blockage. A ventilation-perfusion scan, or V/Q scan, also called lung scintigraphy or ventilation-perfusion scintigraphy, can reveal areas of the lung that are ventilated, but not perfused, called a V/Q mismatch. Lab tests include a D-dimer test to detect fibrin breakdown products, which are usually present when there’s a blood clot.

Small clots may resolve on their own, however, large clots usually need treatment with fibrinolytic medications like tissue plasminogen activator, or tPA, to help break down the clot, and  anticoagulants like low molecular weight heparin to decrease blood coagulation. A  pulmonary embolectomy can also be done to surgically remove the clot. For those at risk of developing further blood clots, anticoagulant medications may be given long term, or an inferior vena cava filter, or IVC filter, can be surgically placed into the inferior vena cava to prevent blood clots from entering the pulmonary artery and lungs.