 Hello and welcome to Approach to PE Part 1. In this video, we'll talk about the causes of pulmonary embolism and its presentations. What is a PE? A PE is a clot in the pulmonary arterial tree. It can be in the main pulmonary arteries, the segmental arteries, and the subsegmental arteries. Why do we care? Why is PE a bad thing? Acute PE causes two main problems. Respiratory problems and cardiac problems. For the lung, acute PE causes ventilation-perfusion mismatch. More specifically, there are now parts of the lung that has ventilation but no perfusion. That causes hypoxemia. For the heart, pulmonary embolism causes increased pulmonary vascular resistance, causing a strain in the right ventricle. If it is severe, it can lead to cardiovascular collapse. Most pulmonary embolism did not originate from the lung. Rather, they have migrated from somewhere else. The most common sites are from deep vein thrombosis of the lower limbs. These deep veins include the following, anterior tibial, posterior tibial, and perineal vein from below the knee, anterior tibial vein behind the knee, the superior and deep femoral vein, the common femoral vein, and further up into the external alliac veins. Any clot in the deep vein system have a chance of migrating into the lung and cause a PE. What causes PE? In Virgil's triad, there are three main reasons for thrombosis formation that include stasis where the blood has not been moving very much, such as mobility and endothelial injury. What specific clinical conditions can contribute to this? For stasis, that includes any conditions that make the patient immobilized. That include major surgeries, being put into long leg casts, long flights or train rides, being intubated. What about hypercoagulability? Either something the patient is born with or something with cost. Congenital reasons can include protein CNS deficiency, Vector V Leiden, and other inborn hematological problems. Other acquired reason for hypercoagulability can include hormone replacement or oral contraceptives. Other illnesses that have associated hypercoagulability include lupus, any type of malignancy, pregnancy in the peripartum period, and inflammatory bowel disease including ulcerative colitis and Crohn's. What about for endothelial injury? That includes central venous catheters and surgery. These are the reasons patients are more predisposed to getting DVT and PE, and therefore on history you want to elicit these risk factors. Now let's go in to see how patients present. We'll first talk about symptoms and then we'll look at the signs and physical exam. For symptoms, patients often present with chest pain and or shortness of breath. The chest pain can be pleuritic. That is, the patient feels the pain is worse when they take in a big breath. It can be associated with a cough or hemoptysis. For the shortness of breath, patients can describe poor exercise tolerance, or since the patient's breathing faster, they're complaining of anxiety symptoms. Patients with PE and DVT can also have no symptoms at all. On the other hand of the spectrum, patients can present with cardiovascular collapse, ranging from a syncopal episode to cardiac arrest. On physical examination, these are the changes that you might see. Tachycardia, tachypnea, hypotension, fever, low oxygen saturation. Of these changes, tachypnea is most often seen. On the cardiac exam, you should again see tachycardia. You might appreciate an extra heart sound, such as S3 or S4. You might hear rails on the rest exam. You might see signs compatible with the DVT in the lower limb, such as swelling, redness, and warmth. In summary, we discuss the causes and presentations of patients with PE. Keep in mind the triad of conditions that can contribute to them, and remember to ask for those on history. In part two, we discuss the different diagnostic testing we can use. Hope you find that useful. Thank you for watching.