Pulmonary embolism: Clinical sciences

Pulmonary embolism, or PE, is a blockage of the pulmonary artery or one of its branches by an embolus, which is a traveling blood clot, tumor, fragment of fat, or air, that originates from somewhere else in the body.

In most cases, the embolus originates from a thrombus in the iliac, femoral, or popliteal veins that broke loose. Once the embolus reaches the pulmonary circulation, it blocks alveolar blood flow and increases dead space ventilation. This causes ventilation perfusion mismatch, eventually reducing blood oxygenation and causing damage to lung tissue. In addition, there’s increased pulmonary vascular resistance and right ventricular afterload, which can lead to right ventricular heart failure. Because of this, patients who are unstable need immediate management, and those who are stable should be evaluated quickly with the Wells criteria.

When assessing a patient with a suspected pulmonary embolism, first do an ABCDE assessment to determine if your patient is stable or unstable. An unstable presentation is commonly caused by a large embolus in the main pulmonary artery. Because of the high mortality-risk in these patients, it’s essential to stabilize their airway, breathing, and circulation first. You should establish intravenous access for fluids or vasopressors, and attach an automatic blood pressure cuff, chest leads, and digital pulse oximeter to monitor blood pressure, cardiac rhythm, and oxygen saturation. Additionally, provide supplemental oxygen to maintain the oxygen saturation above 90%.

On examination, unstable patients typically present with severe hypotension, tachypnea, and tachycardia. They might also have dyspnea, pleuritic chest pain, hemoptysis, fatigue, and weakness. Additional physical findings found in physical examination might reveal rales, JVD, a loud P2, calf tenderness and swelling, and pedal edema. In severe cases, the patient can progress to bradycardia, which can be associated with right ventricular strain and impending shock.

The most common ECG finding in PE is sinus tachycardia, but a less common finding is the S1Q3T3 pattern where there’s a large S wave in lead I, and a Q wave and inverted T wave in lead III. Next, order an emergent CT pulmonary angiography, or CTPA, to assess for intraluminal filling defects in the pulmonary circulation. If there are filling defects in the pulmonary blood flow, the CTPA is considered positive, and the diagnosis is confirmed. You can often rule out PE if it’s negative, but on rare occasions, CTPA can be inconclusive because of interference from motion, patient body habitus, or lung parenchymal disease.

Now, if you diagnose PE and the patient has no bleeding risk, like bleeding disorders, uncontrolled hypertension, or recent major trauma or surgery, immediately initiate thrombolytic therapy with medications such as alteplase to quickly break down the embolus. If there’s a high risk of bleeding, then surgical embolectomy or percutaneous catheter-directed therapy are the best options.

Alright, now let’s discuss how to manage stable patients. You should start with acute management, like obtaining IV access, and monitoring cardiac rhythm, blood pressure, and oxygen saturation. You should also provide supplemental O2 as needed. Once you initiate acute management, you should do a focused history and physical. Stable patients often have mild symptoms, or might even be asymptomatic. They typically present with dyspnea, pleuritic chest pain, hemoptysis, and leg pain or swelling if a DVT is present. Additionally, past medical and family history might reveal risk factors for PE, such as recent prolonged immobilization, recent orthopedic surgery, malignancy, indwelling catheter, obesity, pregnancy, smoking, or oral contraceptive use. Family history of PE or DVT can also indicate possible familial inherited genetic disorders that predispose to PE.