Pulmonary embolism (PE) occurs when a deep vein thrombosis (DVT) — usually from the leg or pelvis — breaks free and lodges in the pulmonary vasculature, obstructing blood flow to the lungs. A massive PE causing haemodynamic collapse is immediately life-threatening; even submassive PE can cause significant right heart strain and long-term pulmonary hypertension. Diagnosis relies on clinical probability assessment, D-dimer testing, and CT pulmonary angiography. Treatment is systemic anticoagulation; massive PE may require thrombolysis or catheter-directed therapy. Patients with haemodynamic compromise require immediate resuscitation and consideration of catheter-based intervention or surgical embolectomy.
