A pulmonary embolism happens when a blood clot (usually from the legs) travels to the lungs and blocks blood flow, a life-threatening emergency that can look like “just anxiety” or “just shortness of breath.” That’s what makes PE so dangerous, it hides in plain sight. Most clots start in the legs (DVT, deep vein thrombosis) and are driven by Virchow’s triad: Stasis (long travel, immobility) Hypercoagulability (cancer, birth control, pregnancy) Endothelial injury ( surgery, trauma, infection ) Wh