A pulmonary embolism (PE) usually happens when a blood clot called a deep vein thrombosis (DVT), often in your leg, travels to your lungs and blocks a blood vessel. That leads to low oxygen levels in your blood. It can damage the lung and other organs and cause heart failure, too.
A PE can be life-threatening, so if you've been diagnosed with DVT, you should be aware of this risk. Follow the treatment plan for your DVT to stop the clot from getting bigger and to keep new clots from forming.