MORE ABOUT PULMONARY EMBOLISM: A little research reveals that pulmonary embolism (PE) is more common than I thought. It's the third most common cause of death in the US, with at least 650,000 cases occurring annually. It's also the first or second most common cause of unexpected death in most age groups. Basically, a PE is a blood clot or other blockage likely to have formed in the lower extremities that then moves to the lungs.