Review Question - QID 100843

A 24-year-old female medical student presents to the emergency department after she develops sudden difficulty breathing and vague chest pain while preparing for exams. The chest pain is non-pleuritic without radiation. She denies any recent travel. She denies any hemoptysis, nausea, vomiting, or leg pain. She only takes oral contraceptives; she denies smoking or alcohol use. Her vitals reveal a heart rate of 120 beats per minute, blood pressure of 100/80 mm Hg, and respiratory rate of 30 per minute. She is afebrile. Otherwise, her physical exam is unremarkable. A CT scan of her chest with IV contrast reveals filling defects along her left pulmonary artery. Which of the following is the most likely mechanism of this finding?