A 32-year-old woman who weighs 125 kg (275 lb) is in the hospital for open reduction and internal fixation of a fractured ankle. She states that the only medication she is taking is an oral contraceptive. Four days after the surgery, she suddenly complains of chest pain and is noted to have difficulty breathing. Pulse oximetry reveals an arterial pO2 of 75%. She becomes unresponsive. During resuscitation, she is noted to have pulseless electrical activity. Despite aggressive efforts, she dies. An autopsy is most likely to reveal which of the following conditions?