Your adult patient has a history of atherosclerosis. He called for assistance after developing sudden-onset pain in the right calf region. On arrival, the patient is conscious and alert with a blood pressure of 160/100, a heart rate of 100, and respirations of 16. He has a pulse, motor, and sensation in all extremities except the right leg, which is pulseless and cool to the touch. Which of the following should be suspected until proven otherwise?