A 67-year-old man with a history of long-standing hypertension presents to the emergency department with sudden-onset, severe “tearing” chest pain that radiates to his back. He is diaphoretic and anxious. BP is 190/105 mm Hg in the right arm and 186/100 mm Hg in the left arm; pulse is 108/min. Cardiac exam reveals a new high-pitched, blowing decrescendo diastolic murmur best heard along the left sternal border. Shortly after arrival, he develops severe abdominal pain and decreased urine output. CT angiography demonstrates an intimal flap beginning in the ascending aorta and extending into the descending thoracic aorta.

Which of the following best explains the mechanism of the new murmur in this patient?