Aortic Dissection Stanford Type A - False Lumen & Intimal Flap

A 60-year-old hypertensive man presents with sudden, tearing chest pain radiating to the back, blood pressure 200/110 mmHg in the right arm and 140/80 mmHg in the left arm, and an early diastolic murmur. CT angiography confirms an ascending aortic dissection. The autopsy specimen shows the ascending aorta opened longitudinally. The structure marked **A** in the diagram—the thin intimal flap separating the true lumen from the false lumen—is the pathological hallmark of this dissection. Which of the following BEST explains the pathogenesis of the intimal tear that initiates this dissection?