This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Vascular surgery, Subject name: Surgery
[{'content': 'Most common site of aoic dissection is ? \nSelect and explain. \nA. Ascending aoa, B. Descending aoa, C. Arch of aoa, D. Infrarenal poion of aoa', 'role': 'user'}, {'content': 'Answer: A \nExplanation: <p> Aoic dissection Dissection of the media of the aoa after splitting through intima creating a channel in the media of the vessel wall. Causes- hypeension, marfan&;s syndrome, collagen diseases, trauma, weakening of elastic layers of the media due to shear forces. Features:- Commonly seen in thoracic aoa(ascending aoa). Dissected aoic arch channel gets lined by endothelium, often reopens distally into the aoa causing double barrelled aoa. Atherosclerosis is not a usual cause for dissecting aneurysm. Clinical features- Pain in the chest, back which is excruciating. Features of ischemia. Treatment- Antihypeensives Surgery: using Dacron graft reconstruction of aoa. {Reference: SRB&;s manual of surgery, 5th edition , page no. 198}', 'role': 'assistant'}]