<Li> B--involves the descending aorta or the arch (distal to the left subclavian artery), without the involvement of the ascending aorta . It includes DeBakey type III . </Li> <P> The Stanford classification is useful as it follows clinical practice, as type A ascending aortic dissections generally require primary surgical treatment, whereas type B dissections generally are treated medically as initial treatment with surgery reserved for any complications . </P> <P> The reason for surgical repair of type A dissections is that ascending aortic dissections often involve the aortic valve, which, having lost its suspensory support, telescopes down into the aortic root, resulting in aortic incompetence . The valve must be resuspended in order to be reseated, as well as to repair or prevent coronary artery injury . Also, the area of dissection is removed and replaced with a Dacron graft to prevent further dissection from occurring . However, type B dissections are not improved, from a mortality point of view, by the operation, unless leaking, rupture, or compromise to other organs, e.g. kidneys, occurs . </P> <P> Among the recognized risk factors for aortic dissection, hypertension, dysplipidemia, and smoking are considered preventable risk factors . </P>

When would a stanford type b require surgery