Classification of aoic dissection depends upon

Aoic dissection occurs when blood splays apa the laminarplanes of the media to form a blood-filled channel within theaoic wall.The clinical manifestations of dissection depend primarily on the poion of the aoa affected; the most serious complicationsoccur with dissections involving the proximalaoa and arch.Thus, aoic dissections generally are classified into two types-Proximal lesions: type A dissections, Distal lesions,type B dissectionsRobbins Basic pathology,9th edition,pg no.347