Case 1, image 1: This 37 year old man died of cardiac tamponade due to an aortic dissection. At autopsy, he had a bicuspid aortic valve. A section of the aorta demonstrates cystic medial degeneration with dissection of blood within the wall.
Case 2, image 1: This 30-year-old woman died as a result of retroperitoneal hemorrhage due to a ruptured dissecting aortic aneurysm. Her underlying disease was Marfan syndrome.
Case 2, image 2: Note the dissection between media and adventitial layers. and outer layers of aotic wall.
Case 2, image 3: This elastin stain demonstrates fragmentation of elastic fibers.
Case 2, image 4: For comparison, an area that appears normal (stained with elastin).
An aortic dissection can cause many complications including spreading to other arteries, blocking blood flow in the true lumen (thus decreasing delivery of blood to vital organs), weakening the aorta wall which leads to aneurysms and rupture.
Risk factors include hypertension, connective tissue disorders (i.e. Marfan syndrome), disorders affecting the aortic valve (i.e. bicuspid aortic valves), atherosclerosis, stimulant abuse (i.e. cocaine or methamphetamine) and trauma. Most aortic dissections due to hypertension present in the 6th decade and two-thirds occur in men, however, individuals with genetic disorders and stimulant abuse may present much earlier (Juang 2008).
Cystic medial degeneration is characterized by accumulation of basaphilic ground substance with formation of cysts that can be seen in the wall of large arteries. This predisposes to aorta dissection. Cystic medial degeneration can be seen in individuals with connective tissue disorders and also increases with age and high blood pressure (Yuan 2011, Carlson 1970).
Carlson RG, Lillehei CW, Edwards JE. Cystic medial necrosis of the ascending aorta in relation to age and hypertension. The American Journal of Cardiology, Vol 25, Issue 4, April 1970, Pages 411-415.
Juang D, Braverman AC, Eagle K. Aortic Dissection. Circulation 2008;118:e507-3510. Available at: http://circ.ahajournals.org/content/118/14/e507.full
Yuan SM, Jing H. Cystic medial necrosis: pathological findings and clinical implications. Rev Bras Cir Cardiovasc. 2011 Jan-Mar;26(1):107-15.