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Cardiothoracic Surgery Service
LAC+USC Medical Center Student Handout
Aortic Aneurysms and Dissections
- An aneurysm is a full thicknes weakening of the aortic wall. A partial thickness weakening of the aortic wall is a pseudoaneurysm. A tear in the intima and separation of th media along a trajectory of the aorta is a dissection.
- Most aneurysms are of an atherosclerotic etiology. These may be found along the ascending, transverse or descending aorta.
- Repair of aneurysms of the ascending aorta requires CPB. Repair of the aortic arch requires total hypothermic circulatory arrest. Repair of an aneurysm of the descending aorta may be done with simple clamping proximally and distally and insertion of a tube graft (usually of woven dacron).
- The major problem with ascending aortic aneurysm repair is the need to bypass the coronary arteries if they are also involved.
- The problem with repair of the the descending aortic aneurysms is the frequent distal embolization of atherosclerotic debris to the lower extremities or mesenteric arteries with mesenteric ischemia and necrosis. Paraplegia may occur in 5-10% inspite of best efforts.
- Operative mortality for repair of aortic aneurysms is from 5-15%.
- By definition, a dissection is a tear in the intimal layer of the aorta with dissection along the media proximally or distally.
- Dissections may be classified according to two well accepted systems:
Intimal tear in the ascending aorta and dissection anywhere along the aorta.
Intimal tear in the ascending aorta but dissection is limited to the ascending aorta and arch only.
Intimal tear in the descending aorta distal to the left subclavian artery and limited to the descending aorta.
Intimal tear in the ascending aorta but limited to the ascending aorta and arch only.
Intimal tear in the descending aorta disal to the left subclavian artery and limited to the descending aorta.
- The diagnosis of a dissection is made on clinical suspicion after symptoms, a wide mediastinum on CXR, CAT scan or ECHO.
- Most patients will complain of excrutiating tearing pain anteriorly radiating to the back (if ascending) and tearing back pain if descending.
- EKG must be done to rule out myocardial ischemia as the etiology for the pain.
- An ascending aortic dissection may involve the coronary arteries and also present with EKG changes.
- If a CAT scan is non diagnostic or if further detail is required, an aortogram may be done. Care should be taken not to perforate through the thin dissected aortic wall.
- Once a diagnosis of dissection is made, type 1, 2 or A should be operated on emergently. Type 3 or B can be treated medically as long as there are no complications of it (rupture, bowel or limb ischemia, CVA). If any complications occur, surgery is emergently undertaken.
- Medical treatment of a dissection includes antihypertensive IV medication, pain control with morphine. The patient should be in the ICU with monitoring lines.
- Operative mortality is 5-15% depending on the urgency and location of the dissection.
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