Ascending Aorta

Aortic aneurysms may result from a variety of predisposing conditions.

Degenerative dilation of the aortic wall is the most common cause of aneurysm formation. While the causes are not well understood, in some patients the elastic aortic tissue weakens prematurely, leading to progressive aneurysmal change. This process is sometimes referred to as cystic medial degeneration.

 Atherosclerotic disease may produce calcification in the wall of the aorta, and other blood vessels, which damages cells in the media, leading to subsequent dilatation. Poorly controlled hypertension, as it subjects the aortic walls to higher pressure, may also contribute to aneurysm growth. Atherosclerosis has been found to be related to such factors as elevated cholesterol levels, cigarette smoking, diabetes, poor physical conditioning, and genetic predispositions.

 Genetic diseases, such as Marfan’s Syndrome or Ehlers-Danlos Syndrome, may lead to progressive dilatation of all segments of the aorta due to abnormalities in collagen, one of the proteins that are vital to the integrity of the aortic wall.

Aortic dissections may result in chronic dilatation of the aorta over time. An aortic dissection is caused by a tear in the inner lining of the aorta which allows blood to track within the wall of the aorta. Dissections of the ascending aorta must be repaired immediately, but dissections of the descending aorta may heal with careful blood pressure control. However, since the wall of the aorta is weakened, it may progressively dilate over time.

Inflammatory conditions, such as Takayasu’s arteritis, may produce aneurysmal changes of the aorta as one of their manifestations.

Trauma, for example from motor vehicle accidents, may damage the wall of the aorta, leading to late aneurysm formation.

Bicuspid aortic valves may produce chronic dilatation of the ascending aorta, and may require replacement of both the aortic valve as well as the ascending aorta.

The decision to replace the ascending aorta is based on a number of criteria, namely symptoms, size, growth rate, and family history.

Symptoms

In the setting of an ascending aortic aneurysm, chest pain is a concerning symptom and may prompt definitive repair urgently. If you have an aneurysm and are experiencing chest pain, you should contact your physician or the nearest emergency room immediately.

Size 

While there is no absolute size cutoff, most surgeons will begin to recommend repair of ascending aortic aneurysms when they reach approximately 5cm in size. For patients with Marfan’s Disease, surgery may be recommended for smaller sizes. Patients undergoing cardiac surgery for other reasons, primarily those with bicuspid aortic valves, may require concomitant aortic replacement at smaller sizes. Patients with ascending aortic aneurysms greater than 4cm should be followed with CT scans at regular intervals to evaluate growth of the aneurysm, as directed by their physician.

Growth Rate 

The rate of change in size of an ascending aortic aneurysm may also influence the timing of surgery. Generally, the faster the aneurysm grows, the sooner it should be repaired.

Family History

Operation may be recommended sooner based on a patient’s individual family history. Those with history of genetic diseases, such as Marfan’s, Ehler’s-Danlos or other family history of aortic diseases may be candidates for surgical treatment earlier in their course.

Graft Replacement

For ascending aneurysms that do not involve the aortic valve, simply removing the diseased portion of the aorta and replacing it with a tube graft is sufficient treatment. The aorta is usually replaced with a synthetic graft made of Dacron – a material which is strong and long-lasting. To perform the operation, the heart is stopped and the patient is placed on cardiopulmonary bypass while the segment of aorta is replaced. The aneurysmal portion of the aorta is excised and the tube graft sewn to the remaining aorta.

Bentall Operation

For ascending aortic aneurysms associated with an abnormal aortic valve, the operation involves removing both the aorta and the aortic valve. Referred to as the Bentall Operation, both aortic valve and ascending aorta are replaced with a Dacron graft to which is attached a prosthetic aortic valve. As part of the operation, the coronary arteries are removed from the aorta and re-attached to the aortic graft.

Valve-Sparing Aortic Root Replacement

In patients whose aneurysm involves the aortic root but whose aortic valve is normal, the valve can be saved using this procedure. The ascending aorta and coronary arteries are removed just above the aortic valve and a graft is attached at this level. The coronary arteries are then re-attached to the aortic graft.

Freestyle Aortic Root Replacement

Another approach for aortic root aneurysms is implantation of a Freestyle aortic root, which is a preserved ascending aorta with the aortic valve that have been harvested from a pig. The patient’s own aortic valve and ascending aorta are excised, and the Freestyle graft is sewn into place, similar to a Bentall operation. The patient’s own coronary arteries are re-attached to the Freestyle graft.

Prevention of stroke remains one of the central challenges in aortic surgery, and our practice takes numerous precautions to minimize the risk of neurologic complications. Strokes in complex aortic surgery may be the result of emboli (usually tiny particles of calcium or debris) which travel to the brain and cause damage. Some of our strategies for neurologic protection are below.

Axillary Cannulation
As many patients with aortic disease have widespread atherosclerotic disease throughout the aorta, we routinely avoid using the ascending aorta itself for access for cardiopulmonary bypass. Our standard approach for aortic surgery uses the left axillary artery for connection to the cardiopulmonary bypass circuit, which has been associated with decreased embolic associated neurologic complications.

Deep Hypothermic Circulatory Arrest (DHCA)
For many complex aortic operations, it is necessary to completely stop all blood flow within the body for a short period of time to gain safe access to certain areas of the aorta. This is accomplished by cooling the patient to very low temperatures using the cardiopulmonary bypass circuit as well as cooling blankets and packing ice around the patient’s head. With appropriate cooling and other adjunctive measures, blood flow can be stopped safely with full neurologic recovery.