Aortic aneurysm repair involves the removal of a dilated (enlarged) portion of the aorta replaced by a woven or knitted Dacron graft to continue uninterrupted blood flow through the aorta and all branch vessels.
Aortic aneurysm repair is performed when a portion of the aorta has become dilated as a result of medionecrosis in the ascending aorta or atherosclerosis in the arch and descending segments. Congenital defects in connective tissue are also a risk factor. A history of blunt trauma may be associated with this disease propagation. Prior to 1950, patients exposed to syphilis were at risk of developing aortic aneurysm. Risk of clot formation and rupture of the aneurysm, seen in 50% of cases, as well as dilation to a size greater than 4 in (10 cm) promote repair of the aneurysm by surgical techniques.
After general anesthesia is administered, the surgeon will make an incision through the length of the sternum to repair an ascending, arch, or thoracic aortic aneurysm. Abdominal aneurysms are approached through a vertical incision in the abdominal wall. Depending on the location of the aneurysm, cardiopulmonary bypass with deep hypothermic circulatory arrest (arch), cardiopulmonary bypass (ascending), or left heart bypass (thoracic) may be required. All procedures require some amount of anticoagulation, usually heparin, to be administered to prevent blood clot formation. Clamps will be applied across the aorta to prevent blood flow into the aneurysm. The aneurysm will be opened to an area where the tissue is healthy. The healthy tissue will be sutured to a synthetic fiber fabric graft. The fabric is knit or woven Dacron fibers and may be impregnated with collagen, gelatin, or other substances. Blood flow is reinstituted to check for a secure seal. Additional sutures will be added to prevent leaking. The incision is then closed at the completion of the procedure with blood drains penetrating the incision during healing.
Ascending aortic aneurysms may involve the aortic valve or coronary arteries. If the aortic valve is damaged, a graft with an integral aortic valve is used. The coronary arteries are reconnected to the graft.
Aortic arch aneurysms require the reattachment of the arch vessels, the innominate artery, the left common carotid artery, and the left subclavian artery. To decrease surgery time, these three vessels can be treated as a single vessel by using part of the patient’s native aorta to create an island. This island is then connected to the graft.
Thoracic aneurysms require special care to protect the spinal vessels that supply blood to the spinal cord. Protecting the spinal cord during repair is still an area of intensive research. Some surgeons feel that rapid implant of the graft to restore blood flow is the best method to protect the spinal cord. A bypass graft called a Gott shunt can be used to redirect the blood flow around the area during surgical repair. Left-heart bypass provides the same benefit as a Gott shunt, with the addition of a mechanical pump for more controlled blood flow to the abdomen and lower extremities.
The abdominal aortic aneurysm is repaired by rapid anastomosis of the graft to return blood flow to the circulation. If the renal arteries are involved in the aneurysm, they will be reattached to the graft. Additionally, if the superior celiac, mesenteric, or inferior celiac arteries are involved, they will also be reattached to the graft. Finally, it is common for the bifurcation (separation into two) of the iliac arteries to be involved; this may require a Y-shaped graft to be used to reattach both lower limb vessels.
The patient is usually placed under general anesthesia for the duration of surgery. The advantages to general anesthesia are that the patient remains unconscious during the procedure, which may take from two to five hours to complete; no pain will be experienced nor will the patient have any memory of the procedure; and the patient’s muscles remain completely relaxed, lending to safer surgery.
Once an adequate level of anesthesia has been reached, an incision is made across the lower abdomen. For a complete abdominoplasty, the incision will stretch from hipbone to hipbone. The skin will be lifted off the abdominal muscles from the incision up to the ribs, with a separate incision being made to free the umbilicus (belly button). The vertical abdominal muscles may be tightened by stitching them closer together. The skin is then stretched back over the abdomen and excess skin and fat are cut away. Another incision will be made across the stretched skin through which the umbilicus will be located and stitched into position. A temporary drain may be placed to remove excess fluid from beneath the incision. All incisions are then stitched closed and covered with dressings.
Individuals who have excess skin and fat limited to the lower abdomen (i.e., below the navel) may be candidates for partial abdominoplasty. During this procedure, the muscle wall is not tightened. Rather, the skin is stretched over a smaller incision made just above the pubic hairline and excess skin is cut away. The incision is then closed with stitches. The umbilicus is not repositioned during a partial abdominoplasty; its shape, therefore, may change as the skin is stretched downward.
A simple x ray may provide the initial diagnosis of aortic aneurysm. Initial diagnosis can be made with non-invasive transesophageal echocardiography or ultrasound. Additional tests such as magnetic resonance imaging (MRI) or computed tomography (CT) will allow for additional visualization of the aneurysm. An angiography is the preferred method for determining the severity. Blood vessel and aortic valve health can be evaluated.