Open aortic surgery

Open aortic surgery ("OAS", also known as Open aortic repair, "OAR") describes a technique whereby an abdominal or retroperitoneal surgical incision is used to visualize and control the aorta for purposes of repair. OAS is used to treat aneurysms of the abdominal and thoracic aorta, aortic dissection, acute aortic syndrome, and aortic ruptures. In 2003, OAS was surpassed by endovascular aneurysm repair (EVAR) as the most common technique for repairing abdominal aortic aneurysms in the United States. In OAS for abdominal aortic aneurysm, the aneurysmal portion of the aorta is replaced with a graft, usually made of dacron or PTFE.

Open aortic surgery is distinct from aortic valve repair and aortic valve replacement, as OAS describes surgery of the aorta, rather than of the heart valves. Pathology of the aortic valve, aortic root and ascending aorta are treated with the Bentall procedure.

Uses

OAS is used to treat patients with aortic aneurysms greater than 5.5 cm in diameter, to treat aortic rupture of an aneurysm any size, to treat aortic dissections, and to treat acute aortic syndrome. It is used to treat infrarenal aneurysms as well as juxta- and pararenal aneurysm and thoracoabdominal aneurysms, as well as non-aneurysmal aortic pathology. Disease of the aorta proximal to the left subclavian artery in the chest is the provence of cardiac surgery and is treated via procedures such as the valve-sparing aortic root replacement.

Prior to the advent of EVAR, OAS was the only surgical treatment available for aortic aneurysms. It is still preferred at some institutions and by some patients as it may be more durable than EVAR and does not require post-operative surveillance CT scans.

Reasons to avoid

The shift away from open aortic surgery towards endovascular surgery since 2003 has been driven by worse perioperative mortality associated with OAS, particularly in patients in relatively frail health. Unlike endovascular repair, there are no strict anatomic contra-indications to open repair; Rather, open repair is viewed as a last resort for patients with unfavorable anatomy for endovascular repair.

Technique

Approach

The infrarenal aorta can be approached via a transabdominal midline or paramedian incision, or via a retroperitoneal approach. The paravisceral and thoracic aorta are approached via a left-sided posteriolateral thoracotomy incision in approximately the 9th intercostal space.

Sequential aortic clamping

At medical centers with a high volume of open aortic surgery, the fastest option for open aortic surgery was sequential aortic clamping or "clamp-and-sew", whereby the aorta was clamped proximally and distally to the diseased segment, and a graft sewn into the intervening segment. This technique leaves the branches of the aorta un-perfused during the time it takes to sew in the graft, potentially increasing the risk of ischemia to the organs which derive their arterial supply from the clamped segment. Critics of this technique advocate intra-operative aortic perfusion. In infrarenal aneurysms, the relative tolerance of the lower extremities to ischemia allows surgeons to clamp distally with low risk of ill effect.

Techniques to limit Ischemia

A number of techniques exist for maintaining perfusion to the viscera and spinal cord during open thoracoabdominal aortic aneurysm repair, including left heart bypass, balloon perfusion catheter placement in the visceral arteries, selective spinal drainage and cold crystalloid renal perfusion. There is limited evidence supporting these techniques.

Graft configuration

The abdominal aorta is anastomosed preferentially to the main limb of a tube or bifurcated graft in an end-to-end fashion to minimize turbulent flow at the proximal anastomosis. If normal aorta exists superior to the iliac bifurcation, a tube graft can be sewn distally to that normal aorta. If the distal aorta is diseased, a bifurcated graft can be used in an aorto-billiac or aorto-bifemoral configuration. If visceral vessels are involved in the diseased aortic segment, a branched graft can be used with branches sewn directly to visceral vessels, or the visceral vessels can be separately revascularized.

Reimplantation of the Inferior Mesenteric Artery

Because of collateral blood flow from the SMA via the marginal artery, the Inferior mesenteric artery usually does not have to be reimplanted into the aortic graft when performing an open abdominal aortic aneurysm repair.

Risks/Complications

Open aortic surgery is widely recognized as having higher rates of perioperative morbidity and mortality than endovascular procedures for comparable segments of the aorta. For example, in infrarenal aneurysms, perioperative mortality with endovascular surgery is approximately 0.5%, vs 3% with open repair.

Other risks/complications with aortic surgery depend on the segment of aorta involved, and include renal failure, spinal cord ischemia leading to paralysis, buttock claudication, ischemic collitis, embolization leading to acute limb ischemia, infection, and bleeding.

Recovery after OAS

Recovery after OAS is substantial. Immediately following surgery, patients can expect to spend 1–3 days in the intensive care unit, followed by 4–10 days on the hospital ward. After discharge, patients will take 3–6 months to fully recover their energy and return to their pre-operative daily activities.

See also

Aortic valve repair