The aorta, the largest artery in the body, originates in the left ventricle of the heart. It arches above the heart then down through the chest to the abdomen. It sends branches to the head, arms, the organs in the abdomen, and the legs to supply the body with oxygen and nutrients.
Aortic Aneurysms
An aortic aneurysm is a bulging or ballooning of a weakened part of the aortic artery wall. An aneurysm forms when blood pumping out of the heart pushes against and stretches the weakened portion of the aorta wall. When the bulging portion is more than two times the aorta's normal diameter it is considered an aneurysm. Aortic aneurysms are named according to their location:
- thoracic aortic aneurysms are those that form in the chest cavity
- thoracoabdominal aneurysms extend from the chest into the abdomen
- abdominal aortic aneurysms occur in the abdominal portion of the aorta
Regardless of their location, aortic aneurysms are dangerous because of the risk that they will rupture, causing life-threatening bleeding or hemorrhage.
Aortic Dissection
An aortic dissection is a split or tear along the inner layer of the aorta's wall. Dissections occur more frequently in regions of the aorta where pressure on the artery wall from blood flow is high, such as its first arching segment above the heart. When the aortic wall tears, blood fills the pocket between the inner and outer layers, often increasing the length of the tear. As the blood-filled space between the layers expands, it can weaken the aortic wall resulting in an aneurysm formation or the flap of the tear can block off critical blood vessels going to the bowels, kidney, or legs.
Risk Factors and Symptoms
The most common cause of aortic aneurysms is atherosclerosis, which weakens the wall of the aorta. However, the most common cause of aortic dissection is high blood pressure. Other risk factors associated with either type of aortic disease include:
- cigarette smoking
- trauma
- inflammatory diseases of the aorta (aortitis)
- inherited diseases, such as Marfan's or Ehlers-Danlos syndrome
- a family history of aortic disease
Most people with thoracic or abdominal aortic aneurysms have no symptoms and are discovered while the patient is having an x-ray study for another reason or on physical exam. Some patients complain of vague pain in the chest or abdomen and they may have a persistent cough and hoarseness. Large abdominal aneurysms can result in a pulsing feeling in the abdomen or chest.
When an aneurysm ruptures, the internal bleeding can cause intense back, abdominal, or chest pain. People with a ruptured aneurysm may also experience signs of shock such as shaking, dizziness, fainting, sweating, rapid heartbeat, and sudden weakness.
Symptoms of aortic dissection include sudden, intense pain across the chest, and sometimes in the back between the shoulder blades.
Doctors commonly diagnose aortic aneurysm and dissection using tests including:
- ultrasound
- angiography
- computerized tomography (CT) scan
- magnetic resonance imagery (MRI)
Treatment for Aortic Disease
Minimally Invasive Procedures
Doctors sometimes treat aortic diseases using endovascular surgery techniques. "Endovascular" means inside the blood vessels, and these procedures are performed with a catheter, a very thin tube in which the aneurysm can be repaired as the catheter is inserted into and threaded through a blood vessel to the site of the problem. Vascular specialists treat both aneurysms and dissections with minimally invasive procedures that have a significantly shorter recovery time and better chance of survival compared to traditional, open surgical repair.
Endovascular Stent Graft Abdominal Aortic Aneurysm Repair (EVAR): Vascular specialists can repair aortic aneurysms with endovascular stent grafts in many patients including those whose overall health makes open surgery too dangerous. During the procedure they insert a catheter into an artery in the groin and, using x-ray guidance, thread the catheter to the damaged area of the aorta. Within the catheter is a stent graft, a tube made of a special synthetic material, that can expand as it is released from the catheter. At the aneurysm (or dissection) the stent graft is expanded so that it attaches to the aorta above and below the area of disease thereby "bridging or re-lining" the damaged portion of the aorta. The stent graft provides a reinforced channel for the blood to flow through, reducing the pressure on the damaged area of the artery and helping to prevent a rupture. Patients generally go home the following day.
Fenestrated Endograft: In about 10 percent of patients with an abdominal aortic aneurysm, the defect in the aorta wall occurs very close to the arteries that branch off to the kidneys. Treatment of an aneurysm in this location is complex and often requires open surgery to repair the weakened wall. Vascular specialists at NewYork-Presbyterian Hospital are treating patients with these complex aneurysms using a new type of stent graft, called a fenestrated endograft, which they implant during a minimally invasive procedure. Each stent graft (the Zenith Fenestrated AAA Endovascular Graft by Cook Medical) is custom-made from a 3-D computer model of the patient's anatomy, which is based on a spiral CT scan. Holes, or fenestrations, are positioned in the stent graft precisely where the patient's renal or bowel arteries branch off, ensuring that blood can flow to the kidneys and nearby organs from the aorta. Specialists at NewYork-Presbyterian are offering these grafts through a clinical trial.
Thoracic Aneurysm Repair (TEVAR): Vascular specialists can repair aneurysms in the portion of the aorta above the bowel arteries, the thoracic aorta, with a procedure called thoracic endovascular aneurysm repair or TEVAR. This procedure is very similar to that used to repair the upper portions of the aorta (EVAR, outlined above). During the procedure they insert a catheter into an artery in the groin and, using x-ray guidance, thread the catheter to the damaged area of the aorta. Within the catheter is a stent graft, a tube made of a special synthetic material and a self expanding metal scapholding. At the aneurysm (or dissection) the stent graft is deployed so that it bridges and excludes the thoracic aneurysm. The stent graft provides a reinforced channel for the blood to flow through, reducing the pressure on the damaged area of the artery and helping to prevent a rupture. Patients generally go home within several days.
Hybrid Approach: Patients who have extensive aortic aneurysms (affecting both the ascending aorta and aortic arch, and the descending thoracic or thoracoabdominal aorta) as well as coexisting conditions such as respiratory problems may require a combination of open and minimally invasive surgery. This type of surgery is called a hybrid approach. The hybrid procedure requires surgical bypass of the critical aortic vessels, followed by the placement of a minimally invasive endovascular graft. This technique still requires some open surgery but in most cases is less invasive and stressful than the traditional open surgical techniques.
Traditional Surgery
Not all people with aortic disease are candidates for the minimally invasive procedures outlined above. The stent grafts are only made in certain sizes and in some cases critical aortic branches have to be re-implanted into the graft itself.
Abdominal Aortic Aneurysm Repair (AAA): To repair an aneurysm in the abdominal aorta, the portion of the aorta below the kidneys, vascular surgeons make an incision in the abdomen, clamp the aorta to reduce blood flow, then open the aneurysm and sew in a graft within the aneurysm sac to reinforce the affected vessel walls. The graft is a woven tube made of a synthetic material. Blood flow is contained inside the graft alleviating pressure on the weakened walls of the aneurysm and allowing normal blood flow to the legs and other organs.
Thoraco-Abdominal Aneurysm Repair (TAA): Aneurysms that affect the portion of the aorta above the kidneys into the chest are called thoracoabdominal aortic aneurysms. To repair an aneurysm in this portion of the aorta, vascular or cardiovascular surgeons make an incision in the chest and sometimes the abdomen, clamp the aorta to temporarily stop blood flow, then open the aneurysm and sew in a graft to replace the affected vessel walls. Blood vessels to the left arm, spinal cord, bowels and kidney can be connected to the graft as necessary. This is major surgery but is the only option and can be life-saving. Blood flow is contained inside the graft alleviating pressure on the weakened walls of the aneurysm and allowing normal blood flow to the legs and other organs.
Definitions
Aortic Rupture: aortic aneurysms, weakened, bulging areas in the aorta walls, can burst or rupture, causing life-threatening bleeding or hemorrhage.
Aortic Dissection: A dissection is a split or tear along the inner layer of the aorta's wall. Blood usually fills the pocket created by the tear between the inner and outer layers, often increasing the length of the tear.
Aortic dissections are classified into one of two types (A or B) depending on the site of the tear. Type A dissections originate in the ascending aorta, the portion that arches upward from the heart and may propagate into the descending aorta, the portion that arches downward toward the abdomen). Type B dissections are limited to the descending segment of the aorta.
Infra aneurysm: The most common type of abdominal aortic aneurysm is an infra, or infrarenal aneurysm, which occurs in the portion of the aorta below the kidneys.
Short neck aneurysm: An aneurysm that occurs close to the point where the aorta attaches to the kidneys, leaving a short length or "neck" between the two structures, is a short neck aneurysm. These aneurysms are more difficult to repair than other types and often require open surgical repair or a fenestrated aortic endovascular graft.
Juxtarenal aneurysm: A juxtarenal abdominal aortic aneurysm occurs in the abdominal aorta and extends up to, and includes, the lower part of the kidney arteries. These generally require open repair but at NewYork-Presbyterian may be able to be repaired with a custom endovascular graft.