Thoracic Aortic Aneurysm
The aorta is the largest blood vessel in the body, the size of a garden hose. It begins in the chest, proceeds to the abdomen, and its branches supply all the vital organs including the brain, arms, intestines, kidneys, liver, and legs. The beginning of this blood vessel is the thoracic aorta.
Many conditions can cause the thoracic aorta (in the chest) to enlarge, forming a thoracic aortic aneurysm. The aneurysm may remain unknown to the patient until it ruptures or dissects, causing severe illness or sudden death. Risk factors for developing a thoracic aortic aneurysm include:
- Smoking, high blood pressure, high cholesterol (risk factors for atherosclerosis or hardening of the arteries)
- Brain aneurysm
- Abdominal aortic aneurysm (aneurysm in the abdomen)
- Bicuspid Aortic Valve (heart murmur)
- Aortic Coarctation (birth defect of the thoracic aorta)
- Kidney cysts
- Prior surgery on the aorta
- Patients with family members who have had aortic aneurysm, sudden cardiac death, or certain genetic conditions such as Marfan’s Syndrome
An aneurysm can develop anywhere along the aorta:
- Aneurysms that occur in the section of the aorta that runs through the abdomen (abdominal aorta) are called abdominal aortic aneurysms (AAA or “triple-A”)
- Aortic aneurysms that occur in the chest area are called thoracic aortic aneurysms and can involve the aortic root, ascending aorta, aortic arch or descending aorta (TAA)
- Aneurysms that involve the aorta as it flows through both the abdomen and chest are called thoracoabdominal aortic aneurysms (TAAA)
Multiple surgical approaches may be used in treating aneurysms.
Surgery for Aortic Dissection
Aortic dissection is a condition that forces the layers of the wall of the aorta apart. Bleeding or weakening of the middle layer of the aortic wall results in separation of the layers of the aorta. Blood enters this space, and the space enlarges, causing an aortic dissection, or tear. The person experiencing this condition will feel severe, sharp, ripping pain in the chest and back.
Acute aortic dissection can be treated surgically or medically. Medical management is the treatment of choice for descending aortic dissections unless they are leaking or ruptured. Medical management includes anti-hypertensives (blood pressure medications), including beta-blockers, which specifically act to slow the heart rate and decrease the tearing forces.
Ascending aorta dissections, near the heart, are almost always a surgical emergency. The area of the aorta with the tear is removed and replaced with a Dacron graft (artificial polyester blood vessel). This is done using the heart lung machine, and is an “open heart” procedure.
Thoracic Endovascular Aortic Repair (TEVAR) is a minimally invasive procedure to repair thoracic aortic aneurysms (TAAs).
To repair the aorta, doctors place a stent graft device through a small hole in the groin. This device is made of a fabric-covered metal mesh, which is fully opened under x-ray. The device repairs the diseased aorta and helps to keep it open and allow blood to flow properly to the rest of the body. Depending on the type of disease, the TEVAR procedure usually provides a cure.
Aortic Valve Repair/Replacement
The heart has four valves, one for each chamber of the heart. The valves keep blood moving through the heart in the right direction. The aortic valve is located between the left ventricle and the aorta. It is the last valve the blood flows through before leaving the heart.
The aortic valve consists of three “leaflets” ensure the blood doesn’t flow backward after it is pumped out of the heart. Aortic valve problems usually result in a valve that is leaky (insufficiency) or a valve that doesn’t open fully (stenotic). Sometimes a valve can be both insufficient and stenotic.
Surgery on the aortic valve is common, and there are multiple ways to repair or replace a damaged or defective aortic valve. The two primary decisions the cardiac surgeon will consider are whether the valve can be repaired or must be replaced, and which surgical approach will work best.
In certain limited circumstances, especially if the valve is leaky due to an aortic aneurysm, aortic valve repair can be performed during aneurysm surgery. This is called an aortic valve-sparing root replacement (David procedure or Yacoub procedure)
In most cases of surgery on a damaged aortic valve, however, replacement rather than repair will be the best option. There are two primary kinds of replacement valves. Factors such as age and the overall state of the patient’s health will affect which type of valve is most appropriate:
- Mechanical valves are made of very durable artificial materials, including titanium, carbon, polyester, Dacron and Teflon, and are typically very long lasting.However, use of a mechanical valve usually requires patients to take blood-thinning medication warfarin (often referred to by the brand name of Coumadin) for the rest of their lives.
- Biological valves, also known as tissue valves or bioprosthetic valves, are made of animal tissue, often from a pig or a cow. With this type of valve, blood thinners are not usually required; however, biological valves have a limited life span of 10 to 20 years, so a second valve replacement operation may be required at some point. Biological valves are used in the majority of aortic valve replacement operations.
The appropriate surgical approach will depend on such factors as whether the valve can be repaired or must be replaced, how damaged it is, and the overall state of the patient’s health. The surgeon will determine which of the following procedures is most appropriate:
- Open-heart surgery to repair or replace an aortic valve involves making a seven- to 10-inch incision over the middle of the sternum, or breastbone, then dividing the sternum to allow access to the heart. In some cases a less invasive option, involving a smaller sternal incision, is possible. Then the damaged valve is either repaired or replaced. In other cases, a technique known as axillary cannulation (or the insertion of a drainage tube, known as a cannula, in an artery in your armpit, or axilla) can allow aortic surgery to be performed without hypothermic circulatory arrest; this advance may reduce the incidence of postoperative strokes and neurological deficits.
- Transcatheter aortic valve replacement (TAVR) is a relatively new, minimally invasive option that may be appropriate in patients judged to be at high-risk for traditional aortic valve surgery.
- Composite graft surgery is an appropriate option if the aortic valve is damaged, and the part of the aorta closest to the heart (known as the aortic root) is affected by either an aneurysm or tear.This procedure involves both replacing the aortic valve with either a mechanical or a biological valve and repairing or replacing the damaged portion of the aorta itself.
Bicuspid Aortic Valve
Bicuspid aortic valve (BAV) is an inherited form of heart disease in which two of the leaflets of the aortic valve fuse during development in the womb, resulting in a two-leaflet valve (bicuspid valve) instead of the normal three-leaflet valve (tricuspid valve). With this deformity, the valve sometimes does not function perfectly, but it may function adequately for years without causing symptoms or obvious signs of a problem.
Recent studies suggest that bicuspid aortic valve disease is caused by a connective tissue disorder that also causes other circulatory system problems. People with bicuspid aortic valve disease also may have abnormal coronary arteries, aortic aneurysm or an abnormal thoracic aorta (the portion of the aorta that passes through the upper chest) as well as unstable high blood pressure. About 2% of the population has BAV, and it is twice as common in males as in females.
If surgery is required for bicuspid aortic valve, various techniques may be used. It is possible in selected patients, to repair a leaky bicuspid valve in conjunction with repair of an aortic aneurysm. Other approaches include valve and aorta replacement (aortic root replacement), and valve replacement alone.