AORTIC ANEURYSM

AORTIC ANEURYSM

An aneurysm is a blood vessel that has become enlarged. 

Generally, an enlarged blood vessel "becomes" an aneurysm once it is 1.5x normal size. 

Pretty much any blood vessel - artery or vein - can become aneurysmal. 

Some commonly problematic sites of aneurysms are the Circle of Willis in the brain, the abdominal aorta, and the thoracic aorta (in the chest). 

Normal aortic valve lealfets are thin and pliable and move very easily. 

Notice how smooth these normal leafets appear, and how they are thin - you can almost see thru them. 

These normal leaflets will open easily, meaning it takes very little force to move the leaflets out of the way. 

And when these normal leaflets open, they open completely, nearly touching the wall of the aorta, allowing for a lot of space for the blood to move out of the heart. 

The aorta is the largest blood vessel in the body. 

The aorta arises from the heart and carries blood to the body. 

Where the heart stops and the aorta starts is called the aortic root. The aortic valve separates the heart from the aorta. 

The coronary arteries - the arteries of the heart itself - arise from the aorta at the aortic root. The left main and right coronary arteries are the first two branches of the aorta. 

The aorta comes upward toward the head, a portion called the ascending aorta. 

The aorta then gives branches to the arms and head, making a turn in the portion called the aortic arch. 

The aorta then courses down toward the legs as the descending thoracic aorta. Once it passes thru  the diaphragm, it becomes the abdominal aorta. 

At about the level of the belly button, the aorta splits to become the iliac arteries, which course toward the legs. 

An aortic aneurysm often does not cause symptoms. There are no sensory nerve endings in the aortic wall to transmit pain or other conscious neurologic signals. 

Often, an aneurysm is found because a scan was performed looking for something else, or if a complication of the aneurysm occurs. 

If an aneurysm becomes very large, it can cause symptoms, as it begins to push in on structures nearby. This is rare, however. 

The main problem with aortic aneurysms is that as they enlarge, the wall of the aortic becomes thinner. It is a bit like a balloon that inflates with air - eventually, if it becomes large enough, the integrity of the wall can fail. 

The normal size of the aorta - at the root and ascending portions - is 2.5 to 3.0cm. 

So an aorta that measures 3.5cm on a scan is enlarged and an aorta that measures 4.5cm is an aneurysm. 

Aortic aneurysms grow at an average rate of 0.1cm/yr. 

Some patients will have an aorta that grows faster and some slower. Some aortic aneurysms do not seem to change much over time. 

In general, it is expected than an aortic aneurysm will increase in size over time. 

There is no known way to make an aneurysm shrink. 

Medications are important in the sense that the blood pressure must be controlled. Very high blood pressures can be dangerous for a patient with an aortic aneurysm. 

But otherwise there are no medications which directly affect an aneurysm to slow down its growth. 

Vitamins and supplements have not been shown to help shrink aneurysms. The normal American diet will provide adequate vitamins and minerals for natural aortic repair. 

Smoking cigarettes can be particularly dangerous for patients with aortic aneurysm. Chemicals in the cigarettes can weaken the aortic proteins and interfere with repair mechanisms, thereby allowing an aneurysm to grow faster than it otherwise might. 

If an aneurysm "pops" like a balloon, it is said to have ruptured. 

An aortic rupture in the ascending portion of the aorta is nearly universally fatal. 

Most of those patients do not reach the hospital; many do not even get a chance to call 911. 

If a rupture occurs in the abdominal aorta, some patients will survive to the hospital and some may survive emergency operation. 

Sometimes the aorta may tear but not all 3 layers are violated. This is called an aortic dissection. 

An aortic dissection involves a tear in the inner layer of the aorta. The outer layer remains intact. 

Blood gets in between the layers, that is to say it dissects between the layers. 

A false channel aka false lumen is created as the dissecting blood spreads. The dissection can spread from the point of tearing toward the heart and can also spread down toward the legs. 

A false channel aka false lumen is created as the dissecting blood spreads. The dissection can spread from the point of tearing toward the heart and can also spread down toward the legs. 

An aortic dissection is a life-threatening problem. 

A dissection can be life-threatening in part because it does not take much for the outer layer of aorta to subsequently tear and the dissection turn into a rupture, thereby taking the person's life. 

Also, if the dissection involves the ascending aorta - near the heart - the aortic valve can tear away from the aortic root, causing severe leakage. 

And the aorta can leak blood into the sac around the heart - the pericardium - such that the heart is constrained and struggles to pump. 

A dissection which involves the aorta near the heart - the ascending aorta - is called a Type A dissection. A dissection which affects the descending aorta is called a Type B dissection. 

It is not known why aortic aneurysms develop. 

For most patients, it seems to be a combination of potential factors such as genetic predilection, blood pressure, plaque build-up, and smoking. Trauma and infection may also be rarer causes. 

Certain genetic conditions - among them notably Marfan Syndrome - can cause aneurysms at a young age and can run in families. 

Patients at high risk for aneurysm development may benefit from screening and should seek an evaluation by their physician. 

A CT scan is often used to assess the size of an aortic aneurysm. An echo cardiogram can also measure the aorta, but several portions of the aorta cannot be seen on echo. 

The emergency operation to address a Type A aortic dissection is similar to the elective operation used to treat an aortic aneurysm. 

A general anesthetic is given. 

A sternotomy is performed whereby the sternal bone is cut. 

The heart and lung machine is used so that the heart can be stopped and the blood moving thru the aorta can be stopped. Blood goes to the rest of the body via the heart and lung machine. 

The torn section of ascending aorta is replaced. Fancy medical tubing is sewn in its place. The fabric is Dacron. 

Dacron is flexible but will not tear or leak blood, even over many years. 

If any additional damage has been done - such as the aortic valve tearing away from the aortic root and leaking - then the damage will also be repaired at that time.

The heart is restarted and the chest incision is closed. 

Unfortunately, emergency surgery for Type A dissection has a high risk of death. In published studies, about 30% of patients with Type A dissection who go for emergency surgery will not survive. 

FREQUENTLY ASKED QUESTIONS

Q: I had a scan and my aneurysm was 4.8cm, now a scan shows it is 4.7cm - did it shrink?

A: Anything is possible but usually aneurysms do not shrink; that is, they do not have a decrease in size that sustains over time. The aorta does expand and contract a little bit with each heart beat and as the blood/pressure-wave moves thru it, so it is theoretically possible for one scan to catch the aorta in an expanded state and another scan to catch it in a contracted state. More likely, however, is that 1 or 2mm is the margin of error for the test. 

Q: How common are aortic aneurysms?

A: It is not known precisely how many people have aneurysms since some of them remain silent clinically throughout the person's lifetime. However, according to the Centers for Disease Control, aortic aneurysms are responsible for roughly 10,000 deaths in the US each year. Many more patients have aneurysms that do not cause a complication in a given year.  

Q: I need to have my aneurysm replaced - will I need to take special medicines for the Dacron graft?

A: The short answer is no. No special medicines are needed after implantation of an aortic graft. Your body will not "reject" the graft. You will likely be on medicines for other reasons such as blood pressure medicines and likely an Aspirin. But a graft can be safely placed with no special medicines afterward.

Q: Is there a way to fix an aortic aneurysm without open surgery?

A: Yes and no. An endovascular approach can be used for many descending aneurysms. This technology is called TEVAR - Thoracic EndoVascular Aortic Repair. This is like a very large stent that can be placed thru an artery in the groin and does not require an open operation. An ascending aneurysm cannot currently be fixed with an endovascular technology, so open surgery is the only option. There are medical researchers working on developing the technology for the ascending portion of aorta. 

The most common artery to develop an aneurysm is the aorta. 

Any portion of the aorta can become aneurysmal. 

A Type A dissection involves the ascending aorta. It can also affect any other portion of aorta. A Type A dissection is particularly dangerous because the aortic valve can tear away and/or blood can develop around the heart. 

A Type A dissection requires emergency surgery to replace the torn portion of aorta near the heart. 

A Type B dissection often does not require an emergency operation. The initial therapy is often to control the blood pressure very strictly. 

If an aneurysm is found on imaging but is not dissected, a determination should be made about whether it can be watched or if surgery needs to be done. 

There are many factors which go into deciding whether surgery would be beneficial to the patient. One major determinant is aneurysm size. 

Autopsy studies have shown that the risk of death and major complications with ascending aortic aneurysm goes way up at a size of 6cm. 

So most patients will benefit from replacing the aneurysm at a size smaller than 6cm. It is common for patients to undergo replacement of the aneurysm at 5.0 to 5.5cm. 

Other factors can play into the decision, such as age, family history, growth rate, or presence of symptoms. Pt body size can affect the decision as well- Shaquille Oneal and Danny Devito have naturally different sizes of aortas.

 

Also, if the patient has a bicuspid aortic valve, the aneurysm is usually replaced at a smaller size than wit a normal (tricuspid) valve.  

If the patient is getting a heart surgery for another reason, then the aneurysm may be replaced at a smaller size.

In addition, the risk of stroke and other major complications is higher with emergency surgery for dissection than with elective operation. 

God bless & heal you! 

J. Mark Pool, MD

ABTS Board-certified

214-692-6135

Member of Society of Thoracic Surgeons