Replacement

of Aortic

Aneurysm

The aorta is the largest blood vessel in the body. It channels blood from the heart to the body. 

The aorta is described as having several portions. 

The first portion of aorta as it comes up from the heart is the ascending aorta. 

The aorta then turns in the portion called the arch.

The aorta then courses down, the descending thoracic aorta. This then becomes the abdominal aorta lower down near the belly button. 

An aneurysm can form in the aorta. Any of the portions of aorta can develop an aneurysm. Actually, an aneurysm can occur in virtually any artery. Or even a vein. 

An aneurysm is a blood vessel that is too big, or bulging out. More specifically, an aneurysm is a blood vessel that has increased in size to 1 and 1/2 times normal diameter. 

The aorta is usually 2.5-3cm in diameter. So an aneurysm is usually 4-4.5cm in diameter. The aorta is not a perfect circle in cross-section, but it is pretty close. 

It is not known exactly why aneurysms form. They seem to occur because of a weakened area of the aortic wall which allows for expansion. Risk factors such as diet, lack of exercise, genetics, cholesterol, immune system, stress, and smoking seem to contribute to aneurysm growth. Also, high blood pressure can cause aneurysms to grow faster. 

Aneurysms can "run" in families but are not usually passed down in every generation like eye color. 

Aneurysms often do not cause symptoms until they are very large. This is because there are no nerves in the aorta, so there are no pain signals from changes in the wall. So, many patients do not know they have an aneurysm. Often an aneurysm is found because a scan was done looking for something else. 

The main problem with aneurysms is that as they get bigger, the wall of the aorta becomes thinner, and like a balloon, eventually the aorta can pop. 

The CDC estimates that ~45,000 Americans die each year from aortic diseases. This is more than die from motor vehicle collisions. 

The aortic wall has 3 main layers. These layers give the aorta strength and elasticity - the aorta expands and contracts slightly with each heartbeat. 

A tear can form in the inner layer, allowing blood to get between the layers, like a bad bruise. 

A tear in the inner layer and the blood getting between the layers like a bruise may not sound so bad, but it is an emergency situation called an aortic dissection - because the blood is dissecting between the layers. The bruising aka dissection can spread and cut off the blood flow to organs, such as the kidneys or bowel or even the brain or heart itself. 

Plus, it doesn't take that much more tearing for the other two layers to tear, in which case now there is a hole in the aorta - this is called a rupture. A rupture of the ascending aorta is nearly universally and promptly fatal. Most patients with a ruptured ascending aorta do not make it to the hospital.  

Patients may experience severe pain when a dissection occurs. The pain is not generally "bad" where patients wonder if they need to go to the ER; it is generally "the worst pain imaginable" and some patients get the feeling that they are going to die. Sometimes an aortic dissection is initially mistaken for a heart attack.

 

Nonetheless, some patients describe pain more akin to heartburn and some patients do not have chest or back pain. 

 

Emergency surgery is key to survival, if the ascending portion of the aorta is affected. If the arch or descending aorta is affected and not the ascending portion, then surgery may be needed but often not as an emergency. 

In general, the larger the aneurysm, the higher the risk of rupture or dissection. 

Autopsy studies have shown that the risk of death from rupture or dissection goes way up at a diameter of 6cm. 

Knowing when to operate on a patient with an aneurysm depends on several factors:

     Aneurysm diameter - Almost any patient with an ascending aneurysm 5.5cm or larger will want to consider elective replacement, though often surgery is recommended at a smaller size.

     Aneurysm growth - Most aneurysms grow slowly over time. The average growth rate for an ascending aneurysm is 0.1cm per year. If an aneurysm grows much faster, replacement may need to be considered. 

     Bicuspid aortic valve - If a patient has an aortic valve with 2 parts instead of the usual 3, the ascending aorta can be even weaker and replacement may be considered at a size of 4.5-5cm. 

     Family history - If a patient has a family history of aortic rupture or dissection, replacement may be considered at a smaller size than if there is no family history. 

     Marfan Syndrome - Patients with Marfan Syndrome can develop large aneurysms at a young age. Patients are often very tall and thin. 

There are no medications that will fix an aortic aneurysm. Indeed, there are no medicines that have been shown to be effective in shrinking an aneurysm.

 

Certain vitamins are needed for the proteins that make up the aortic wall, but these are including in a typical American diet. So, it is not necessary to take extra vitamins or supplements for an aneurysm. 

It is important to control blood pressure when it comes to aneurysms. A very high blood pressure can be dangerous in the context of an aortic aneurysm. Plus, a high pressure can lead to faster growth of an aneurysm. 

Smoking is an absolute no-no when it comes to aneurysms. The chemicals in the cigarettes can weaken the proteins in the aortic wall and cause the aneurysm to grow faster. If you have an aneurysm - or even if you don't - stop smoking! 

OPERATION

Currently, an ascending aortic aneurysm can only be replaced with open surgery. 

A sternotomy is used to access the heart and aorta. In general, a minimally-invasive approach is not safe to address an aortic aneurysm. 

The heart and lung machine is used. The section of aorta that is aneurysmal is cut out. The section is replaced with fancy fabric tubing - most of the time, the fancy fabric used is Dacron. 

The length of operation varies depending on how extensive the aneurysm is. It usually takes Dr. Pool about 3 hours to replace an ascending aortic aneurysm, if no other problems with the heart or aorta need to be taken care of at the same time. 

The Dacron fabric is slightly elastic but it will not grow with time or weaken or tear or burst/rupture. No special medicines are needed after the Dacron is implanted. 

 

God bless & heal you! 

J. Mark Pool, MD

ABTS Board-certified

214-692-6135

Member of Society of Thoracic Surgeons