Learn how physicians at the Massachusetts General Hospital Thoracic Aortic Center diagnose and treat thoracic aortic disease, a condition that affects the portion of the aorta that is in the chest and requires treatment from both cardiac and vascular specialists.
What is a thoracic aortic aneurysm?
An aneurysm is a dilatation - or a bulging ballooning out - of the walls of an artery. An aortic aneurysm is bulging out of the walls of the aorta, which is the largest artery in the body and carries oxygen-rich blood from the heart to the rest of the body. Aneurysms that involve the part of the aorta in the chest (thorax) are called thoracic aortic aneurysms, whereas those involving the part of the aorta in the belly or abdomen are called abdominal aortic aneurysms.
Thoracic aortic aneurysms and abdominal aortic aneurysms have different causes and are managed a bit differently. There are a number of health factors that can contribute to the formation and growth of thoracic aortic aneurysms, including the natural aging process, hypertension (high blood pressure), atherosclerosis (cholesterol buildup and hardening of the arteries), a prior aortic dissection, giant cell arteritis (arterial inflammation), Takayasu arteritis or syphilis. Certain congenital conditions (abnormal conditions present at birth) are also associated with aortic aneurysms, such as a bicuspid aortic valve, Marfan syndrome, Ehlers Danlos syndrome and Turner syndrome. Those who have a family history (ex: parents, siblings or children) with thoracic aortic aneurysms may share a genetic abnormality and therefore are more likely to have a thoracic aortic aneurysm themselves.
What is a bicuspid aortic valve?
The aortic valve is located at the base of the aorta where it meets the heart. The purpose of the aortic valve is to open when the heart beats to allow blood to be pumped from the heart into the aorta and out to the body and then, when the heart relaxes, to close and prevent blood from leaking backward into the heart. The normal aortic valve is “tricuspid” in that it has three separate leaflets or cusps (tricuspid: three cusps). These leaflets hang down from the walls of the aorta and, when the valve is closed, meet in the middle to form an effective seal.
In some cases, however, the aortic valve does not form properly during the heart’s embryonic development (when the baby’s body is forming during pregnancy), resulting in only two rather than the normal three aortic cusps; the abnormal valve is therefore called a “bicuspid” aortic valve (bicuspid: two cusps). In some cases such bicuspid valves may function relatively well, but in most cases they are either narrowed (a condition known as aortic stenosis) or they leak (a condition known as aortic insufficiency or regurgitation).
It is now recognized that approximately 50 percent of those born with a bicuspid aortic valve also have a dilated ascending thoracic aorta (the part of the aorta arising from the heart and going up the front of the chest). If this segment enlarges significantly it is called an ascending thoracic aortic aneurysm. The aorta enlarges due to a weakness in the aortic wall that is due to a process called cystic medial degeneration, similar to a pattern seen in Marfan syndrome, in which the structural elements that give the aortic wall its strength are either abnormally weak or reduced in number. Therefore, it is essential that anyone who has a bicuspid aortic valve undergo an imaging study, such as a CT scan, MRI scans or echocardiogram (ultrasound examination of the heart), to see if his or her ascending thoracic aorta is enlarged.
What is Marfan syndrome?
Marfan syndrome (also known as Marfan’s syndrome or the Marfan syndrome) is a genetic disorder that predisposes to the formation of thoracic aortic aneurysms. It is due to an abnormality in the gene responsible for the formation of fibrillin-1, which is a major structural component of the fibers called elastin that give the normal aorta its remarkable strength. A defect in elastin makes the aorta weak, and a weak aorta is prone to stretch over time and become an aneurysm. Patients with Marfan syndrome are at markedly increased risk for both aortic aneurysm formation and the occurrence of aortic dissection.
I’ve been diagnosed with a thoracic aortic aneurysm, but I don’t have any symptoms. Should I still be concerned?
Most of the time thoracic aortic aneurysm aneurysms (aneurysms in the chest) do not cause any symptoms when first diagnosed. Most of these aneurysms are instead discovered incidentally when patients undergo a chest x-ray, an echocardiogram (ultrasound examination of the heart) or a CT scan of the chest that was ordered for some other reason. Unfortunately, in some cases aneurysms may go undetected until they grow large enough that they either rupture or cause a tear that results in a life-threatening condition known as aortic dissection. The size of the aneurysm as determined on a CT is the most important piece of information in determining the need for treatment.
How do my doctors determine when I need surgery?
Surgery is recommended when aneurysms grow large enough that they have a significant risk of tearing. The purpose of surgery is to repair or replace the aneurysm to prevent such a life-threatening tear from occurring. The specific size at which we operate differs depending on the location of the aneurysm, how quickly the aneurysm is growing and the age of the patient. In general we will operate on aneurysms of the ascending aorta when the reach anywhere from 5.0 to 5.5 cm in size (6.0 cm for older or higher risk patients) and on aneurysms of the descending aorta when the reach 6.0 cm in size. In some cases, even when an aneurysm is this large, we may still recommend surgery if it is causing problems for the heart or other organs, or if it is producing pain, shortness of breath or circulation problems.
Why don’t you just operate to fix all thoracic aortic aneurysms, regardless of the size?
The surgery to repair aortic aneurysms carries a small but real risk. (This risk varies based on the patient’s age, the patient’s overall health condition, the location and extent of the aneurysm and the volume of aortic procedures performed by the surgeon and at the center where the surgery is performed). When aneurysms are relatively small, the risk of an aortic tear or rupture is small, so the risk of surgery outweighs the risk of going without surgery. However, when an aortic aneurysm is larger, as discussed in the prior answer, the risk of surgery is generally lower than the risk of no surgery, so surgery is recommended.
What do you use to replace the part of the aorta with the aneurysm when you perform surgery? How long does the replacement part last?
The aorta is replaced with an artificial tube, not unlike replacing a broken piece of pipe with a new one. However, in this case the replacement tube is made out of a tightly woven fabric called Dacron® or Gore-Tex®. The woven material is durable and the graft will last for your lifetime.
Do I need to take antibiotics when I go to the dentist or have invasive procedures when I have an artificial aortic graft?
No. Although people with artificial heart valves do have to take antibiotics for dental work in an effort to prevent their new valves from getting infected, fortunately those with an artificial aorta do not. The body covers over the aortic graft with a surface coating of cellular material called a neo-intima, and the risk of subsequent infection of the graft is extremely small. Nevertheless, we do recommend avoiding any unnecessary dental cleanings for the first six months following your surgery, just to minimize any potential risk as the body is first healing.
Can I have some sort of stent instead of regular surgery to fix my aortic aneurysm?
In certain circumstances, and for certain aneurysms that do not involve the ascending aorta, there is a new technique known as stent graft repair. It is the equivalent of a minimally invasive approach for aneurysm repair. Such stent-graft procedures can only be performed at select medical centers by physicians specifically trained in this field. In addition, these stent-grafts can only be carried out when the patient’s aortic anatomy is appropriate; if not, a standard surgical procedure will have to be performed. The major advantage of this method is the avoidance of the large chest incision that open surgery requires.
What will my doctor do if my thoracic aortic aneurysm is not large enough to require surgery?
When an aneurysm is not large enough that you need surgery, your doctor will treat you with medications to control your blood pressure and heart rate, in order to reduce the force of your blood against the wall of the aorta. The size of your aorta will be followed closely with repeated CT scan, MRI scans or echocardiograms (ultrasound examination of the heart) to monitor for any growth. If the aneurysm grows large enough in size, surgery may then be recommend.
I don’t have high blood pressure. Why do I have to take medication?
Even if your blood pressure is not particularly high, when you have an aortic aneurysm the goal is for your blood pressure to run on the lower side of normal, since your blood pressure is literally the pressure of the blood against the weakened wall of the aorta. The lower the blood pressure the less the force that leads to stretching of the aortic aneurysm over time. Typically the goal is to have your systolic blood pressure (the higher number) in the range of 105 to 125.
My uncle and I both have a thoracic aortic aneurysm. Will others in my family also have an aneurysm?
Many patients with ascending thoracic aortic aneurysms at younger ages (30s, 40s and 50s) have Marfan syndrome or a bicuspid aortic valve as the cause. However, there are other people who have aneurysms at a young age, and it appears to run in their family. A number of such families have been studied and found to have a genetic abnormality that accounts for the aortic aneurysms. This is now called a familial thoracic aortic aneurysm syndrome. A number of gene mutations (abnormal genes) have been identified that are associated with such aneurysms, and more probably exist.
Since no single gene is responsible, there is not yet a routine genetic test that can be used to screen for the syndrome. Consequently, whenever a patient less than 70 has an ascending thoracic aortic aneurysm that is otherwise unexplained, we strongly recommend that all first-degree relatives (parents, siblings or children) be screened since other family members might also have unrecognized thoracic aortic aneurysms. If you would like assistance in discussing a possible familial thoracic aortic aneurysm syndrome or in screening your family members, contact the Thoracic Aortic Center for a consultation.
Do I need to have to have an artificial aortic valve as part of my operation? If so, what are my choices?
Often aneurysms of the ascending thoracic aorta will produce a leaking aortic valve (aortic insufficiency) as a consequence. Most of the time when we surgically repair the aorta we can repair the aortic valve at the same time and avoid the need for replacement. In some cases we do this simply by reshaping the aortic root, which is a relatively straightforward procedure. However, in other cases, the aortic root itself is dilated and saving the valve requires a procedure known as a valve-sparing aortic root repair, which is a complex operation that involves excising the valve tissue, implanting an artificial aortic graft and then reimplanting your own valve inside the artificial aorta. This procedure is relatively new and still only performed by a handful of experienced cardiac surgeons.
Finally, in certain cases the aortic valve itself is diseased and quite abnormal, so it does have to be replaced with an artificial valve at the time of surgery. The new valve can be made of metal or made of tissue, such as a from a cow’s heart. The metal valve can last forever, but requires that you take blood-thinning pills (Coumadin or warfarin) forever as well. A tissue valve has the advantage that blood thinners are not required, but does not last forever. We typically estimate that a tissue valve will have to be replaced again after about 15 years, but this time frame may be quite variable. In patients younger than 65 we usually recommend a metal valve, and in those older than 65 we usually recommend a tissue valve. However, other factors such as health problems may alter this recommendation.
Can the aneurysm come back if I have surgery to fix my thoracic aortic aneurysm? Will I still need to take medication after surgery?
When a portion of the aorta is replaced surgically, we replace it with an artificial tube-graft. Therefore, the aneurysm is removed and cannot recur in that location. In some instances, such as with some aneurysms of the ascending thoracic aorta, there is only one segment of the aorta that is abnormal so once that segment has been replaced the risk of aortic aneurysms forming elsewhere is only slight.
However, when aneurysms are due to a systemic problem, such as atherosclerosis or Marfan syndrome, the risk of future aneurysms in other segments of aorta is significant. Therefore, almost all patients who have had a thoracic aortic aneurysm repair should still undergo periodic surveillance imaging with CT scans or MRI scans indefinitely. Given that after surgery most patients still have a risk of future aortic aneurysms, it is customary to continue using blood pressure medications to keep the blood pressure at the lower side of normal for the long run.
How often do I need to see the doctor after surgery? You return for a first postoperative visit about four to six weeks after the surgery. Typically follow up visits will occur every six or 12 months thereafter, depending on the anatomy of the remaining portions of the aorta.
Do I need to come back to Boston for all of my follow-up visits?
If you have your surgery at the Massaschusetts General Hospital Thoracic Aortic Center, we typically prefer to follow you after the surgery to make sure your blood pressure is optimally controlled and to carry out follow-up imaging studies (CT or MRI scans) of the remaining portions of your aorta. However, if you live a considerable distance from Boston or if you have a close relationship with a local cardiologist or vascular surgeon, we can arrange to have you followed by your local specialist for routine visits with the expectation that you will return to the Thoracic Aortic Center should there be any significant changes in your aortic anatomy.
What is an aortic dissection? How is it different from an aneurysm?
An aortic dissection is a life-threatening condition that occurs at a rate of about three cases per 100,000 people per year. It involves a tearing away of the innermost lining of the aorta. It is not unlike when you put on an old winter coat, but as you slide your arm into the sleeve your fingers catch a tear in the sleeve’s lining, leading your arm into the space between the inner lining and the outer layer of the coat sleeve. Similarly, an aortic dissection occurs when a weakened aortic wall develops a tear in its inner lining, known as the intima, which in turn allows blood from within the aorta to penetrate into the strong middle layer of the aorta called the media. Although most patients with an aortic dissection have an underlying aortic aneurysm, some do not. Similarly, not all patients with a thoracic aortic aneurysm go on to develop an aortic dissection.
What are the symptoms of an aortic dissection?
Almost all patients with an acute aortic dissection experience pain. The pain is typically severe and located in the chest, neck or back. Sometimes it is located in the abdomen or legs depending on the location of the aortic dissection. In fact, the pain may migrate as the dissection propagates. The pain is often a sudden onset and is at its most severe at the start. It is often described as "sharp," "stabbing" or "tearing." The symptoms are usually different from those associated with a heart attack, but there can be overlap. It is essential that anyone with a thoracic aortic aneurysm knows the symptoms associated with aortic dissection and can undergo an assessment in a nearby emergency department, including a CT scan to determine whether or not an aortic dissection has occurred.
What is the risk from an aortic dissection?
The early mortality (death rate) is about one percent per hour, so the sooner it is diagnosed and treated, the better the outcome. Aortic dissections that involve the ascending thoracic aorta (referred to as type A) are at high risk of aortic rupture, which can be fatal. This condition requires urgent surgery to replace the ascending portion of the aorta. Conversely, aortic dissections that do not involve the ascending thoracic aorta (referred to as type B) are at much lower risk of aortic rupture, and are therefore managed with medications rather than surgery, in most cases.
If I had a CT scan performed locally, will I need another one performed when I am evaluated at the Thoracic Aortic Center?
Although it may have been a CT scan that detected or defined your thoracic aortic aneurysm, not all CT scans are the same. The standard CT scan images the body in cross section, like slicing a loaf of bread. The images on the film or computer screen are individual slices. However unlike a loaf of bread, the aorta is not a linear or straight structure, so the CT scan may not cut the aorta on axis (straight across) but rather off axis (at an angle), making the aorta appear wider than it really is. This can make it difficult to accurately measure the true size of an aneurysm.
Fortunately, at Mass General Hospital we have sophisticated CT scanners with special software that can take a series of hundreds of individual images or slices, and digitally reconstruct them to produce a three-dimensional image of the aorta and other arteries. Our computers can then allow us to look at and measure the aorta from any angle, which permits far more accurate calculations of aneurysm size. This technique is called CT angiography, or CTA with 3-D reconstruction. Because of this, even if you have had a CT scan, MRI scan or echocardiogram elsewhere, we may still wish to perform a CTA here.
If surgery is required for an aortic dissection, does it have to be done urgently?
Yes. Since the early mortality (death rate) is about one percent per hour, the sooner surgery is performed, the better.
I had seen the doctor for pain in my legs on walking when they found the aneurysm. Will the pain be gone after surgery?
Certain patients with abdominal aortic aneurysms also have blockages in the arteries to the legs, and in certain cases such blocks are repaired at the same operation to repair the abdominal aneurysm. However, if the blockages are located in the legs themselves a second procedure is most likely required for treatment.
My aneurysm has affected my kidneys. Will the surgery fix my kidneys?
Frequently patients with complex aneurysms also have blockages in the arteries to the kidneys, and such blockages are typically corrected during the operation to fix the thoracoabdominal or abdominal aneurysm. In certain cases, this may improve the overall function of the kidneys.
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