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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.
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.
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.
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.
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.
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.
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.
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