Guest: Dr. John Ikonomidis
Host: Dr. Pam Morris
Dr. Pam Morris: Hi, I am Dr. Pam Morris and I am here today with Dr. John Ikonomidis and we are talking today about aneurysms of the ascending aorta. How common is this problem, Dr. Ikonomidis?
Dr. John Ikonomidis: Ascending aortic aneurysms are not very common. There is a fair amount of population based studies performed on this, probably the most of which comes from Yale University, that show that the incidents of ascending aortic aneurysms is probably 6 per 100,000 patient years. In other words, it is a relatively uncommon condition, much more uncommon for example than aneurysms of the abdominal aorta which you hear about a lot more.
Dr. Pam Morris: Let’s define for our listeners what an aneurysm is exactly.
Dr. John Ikonomidis: An aneurysm is a localized or diffuse dilation of the aorta, greater than 1.5, one and one half times, its normal diameter and it involves all of the layers of the wall of the aorta.
Dr. Pam Morris: We are talking specifically about the aorta as it leaves the heart through the aortic valve?
Dr. John Ikonomidis: Correct. In the chest, the aorta is classified into three regions. The first region is the so called ascending aorta which starts at the base of the heart and travels up towards the head and it stops at approximately the top of the breast bone. That section of the aorta is referred to the ascending aorta. At that point, it then arches backwards into the left and gives off three blood vessels that supply the head and the arms. That section of the aorta is referred to as the aortic arch. When the aorta begins to go aside the spine on the left hand side, down to the diaphragm which is the muscular sheath that separates the lungs from the belly, that section of the aorta is referred to as the descending thoracic aorta. What we are talking about today is the first section of the aorta, the ascending aorta, between the heart and the aortic arch.
Dr. Pam Morris: What sorts of diseases would cause an aortic aneurysm?
Dr. John Ikonomidis: The causes include degenerative causes which have as risk factors hypertension, high blood pressure, smoking, high cholesterol. That forms a very large group. There are hereditary conditions which predispose to aneurysms, some of which involve so called connective tissue diseases. So, things like Marfan syndrome, Ehlers-Danlos syndrome are relatively rare but real causes of ascending aortic aneurysms. There is a Familial Thoracic Aortic Aneurysm syndrome in which patients do not have identifiable connective tissue disease, but clearly aortic aneurysms run in the family.
There are certain other abnormalities which predispose to aortic aneurysms, the most common of which is something called a bicuspid aortic valve. The aortic valve is one of the heart valves that is between the left ventricle, which is the main pumping chamber of the heart, and the ascending aorta which the left ventricle pumps into. So, the idea is that when the left ventricle empties into the aorta, it then relaxes again to fill up with blood. To prevent the blood in the aorta from leaking back into the ventricle, there is a valve there that closes. That valve is the aortic valve. In the majority of individuals, that valve has three parts or cusps which open and close. In about one percent of the population, two of those cusps are fused at birth causing a so called bicuspid aortic valve as opposed to a tricuspid aortic valve. In those patients, there is a predisposition towards aortic aneurysms and we see that fairly commonly.
Dr. Pam Morris: I would imagine that the degenerative diseases would tend to occur in older individuals perhaps, where the congenital or genetic problems might appear earlier in life.
Dr. John Ikonomidis: Absolutely. Patients with Marfan syndrome or Ehlers-Danlos syndrome or other hereditary conditions, we often see those patients present in the 20s and 30s. They can present at any time but it is not uncommon to see them quite young. Patients with bicuspid aortic valves, patients are in their 50s and 60s. In patients with degenerative aneurysms, probably 60s, 70s.
Dr. Pam Morris: Are there any symptoms, anything that would alert a patient to the fact they might have an aortic aneurysm?
Dr. John Ikonomidis: If the aortic valve is not affected, and I could into that a little bit more if you would like, there are no symptoms, absolutely none. In fact, most of the time these conditions are uncovered when a patient has a routine physical examination which includes a chest x-ray, in which an abnormality is found on the chest x-ray, or a patient presents to the emergency department with a bad cold and maybe they are coughing up some colored stuff and they would like some antibiotics, and somebody gets the chest x-ray and sees an abnormality with the aorta, a CT scan is obtained and the diagnosis is made.
If the patient has involvement of the aortic valve, and the aortic valve requires normal integrity of the aorta for it to function, and if the aorta starts to dilate, the valve begins to splay open and it can become leaky. That leaky aortic valve with blood leaking back into the left ventricle can cause the ventricle to start to dilate and tire and that results in heart failure symptoms. So, patients can present with fatigue and shortness of breath.
Dr. Pam Morris: How do you decide when it is necessary to repair an aneurysm of the ascending aorta?
Dr. John Ikonomidis: Numerous criteria. One criterion is if the aorta reaches a size two times greater than an adjacent segment of normal aorta, diameter wise. Absolute size criteria for the ascending aorta is about 5.5 centimeters and it has been suggested that because patients come in different shapes and sizes that one size may not be appropriate for all. So, there is some data now that suggests that you should standardize the diameter of the aorta by the patient’s body surface area which is a product of height and weight to decide the appropriate criteria for resection, for removal.
Than danger of course here, in patients that are asymptomatic, is you are trying to prevent death, because as the aneurysm enlarges, it predisposes to rupture and that is usually a fatal event.
Dr. Pam Morris: When you have identified an aortic aneurysm, of the ascending aorta, that needs to be repaired, what are some of the considerations for the surgical procedure that would be undertaken?
Dr. John Ikonomidis: Consideration number one is the extent of the repair, and that is usually evaluated with a CT scan that is specially configured to image the aorta. Through that scan, we decide exactly how much of the aorta needs to be replaced. That is the first issue. The second issue is the aortic valve. An echocardiogram is performed to evaluate whether or not the valve is leaking or there is other concomitant disease of the valve which would require that it be replaced. Finally, a coronary angiogram is performed to assess the blood vessels that supply the heart, to make sure that there are not significant blockages in the coronary arteries. If there are, then bypass grafting would also be required at the time of surgery.
Dr. Pam Morris: What are some of the types of surgical procedures that are considered?
Dr. John Ikonomidis: The simplest is removal of the diseased portion of the aorta and replacement with a cloth graft which is just a tube made out of a material called Dacron. Patients with significant aortic valve disease may need to have their aortic valve replaced. So, sometimes the aortic valve is replaced, a portion of non-dilated aorta is left intact around the aorta and the coronary arteries and then the graft is placed. In other cases, the aortic valve needs replacement but the entire ascending aorta is destroyed by the aneurysm, in which case it is completely removed, including the valve, and an aortic root replacement is performed with, usually, a valve that is sewn right into a graft. The whole thing is implanted and the coronary arteries are sewn into that.
There are certain patients in which the aortic valve is actually normal but is leaking because of the aneurysm. So, it stands to reason, therefore, that if the aortic root can be remodeled back to its normal geometry, the valve will become competent again. So, that particular operation is referred to as a valve-sparing aortic root replacement, which we also offer at the Medical University.
Dr. Pam Morris: I would imagine that procedure is quite challenging.
Dr. John Ikonomidis: It is technically a little bit more difficult and there is a learning curve early on. In our institution, we have performed about 60 of those which is a very respectable number within the nation. Most cardiac surgical programs in the nation do not offer valve-sparing aortic roots. It is an excellent operation if properly performed, especially in young people in whom replacement of the aortic valve with a prosthesis, such as a tissue prosthesis or a mechanical valve, may not be the option in terms of durability.
Dr. Pam Morris: Well, we are also learning so much about the way the body was created at birth often times functions better than replacing it with alternatives.
Dr. John Ikonomidis: Absolutely. What we have learned not just in the area of aortic valve surgery but other heart valves, is that if you can repair the valve, it often does better than actually having to remove it and replace it with a biological or mechanical substitute.
Dr. Pam Morris: Well, Dr. Ikonomidis, thank you so much for talking with us today about valve-sparing aortic root surgery.
Dr. Ikonomidis: My pleasure.
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