Guest: Dr. John S. Ikonomidis - Cardiothoracic Surgery
Host: Dr. Pamela Morris - Cardiologist.
Announcer: Welcome to an MUSChealth podcast.
Dr. Pamela B. Morris: Hi, I am Dr. Pamela Morris and I am talking today with Dr. John Ikonomidis, who is Surgical Director of the Cardiac Transplantation Program at the Medical University of South Carolina. We are talking now about aneurysms of the descending thoracic aorta. John, let’s define that area of the body for the listener.
Dr. John S. Ikonomidis: The aorta can be viewed as a large tube that conveys blood and it is the main conduit that transmits oxygenated blood from the heart to the whole body. It starts at the base of the heart, in the front of the chest, it rises from the base of the heart up to the top of the breast bone and that’s referred to as the ascending aorta. At this point, it arches backward into the left, where it gives off three branches that supply the head and the arms and that segment of the aorta is referred to as the aortic arch. After the last branch, arterial branch, that supplies the left arm, it then curves downward and runs along the spine on the left-hand side and crosses the diaphragm, which is the muscular sheath that separates the chest from the abdomen and that section of aorta from that last branch of the arch to the diaphragm is referred as descending thoracic aorta. From there, it goes into the abdomen and then proximally at the belly button branches to the iliac arteries that supply the legs and while it’s in before that time between the diaphragm and the belly button, there are three major branches that are given off to supply the abdominal organs. So, the section of interest for this discussion is the descending thoracic aorta. Now, it is that section of the aorta in the back of the chest beside the spine, above the diaphragm, and below that last branch of the aortic arch, that particular section.
Dr. Pamela B. Morris: What are some of the causes? What would cause the aorta to dilate in the area of the chest?
Dr. John S. Ikonomidis: The most common cause in that area is degenerative and this occurs in patients that have high blood pressure, that have severe atherosclerotic disease, lot of plaque in the aorta that initiates the process that causes the aorta to dilate and there are certain hereditary conditions that predispose through aortic aneurysms such as Marfan syndrome and Ehlers-Danlos syndrome, which are connective tissue diseases, and in addition, there are some familial aneurysm syndromes in which no particular pathology is identified other than to say that these aneurysms tend to run in these families and they have specific genetic abnormalities that predispose to this that we haven’t quite completely worked out the disease process yet.
Dr. Pamela B. Morris: I would imagine in the cases of a degenerative aneurysm of the aorta, the typical things that we do to prevent heart disease, could also prevent formation of any aneurysm, control of blood pressure, control of cholesterol, etc.
Dr. John S. Ikonomidis: You raised a very good point because aortic aneurysm disease is a disease in which there is no active treatment form other than surgery, once aneurysm is diagnosed. We do not have a pill or a procedure, which arrests or reverses any aneurysm once it starts to form. So, the best that we can do is to control the risk factors, so absolutely correct. You want to reduce the contractility of heart to some extent, we do that with medicines called beta-blockers, you can control blood pressure by other means, other medicines, and lifestyle modification such as limiting fatty intake, lowering cholesterol, and stopping smoking; all those sorts of things.
Dr. Pamela B. Morris: Are there any symptoms that would alert a patient to the fact that they are developing any aneurysm or have developed any aneurysm?
Dr. John S. Ikonomidis: There is not a specific symptom that is completely diagnostic for any aneurysm. Majority of patients are asymptomatic. The first presentation is often bursting of the aneurysm and that usually results in death. There is a subpopulation of patients that develop some back pains and this occurs as a result of the enlarging aneurysm rubbing against the spine and the nerves and can cause some discomfort, which may lead to a workup that would result in the diagnosis of the aneurysm.
Dr. Pamela B. Morris: When you are fortunate enough to have a warning that any aneurysm is present, how do you diagnose the presence of the aneurysm and whether or not it is time for surgery?
Dr. John S. Ikonomidis: Most common test is CT scan, which not only diagnoses the aneurysm, but will also tell you the full extent of it and the size of it and we decide on fitness for surgery based on size criteria for the descending thoracic aorta. The sizes of the aorta of 6 to 6.5 cm that can be modified to some extent for patients who have connective tissue disorders and which is anticipated that the aneurysm may grow faster, in which case, we may go down to 5.5 cm and some people have argued that since not all patients are created equal, there is large patients and small patients and absolute size may not be appropriate and there is data to suggest that, so we also standardized the diameter of the aorta by the patient’s body surface area, which depends on height and weight and come up with a criteria for resection that way.
Dr. Pamela B. Morris: Once you have decided that it is the time for surgical repair of any aneurysm, what are the different surgical procedures that are available to you?
Dr. John S. Ikonomidis: Historically, the only surgical procedure that was available was an open surgical repair and this involved putting the patient to sleep and entering the left chest through a very large incision in the chest, which usually requires breaking of one or more ribs to get appropriate exposure, pretty morbid procedure and then placement of clamps on normal aorta above and below the aneurysm, removal of the aortic aneurysm, and then replacement with the cloth graft that is made out of Dacron. This is often done with some sort of circulatory support involving bypass or some other type of support, which is instituted in the artery and vein below where the aneurysm is to protect the abdominal organs while the clamps are on. It’s a complicated procedure. It has a lot of morbidity related to it, risk of stroke, risk of lung complications, risk of kidney complications, risk of heart attack, and these patients who come for these repairs are often sick to begin with and have numerous comorbidities and so its pretty risky.
Dr. Pamela B. Morris: Certainly, less invasive approaches are desirable.
Dr. John S. Ikonomidis: Absolutely, and in the late 80s, a group at Stanford University began to experiment with a procedure called endovascular stent grafting in which a graft, which is mounted on a stent, can be placed within the aneurysm from the inside of the aneurysm and then deployed so as to exclude the aneurysm.
Dr. Pamela B. Morris: So, much like the stents were seeing now in the coronary arteries.
Dr. John S. Ikonomidis: Absolutely, with the exception that the stents that are used in the coronary arteries are not covered to create a loose analogy, they are like little pieces of chicken wire that are used to stent open blockages once they are expanded with a balloon. That is not exactly the case with endovascular stent grafting, where the stent is covered with a fabric that is in impervious to blood. So, the idea is that the aneurysm is excluded from pressurized blood to prevent further expansion of it. So, this is a covered stent as opposed to stents that are used in the heart, which are open stents. The first endovascular stent graft FDA approved for use was approved only two years ago and its only true indication, the only FDA approved indication, for aneurysm for deployment of the stent graft is for aneurysms. Currently, in the state of South Carolina, there are probably three or four programs which offer the procedure. We were the first to introduce it into the state and we probably have the largest experience with it and so far the results have been very good. The advantage of this procedure is that you can offer aneurysm repair, the patients that have multiple disease states that would, otherwise, render them not suitable for surgery because of high risk. The advantage of stent grafting, of course, is that no large chest incision is required, often we can access one of the arteries in the patient’s upper leg, which involves an incision of only 2 or 3 inches and the procedure at time is often cut in the half or two-third of what a standard aneurysm operation would be. In addition, the hospital stay for these patients is in the order of two to three days as opposed to up to two weeks for patients that have open repair through the chest. So, it’s definitely a viable advancement and it is a very good alternative, especially in very sick patients who don’t have other options.
Dr. Pamela B. Morris :Are there certain types of patients that are the best candidates for the stent grafting?
Dr. John S. Ikonomidis: Absolutely, in order for a stent graft to be successfully deployed, there has to be a normal segment of aorta above and below the aneurysm that will hold the stent graft and not dilate overtime and we need approximately a 3-cm neck on either side to deploy it. Other considerations would include relatively clean vascular tree below the aneurysm to allow placement of a rather large introducer in the vascular tree that would be used to deploy the stent graft, so we look at really the patient’s whole vascular anatomy not just the anatomy of the aneurysm prior to consideration for them not would be a candidate for stent graft.
Dr. Pamela B. Morris: Patients who receive coronary stents, require a period of time where they are treated with agents that either thin the blood or affect the blood’s clotting system; is that necessary for the endovascular stent?
Dr. John S. Ikonomidis: No it is not necessary.
Dr. Pamela B. Morris: So, no long-term treatment following the procedure as needed.
Dr. John S. Ikonomidis: There is no medicine specific to the stent graft that’s required.
Dr. Pamela B. Morris: Well, that certainly is an advantage for the patient long-term as well.
Dr. John S. Ikonomidis: Absolutely.
Dr. Pamela B. Morris: What about followup, in long-term followup after placement of an endovascular stent?
Dr. John S. Ikonomidis: The patients in hospital have a CT scan prior to discharge to confirm that the stent is properly placed and that there is no leakage of blood around the stent graft into the aneurysm, they receive CT scans in three, six, and nine months and then yearly thereafter.
Dr. Pamela B. Morris: And how long an experience do we have thus far with the stent graft?
Dr. John S. Ikonomidis: We deployed our first stent graft approximately five years ago and so we have varying followup from five years up.
Dr. Pamela B. Morris: And thus far a good durability.
Dr. John S. Ikonomidis: Very good durability thus far.
Dr. Pamela B. Morris: That’s great. Well, thank you Dr. Ikonomidis for talking with us today.
Dr. John S. Ikonomidis: My pleasure.
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