Ascending aortic aneurysm

ASCENDING AORTIC ANEURYSMS

Large ascending aortic aneurysm

Ascending aortic aneurysms are the second most common aortic aneurysm to abdominal aortic aneurysms. Most ascending aortic aneurysms are diagnosed in patients in their sixth and seventh decade of life. They are commonly diagnosed later in life and when the aneurysm is large. These aneurysms are located above the heart and can cause the aortic valve to leak. In the figure to the right, the 3-D CT scan reconstruction of the aorta shows the large ascending aortic aneurysm. The aneurysm looks like a oval object above the heart.

Patients with connective tissue disorders or those with a bicuspid aortic valve are usually diagnosed earlier in life. Patients with a bicuspid aortic valve will be diagnosed earlier in life because these patients will likely have a murmur that initiates a work-up. Approximately 2/3 of patients with a bicuspid aortic valve will develop an ascending aortic aneurysm during their lifetime.

Patients with Marfan’s disease, Ehler’s-Danlos Syndrome, Loey-Dietz Syndrome or Familial Thoracic Aneurysm Syndrome will be screened and diagnosed as a young child or adolescent. Although some patients with connective tissue disorder will not be diagnosed until the time of an aortic rupture or aortic dissection. In such cases, the patient and the family will undergo genetic counseling and testing to confirm the clinical suspicion. Ideally, theses young patients will be monitored carefully through their young life for change in the aortic diameter. These patients need a multi-disciplinary team to care not only for the problems with their cardiovascular system but for problems affecting other organ systems.

Giant cell arteritis is a inflammatory disease of medium and large sized arteries which can affect the ascending and aortic arch and lead to formation of an aortic aneurysm. Most patients will have a history of temporal arteritis prior to making the diagnosis of a thoracic aortic aneurysm. If patient have a small ascending aortic aneurysm they may be a candidate for systemic steroids. Regardless, they need careful monitoring of their aortic aneurysm.

Most common causes of ascending aortic aneurysms are long-standing high blood pressure and smoking. Life style modifications is very important when managing such patients.

Most patients with ascending aortic aneurysms do not have any symptoms. The most common symptom of an ascending aortic aneurysm is a dull, vague chest pain. Some patients will have symptoms related to compression of other structures in the chest like the trachea or esophagus. Patients can have symptoms like shortness of breath or fatigue secondary to the leak in the aortic valve. The aortic valve will be stretched as the aneurysm grows leading to incompetence (leakage) of the valve.

Radiology

Most ascending aortic aneurysms will be discovered on chest x-ray or other imaging studies of the chest. The chest x-ray is usually performed to work-up other medical problems. Also, echocardiograms (ultrasound of the heart) will provide the first clue that an ascending aneurysm is present. Once the aneurysms is discovered, either by chest x-ray or echocardiogram, the exact dimensions and extent of the aneurysm is better delineated by MRA or CTA (scan) angiogram (illustration on the right shows a cross-sectional view of the chest).

This is another example of a large
( 9 cm ) ascending aortic aneurysm. In fact, this particular patient has a chronic aortic dissection. This particular patient underwent a successful David Procedure.

The majority of aneurysms can be treated medically until the aortic diameter has reached approximately 5.0- 5.5 cm. The medical approach to ascending aortic aneurysms emphasizes: blood pressure control, smoking cessation, low cholesterol diet, and a light aerobic exercise program.

Beta-blockade (i.e. metoprolol, atenolol) is the mainstay of the medical regimen because it lowers the heart and blood pressure which, in turn, lowers the stress on the aortic wall. Beta-blockers have been shown to decrease the rate of growth of aortic aneurysms in a small study of Marfan patients.

Angiotensin II receptor blocker, losartan, has been shown to slow down aortic root dilatation in the mouse model of Marfan. Transforming Growth Factor beta (TGF beta) has been shown to be involved in the aortic aneurysm formation in Marfan mice. At this time, there is no definitive proof to suggest losartan is effective in slowing down the growth of non-Marfan aortic aneurysms. In most cases, if a patient requires a blood pressure medication, their cardiologist may select a medication like losartan since it may have an additional benefit on slowing down the growth of their aneurysm.

Natural history of conservative management

Patients with a moderately dilated ascending aorta (4.0-5.0 cm) can be managed successfully without the need for surgical intervention. Currently, patients with aneurysms between 5.0 and 5.5cm can be managed with medically therapy if they can be monitored with biannual or annual imaging depending on patient's history, growth pattern and symptoms. The natural history of large ascending aortic aneurysms can be somewhat unpredictable. The survival of patients with large aortic aneurysms treated conservatively is markedly lower than a patient with a normal diameter aorta. Therefore, once the ascending aorta reached 5.5 cm they risk of surgery outweighs the risk of conservative management.

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Surgical Considerations

The two main reasons to operate on an ascending aortic aneurysms is to prevent rupture and increase survival. The current guidelines for surgical treatment of ascending aortic aneurysms are based mainly on expert opinion rather than concrete evidence.

Natural history studies of medically treated aortic aneurysm growth patterns have elucidated aortic diameters that are associated with significantly more aorta-related complications (i.e. rupture, dissection or death). The absolute aortic diameter to consider surgical therapy can vary based on the cause of the aneurysm, the presence of a connective tissue disorder, age, other medical conditions, and associated aortic valve problems. In general, an ascending aortic diameter of 5.5 cm or larger is considered appropriate for surgical therapy. However, patients with a connective tissue disorder such as Mafan or Loey-Dietz Syndrome may be considered for surgery at a diameter of 4.5 to 5 cm because they are likely to have complication at a smaller diameter. A strong family history of sudden death, dissection, or rupture will normally lead to earlier surgical intervention at a diameter of 4.5 to 5.0 cm. Patients with an incompetent (leaky) or stenotic (tight) aortic valve may require surgery before the aortic diameter reaches 5.5 cm.