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. Nevertheless, 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 in such cases the patient will likely have a murmur that will initiate a work-up. 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. These young patients will be monitoring carefully through their young life for change in the aortic diameter. Giant cell arteritis is a inflammatory disease of medium and large 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. More common causes of ascending aortic aneurysms are long-standing high blood pressure and smoking.
Most patients with ascending aortic aneurysms do not have any symptoms. The most common symptom of an ascending aortic aneurysm is dull and vague chest pain. Some patients will have symptoms related to compression of other structures in the chest like the trachea or esophagus. Another set of patients will have symptoms like shortness of breath or fatigue which can be secondary to aortic valve regurgitation. The aortic valve will be stretched as the aneurysm grows leading to incompetence (leakage) of the valve.
Most patients with ascending aortic aneurysms do not have any symptoms. The most common symptom of an ascending aortic aneurysm is dull and vague chest pain. Some patients will have symptoms related to compression of other structures in the chest like the trachea or esophagus. Another set of patients will have symptoms like shortness of breath or fatigue which can be secondary to aortic valve regurgitation. 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).
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 mos cases, if a patient requires a blood pressure medication, their cardiologist may select a medication like losartan since it may have an additional benefit.
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 mos cases, if a patient requires a blood pressure medication, their cardiologist may select a medication like losartan since it may have an additional benefit.
Natural history of conservative management
Patients with a moderately dilated ascending aorta (4.0-5.0cm) 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 close monitored with biannual or annual imaging depending on patient's history, growth pattern and symptoms. Conversley, the natural history of large ascending aortic aneurysms can be somewhat unpredictable. However, the survival of patients with large aortic aneurysms treated conservatively is markedly lower than a patient with a normal diameter aorta.
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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 complications 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.
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 complications 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.
