Ascending

Ascending Aorta

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.  Although patients with connective tissue disorders or have a bicuspid aortic valve are usually diagnosed earlier in life.  Patients with a bicuspid aortic valve will be diagnosed earlier in life due to a murmur.  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 due to malformations in other organ systems.  Most of these young patients will be monitoring carefully through their young life for change in the aortic diameter.  Moreover, pseudoaneurysms of the ascending aorta are commonly associated with infection or trauma.  Atherosclerotic ulceration, previous cardiac surgery, or aortic injury of the ascending aorta can be a nidus for infection (i.e. mycotic aneurysm).   Giant cell arteritis is a granulomatous inflammatory disease of the medium and large arteries affected the ascending and aortic arch.  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.

Symptoms

Most patients 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 symptoms can be secondary to aortic valve incompetence.  The aortic valve will be stretched as the aneurysm grows leading to incompetence of the valve.  Patients can develop shortness of breath, chest pain, leg swelling, and fatigue.

Diagnosis

Most ascending aortic aneurysms will be discovered on chest x-ray or other imaging studies of the chest.  The x-ray is usually performed to work-up other medical problems.  Also, echocardiograms will provide the first clue of an ascending aneurysm when examining a patient because of a murmur or new symptoms related to aortic valve incompetence.  Once the aneurysms is discovered either by chest x-ray or echocardiogram, the exact dimensions and extent of the aneurysm is better delineated by MRI or CT (scan) angiogram.

Treatment

The majority of aneurysms can be treated medically until the aortic diameter has reached approximately 5.5cm.  The medical approach to ascending aortic aneurysms is through blood pressure control, smoking cessation, low cholesterol diet, and light aerobic exercise program.  Beta-blockade is the mainstay of the medical regimen because it lowers the heart and blood pressure that in turn lowers the shear stress on the aortic wall.  Beta-blockers have been shown to decrease the rate of growth of aortic aneurysms in small cohort of Marfan patients1.  Angiotensin II receptor blocker, losartan, has been shown to slow down aortic root dilatation of in Marfan patients2.  Transforming Growth Factor beta (TGF beta) has been shown to be involved in the aortic aneurysm formation. Losartan, an Angiotensin II type 1 receptor blocker inhibits TGF beta in a mouse model of Marfan syndrome leading to inhibition of aortic growth3.  At this time, there is no evidence to suggest losartan is effective in degenerative and atherosclerotic aortic aneurysms.

The guidelines for surgical treatment of ascending aortic aneurysms are based mainly on expert opinion than concrete evidence.  Natural history studies of aortic aneurysm growth patterns have elucidated aortic diameters that are associated with significantly more aorta-related complications. 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 5.5cm or larger is considered appropriate for surgical therapy4.  However, patients with a connective tissue disorder may be considered for surgery at a diameter of 4.5cm because they tend to have complications at a smaller diameter.  Patients with an incompetent or stenotic aortic valve may require surgery before the aortic diameter is at or above 5.5 cm.  In general, if the aorta is 4.5 cm or greater at the time of surgery, the aorta should be replaced to avoid late aortic complications and need for re-operation5.

References

  1. Shores J, Berger KR, Murphy EA, Pyeritz RE. Progression of aortic dilatation and the benefit of long-term beta-adrenergic blockade in Marfan’s syndrome. N Engl J Med. 1994 May 12;330(19):1335-41.
  2. Brooke BS, Habashi JP, Judge DP, Patel N, Loeys B, Dietz HC 3rd. Angiotensin II blockade and aortic-root dilation in Marfan’s syndrome. N Engl J Med. 2008 Jun 26;358(26):2787-95.
  3. Habashi JP, Judge DP, Holm TM, Cohn RD, Loeys BL, Cooper TK, Myers L, Klein EC, Liu G, Calvi C, Podowski M, Neptune ER, Halushka MK, Bedja D, Gabrielson K, Rifkin DB, Carta L, Ramirez F, Huso DL, Dietz HC. Losartan, an AT1 antagonist, prevents aortic aneurysm in a mouse model of Marfan syndrome. Science. 2006 Apr 7;312(5770):117-21.
  4. Coady MA, Rizzo JA, Hammond GL, Kopf GS, Elefteriades JA. Surgical intervention criteria for thoracic aortic aneurysms: a study of growth rates and complications. Ann Thorac Surg. 1999 Jun;67(6):1922-6; discussion 1953-8.
  5. Borger MA, Preston M, Ivanov J, Fedak PW, Davierwala P, Armstrong S, David TE. Should the ascending aorta be replaced more frequently in patients with bicuspid aortic valve disease? J Thorac Cardiovasc Surg. 2004 Nov;128(5):677-83.