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Areas of Expertise
Thoracic Aortic Aneurysms

Aneurysms of the thoracic aorta (TAA’s) have an estimated incidence of 5.9 to 10.4 cases per 100,000 people in a given year. Unlike abdominal aortic aneurysms, TAA’s are being discovered at a younger age (from people in the 50s and up) and occur with less gender difference (about 1.7 times male more than female). A TAA can be in continuum with an aortic enlargement in the abdomen, which is then termed a thoracoabdominal aortic aneurysm (TAAA). Rupture of a TAA is a catastrophic event, with about 50% of patients reaching the hospital alive and a mortality of 100% if not treated urgently. Timely emergent surgery in this setting still has a staggering mortality of greater than 50%. Hence, identifying the causes of TAA’s and risk factors leading to increased rupture rate is the key to early diagnosis, thus preventing rupture.

thoracoabdominal aneurysmThe causes of TAA’s include atherosclerosis, genetic predisposition (Ehler’s Danlo’s disease, Marfan’s disease, or other connective tissue diseases), infection, or degeneration of the aorta after prior aortic dissection (up to 20%). Similar to AAA, smoking is an extremely important risk factor influencing aneurysm growth, followed by hypertension. The most important risk factor for rupture is aneurysm diameter, which is related to size; whereas advanced age, presence of pain, and history of COPD also predict higher likelihood of rupture as well. The aneurysm diameter expansion of greater than 1cm per year is indicative of impending rupture, and treatment is indicated.

Signs and Symptoms

Many patients with TAA’s do not have symptoms. The diagnosis can be possibly made after obtaining an X-ray, CT scan, or MRI of the upper body for another reason. If the TAA is enlarged with compression of adjacent structures in the chest, the patient may present with hoarseness (stretching of the nerve connected to vocal cord), respiratory symptoms (mass effect to the trachea), or dysphagia (obstruction to the esophagus). When moderate pain of the chest, back, flank, or abdominal occur, the presence of a TAA or TAAA must be suspected with imaging workup along with possible heart, lungs, gastrointestinal, or neuromuscular causes of symptoms.

Sudden onset intensely severe pain in the chest or back accompanied by dizziness, lost of consciousness, and/or shortness of breath, is very concerning for TAA rupture, similar to AAA rupture. Additionally, coughing up blood with the above symptoms is worrisome for rupture into the bronchial tree, suggesting the presence of erosion of a TAA into the trachea. These are life-threatening signs that warrant emergent treatment. Massive bleeding from the rupture will result in sudden drop in blood pressure, leading to a fast decline to impending death if not treated surgically.

Diagnostic Testing

Whether a patient with TAA is symptomatic or not, CT scan is the diagnostic test of choice in the evaluation of TAA. Although the aneurysm may be found incidentally on chest X-ray, MRI, echocardiogram, or even abdominal ultrasound for TAAA’s, a CT scan is the standard modality to provide a detailed anatomical understanding and accurate sizing for pre-operative planning. Occasionally, MRI or standard angiogram may serve as alternate or adjunct diagnostic test depending on the clinical scenario.

Treatment

Determination of whether a patient with TAA should receive surgical treatment is weighing the balance of the risk/benefit ratio – is the risk of surgery greater than the risk of aortic rupture? As discussed above, risk of rupture is related to size of the aneurysm. The thoracic aorta typically ranges from 2-3cm in diameter, depends on the segment involved. There is no general number cut-off for surgery, but it is generally recommended that a dilation of approximately twice the normal size at a given area should be repaired surgically. We also need to take into account the height of the patient, as there is natural variation in size proportionally, as well as other risk factors for rupture listed above. Specifically for symptomatic patients, surgical repair is more often than not recommended.

Historically, TAA’s are repaired with a large open incision in the chest. The very nature of open aortic surgery is high risk, particularly in the chest. Current United States estimation for mortality after an elective open thoracic aneurysm repair is 22%, unchanged in the last 50 years. This number increases to 54% percent if the surgery is emergent with a ruptured aneurysm. A minimally invasive approach to aneurysm repair is the endovascular stent-graft placement, which has been the major advancement in vascular surgery since the 1990s. The general endovascular technique involves accessing peripheral arteries at the groins, with the deployment of a stent-graft at the area of concern to cover up the aneurismal portion. For TAA’s, elective thoracic endovascular aneurysm repair (TEVAR) provides an alternative with significantly less hospital stay, faster recovery time, lower peri-operative morbidity, and lower short-term mortality, compared to open surgery. TEVAR also provides the benefit of conscious sedation as an anesthesia option for those who cannot tolerate general anesthesia. In the long run, although there is no difference between survival and long-term morbidity for patient who underwent TEVAR compared to open surgery, TEVAR provides an opportunity for patients who otherwise would be too high risk for open surgery, and thus preventing an impending rupture.

Our center specializes in both open and endovascular aortic aneurysm repairs. For each patient with TAA, the age, height, risk factors, and operative risk for the patient would be considered along with an in depth study of the anatomical suitability for surgery. Each case would be discussed by a group of vascular surgeons and cardiothoracic surgeons, and the best type of treatment plan would be devised uniquely for each patient. Depends on each clinical scenario, sometimes additional procedures may be necessary. After surgical treatment, patients typically receive follow-up CT scan for postoperative monitoring at 6 months to 1 year intervals. Our center believes in tailoring treatment to specific patient needs as well as commitment to continuity, thus providing the best overall care for vascular disease.

 

 

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University of Southern California Department of Surgery
Keck School of Medicine of USC
1520 San Pablo St., Suite 4300, Los Angeles, CA 90033-5330
Email: vascular@med.usc.edu
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