Thoracic Aortic Aneurysm

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Introduction   

The aorta is the largest and most central artery in the body and has two major arteries: the thoracic and abdominal aorta. The three segments of the thoracic aorta include the ascending aorta, the aortic arch, and the descending aorta [1]. The aorta is responsible for supplying blood flow, nutrients, and hormones to the entire body, while the aortic branches facilitate blood flow to internal organs and surrounding tissue [2].  

Many healthcare practitioners are more familiar with abdominal aortic aneurysm (a bulging or weak spot in the abdominal aorta) or abdominal aortic dissection, which is when a tear occurs, restricting blood flow to the body. This is a medical emergency requiring immediate treatment [2].  

A thoracic aortic aneurysm can also occur, which is an outpouching or bulge in the thoracic aorta from decreased elasticity or weakening in the aortic tissue. Due to the weak vessel walls, dilation or ballooning of the artery occurs [3].  

TAAs can be found in two different shapes. Fusiform-shaped aneurysms are more common and balloon out on all sides of the aorta, whereas saccular-shaped TAAs are unilateral. To be diagnosed as a true aneurysm, all three layers of the vessel wall must be compromised [3]. 

“Sixty percent of thoracic aortic aneurysms involve the aortic root and/or ascending aorta, 40% involve the descending aorta, 10% involve the arch, and 10% involve the thoracoabdominal aorta” [4]. The size, shape, and location of the TAA will dictate the appropriate course of treatment and management.  

Causes of Thoracic Aortic Aneurysm 

Ascending thoracic aortic aneurysm often occurs due to elastic fiber erosion. Medial degeneration then leads to aortic dilation. This degeneration can occur naturally with age, but it is also exacerbated by chronic hypertension. There is also a familial component to TAA, and those with family members diagnosed with TAA are at increased risk [4].  

Several risk factors increase one’s risk of developing TAA, including male gender, chronic hypertension, chronic obstructive pulmonary disorder, smoking, and coronary artery disease. A prior history of aortic dissection is also an indicator of future TAA [5]. TAA can be an acquired condition from an autoimmune disorder, infection, or traumatic injury to the chest.  

Atherosclerosis is one of the most common causes of TAA. Aneurysms rarely occur in the ascending thoracic aorta and are predominantly found in the descending thoracic aorta [4]. Plaque buildup on the walls of the aorta can occur over time, weakening the tissue and leaving it more vulnerable to bulging. As the heart continues to pump forcefully, the arterial wall loses strength, and an aneurysm develops [4].  

Those with connective tissue disorders are also at higher risk for TAA. According to the Marfan Foundation, people with Marfan syndrome are 250 times more likely to experience an aortic dissection [6]. Marfan syndrome alters the proteins responsible for making healthy connective tissue that supports muscle, internal organs, bones, and tissues [7]. This compromises the integrity of the aortic structure by decreasing contractility causing TAA or even dissection [8]. 

Nurses who manage patients with hypertension should not only educate patients that high blood pressure increases the risk of stroke but that it is also a primary risk factor for TAA. Studies show that elevated blood pressure directly correlates to thoracic aortic dilation [8].  

Epidemiology of Thoracic Aortic Aneurysm 

Aortic disease accounts for 13,000 deaths in the United States annually, with thoracic aortic aneurysm being the 18th leading cause of death. Of these deaths, almost sixty percent of them are men. However, women who develop TAA are proven to have worse clinical outcomes and have an increased risk for actual dissection [5]. Studies denote the incidence of TAA is on the rise due to advancements in diagnostics and increasing life expectancy [5]. 

Signs and Symptoms of Thoracic Aortic Aneurysm & Dissection 

Most patients with TAA are completely asymptomatic and might not even know they have one. Often, TAAs are diagnosed when patients are undergoing imaging for a separate issue. Aneurysm of the aortic root can cause leakage of the aortic valve, resulting in a heart murmur. This might be recognized on an examination warranting further evaluation. 

TAA can lead to aortic dissection or rupture, which is often fatal. Ascending aortic rupture or dissection causes chest pain that has been described as sharp or tearing. Dissections in the descending aorta cause pain in the upper back or abdomen. Patients may also experience nausea, vomiting, leg pain, and shortness of breath [9]. 

Patients may present with weak pulses or blood pressure that greatly differs when taken on different sides. Due to the grave outcomes of thoracic aortic dissection or rupture, patients with a history of TAA should make sure they seek immediate medical evaluation in the emergency department and alert the healthcare provider of their diagnosis [9].  

Diagnosis of TAA 

A thoracic aortic aneurysm is relatively simple to diagnose using both computed tomography angiography (CTA) and magnetic resonance imaging (MRI). Both tools can be used to diagnose and measure TAA. Echocardiography, an ultrasound of the heart, can also be implemented for TAA diagnosis. However, the echo is limited, and the descending aorta isn’t easily visualized using this method. It is successful in identifying aneurysms in the aortic root, but MRI and CT should be employed for TAA diagnosis [9]. 

Treatment for TAA 

Medical treatment for TAA and dissection prevention is, unfortunately, relatively limited. There has been some success in slowing the growth of TAA’s with beta-blockers such as metoprolol and propranolol. Beta-blockers can reduce pressure and stress on the wall of the aorta, which in turn slows the growth of the aneurysm reducing the risk of death for some patients [9]. 

Patients with Marfan Syndrome have been treated with angiotensin receptor blockers like losartan, which slow the growth of TGF beta protein, which contributes to TAA development [9].  

“Aneurysms of the aortic arch and descending aorta are most often associated with atherosclerosis. In patients with plaque (atherosclerosis) in the arteries, additional medical treatment is recommended to reduce the risk of heart attack and stroke” [9]. Patients with atherosclerosis are often prescribed aspirin or another blood thinner to reduce these risks. A statin may also be prescribed to decrease cholesterol levels [9].  

Nursing Management  

Nurses play a key role in supporting patients with TAA. Their primary duty is to offer education and tools to aid in blood pressure management. Nurses should provide education on smoking cessation, reducing cholesterol, and the importance of medication compliance when taking blood thinners, statins, or blood pressure medications. Patients should have a solid understanding that adhering to a healthy lifestyle and medication compliance will reduce the risk of TAA rupture of dissection. 

Nurses should also ensure patients know when to seek immediate medical attention should the following symptoms arise. 

• Severe abdominal pain 

• Chest pain, especially If it is sharp or tearing in nature 

• Nausea and/or Vomiting  

• Shortness of breath 

• Heavy leg pain 

If a nurse is managing a patient in the hospital for TAA or suspected rupture, blood pressure management continues to be a primary factor. The ideal blood pressure in this case is 120/90. The nurse should administer IV or oral blood pressure medications as ordered. They should also check for blood pressure differences on both sides of the body to assess for dissection. In addition, nurses should monitor distal leg pulses for appropriate perfusion [10]. 

Should the patient develop shortness of breath, develop abdominal or back pain, exhibit mottling or ecchymosis around the abdomen, become hypotensive, or have complaints of chest pain, the provider needs to be made aware immediately [10].  

If the patient undergoes surgery for rupture, the nurses will be integral in recovering the patient in the hospital and providing discharge planning. When the patient can be safely discharged, the patient and family members should be educated to keep the surgical site clean and dry, to take blood pressure medications exactly as prescribed, and to seek immediate care for severe back or abdominal pain. Nurses should discuss the optimum blood pressure range of 120/90 or whatever range the physician deems acceptable [10].  

Health teaching and health promotion should occur at each follow-up visit. This should include discussing a healthy lifestyle, diet recommendations, smoking cessation, blood pressure management, and regular physical activity [10].  

Emerging Trends 

Surgeons are now implementing a minimally invasive approach to surgical repair of TAA called thoracic endovascular aortic repair (TEVAR). This is a prophylactic surgical repair that aims to reduce the risk of dissection or rupture [11]. 

 “TEVAR represents a minimally invasive approach, in which aortic repair is accomplished via the retrograde transarterial advancement of an expandable stent graft. The goal of this intervention is to prevent the further expansion and ultimate rupture of the TAA and is generally less invasive than an open repair [11].” 

TEVAR offers a more minimally invasive alternative to traditional open surgery. It has been associated with fewer complications and quicker recovery. However, the course of surgical intervention should be determined on an individual basis. Even with these advances, comparative studies need to be conducted to determine the safety and durability of the TEVAR and the open surgical option [11].  

Conclusion

A thoracic aortic aneurysm is caused by a weakening of the vessel wall where an outpouching or ballooning occurs. Several risk factors influence TAA development, including hypertension, smoking, familial predisposition, and conditions such as Marfan Syndrome. TAA can be diagnosed with CT scans, MRIs, or echocardiograms.  

Nurses should educate their patients on maintaining a healthy lifestyle through physical activity, smoking cessation, and lipid control. They should also ensure their patients understand the importance of blood pressure control. Certain medications, such as metoprolol, can help decrease the size of TAA. Patients with TAA should be thoroughly informed of the signs and symptoms of rupture and know to seek immediate medical attention if they suspect rupture or dissection.  

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