Aortic Aneurysms
Aneurysms can develop anywhere along the aorta, which runs from the left ventricle of the heart through the abdomen to the iliac artery. When they occur in the upper part of the aorta, they are called thoracic aortic aneurysms. Aneurysms can occur anywhere in the thoracic aorta, including the ascending aorta near the heart, the aortic arch in the curve of the thoracic aorta, and the descending aorta in the lower part of the thoracic aorta.
Aneurysms that form in the lower part of the aorta are called abdominal aortic aneurysms and are more common than thoracic aortic aneurysms. An aneurysm can also occur in between the upper and lower parts of your aorta. This type of aneurysm is called a thoracoabdominal aneurysm.
Aneurysms are defined as a focal dilatation in an artery, with at least a 50% increase over the vessel’s normal diameter. Therefore, the enlargement of the diameter of the abdominal aorta to 3 cm or more fits the definition. All aortic aneurysms are potentially life-threatening.
Figure A shows a normal aorta. Figure B shows a thoracic aortic aneurysm, which is located behind the heart. Figure C shows an abdominal aortic aneurysm, which is located below the arteries that supply blood to the kidneys.
Causes
Factors that can contribute to an aneurysm’s development include:
Atherosclerosis – the presence of plaque buildup on the artery walls make them less flexible, and the additional pressure can cause them to weaken and bulge.
High blood pressure – along with the use of tobacco and stimulant drugs, such as cocaine, that elevate blood pressure.
Age – atherosclerosis and aneurysms are more common in the elderly and in men over the age of 65. Rarely, childhood cardiac defects may also increase the risk in the pediatric population.
Genetic conditions – Younger people with an ascending aortic aneurysm often have a genetic cause. People who are born with Marfan syndrome, a genetic condition that affects the connective tissue in the body, are particularly at risk of a thoracic aortic aneurysm. Those with Marfan syndrome may have a weakness in the aortic wall that makes them more susceptible to aneurysm. People with Marfan syndrome often have distinct physical traits, including tall stature, very long arms, a deformed breastbone and eye problems. Other rare genetic disorders, such as Ehlers-Danlos and Loeys-Dietz syndromes, also increase the risk of thoracic aneurysm..
Inflammatory conditions – such as giant cell arteritis and Takayasu arteritis
Aortic valve disease – the appears to be especially true in the pediatric population
Untreated infection – for example, syphilis, chlamydia and salmonella
Traumatic injury of the aorta – high speed motor vehicle crashes or high impact falls cause a shearing force that can rupture the aorta or cause tears leading to the development of aneurysms.
Symptoms
Thoracic and abdominal aortic aneurysms often grow slowly and without symptoms, making them difficult to detect. Many aneurysms are found in the course of evaluation for other diseases. Symptoms usually occur when the aneurysm ruptures or dissects. Some aneurysms will never rupture. Many stay small and cause no complications, although some expand over time.
An aortic aneurysm is different from an aortic dissection. In aortic dissection, a tear occurs in the wall of the aorta. This causes bleeding into and along the aortic wall and, in some cases, completely outside the aorta (rupture). Patients with ruptured ascending aortic aneurysms may present with frank shock, cyanosis, mottling, altered mental status, tachycardia, and hypotension. Abrupt onset of pain due to rupture may be quite dramatic. Associated physical findings may be very subtle until the patient decompensates from hypovolemic shock. Patients may have normal vital signs in the presence of a ruptured ascending aortic aneurysm as a consequence of retroperitoneal containment of hematoma. At least 65% of patients with a ruptured ascending aortic aneurysms die of sudden cardiovascular collapse before arriving at a hospital.
As a thoracic aortic aneurysm grows or dissects the patient may experience:
Tenderness or pain in the chest
Scapular or thoracic back pain
Syncope, diaphoresis
Tachycardia
Hoarseness
Cough
Shortness of breath
In an abdominal aneurysm expansion, the patient may experience:
Sudden, severe, and constant low back or flank pain
Full feeling in the abdomen
Nausea and vomiting
Abdominal or groin pain
Diaphoresis or syncope
Orthostatic hypotension
The most clinically significant presentation of abdominal aneurysms is a palpable mass upon routine physical examination. The presence of a pulsatile abdominal mass is virtually diagnostic but is found in fewer than half of all cases.
Diagnosis
No specific laboratory studies can be used to diagnose aortic aneurysms. Patients with history of atherosclerosis or hypertension may have elevated lipid levels and or renal abnormalities. Imaging studies are usually diagnostic and include:
Ultrasonography is the standard imaging technique for diagnosis. Plain radiography is rarely of diagnostic value but aortic wall calcification can sometimes be seen.
Computed tomography (CT) and CT angiography (CTA) are the main modality for defining and planning open or endovascular repair; these images help in defining aortic size, involvement of visceral arteries, and potential of extension into the renal aorta.
Magnetic resonance imaging is particulate helpful in patients with renal disease who may not handle contrast loading.
Treatment
Aortic dissection is a life-threatening emergency. It’s important to treat an aortic aneurysm before dissection or rupture occurs. If dissection occurs, patients can still be treated with surgery and medications, but they will have a higher risk of complications.
The goal in the treatment of aneurysms is to prevent the growth and dissection of the aneurysm. Initial treatment of small aneurysms is through the use of beta blockers and calcium channel blockers to lower blood pressure and relax the vascular wall. Lifestyle changes also encouraged are abstaining from smoking or recreational drug use and avoiding emotionally charged situations that raise blood pressure. The patient should be instructed to avoid heavy lifting or physical exertion. If the patient’s job requires heavy lifting, this may exacerbate stress levels. Patients who are not surgical candidates or have small non-symptomatic aneurysms should be taught to report to the emergency room if they experience symptoms.
The two main types of surgery to repair aortic aneurysms are open abdominal or open chest repair and endovascular repair (EVAR) or transluminal endovascular aneurysm management (TEAM). The TEAM approach is usually only used in abdominal aneurysms. This involves gaining access to the lumen of the abdominal aorta, usually via small incisions over the femoral vessels. Afterwards an endograft, typically a polyester or Gore-Tex graft with a stent exoskeleton, is placed within the lumen of the aortic aneurysm and extending distally into the iliac artery. Most large or leaking aneurysms will require an open approach. In this surgery the aneurysm is removed and replaced with a Dacron or Teflon graft.
Nursing care post-operatively should include:
- Assess for signs of hypovolemia – tachycardia, changes in arterial pressure or central venous pressure, diaphoresis, or changes in intake and output. Patients undergoing TEAM approach require larger amounts of fluid due to contrast effects. Frequent evaluation for expanding groin hematoma should been done.
- Monitor for thromboembolic events – petechial marks, shortness of breath, pain in the extremities, or weaken peripheral pulse.
- Monitor for spinal ischemia due to graph occlusion or emboli – assess motor and sensation in all extremities, monitor bladder and bowel function.
- Assess renal perfusion – intake and outputs, specific gravity, serum BUN, creatine and hematuria.
- Monitor for ischemic bowel – abdominal pain, distention, ileus, constipation, nausea and vomiting.
Grafts and stents will require long term follow up care and evaluation for leaks and kinks. Leaks around the graft site and leaks into the aneurysm sac around the stent are the most common.
Discharge instructions
Although it may not be possible to prevent an aneurysm, early diagnosis and treatment can help prevent rupture and dissection. A healthy diet includes a variety of fruits, vegetables and whole grains. It also includes lean meats, poultry, fish, beans, and fat-free or low-fat milk or milk products. A healthy diet is low in saturated fat, trans-fat, cholesterol, sodium (salt) and added sugar. Moderate physical activity, meditation, yoga and stress reduction may help with the physical and psychological stress of the diagnosis and treatment.
Aneurysms can develop and grow large before causing any signs or symptoms. Thus, people who are at high risk for aneurysms may benefit from early, routine screening.
Source:
Ahmad, MM et. al. (2016). THORACIC AORTIC DILATATION IS A HEREDITARY DISEASE: A LARGE CROSS SECTIONAL IMAGING STUDY. JACC, 67 (13), 1712. Retrieved from https://www.clinicalkey.com/#!/content/journal/1-s2.0-S0735109716317132.
Aggarwal, S et. al. (2011). Abdominal aortic aneurysm: A comprehensive review. Experimental and Clinical Cardiology. 16 (1), 11-15. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3076160/.
Aneurysm. Retrieved from https://www.nhlbi.nih.gov/health/health-topics/topics/arm/types.
Aortic Aneurysm Fact Sheet. Retrieved from https://www.cdc.gov/dhdsp/data_statistics/fact_sheets/fs_aortic_aneurysm…
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