Test 1

Abdominal Aortic Aneurysm

Text A: Overview of Abdominal Aortic Aneurysm (AAA)

An abdominal aortic aneurysm (AAA) is a localized enlargement of the abdominal aorta such that the diameter is greater than 3 cm or more than 50% larger than normal. They usually cause no symptoms except when ruptured. Occasionally, abdominal, back, or leg pain may occur. Large aneurysms can sometimes be felt by pushing on the abdomen. Rupture may result in pain in the abdomen or back, low blood pressure, or loss of consciousness, and often results in death.

AAAs occur most commonly in those over 50 years old, in men, and among those with a family history. Additional risk factors include smoking, high blood pressure, and other heart or blood vessel diseases. Genetic conditions with an increased risk include Marfan syndrome and Ehlers-Danlos syndrome. AAAs are the most common form of aortic aneurysm. In the United States, screening with abdominal ultrasound is recommended in males between 65 and 75 years of age with a history of smoking. In the United Kingdom, screening all men over 65 is recommended. Australia has no guideline on screening.

Once an aneurysm is found, further ultrasounds are typically done on a regular basis. Treatment is generally recommended when the diameter grows to >5.5 cm in males and >5.0 cm in females. Management may include observation, surgical repair, or endovascular aneurysm repair. Repair is usually recommended if the aneurysm is rapidly growing or symptoms occur. Open surgery has similar outcomes to endovascular repair. However, endovascular repair has a lower risk of early death but may not always be an option. Surgery may be done either through an open incision or through a number of small incisions.

In 2013, aortic aneurysms resulted in 168,200 deaths, up from 100,000 in 1990. In the United States, AAAs affect between 2% and 8% of males over the age of 65. Rates are about six times lower in females. In those with an aneurysm less than 5.5 cm, the risk of rupture in the next year is below 1%. Among those with an aneurysm between 5.5 and 7 cm, the risk is about 10% while for those with an aneurysm greater than 7 cm the risk is about 33%. Mortality if ruptured is 85% to 90%. During 2013, aortic aneurysms were the cause of 9,863 deaths in the United States.

Text B: Signs, Symptoms, and Diagnosis of AAA

Abdominal aortic aneurysms are commonly divided according to their size and symptomatology. An aneurysm is usually defined as an outer aortic diameter over 3 cm (normal diameter of the aorta is around 2 cm), or more than 50% of normal diameter. If the outer diameter exceeds 5.5 cm, the aneurysm is considered to be large. The common signs and symptoms of abdominal aortic aneurysm include:

1. Pulsating sensation in the abdomen
2. Severe, sudden pain in the abdomen or back – if the aneurysm is about to rupture
3. Pain, discoloured skin, sores on feet and toes (rare) – due to material shed from the aneurysm

On physical examination, a palpable and pulsatile mass can be noted. Bruits can be present in case of renal or visceral arterial stenosis.

Abdominal X-ray can show the outline of an aneurysm when its walls are calcified. However, most AAAs do not have calcified walls and cannot be seen on plain X-ray films. Ultrasound imaging is the preferred modality for screening and diagnosis. It is noninvasive, widely available and has a high sensitivity, especially when the scan is done in a longitudinal plane. CT scan has nearly 100% sensitivity for aneurysm and is also useful in preoperative planning, detailing the anatomy and possibility for endovascular repair. In the case of suspected rupture, it can also reliably detect retroperitoneal fluid. Alternative less often used methods for visualization of an aneurysm include MRI and angiography.

Text C: Treatment Options for AAA

The treatment options for asymptomatic AAA are immediate repair and surveillance with a view to eventual repair. The threshold for repair varies slightly from individual to individual, depending on the balance of risks and benefits when considering the current size of the aneurysm and its rate of growth. The size of an individual’s native aorta may influence this, along with the presence of comorbidities that increase operative risk or decrease life expectancy. Evidence generally supports repair of an AAA that is ≥5.5 cm in a typical male and that repair of an AAA <5.5 cm does not provide a survival advantage, with few exceptions. Based on this evidence, authorities recommend elective repair of AAAs >5.5 cm in size and conservative treatment for smaller aneurysms. For females, elective repair of AAAs >5.0 cm is recommended due to the higher rate of rupture in females and increased mortality from ruptured AAAs in females compared to males.

The two modes of repair available for an AAA are open aneurysm repair and endovascular aneurysm repair (EVAR). An intervention is often recommended if the aneurysm grows more than 1 cm per year or it is bigger than 5.5 cm. Endovascular treatment with EVAR has lower short-term mortality and morbidity, lower duration of hospital admission, and earlier return to day-to-day activities. As compared to open surgical repair, EVAR has a lower risk of death in the short term and a lower risk of wound complications, but there is no long term survival difference between the two procedures. A 2017 Cochrane systematic review found tentative evidence of no long-term difference in outcomes between EVAR and open surgery, but the results were not conclusive.

 Text D: Prevention and Screening of AAA

 Screening for an AAA is not recommended for individuals who do not have risk factors for developing an aneurysm such as family history, smoking, high blood pressure and peripheral artery disease. Individuals with these risk factors, especially men over the age of 60, are at a higher risk of developing an aneurysm and should be screened. Additionally, individuals with a family history of AAA should be screened, as a genetic predisposition exists.

 Since smoking is the most important risk factor for the development of AAA, smoking cessation is a potential strategy to prevent the development and progression of AAA. The use of medications such as statins, beta blockers, ACE inhibitors, and antibiotics (e.g. doxycycline) are being investigated as methods to lower the risk of AAA expansion and rupture. However, while statins and anti-hypertensive medications are helpful in reducing the risk of cardiovascular disease, there is no clear evidence that they prevent the development or progression of AAA.

Screening consists of an abdominal aortic
ultrasound to determine the size of the aneurysm. Monitoring is usually
recommended if the aneurysm is small in size, while surgery is recommended if
the aneurysm is large or rapidly growing. The United States Preventive Services
Task Force (USPSTF) recommends a single screening abdominal ultrasound for AAA
in men aged 65–75 years who have ever smoked (at least 100 cigarettes in a
lifetime). The American Heart Association recommends a single ultrasound
examination for all men and women aged 65–75 years with a family history of AAA
and men 65–75 years who have smoked at least 100 cigarettes in their lifetimes.
Evidence to support screening in women aged 65–75 years who have ever smoked or
have a family history of AAA is insufficient; women aged <65 years with no
family history should not be screened.