Phys Final - AAA PDF

AAA · An aneurysm is a permanent, localized dilation or abnormal outpouching of the wall of a blood vessel with an increase in diameter of 50%. o More than 90% of abdominal aortic aneurysms are inferior to the renal arteries, and many (i.e., two thirds)...

AAA · An aneurysm is a permanent, localized dilation or abnormal outpouching of the wall of a blood vessel with an increase in diameter of 50%. o More than 90% of abdominal aortic aneurysms are inferior to the renal arteries, and many (i.e., two thirds) extend into the common iliac arteries, which provide blood to the lower extremities. o An aneurysm of the abdominal aorta (AAA) is defined by an aortic diameter that exceeds 3 cm (normal infrarenal aorta 2 cm). o The term aneurysm is derived from the Greek word aneurysm, meaning “widening.” · Prevalence: o Abdominal aortic aneurysms can affect anyone, but they most commonly occur after 60 years of age. o In the United States, these abnormalities are present in 5–7% of the population older than age 60, and males are five times more likely than females to be affected. o Peak incidence occurs at age 70. o Abdominal aortic aneurysms are significantly more common in Caucasians than in African-Americans, Asians, or persons of Hispanic heritage. o The frequency has tripled during the last 30 years and, as the population ages, is expected to increase further. o The increasing incidence has been noted in other Western countries as well and appears to be more than a reflection of the increasing age of the population and improved diagnostic methods. · Significance: o Abdominal aortic aneurysms typically increase in size by approximately 10% of their diameter each year. o Most AAAs are asymptomatic. o However, once they progress to a diameter of 5 cm, they can rupture and cause profuse bleeding and hypovolemic shock (a medical emergency) or exert pressure on adjacent viscera. o Due to the element of stagnant blood flow (i.e., stasis) within the dilated pouch, AAAs may also give rise to thrombi (i.e., intravascular blood clots). o Thrombi may fragment, circulate as thromboemboli, and cause sudden obstruction of smaller vessels (e.g., cause a stroke when emboli obstruct cerebral vessels). o Approximately 40,000 patients undergo surgical treatment for AAAs in the United States each year, and more than 15,000 deaths are attributed to this condition annually. o Abdominal aortic aneurysms are currently the 9th leading cause of death in men and the 13th most common cause of death in women in the United States. o The mortality rate from a ruptured aorta is approximately 90%. · At least 80% of aortic aneurysms arise from atherosclerosis, which weakens the aortic wall in localized areas. o Blood pressure within the aorta subsequently causes dilation at the site of weakness. o Other causes of AAA include:  § inherited diseases (such as Ehlers-Danlos syndrome) of defective connective tissue (e.g., elastin) components responsible for the strength of the aorta § physical trauma to the aorta § aortitis, in which an inflammatory process in the wall of the aorta results in localized regions of weakening § mycotic (i.e., fungal) infections that may be associated with immunodeficiency, intravenous drug use, or open-heart surgery. o Microorganisms circulating in the blood occasionally become lodge in the wall of the aorta. · The pathophysiologic process of an aortic aneurysm is that the aorta becomes weakened due to repeated stress, causing the vessel to dilate and potentially rupture. o The specific inciting factors are unknown, but a genetic predisposition clearly exists. o Elastin is the principal load-bearing element in the aorta, and both elastin fragmentation and degeneration are observed in the aortic wall at the site of an aneurysm. · Other clinical findings include: o groin pain o embolic phenomenon to the toes o elevated erythrocyte sedimentation rate o fever · Patients with ruptured aortic aneurysms present with: o severe back o Abdominal and flank pain o temporary loss of consciousness o hypotension (i.e., systolic blood pressure 90 mm). · Abdominal ultrasonography is the screening test of choice, is 98% accurate in measuring aneurysm size, and is valuable for monitoring aneurysm growth in patients with small aneurysms. · Serious Complications and Prognosis: o The diameter of the aneurysm highly correlates with the risk for rupture. o The probability for rupture within 1 year is 2% for 4.0–5.9 cm aneurysms. o 7% for 6.0–6.9 cm aneurysms. o 25% for 7 cm aneurysms. o Up to 90% of patients die from hemorrhagic shock before they reach the hospital or in the immediate perioperative period. o Mortality following elective open or endovascular repair is 1–5%. o In general, a patient with an AAA 5 cm in diameter has a three-fold greater chance of dying from rupture of the aneurysm than from surgical resection. The 5-year survival rate after surgical repair is 60–80%. o Five to ten percent of patients will develop another aortic aneurysm either adjacent to the graft or higher up in the thoracic aorta. · Acute myocardial infarction (i.e., heart attack), arrhythmia (i.e., irregular heart rhythm), and stroke are the most common complications of this type of surgery. o Endovascular stent grafting has evolved over the last decade as an alternative treatment for AAA.  o Through a small incision made in the groin, a long, thin guide wire is threaded into the aorta to the aneurysm. o A tube (catheter) containing the stent graft (which resembles a meshed collapsible straw) is guided over the wire and positioned into the aneurysm. o The stent graft is activated by heat and expands, forming a stable channel for blood flow. o Contraindications for operative intervention include severe COPD, severe cardiac disease, active infection, and other medical problems that preclude surgical intervention. o Patients with these conditions may benefit best from endovascular stenting of the aneurysm. · The procedure can be performed with epidural anesthesia, often in 2 hours and with minimal blood loss. o These advantages have made repair of AAA feasible in high-risk patients previously considered inoperable. o Additional advantages of endovascular repair include reduced incisional pain and fewer cardiopulmonary complications. o Most patients are discharged from the hospital on the second post-operative day. o Long-term durability of endovascular grafts needs to be established, however, before comparisons can be made with open repair for use in the good operative risk patient with asymptomatic AAA. o The mortality rate during surgery to insert a graft is approximately 2–5%.