Aorta Diseases of the Aorta

AORTA

DISEASES of the AORTA

In medical terns, the aorta is the main trunk of the systemic arterial circulation and is comprised of four main parts -- the ascending aorta, the arch of the aorta, the thoracic portion of the descending aorta and the abdominal portion of the descending aorta. Structurally, the aorta starts at the opening of the left ventricle, where it has a diameter of about 3 cm, then rises a short distance toward the neck, bends to the left and dorsally over the root of the left lung. It then descends within the thorax on the left side of the vertebral column and passes through the aortic hiatus of the diaphragm into the abdominal cavity. Opposite the caudal border of the fourth lumbar vertebra, it narrows to about 1.75 cm in diameter and branches into the two common iliac arteries (Glanze, 1990, 83).

Despite its great importance to the human circulatory system, the aorta "can manifest disease in only a limited number of ways" for when affected by disease, the aortic walls "may dilate, producing an aneurysm, or it may split in its long axis, producing dissection." The results of both of these conditions may encompass a fatal rupture or some type of obstruction which affects the heart's ability to pump blood throughout the body. In contrast to these few clinical manifestations, "an array of disease processes can involve the aorta" and not surprisingly, "there is considerable overlap in the clinical presentation of these disorders," an indication that diseases associated with the aorta may occur concurrently (Lindsay, 2007, Internet).

AORTIC ANEURYSM:

Clinically, an aneurysm is an abnormal bulging or swelling of a section of a blood vessel and since the aorta carries oxygen-rich blood to every part of the human body, it is technically called an artery. As Glanze points out, an aortic aneurysm is "a localized dilation of the wall of the aorta caused by atherosclerosis," a common arterial disorder characterized by yellowish plaques of cholesterol, lipids and cellular debris in the inner layers of the walls of large and medium-sized arteries (1990, 106). There are three basic types of aortic aneurysms. First, a fusiform aneurysm occurs when all three layers of the vessel are affected, causing weakness along the extended area of the vessel in the form of large, bulging region; second, a dissecting aneurysm in which the weakness develops between the inner and outer layers of the aortic wall, resulting in a bulge as blood from the interior of the vessel is "pushed around the damaged section in the wall and collects between these layers," and third, a saccular aneurysm which occurs only when the middle muscular layer of the vessel exhibits a sack-like bulge (Glanze, 1990, 107).

The causes and symptoms of aortic aneurysms occur in various portions of the aorta. When the aneurysm is located in the region of the aorta within the chest, this is known as thoratic aortic aneurysms; conversely, those that occur in the section of the aorta within the abdomen are known as abdominal aortic aneurysms. The first type does not normally exhibit any noticeable symptoms, yet as the aneurysm increases in size, pain in the chest, shoulder, neck, lower back and abdomen can result. The second type "occurs more often in men and can cause pain in the lower back, hips and abdomen." This type of aneurysm "usually means that it could burst at almost any time" (Henein, 2004, 167).

As to a diagnosis of this condition, silent and stable aneurysms are often detected when an individual has an X-ray as part of a routine examination of the thorax or for other medical reasons. In other instances, when chest, abdominal or back pain is severe, an aortic aneurysm is often suspected and X-ray/radiographic studies can then confirm or rule out this condition. Under the best of conditions, the "non-invasive technique of ultrasound is used to define the size and location of abdominal aortic aneurysms" (Glanze, 1990, 84). As to treatment, aortic aneurysms are potentially life-threatening and even small aneurysms must be monitored for their rate of growth, while large aneurysms often require some type of surgical repair. The most common method is to remove the bulging portion of the artery wall and replace it with Dacron fiber material. As to the prognosis, less than 2% of those who undergo surgical repair for an aortic aneurysm die; however, "if the aneurysm is left untreated and is allowed to rupture, less than 50% will survive" (Otto, 2004, 215).

AORTIC COARCTATION:

This condition is usually a congenital cardiac anomaly characterized by "a localized narrowing of the aorta which results in increased pressure proximal to the defect and decreased pressure distal to it." Symptoms are generally related to the changes in pressure created by the constriction. The most common site is "just beyond the origin of the left subclavian artery from the aorta, resulting in high blood pressure in the upper extremities and head and low blood pressure in the lower extremities" (Glanze, 1990, 272).

Clinical manifestations include "upper extremity hypertension... together with feeble pulses and hypotension in the legs, similar to those of the more common postductal coarctation.

Attention may be directed to the unusual location of the stenosis by a bruit in the lumbar or umbilical area" (Lindsay, 2007, Internet). The patient may also experience dizziness, headaches, fainting, a reduced or absent femoral pulse and muscle cramps in the legs during vigorous exercise.

Diagnosis is often based on pressure changes in the upper and lower body and through specific radiologic findings. Surgical repair is recommended for even minor defects, due to the "high incidence of untreated complications, such as aortic rupture, congestive heart failure and severe hypertension which "significantly shortens the life expectancy of patients" with this condition (Lindsay, 2007, Internet).

AORTIC DISSECTION:

Although considered rare, aortic dissection (i.e., tearing) can be potentially fatal, due to the fact that blood is allowed to pass through the inner lining and between the layers of the aorta. With this condition, when a defect develops, blood pressure can force the tear to open and allow blood to pass freely through it. Since the blood is under pressure, it splits or dissects the middle layer of the vessel, thus creating a new channel for the flow of blood. The length of this channel grows incrementally and can result in "the closing off of the connection points to other arteries, thus causing a heart attack, stroke, abdominal pain and nerve damage" (Walsh, 1999, 235).

Not surprisingly, the main symptom is sudden and intense pain which can be so overwhelming that the patient may collapse. This pain is generally experienced in both the chest and the back and between the scapula. Due to the potentially fatal nature of this condition, patients are treated immediately with specific drugs which reduce blood pressure and the heart rate. In some cases, surgery is performed to remove damaged sections of the aorta which are then replaced by a synthetic graft.