Aneurisma de Aorta Torácica

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Aneurisma de Aorta Torácica

Mensagem  Convidad em Seg Jul 15, 2013 2:40 pm

CLINICAL PRESENTATION — Patients with thoracic aneurysms are often asymptomatic at the time of presentation. However, depending upon aneurysm location, chest, back, flank, or abdominal pain can be a presenting symptom. Symptoms are usually attributed to compression or distortion of adjacent structures or vessels, a vascular consequence such as aortic regurgitation, or thromboembolic sequelae.
Ascending aneurysms can present with heart failure due to aortic regurgitation from aortic root dilatation and annular distortion. In addition, compression of a coronary artery can result in myocardial ischemia or infarction, while a sinus of Valsalva aneurysm can rupture into the right side of the heart, producing a continuous murmur and, in some cases, heart failure.

Ascending and arch aneurysms can erode into the mediastinum. Such patients can present with one or more of the following: hoarseness due to compression of left vagus or left recurrent laryngeal nerve; hemidiaphragmatic paralysis due to compression of the phrenic nerve; wheezing, cough, hemoptysis, dyspnea, or pneumonitis if there is compression of the tracheobronchial tree; dysphagia due to esophageal compression; or the superior vena cava syndrome. Aneurysmal compression of other intrathoracic structures or erosion into adjacent bone may cause chest or back pain.

Aneurysmal compression of branch vessels or the occurrence of embolism to various peripheral arteries due to thrombus within the aneurysm can cause coronary, cerebral, renal, mesenteric, lower extremity, and, rarely, spinal cord ischemia and resultant symptoms.

The most serious complication of thoracic aortic aneurysm is rupture, most often into the left intrapleural space or intrapericardial space. A descending thoracic aortic aneurysm can rupture into the adjacent esophagus, producing an aortoesophageal fistula and presenting with hematemesis. Rupture is often catastrophic, being associated with severe pain and hypotension or shock. Aortic dissection can also occur, but is a less common manifestation of aortic aneurysm.
DIAGNOSIS — A variety of noninvasive and invasive methods are useful for the diagnosis and evaluation of a thoracic aortic aneurysm.

Chest x-ray — A common way in which asymptomatic aneurysms are detected is on routine chest radiography. The aneurysm produces a widening of the mediastinal silhouette, enlargement of the aortic knob, or displacement of the trachea from midline (imagem). Other reported features include displaced calcification, aortic kinking, and opacification of the aorticopulmonary window.

However, chest x-ray cannot distinguish an aneurysm from a tortuous aorta and many aneurysms are not apparent on the chest x-ray. The frequency with which this occurs was illustrated in a series of 36 patients presenting with acute onset of chest or back pain within the prior 14 days who were found to have non-dissecting thoracic aortic aneurysms; radiographic abnormalities were detected in only 22 (61 percent). For this reason as well as better visualization, additional imaging studies are obtained in virtually all patients suspected of having a thoracic aortic aneurysm.
CT/MR/Arteriography — Computed tomography (CT) with intravenous contrast and magnetic resonance (MR) are the preferred imaging tests to detect a thoracic aortic aneurysm, determine its size, and define aortic and branch vessel anatomy (imagem) MR is preferred for aneurysms involving the aortic root. However, CT is used more often than MR in the acute setting to rule out dissection due to availability, efficiency, and proximity to the emergency department.
Among patients with known bicuspid aortic valves, the 2006 ACC/AHA guidelines recommend CT or MR imaging when morphology of the aortic root or ascending aorta cannot be accurately assessed by echocardiography. MR or CT is reasonable in patients with bicuspid aortic valves and aortic root dilatation on echocardiography to further quantify severity of dilatation and involvement of the ascending aorta.
Contrast arteriography provides sharper resolution of luminal characteristics and may be a better method for evaluating branch vessel pathology; however, multislice CT and MR show sufficient detail under most circumstances. Arteriography is also invasive with potential nephrotoxicity from contrast medium, and is unable to discern extraluminal aneurysmal size, but is necessary for placement of thoracic aortic endografts.

Echocardiography — An aortic aneurysm is often initially diagnosed on echocardiography indicated for other reasons. The 2003 ACC/AHA practice guidelines for echocardiography recommended echocardiography for the diagnosis of aortic aneurysm [34]. Transthoracic echocardiography (TTE) is the preferred procedure, with transesophageal echocardiography (TEE) usually being performed only if the examination is incomplete or additional information is needed. There are, however, two settings in which TEE is preferred: for examination of the entire aorta, especially in emergency situations; and for imaging when coexistent dissection is suspected.
Among patients with known bicuspid aortic valves, the 2006 ACC/AHA guidelines on valvular heart disease recommend an initial TTE to assess the diameters of the aortic root and ascending aorta. Patients with aortic root or ascending aorta diameter greater than 4.0 cm (lower threshold compared with patients who do not have bicuspid aortic valve) should undergo serial evaluation of aortic root/ascending aortic size and morphology by echocardiography, computed tomography or magnetic resonance on a yearly basis. A lower threshold for ascending aorta diameter should be considered in patients of small stature.


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