March 10, 2021
Written by: Lori Green, BA, RDMS, RDCS, RVT
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Aortic Aneurysm and Dissection are potentially life-threatening conditions that can be rapidly evaluated using Focused echocardiography.
Aortic dilatation or enlargement is the most common aortic abnormality. Abnormal dilatation of the aorta is an aneurysm. The normal adult aorta at the root level should not exceed approximately 3.7 cm and the abdominal aorta should measure less than 3.0cm. Aneurysms can occur anywhere on the aorta. The most common causes are cystic medial necrosis, hypertension, atherosclerosis, Marfan’s syndrome, collagen vascular disorders, and inflammatory diseases. Lesser causes of aortic aneurysms are tertiary syphilis, which is now uncommon in the United States, aortic arteritis, and blunt trauma.
Depending on the location, aortic regurgitation of varying amounts may be present.
2-D imaging in the parasternal long and short axis views using transthoracic echocardiography helps to visualize the ascending aorta and a portion of the descending aorta. Portions of the ascending aorta, arch, and descending can be seen from a suprasternal view, however, this view cannot be obtained on all patients.
Evaluation of aneurysm extension into the abdominal aorta may be evaluated using the sector phased array transducer (same used for the transthoracic views) or a curvilinear transducer.
Aortic dissection is a result of the intima of the vessel wall separating from the media or middle layer of the arterial wall. An intimal flap, or false channel is formed between the tear and the vessel. Several complications can occur as a result of this: the false lumen can expand and compress the true lumen which supplies the arterial branches arising from the aorta, the intimal tear or flap can extend down the lumens of major arterial branches, thromboses can occur as a result of stasis of blood in the false lumen, and the vessel can rupture.
Causes of aortic dissection are associated with preexisting aneurysms, trauma, bicuspid or unicuspid valve disease, and chronic hypertension. Chronic hypertension is the most prevalent risk factor in patients with dissections. Patients with a unicuspid or bicuspid valve have an approximately five times higher incidence of dissection than normal patients. Aortic regurgitation and left ventricular dilatation may be associated findings.
Aortic dissections are classified according to the location and extent of the dissection in the aorta. The two most common classifications are the DeBakey and Stanford classifications.
The DeBakey classification breaks the dissections down to Types I, II, or III, III a and b.
DeBakey Classification of Aortic Dissection
Type I Intimal starts at the proximal ascending aorta and the dissection extends from the ascending aorta, arch, and portions of the descending and abdominal aorta.
Type II The dissection is only in the ascending aorta.
Type III The dissection may be limited to the descending thoracic aorta.
Type IIIa The dissection may involve the abdominal aorta and iliac vessels.
Type IIIb The dissection may involve the ascending aorta and arch.
Stanford Classification of Aortic Dissection
Type A All cases that involve the ascending aorta.
Type B All cases that involve the descending aorta.
Imaging of an aortic dissection may be technically limited on the transthoracic echocardiogram. Views of the aortic root and ascending aorta may be obtained from a variety of planes including the parasternal long and short axis, apical long and five chamber, subcostal and suprasternal views. Transesophageal echocardiography has proven to be an excellent means of assessing the aorta for the detection of a dissection and is considered by some to be just as accurate, if not more than CAT scan and aortography.
Marfan’s syndrome is a hereditary disease of the fibrillin-1 gene resulting in abnormalities of connective tissue, bones, muscles, ligaments, and skeletal structures. Patients may exhibit arachnodactyly, pectus excavatum, aortic aneurysm, and mitral valve prolapse. The effects of Marfan’s syndrome on the heart are manifested by aortic root enlargement or aneurysm, commonly at the level of the sinuses of Valsalva, but may be anywhere. Rupture of the aortic aneurysm can occur and surgical intervention is suggested when the aneurysm size exceeds 5.5cm.
Even though it is more common to have a dissection associated with an aneurysm, Marfan’s patients may have an aortic dissection in the absence of an aneurysm. The anterior mitral leaflet is usually elongated and prolapses. Patients with a dilated aortic root may have varying degrees of aortic regurgitation. Mitral regurgitation may result as a consequence of the mitral valve prolapse.
Gulfcoast Ultrasound Institute, Inc. is the leading provider of ultrasound education for all specialty applications. You can learn more about how to evaluate aortic aneurysms/ dissections in a variety of the live, in-person hands-on courses, blended-education programs, and/or as part of an online activity. Evaluation of the aorta and much more is offered in the following upcoming live, hands-on programs:
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