Guidelines and standards
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semi-invasive nature and the difficulty directly comparing dimensions over time.
tive aortic root replacement, dismissal or early (within 6 months) TTE and CT or MRI are generally performed to establish a baseline aortic assessment for patients with Marfan syndrome. Annual TTE and CT or MRI of the aorta are generally recommended after aortic root replacement. The frequency of aortic imaging is individualized depending on patient characteristics, such as the type of operation performed and the extent of aortic dilatation elsewhere. Serial post- operative follow-up imaging should focus on progression of disease affecting the native aorta, and common postoperative complications, including the development of pseudoaneurysm and coronary anasto- motic aneurysms. c. Postdissection Aortic Imaging in Marfan Syndrome.–Patients with Marfan syndrome with repaired type A aortic dissection should undergo serial aortic imaging with CT or MRI; the imaging frequency depends on the extent of aortic dissection and the type of repair. Patients with Marfan syndrome with type B aortic dissection that has not been repaired require regular follow-up imaging (see section III.B, ‘‘Aortic Dissection’’).
dominant fashion, so transthoracic echocardiographic screening is rec- ommended for the first-degree relatives of an affected individual unless a gene mutation has been identified and genetic testing can be used to identify affected family members. 1 All affected family members should undergo regular aortic imaging. Although there are no specific guide- line recommendations for ‘‘regular’’ imaging, serial imaging should depend on the age and specific features of a given individual. 2. Other Genetic Diseases of the Aorta in Adults. Two genetic conditions associated with thoracic aortic disease, BAV and Marfan syndrome, are relatively common and are discussed elsewhere in this review. Many additional predisposing conditions for aortic aneu- rysm formation and dissection are listed in Table 18
. The scope of this document does not permit a detailed discussion of these less common entities, but a few pertinent details are mentioned. Importantly, awareness of these disorders and their potential risk is critical not only to presenting patients but also to their close relatives.
BAV, aortic coarctation, and aortic dilatation or dissection. Aortic dila- tation in patients with Turner syndrome has been reported to occur in up to 40% of cases. Imaging of the aorta in these patients must include the ascending aorta, aortic arch, and proximal descending aorta. As in other cases, aortic dilatation coexists with a BAV and/or coarcta- tion. 256-258
Patients with Turner syndrome have a small stature compared with same-age individuals in the general population, so all aortic measurements should be indexed to BSA. An indexed aortic diameter of >2 cm/m 2 in the ascending aorta should be followed annually, as the risk for aortic dissection is increased. 258
b. Loeys-Dietz Syndrome.–Loeys-Dietz syndrome results from a gene mutation of transforming growth factor b receptor 1 or 2 and is inherited in an autosomal-dominant fashion. 259 Aortic root aneu- rysms are present in the majority of patients with Loeys-Dietz syn- drome. Involvement of other aortic segments and smaller arteries in the form of aneurysms or marked tortuosity are characteristic in this population. 259,260 Dissection can occur at dimensions smaller than in other inherited disorders of connective tissue. Although an annual comprehensive arterial imaging protocol with MDCT or MRI has been recommended, 261
the strategy for follow-up is not well established and should be individualized from annually to every 2 to 3 years depending on abnormalities present, family risk of com- plications, and degree of evolution. Interpretation should include in- formation about the caliber of the aortic root, the ascending and descending aorta, and the pulmonary artery (pulmonary artery dilata- tion may also occur). If progression of aortic disease has occurred, it should be monitored every 6 months (every 12 months for other ar- teries) given the markedly increased risk for dissection or rupture.
familial TAAs, predominantly with an autosomal-dominant inheri- tance. Aneurysms in relatives may be seen in the thoracic aorta, the abdominal aorta, or the cerebral circulation. Therefore, comprehen- sive imaging for screening of first-order relatives of probands with TAA is advisable. 262 The frequency and modality of vascular imaging in affected persons is similar to that outlined for Marfan syndrome but should be individualized. 263
syndrome (type IV) is a rare autosomal-dominant disorder with vascular involvement characterized by arterial dilatation and rupture. The role of aortic imaging in this population is less clear. Elective sur- gical repair of aortic aneurysms or other vascular involvement carries a high risk because of due to tissue fragility, so the impact of serial aortic imaging is unclear. 264
3. BAV-Related Aortopathy. a. Bicuspid Valve–Related Aort- opathy.–BAVs affect 1% to 2% of the population and are often associ- ated with aortopathy. 265-269 Nearly 50% of patients with BAVs have dilatation of either the aortic root or ascending aorta. 247,268,270 Dilatation of the aortic arch and descending thoracic aorta can also occur but is less common. Recently, it has been reported that patients with BAVs also are at increased risk for intracranial aneurysms compared with the normal population, 271 although the clinical signifi- cance of this is unknown. Progressive dilatation of the aorta may occur irrespective of the functional status of the BAV and places patients at increased risk for aortic dissection or rupture. 272,273
Patients with BAVs may also have coexisting coronary artery anomalies, including reversal of dominance, short left main coronary artery (<10 mm), and anomalous origin of the left circumflex artery from the right coronary Table 18 Genetic conditions associated with aortic disease BAV Marfan syndrome Loeys-Dietz syndrome Turner syndrome Ehlers-Danlos vascular type (type IV) Familial TAA Shprintzen-Goldberg (craniosynostosis) syndrome Journal of the American Society of Echocardiography Volume 28 Number 2 Goldstein et al 157 cusp. 250,270,274-278 Failure to recognize these anomalies may result in risk for coronary artery injury during aortic valve repair or replacement. b. Imaging of the Aorta in Patients with Unoperated BAVs.–TTE is the primary imaging tool for the initial diagnosis and screening as well as serial follow-up of patients with known or suspected BAVs with or without aortopathy. The aortic root or ascending aorta may be dilated. The pattern of dilatation may be associated with BAV morphology. 269 At the time of initial diagnosis of aortopathy in patients with BAVs, imaging with CT or MRI is generally recom- mended to confirm that the size of the aorta measured by TTE is ac- curate. Eccentric dilatation of the aortic sinus adjacent to the conjoined cusp increases the chance of underestimation of the aortic root measurement by TTE, particularly when the measure- ment is obtained only in the long-axis format. CT and MRI also pro- vide important information about the size of the aortic arch and descending aortic segments, which are often incompletely visualized by TTE ( Figure 49 ). Although BAV occurs in >50% of patients with coarctation, coarctation is noted in <10% of patients with BAVs. Nevertheless, whenever a BAV is detected, coarctation should al- ways be sought. c. Follow-Up Imaging of the Aorta in Patients with Unoperated BAVs.–All patients with BAVs and associated aortopathy should un- dergo annual surveillance imaging of the ascending aorta to monitor growth over time. TTE can be used to monitor the aortic root and ascending aorta when correlation between the dimensions measured by TTE and CT or MRI has been confirmed. After the identification of ascending aortic enlargement in a patient with BAV, repeat imaging after 6 months is recommended. If the aorta re- mains stable at 6-month follow-up and is <45 mm in size, and there is no family or personal history of aortic dissection, annual aortic im- aging is recommended. Patients who do not meet these criteria should undergo repeat aortic imaging using TTE every 6 months. Occasionally, patients with BAV-related aortopathy have demon- strated stable dilatation of the ascending aorta over several years; the frequency of aortic follow-up in these patients should be individ- ualized. Patients with BAVs and no demonstrable aortopathy should be screened every 3 to 5 years with TTE for the development of aortic enlargement. Repeat CTor MRI is suggested at least every 3 to 5 years to reassess the aortic arch and descending aorta and reconfirm that transthoracic echocardiographic measurements of the aortic root remain reliable for serial measurements. TEE is generally not used for initial diagnosis and follow-up of BAV- related aortopathy, because of its semi-invasive nature and difficulty comparing dimensions over time. Patients with BAVs with aneurysmal dilatation of the aortic arch or descending thoracic aorta or those with remote histories of type B aortic dissection require regular computed tomographic angiography or MRI to monitor aortic stability. In such cases, imaging should be repeated annually. TTE does not provide reliable imaging for serial follow-up of the dimensions of these portions of the aorta. d. Postoperative Aortic Imaging in Patients with BAV-Related Aortopathy.–After elective aortic root replacement, early (dismissal or within 6 months) TTE and CT or MRI are generally performed to establish a baseline aortic and valve assessment. During the imaging study, it is critical to know what surgical procedure was performed to identify potential residua or sequelae ( Figure 50 ). Annual aortic imag- ing is generally recommended after aortic root replacement or replace- ment of the aorta above the coronary arteries; however, the frequency is individualized depending on patient characteristics, type of operation performed, and duration of follow-up. Dilatation of the remaining ascending aorta, aortic arch, or descending thoracic aorta may continue after the ascending aorta has been replaced. Serial postoperative follow-up imaging should also focus on common postoperative compli- cations, including the development of coronary button pseudoaneur- ysm formation, anastomotic site pseudoaneurysm formation, and progressive dilatation of other aortic segments. Figure 50 (A) Computed tomographic 3D volume-rendered reconstruction of the thoracic aorta in a patient with prior aortic valve and ascending aorta replacement due to bicuspid valve–related aortopathy; the image demonstrates aortic arch dilatation (asterisk). (B) Computed tomographic 3D volume-rendered reconstruction of the thoracic aorta in a patient with BAV and aortopathy with prior aortic valve and supracoronary aortic replacement; the image demonstrates features of asymmetric aortic root dilatation (asterisk). 158 Goldstein et al Journal of the American Society of Echocardiography February 2015
e. Family Screening.–Because aortopathy has been demonstrated in first-degree relatives of patients with BAV syndrome, screening first- degree relatives with TTE is recommended to identify dilatation of the aortic root or ascending aorta. 279 Key points of imaging related to genetic diseases of the aorta are listed in Table 19
. V. TRAUMATIC INJURY TO THE THORACIC AORTA Traumatic injuries to the aorta may result from either blunt (nonpene- trating, indirect) or sharp (penetrating, direct) trauma. Penetrating trauma is usually caused by stab or bullet wounds that puncture the aortic wall. Rare causes include misplacement of spinal fixation screws and lacerations from spinal fractures. 280,281
Penetrating aortic trauma injures the aorta from outside to inside, does not have a predilection for site, and is usually fatal. 280,282-284 Blunt aortic injuries (BAIs) are far more common and are therefore the focus of this review. In BAI, the aortic wall is damaged from the inside to the outside, from the intima to the adventitia. The most common location of BAI is at the aortic isthmus just distal to the left subclavian ar- tery.
284-287 The second most common location is the supravalvular portion of the ascending aorta. 285,286,288,289 Motor vehicle accidents (especially at speeds of >40 mph) account for 75% of cases in most series of BAI, 280,287,290,291 but falls from heights of >10 feet, crush injuries, explosions, motorcycle and aircraft crashes, pedestrian injuries, and direct blows to the chest are also known to produce similar injuries. 284,290-292 A. Pathology The aortic isthmus is the most common location for BAI (80%–95%), followed by the ascending aorta and then the diaphragmatic aorta. 284,286-289 Those regions represent transition points between relatively fixed and mobile aortic segments. These transition points have the greatest exposure to shear and hydrostatic forces generated by abrupt deceleration. Unfortunately, investigators in the field have not been consistent in the terms they use to describe the result of BAI. Pathologists have described these injuries as tears, lacerations, disruptions, transactions, ruptures, dissections, and pseudoaneurysms. Even modern imaging modalities may not be able to define an injury in terms that are precisely consistent with pathologic descriptions. In this text, descriptive terms are used for the pathologic abnormalities that correlate with various imaging methods. Descriptions of images should include the site of the lesion (i.e., ascending aorta, aortic arch, isthmus, descending thoracic aorta, or abdominal aorta), as well as an estimate of the distance of the lesion from a reference anatomic structure (e.g., the aortic valve, the origin of the left subclavian artery, and the diaphragm). The description should also include the length of the aortic injury (in millimeters) and the total circumference of the aorta at the site of its injury. A variety of aortic lesions can result from blunt aortic trauma. 1. Subadventitial aortic rupture involving the intima and media with incomplete circumferential extension: In this most frequent lesion encountered by imag- ing physicians, there is a discrete tear involving the intima and underlying me- dia. The disrupted aortic wall (intima and media) usually protrudes into the aortic lumen, and through the disrupted wall, the aortic lumen communicates with a cavity (saccular false aneurysm) whose wall is composed only of adventitia. The inner surface of the aorta presents an abrupt discontinuation, and the outer contour is deformed by the false aneurysm. The protrusion of the torn aortic wall into the aortic lumen may produce ‘‘stenosis’’ with flow acceleration and a gradient (pseudocoarctation). 2. Subadventitial aortic rupture involving the intima and media with complete circumferential extension (aortic transection): This lesion results in a fusiform Table 19
Genetic TAAs: key points Etiology
Key features Marfan syndrome Aortic root most common loca- tion for aneurysm Characteristic pear-shaped appearance STJ diameter relatively normal TTE initial imaging tool for de- tecting and serial follow-up First-degree relatives require screening BAV
TTE primary imaging tool for diagnosis, screening, and follow-up May involve ascending aorta or aortic root Aneurysms occur even in absence of significant valve dysfunction Screening of aortic valve and ascending aorta recommended even for first-degree relatives Familial thoracic aortic syndrome Ascending aorta more commonly affected Relatively fast growth rate Vascular Ehlers-Danlos syndrome
Aortic complications at a young age
Loeys-Dietz syndrome Widespread, aggressive vas- culopathy Aortic root aneurysms in up to 48% Dissection can occur at dimen- sions smaller than in other in- herited aortic disorders such as Marfan syndrome and BAV Turner syndrome Associated with BAV Aneurysms most commonly occur in ascending aorta Table 20
CXR findings associated with BAIs Widened mediastinum (>8.0 cm or mediastinum-to-chest width ratio > 0.25) Rightward deviation of the trachea or nasogastric tube Obscured aortic knob Opacification of the aortopulmonary window Downward displacement of the left main stem bronchus Widened right paratracheal stripe Left apical pleural cap First and/or second rib fracture Clavicle, sternal, or thoracic spine fracture Hemothorax Intrathoracic free air Journal of the American Society of Echocardiography Volume 28 Number 2 Goldstein et al 159 pseudoaneurysm. Because the intima and media tear is circumferential, protru- sion into the lumen does not occur. The inner surface of the aneurysm is smooth, formed solely by adventitia. As a consequence, the aortic wall is extremely thin and fragile. Imaging typically reveals abrupt change in aortic diameter. 3. IMH: Accumulation of blood within the media may result from blunt aortic trauma because of disruption of the vasa vasorum or the development of small intimal tears. The aortic wall shows a localized, usually crescentic thickening (usually >5 mm). The inner aortic surface is smooth, the aortic lumen is partially reduced, and the outer aortic contour is unaltered. There is no flap and no flow signals within the hematoma. 4. Traumatic aortic dissection: The elastic and collagen fibers of the aortic wall are remarkably strong radially but may relatively easily be split when exposed to transaxial stress. As is true of spontaneous aortic dissection, aortic trauma may produce separation of the media. This lesion is uncommon and can mimic spontaneous aortic dissection but has significant differences. It is usually localized to the area of the aortic injury and does not propagate distally toward the iliac arteries. It typically fails to create two channels and may have a direction transverse to the longitudinal axis of the aorta. Conse- quently, the resulting ‘‘flap’’ is usually thicker and less mobile than the clas- sical intimal flap. The aorta is usually symmetrically enlarged. 5. Lesion of the aortic branches: Partial or total avulsion, pseudoaneurysm, dissection, and thrombosis may occur as isolated injuries to branch arteries or in association with BAI. 6. Superficial lesions involving only the intima: With improvements in imaging technology, ever more subtle lesions are being identified. The term minimal aortic injury is often used to describe a lesion that carries a relatively low risk for rupture. Ten percent of BAIs diagnosed with high-resolution techniques have minimal aortic injuries. 293 Although most of these intimal injuries heal spontaneously and hence may not require surgical repair, the natural history of these injuries is unknown. 294,295 Frank tears produced by BAI but limited to the intima appear as thin, linear mobile intraluminal projections from the aortic wall. No alterations of the diameter or external contour of the aorta are present. Thrombi, often mobile, may be present within the aortic lumen, presumably in areas of exposed collagen. Minimal aortic injury from an imaging standpoint is an injury with the intimal flap <10 mm, accompanied by minimal or no periaortic mediastinal hematoma. 293 B. Imaging Modalities On the basis of a landmark study by Parmley et al., 284
aortography was considered the best study to identify BAI for >40 years. However, aortography is invasive, requires a special team for its performance, and is prone to both false-positive and false-negative results, rendering it a poor choice for screening. 296-299
CT is now the diagnostic test of choice.
285,287,300-304 Other options for the diagnosis of blunt traumatic aortic injury include CXR, TEE, IVUS, and MRI. Each of the imaging techniques has relative advantages and disadvantages. 1. CXR. Although a plain CXR is often an initial study in emergency departments and can sometimes suggest aortic injury, even when the image is not of diagnostic quality, no single or combination of radio- graphic signs demonstrates sufficient sensitivity or specificity to reliably detect or exclude traumatic aortic rupture. 241,280,305 Therefore, further imaging should be performed whenever an abnormality is suspected on clinical presentation or on CXR or when the mechanism of injury Yüklə 9,02 Mb. Dostları ilə paylaş:
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