Multimodality Imaging of Aortitis - JACC: Cardiovascular Imaging

JACC: CARDIOVASCULAR IMAGING

VOL. 7, NO. 6, 2014

ª 2014 BY THE AMERICAN COLLEGE OF CARDIOLOGY FOUNDATION PUBLISHED BY ELSEVIER INC.

ISSN 1936-878X/$36.00 http://dx.doi.org/10.1016/j.jcmg.2014.04.002

Multimodality Imaging of Aortitis Gregory R. Hartlage, MD,*y John Palios, MD,* Bruce J. Barron, MD,y Arthur E. Stillman, MD,y Eduardo Bossone, MD, PHD,z Stephen D. Clements, MD,* Stamatios Lerakis, MD*y Atlanta, Georgia; and Salerno, Italy

JACC: CARDIOVASCULAR IMAGING CME CME Editor: Ragavendra R. Baliga, MD This article has been selected as this issue’s CME activity, available online at http://imaging.onlinejacc.org by selecting the CME tab on the top navigation bar. Accreditation and Designation Statement The American College of Cardiology Foundation (ACCF) is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to provide continuing medical education for physicians. The ACCF designates this Journal-based CME activity for a maximum of 1 AMA PRA Category 1 Credit(s). Physicians should only claim credit commensurate with the extent of their participation in the activity. Method of Participation and Receipt of CME Certificate To obtain credit for this CME activity, you must:

1. Be an ACC member or JACC: Cardiovascular Imaging subscriber. 2. Carefully read the CME-designated article available online and in this issue of the journal. 3. Answer the post-test questions. At least 2 out of the 3 questions provided must be answered correctly to obtain CME credit. 4. Complete a brief evaluation. 5. Claim your CME credit and receive your certificate electronically by following the instructions given at the conclusion of the activity. CME Objective for This Article: At the end of this activity the reader should be able to: 1) state the importance of incorporating the entire clinical picture including risk factors, symptoms, and signs suggestive of infectious and noninfectious aortitis and the value of

selecting the proper imaging test for the right patient; 2) identify clinical characteristics that may favor the diagnositic utility of imaging for extent of disease activity versus extent of anatomical changes to the arterial wall and lumen; 3) summarize the diagnoses and clinical scenarios in which routine screening or serial imaging examination of aortitis disease activity may provide benefit; 4) describe potential vascular complications of aortitis, and define which imaging tests are appropriate for accurate identification; 5) summarize how to differentiate aortitis from intramural hematoma on computed tomography and magnetic resonance imaging; 6) recognize that aortitis patients are at high risk for development of aortic aneurysm and may benefit from screening for early detection, however, providers need to be cognizant of the potential for cumulative radiation and aware of nonradiating alternatives; and 7) discuss the complementary value of dedicated cardiac examinations such as coronary computed tomography angiography, cardiac magnetic resonance, and echocardiography in aortitis with cardiac symptoms or signs such as angina, heart failure, or cardiac murmurs. CME Editor Disclosure: JACC: Cardiovascular Imaging CME Editor Ragavendra R. Baliga, MD, has reported that he has no relationships to disclose. Author Disclosure: Dr. Barron holds stock in Immunomedics, Inc. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose. Medium of Participation: Print (article only); online (article and quiz). CME Term of Approval: Issue Date: June 2014 Expiration Date: May 31, 2015

From the *Department of Medicine, Division of Cardiology, Emory University School of Medicine, Atlanta, Georgia; yDepartment of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, Georgia; and the zDepartment of Medicine, Division of Cardiology, University of Salerno, Salerno, Italy. Dr. Barron holds stock in Immunomedics, Inc. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose. Manuscript received December 21, 2013; revised manuscript received March 11, 2014, accepted April 4, 2014.

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Hartlage et al. Imaging Aortitis

JACC: CARDIOVASCULAR IMAGING, VOL. 7, NO. 6, 2014 JUNE 2014:605–19

Multimodality Imaging of Aortitis Multimodality imaging of aortitis is useful for identification of acute and chronic mural changes due to inflammation, edema, and fibrosis, as well as characterization of structural luminal changes including aneurysm and stenosis or occlusion. Identification of related complications such as dissection, hematoma, ulceration, rupture, and thrombosis is also important. Imaging is often vital for obtaining specific diagnoses (i.e., Takayasu arteritis) or is used adjunctively in atypical cases (i.e., giant cell arteritis). The extent of disease is established at baseline, with associated therapeutic and prognostic implications. Imaging of aortitis may be useful for screening, routine follow up, and evaluation of treatment response in certain clinical settings. Localization of disease activity and structural abnormality is useful for guiding biopsy or surgical revascularization or repair. In this review, we discuss the available imaging modalities for diagnosis and management of the spectrum of aortitis disorders that cardiovascular physicians should be familiar with for facilitating optimal patient care. (J Am Coll Cardiol Img 2014;7:605–19) ª 2014 by the American College of Cardiology Foundation

Aortitis is a pathologic term for the presence of inflammatory changes of the aortic wall. Aortic wall inflammation may be of infectious etiology, but is more commonly of noninfectious origin (1). The classification of aortitis and clinical findings of conditions frequently associated with aortitis can be found in Tables 1 and 2. Patients with noninfectious aortitis related to large-vessel vasculitis may present with symptoms of arterial insufficiency in the case of Takayasu arteritis or a characteristic headache with giant cell arteritis. Incidental vascular findings may be identified in patients presenting with a rash or arthralgias suggestive of collagen vascular disorders, such as rheumatoid arthritis, systemic lupus erythematous, and ankylosing spondylitis. Not uncommonly, aortitis is an unsuspected finding in patients being evaluated for unexplained fever or chest, abdominal, or back pain. Infectious aortitis is associated with various bacterial and viral pathogens, and patients may present with classic risk factors such as exposure history, high-risk behavior, immunosuppression, and recent surgical instrumentation. Both clinical and imaging features, including the pattern of aortic involvement, help distinguish between noninfectious and infectious causes. There is significant overlap of imaging characteristics among aortitis etiologies, and the importance of integrating the entire clinical picture with imaging findings cannot be overstated.

Table 1. Classification of Aortitis Noninfectious aortitis Large-vessel vasculitides Giant cell arteritis Takayasu arteritis HLA B27-associated spondyloarthropathies Ankylosing spondylitis Reiter syndrome Immunoglobulin G4–related aortitis Variable-vessel vasculitides Behcet’s disease Cogan’s syndrome Relapsing polychondritis Rheumatoid arthritis Systemic lupus erythematosus ANCA-associated Wegener arteritis Polyarteritis nodosa Sarcoidosis Neoplastic Other Idiopathic aortitis Inflammatory aortic aneurysm Idiopathic retroperitoneal fibrosis (periaortitis) Radiation-induced aortitis Infectious aortitis Bacterial (e.g., Salmonella or Staphylococcus) Luetic (syphilis)

Imaging Aortitis

Multiple imaging modalities are used in the evaluation of both inflammatory and noninflammatory aortic diseases (2). Nuclear imaging with

Mycobacterial (e.g., Mycobacterium tuberculosis or Nocardia) Viral (e.g., hepatitis B, hepatitis C, and human immunodeficiency virus) ANCA ¼ anti-neutrophil cytoplasmic antibody.



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in general the first modality used for ascending aorta and aortic valve assessment. It provides structural and functional information about the aortic valve and anatomical characterization of the aortic root and ascending aorta (i.e. wall thickness and dimensions). Transesophageal echocardiography (TEE) can image both the ascending and descending thoracic aorta and provides superior spatial resolution compared to TTE. TEE is useful for the assessment of aortic mural complications and pre-operative, post-operative, and perioperative evaluation. Positron Emission Tomography

Figure 1. Positron Emission Tomography Imaging of Giant Cell Aortitis (A) Coronal and (B) sagittal views with localizing noncontrast computed tomography (C) demonstrate intense tracer uptake (arrows) localized to the abdominal aorta.

fluorine-18-fluorodeoxyglucose positron emission tomography (PET) is helpful in assessment of inflammatory activity. Multidetector computed tomography (CT) has excellent spatial resolution and is commonly the imaging modality of choice when aortic pathology is present. Multidetector scanners allow multiplanar reformation and 3-dimensional reconstruction, thus allowing evaluation of both arterial wall changes and abnormalities of the aortic lumen. Cardiovascular magnetic resonance (MR) imaging similarly allows excellent visualization of the arterial wall and vascular lumen, with multiplanar and 3-dimensional reformation. Transthoracic echocardiography (TTE) is

Aortitis is associated with inflammatory cell infiltration of the media and/or periaorta caused by a variety of immunologic, infectious, or traumatic factors. PET utilizes the metabolic accumulation ABBREVIATIONS of fluorine-18-fluorodeoxyglucose in the AND ACRONYMS inflammatory milieu, mostly in monocytes. Fluorine-18-fluorodeoxyglucose does not CT = computed tomography accumulate in normal vascular structures; CTA = computed tomography therefore, any uptake in the aorta is conangiography sidered abnormal. Generally, uptake is MPR = multiplanar reformatting considered significant when aortic signal is MR = magnetic resonance significantly more intense than that of the MRA = magnetic resonance liver (3) (Fig. 1). Uptake can be seen in angiography atheromas and vulnerable plaque, with PET = positron emission tomography focal uptake generally due to atheromata. Due to the simplicity of PET interpretaTEE = transesophageal echocardiogram tion, no specific protocols are needed (4). TTE = transthoracic Although the spatial resolution of PET is echocardiogram limited and provides little anatomic characterization, when combined with computed tomography angiography (CTA) or magnetic resonance angiography (MRA), the sensitivity and specificity is improved due to further delineation of mural and luminal abnormalities and more precise anatomical localization (5). Importantly, initial avid fluorine-18-fluorodeoxyglucose uptake has been reported to normalize with appropriate steroid or antimicrobial therapy for a variety of inflammatory and infectious aortitis causes (6–13). PET was first utilized for imaging aortitis in the late 1990s to help establish a diagnosis in patients with fever of unknown origin. Giant cell arteritis with atypical (extracranial) features and Takayasu arteritis in the early “pre-pulseless” phase was often diagnosed in these patients (14,15). Numerous studies have since demonstrated the utility of PET in giant cell arteritis patients (16) given that temporal artery biopsy is negative in about 15% of typical giant cell arteritis patients and approximately

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Table 2. Clinical Findings of Conditions Frequently Associated With Aortitis Giant cell arteritis Patients are generally age 65 years and older. The temporal artery is classically involved, and patients may have a characteristic headache with scalp tenderness, jaw claudication, and visual disturbancesdpotentially causing permanent blindness. One-half of patients may have coexistent polymyalgia rheumatica. Aortitis may involve the aortic root, causing ostial coronary stenoses and/or valvulitis with aortic insufficiency. Useful aortitis imaging modalities: PET, CT/CTA, coronary CTA, vascular MR/MRA, cine and phase contrast cardiac MR, and TTE. Takayasu arteritis Typically affects patients (women more than men) 55 years of age. Patients typically do not have systemic disease; rather, symptoms such as back pain and ureteral entrapment with hydronephrosis are related to the mass effect of periaortic fibrosis and adhesions in adjacent retroperitoneal structures of the abdomen and pelvis. The thoracic aorta is rarely involved. Biopsy may be required to differentiate periaortic fibrosis from malignant or infectious etiology. Useful aortitis imaging modalities: PET, CT/CTA, vascular MR/MRA, and abdominal ultrasound. CT ¼ computed tomography; CTA ¼ computed tomography angiography; MR ¼ magnetic resonance; MRA ¼ magnetic resonance angiography; PET ¼ positron emission tomography; TEE ¼ transesophageal echocardiogram; TTE ¼ transthoracic echocardiogram.

40% of those with predominantly large vessel involvement (17). Giant cell arteritis has now been established as the most common form of aortitis (18). Furthermore, about 30% of polymyalgia rheumatica (often coexistent with giant cell arteritis) patients have demonstrated large vessel arteritis, including aortitis (19). The sensitivity and specificity of PET in diagnosing giant cell arteritis or polymyalgia rheumatica are reported as 80% and 89%, respectively, in a recent meta-analysis; however, these results must be interpreted with caution due to admittedly nonstandardized PET

interpretation methodologies, inhomogeneous reference standards, and inconsistent use of PET/ computed tomography (CT) (20). Although PET findings normalize during steroid therapy in accordance with clinical findings and inflammatory markers such as erythrocyte sedimentation rate and C-reactive protein, there is no data to support routine follow-up PET imaging to monitor treatment response or predict risk of relapse (21). However, findings suggest that PET may be useful when clinical concern exists for relapse or steroid refractory disease that may benefit from cytotoxic or biological


Figure 2. CTA of Takayasu Aortitis With Various Reformatting Methods (A) Coronal volume rendered image showing stenosis of the distal abdominal aorta and occlusion of the right renal artery (green arrow) with infrarenal abdominal aortic aneurysm (pink arrow). (B) Sagittal maximum intensity projection image demonstrating patency of the stenosed and densely-calcified abdominal aorta and multiple collaterals filling the iliac vessels (yellow arrows). (C) Oblique multiplanar reformatted image demonstrating aneurysmal ascending aorta (AAo) (measuring 4.5 cm) and mild luminal narrowing of the aortic arch (blue arrow). CTA ¼ computed tomography angiography.

therapy (22). Interestingly, PET findings at baseline predict risk of later aortic dilation and may identify patients who are at increased aortic aneurysm risk and who would benefit from follow-up imaging (23). PET is useful in the diagnosis of Takayasu arteritis, potentially in the “pre-pulseless” phase (24). This provides an important window of opportunity to therapeutically intervene prior to the overtly symptomatic and highly morbid “pulseless” phase, which is characterized by severe large vessel stenosis and occlusion (25). The reported ranges of sensitivities and specificities for PET in diagnosing Takayasu arteritis are 69% to 93% and 33% to 100%, respectively, in these generally small studies with highly-variable methodologies (21,26). Like giant cell arteritis patients, effective therapy is associated with activity normalization on PET; however, Takayasu arteritis patients experience excess rates of relapse (up to 50%), despite previously effective steroid therapy (21,25). PET may be useful for routine monitoring of treatment response, as it has been found to be superior to erythrocyte


sedimentation rate and C-reactive protein in identifying patients relapsing on steroids, as these patients may benefit from cytotoxic or biological therapy (21,26). Furthermore, documentation of remission is a prerequisite for revascularization, as surgical revascularization during the active phase of Takayasu arteritis is associated with high rates of graft failure and progression of symptomatic disease at other sites (27). PET may be useful for characterization of idiopathic aortitis and its variants, including chronic periaortitis, idiopathic inflammatory aortic aneurysm, and retroperitoneal fibrosis (28). PET may demonstrate periaortic activity and characterize the extent of activity (21). Combination of PET with CTA or MRA is vital for localizing activity to the periaorta, with associated diagnostic and therapeutic implications (29,30). PET may also identify additional remote sites of fluorine-18-fluorodeoxyglucose uptake suggestive of occult malignancy or infection, and may be useful for identification of treatment relapse (21,28).

Figure 3. Differentiation of Aortitis From Intramural Hematoma Aortitis on (A) noncontrast computed tomography (CT) demonstrating low attenuation of the thickened aortic wall (w34 Hounsfield units [HU]) and (B) computed tomography angiography (CTA) demonstrating enhancement of the thickened aortic wall (w72 HU) after contrast administration. Intramural hematoma on (C) noncontrast CT demonstrating higher attenuation (w50 HU) of clot and (D) CTA demonstrating intimal disruption and subintimal calcium displacement. (E) Aortitis on T1-weighted magnetic resonance (MR) imaging demonstrating hypointensity of the thickened aortic wall (yellow arrow). (F) Intramural hematoma on T1-weighted MR imaging demonstrating increased signal intensity of clot (pink arrow) compared to aortic wall. The green circles are the regions of interest for attenuation value sampling (to determine HU). Ao ¼ aorta.

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Figure 4. Cardiac CTA of Takayasu Aortitis Multiplanar reformatted images demonstrating (A) dense aortic root (AoR) calcification and dilated ascending aorta (AAo) (measuring 4.0 cm), (B) dense calcification of the left main coronary artery and significant ostial stenosis (pink arrow). CTA ¼ computed tomography angiography; MPA ¼ main pulmonary artery; LA ¼ left atrium; LV ¼ left ventricle; RPA ¼ right pulmonary artery; RV ¼ right ventricle.

Computed Tomography

Both CT and CTA are particularly attractive for imaging aortitis and branch vessel arteritis due to unparalleled spatial resolution and scan time generally 2 to 3 mm is considered diagnostic for aortitis, distributions differ by etiology) and inflammatory periaortic soft tissue changes, such as fat stranding. CTA affords excellent vessel to background distinction to facilitate comprehensive assessment of both luminal and mural anatomy (16,22,31). Various 3D reconstruction methods including maximum intensity projection, multiplanar reformatting (MPR), and


volume rendering complement the standard sequential axial views (32) (Fig. 2). Maximum intensity projection and MPR can render an “angiographic” view suitable for measurement of luminal caliber and characterization of ectasia, dilation, stenosis, and occlusion of the aorta and its branches. Axial CTA, MPR, and volume rendering provide detailed mural characterization including extent of thickening and presence of layering thrombus, as well as identification of hazardous mimics of aortitis, such as intramural hematoma and penetrating ulcer, which appear as eccentric crescent-shaped or circumferential thickening with potential intimal or subintimal disruption on contrast imaging (32,33). Pre- and post-contrast imaging can help differentiate aortitis from intramural hematoma, as aortitis will have low attenuation (i.e., 50 Hounsfield units) on both pre- and post-contrast imaging (Figs. 3A to 3D). CTA has also been used to identify complications of advanced aortitis, such as saccular aneurysm, pseudoaneurysm, and thrombosis, in a variety of inflammatory conditions (34–39). CTA is also useful in guiding revascularization in those with arterial insufficiency of branch vessels causing claudication, cerebrovascular ischemia, intestinal angina, renal failure, or refractory hypertension. Electrocardiogram-gated cardiac CTA may be useful for characterizing aortic root and anatomic aortic valvular abnormalities (40,41) (Fig. 4). Coronary CTA readily identifies aortitisassociated ostial and proximal coronary stenosis (Fig. 5) and may be used as a guide for revascularization (5,42).

Figure 5. Coronary CTA of Giant Cell Aortitis The right coronary artery is narrowed as it courses through a thick AoR wall (pink arrows); demonstrated on (A) axial and (B and C) multiplanar reformatted images. RA ¼ right atrium; RV ¼ right ventricle; RVOT ¼ right ventricular outflow tract; other abbreviations as in Figure 4.


Figure 6. CTA of Takayasu Aortitis Axial slices show increased wall thickness (arrows) in the AAo and the descending aorta (DAo) (A), the aortic arch (AoA) (B), and the branch vessels of the arch (C). There is a “double ring” appearance due to an enhancing outer ring of inflamed media and adventitia surrounding poorly enhanced edematous intima (typical of early disease). Abbreviations as in Figure 4.


Serial CT and CTA may be used in screening for aneurysm development in high-risk patients and in routine monitoring of established aneurysms to accommodate timely surgical management to treat those at high risk for rupture (i.e., diameter of 5 cm in aortic root, 6 cm in the thoracic aorta, or 5.5 cm in the abdominal aorta, or expansion of any site by $0.5 cm in a 6-month period) (33). The drawbacks of CT and CTA are inferior characterization of disease activity and mural inflammation, notably in early phases; ionizing radiation; and iodinated contrast media in the case of CTA. Noninvasive angiographic imaging, such as CTA, has become the cornerstone of diagnosis for Takayasu arteritis in patients presenting with bruits, pulse deficits, or symptoms of vascular insufficiency in the characteristic clinical setting (25). These patients often have advanced structural aortic and branch arterial disease. A “double ring” appearance on postcontrast images due to a brightly enhanced outer ring of inflamed media and adventitia surrounding poorly enhanced edematous intima is typical of early Takayasu aortitis (2) (Figs. 6 and 7). Structural findings, such as aneurysm and stenosis of the aorta or branch vessels, has a specificity and sensitivity of 95% and 100%, respectively, for the diagnosis of late-stage disease (43). Significant aortic aneurysms are found in up to 45% of patients, with up to 33% of these rupturing if left untreated. Pulmonary arteritis with resultant aneurysm formation and/or stenosis may be found in about 15% of patients (44). Extracranial giant cell arteritis is the most common etiology of aortitis. CT findings of aortitis

Figure 7. CTA of Takayasu Aortitis (A) Volume rendered image demonstrates eccentricity of the AoA and proximal branch vessels (green arrow). (B) Sagittal and (C) coronal multiplanar reformatted images demonstrate that eccentricity is due to thickened aortic and branch vessel walls with a “double ring” appearance (yellow arrows) without significant luminal dilation. Abbreviations as in Figure 4.

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Figure 8. CTA of Giant Cell Aortitis (A) Coronal multiplanar reformatted image demonstrates diffuse thickening of the thoracic and abdominal aorta (Ao). (B and C) Off-axis maximum intensity projection images of the left subclavian artery showing smooth tapering extending distally (yellow arrows). CTA ¼ computed tomography angiography.

Figure 9. CTA of Immunoglobulin G4 Aortitis (A) Volume rendered image demonstrates eccentric AAo (pink arrow) with patent abdominal aorta and branch vessels. (B to D) Multiplanar reformatted images of the AAo in 3 different planes showing undulating wall thickening and saccular aneurysm (maximal diameter of 4.3 cm). Ao ¼ aorta; other abbreviations as in Figure 4.


are found in >50% of those with a new giant cell arteritis diagnosis, including mural thickening in >40% and frank aneurysm in up to 15% (16). A characteristic finding of giant cell aortitis is long segment thickening with smooth distal tapering, more commonly found in the descending aorta and subclavian arteries (Fig. 8) (5,45). Annuloaortic ectasia and ascending aortic dilation and aneurysm are not uncommon, and may be a result of localized inflammatory activity or functional coarctation of the thickened descending aorta resulting in elevated pressures in the thoracic aorta (16,46). Serial noncontrast chest CT may be considered for routine thoracic aortic aneurysm screening and follow-up in giant cell aortitis patients due to increased risk and associated morbidity and mortality if undetected and untreated, although this strategy does carry significant radiation exposure, most notably for those diagnosed at younger ages (22). Immunoglobulin G4–related aortitis is a recently described entity possessing significant overlap with other aortitides, often demonstrating aortic wall thickening, aneurysm formation, and dense periaortic fibrosis on CTA (47). Unlike the classic idiopathic aortitis spectrum, which primarily affects the abdominal aorta, immunoglobulin G4–related aortitis may involve the abdominal aorta and the thoracic aorta and its branches (48) (Fig. 9), with dense periarterial plaques described on coronary CTA (49). Immunoglobulin G4–related aortitis is particularly aggressive, with aortic dissection present in nearly one-half of the affected patients in a recently reported series (50). Idiopathic aortitis and its variants, including chronic periaortitis, idiopathic inflammatory aortic aneurysm, and retroperitoneal fibrosis, generally affect the abdominal aorta and are all well characterized by CT. Common findings of chronic periaortitis include irregular aortic thickening with dense adhesions. CTA will reveal a concentric enhanced soft tissue mass surrounding the aorta, often causing significant stenosis of the aorta and branches (44). Idiopathic inflammatory aortic aneurysm appears fusiform on CTA, with a dense perianeurysmal fibrotic thickening, often sparing the posterior wall, and occasionally extending to other retroperitoneal structures (51). The periaortic location of thickening with associated luminal findings is pathognomonic, which facilitates early diagnosis and precludes tissue biopsy in classic cases to afford prompt systemic steroid therapy, which may prevent luminal narrowing, aneurysm formation, and progressive retroperitoneal fibrosis



Figure 10. CTA of Infectious Aortitis Axial slice in a patient with nocardia aortitis post-coronary bypass grafting demonstrates a large thick-walled aneurysm of the midAAo measuring 8.1 6.9 cm (pink arrow). Abbreviations as in Figure 4.

(28). Occasionally, the diagnosis is incidentally made on surgical histopathology in unsuspecting patients who have undergone aneurysm repair. The hallmark of periaortic retroperitoneal fibrosis is a dense homogenous soft tissue plaque surrounding the abdominal aorta often enveloping, but not displacing, adjacent features such as the inferior vena cava and the ureters, and may cause resultant lower extremity venous stasis and ureteral obstruction with resultant renal failure; contrast enhancement varies depending on activity (52). Patients with idiopathic aortitis and variants should undergo routine thoracic and abdominal aortic screening due to the risk of recurrent aneurysm, even in other vascular beds (44). CT readily identifies complications of infectious aortitis, and detection of mycotic aneurysms is particularly important due to the risk of fatal rupture in excess of 75% if left untreated. Mycotic aneurysms appear as saccular or lobulated periaortic masses with fluid and gas collections (53) (Fig. 10). Aortic graft infections have findings similar to mycotic aneurysms in the perigraft tissue, and may be associated with pseudoaneurysm or aortoenteric fistulae (54). Syphilitic aortitis demonstrates diffuse thickening, often with 1 or more aneurysms, occasionally with mural thrombi. Tuberculous aortitis is characterized by focal irregular mural thickening, with multiple, often saccular, pseudoaneurysms; a periaortic mass may be present (44). Both syphilitic and tuberculous aortitis may mimic Takayasu aortitis; syphilitic aortitis may demonstrate a characteristic “doublering” (5,44).

Figure 11. Cardiovascular Magnetic Resonance of Takayasu Aortitis Post-contrast images demonstrating aortic wall thickening and enhancement with a “double ring” appearance (pink arrows). (A) Axial view of descending thoracic aorta. (B and C) Multiplanar reformatted coronal views of aortic arch.

Cardiovascular MR

Cardiovascular MR, like CT and CTA, renders multiplanar images and provides 3D reconstruction capabilities in aortitis imaging. Although its spatial resolution is inferior to CT and CTA, MR has superior soft tissue characterization due to multiple dedicated sequence protocols. In addition to identifying mural thickening, MR characterizes mural edema with T2 “edema weighted” sequences, and gadolinium contrast-enhanced MR identifies mural fibrosis; like PET, both potentially yield important information regarding disease activity prior to development of luminal changes (55,56) (Fig. 11).

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Figure 12. Magnetic Resonance Angiography of Aortitis Maximum intensity projection images of the thoracic and abdominal aorta. (A) Takayasu aortitis with severe distal abdominal aortic stenosis (green arrow) and collaterals from the renal and mesenteric circulation (pink arrows) supplying the distal aorta and iliac circulation. (B) Immunoglobulin G4 aortitis with irregular descending aortic contour and ostial occlusion of the celiac trunk (yellow arrow) with collaterals from the mesenteric circulation (blue arrow).

MRA provides luminal information, including vessel stenosis, dilation, and thrombosis, comparable to that of CTA but without the need for iodinated contrast or ionizing radiation (Fig. 12). MRA may utilize either gadolinium contrast-enhanced or noncontrast protocols, which may allay concerns in those with significant renal dysfunction. Coronary MRA is less sensitive than coronary CTA;


however, it may be useful in identifying ostial or proximal coronary involvement in aortitis (57). Due to superior soft tissue characterization, MR may be the best test to identify and exclude aortitis mimics and complications such as aortic dissection, penetrating ulcer, and intramural hematoma (58) (Figs. 3E and 3F). Similar to CT and CTA, MR may be used for screening of aneurysm development and routine monitoring of established aneurysms, and it is useful in guiding revascularization (2). The drawbacks of MR, in addition to a lower spatial resolution than CT and CTA, include scan times that are often in excess of 45 min requiring multiple breath holds; artifacts and safety concerns related to implanted cardiovascular devices; and limitations of MRA including overestimation of the degree of branch point stenoses, poor performance in distal branches, and suboptimal visualization of calcium. Although MR/MRA is comparable to CT/CTA in the structural characterization of inflammatory and infectious aortitis, an added benefit of MR is the option to perform cardiac sequences demonstrating endocardial, myocardial, and pericardial complications related to aortitis, in addition to the assessment of aortic root and valve morphology. Cine and phase-contrast MR are the gold standards for evaluation of myocardial function and aortic regurgitation (56). This is particularly relevant as aortic root inflammation and dilation, valvulitis, and aortic valve insufficiency have been described in both infectious and noninfectious aortitis (2,44) (Fig. 13). Relapsing polychondritis is also associated with significant mitral valve regurgitation that can be

Figure 13. Cardiac Magnetic Resonance of Immunoglobulin G4 Aortitis (A) Short-axis cine of aortic valve in mid-diastole shows a trileaflet valve with central noncoaptation due to annular dilation. (B) Left ventricular outflow tract view cine in mid-diastole demonstrating significant aortic root dilation (4.3 cm at the sinus of Valsalva) and aortic regurgitation (pink arrow). (C) Phase contrast magnetic resonance (same orientation as B) showing significant regurgitant flow in mid-diastole (pink arrow). The measured regurgitant fraction was 49%. Ao ¼ aorta.



characterized and quantified by cardiac MR (2,5). Cardiac Behcet’s disease may manifest as ventricular aneurysm or pseudoaneurysm, intracardiac thrombi, and inflammatory endocardial or myocardial fibrosis that can be characterized by standard cine, pre-contrast T1- and T2-weighted, and delayed contrast-enhanced sequences, respectively (34,56). Ankylosing spondylitis may be associated with subaortic fibrosis identifiable on delayed contrastenhancement cardiac MR, potentially extending into the cardiac conduction system and causing heart block (59,60). Mandatory angiographic evidence of disease renders MR an indispensable component of Takayasu arteritis diagnosis, follow-up, and identification of relapse, particularly in the characteristically young afflicted population, in which cumulative ionizing radiation doses related to CT or PET may be a concern (25). Extensive thoracic and abdominal aortic and branch vessel imaging is recommended, and performance is comparable to CTA and conventional angiography for identification of aortic, branch vessel, and pulmonary artery involvement (MRA sensitivity and specificity reported at 100% for diagnosing late stage disease) (55,56,61). Mural edema and fibrosis identified by MR are useful for early diagnosis and management, although MR is not as sensitive as PET in the earliest stages of Takayasu arteritis, in which visualized inflammation may presage edema and fibrosis (62). The diagnosis of aortitis related to extracranial giant cell arteritis benefits from MR identification of mural changes reflecting early inflammatory changes, as in Takayasu arteritis. The angiographic findings on MRA are analogous to that of CTA and may be used similarly for serial screening and follow-up in giant cell aortitis patients at high risk for aneurysm development or with a diagnosis of aneurysm (2,63). Like PET, MR has no role for routine monitoring of disease activity but may be useful in identifying relapse of extracranial giant cell arteritis in suspected cases (22). Interestingly, unlike PET or CT, MR imaging of the temporal arteries may be useful for the diagnosis of classic cranial giant cell arteritis by demonstrating temporal artery mural thickening, luminal narrowing, and mural gadolinium uptake (16). Idiopathic aortitis and its variants are also well characterized by MR. In addition to characteristic mural and luminal findings similar to that of CTA, periaortitis appears to be hypointense on T1weighted images and hyperintense on T2-weighted images. Periaortic fibrosis intensely enhances on contrast-enhanced MR (28). The dense plaques of

Figure 14. Carotid Ultrasound of Takayasu Arteritis (A and B) Grayscale and (C and D) color Doppler imaging of the common carotid artery. Short-axis views (A and C) demonstrate increased concentric vascular thickness with a bright halo. The long-axis views (B and D) demonstrate the heterogeneous intimal thickening with irregular luminal contour known as the “macaroni” sign.

retroperitoneal fibrosis appear hypointense on both T1- and T2-weighted images in the chronic phase, although the T2 signal may vary depending on the level of activity and edema (52). Regarding noninvasive angiography, contrast-enhanced and, perhaps even more so, noncontrast MRA are likely favorable

Figure 15. TTE of Takayasu Aortitis Parasternal long-axis (A and B) and short-axis (C and D) views, without and with color Doppler, demonstrate increased ascending aortic wall thickness with aortic root diameter of 4.8 cm and a tricuspid aortic valve (AV) with moderate to severe aortic regurgitation. Ao ¼ aorta; TTE ¼ transthoracic echocardiography; other abbreviations as in Figure 4.

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strategies of luminal imaging for diagnostic and aneurysm screening purposes in these patients who are potentially at increased risk of nephrotoxicity due to ureteral obstruction (28). Echocardiography and Vascular Ultrasound

Figure 16. TEE of Takayasu Aortitis Mid-esophageal views of the aortic root (A) without and (B) with color Doppler. There is increased wall thickness with significant dilation of the AoR (C) and AAo (D). TEE ¼ transesophageal echocardiography; other abbreviations as in Figure 4.

Figure 17. TEE of Nocardia Aortitis With Aneurysm Patient with persistent fevers post–coronary artery bypass grafting (CABG). (A) Upper esophageal long-axis view of the ascending aorta (Ao) shows a large focal aneurysm measuring 7.2 cm (double arrow), and (B) short-axis view of the aortic arch shows focal aortic wall thickening. (Note: pre-CABG imaging revealed no abnormality of the ascending aorta.) TEE ¼ transesophageal echocardiography; other abbreviations as in Figure 4.

Although not primarily utilized in the diagnosis of aortitis, TTE, TEE, abdominal ultrasound, and peripheral vascular ultrasound provide useful information. These modalities may demonstrate aortic and branch vessel mural thickening, an echolucent “halo” due to mural edema, and aortic aneurysm (33). Furthermore, Doppler assessment provides functional evaluation of stenotic segments, which may guide management. Importantly, echocardiography is widely used for identifying complications such as aortic root dilation and aortic valve insufficiency, as well as secondary myocardial dysfunction. Echocardiography, specifically high-resolution TEE, may also identify aortitis complications such as aortic dissection, intramural hematoma, and penetrating ulcer (64). Newer 3-dimensional TTE and TEE technology provides high-resolution real-time renderings of aortic root and aortic valve anatomy that may be useful for identification of complications and surgical planning (65,66). TTE and abdominal ultrasound may be useful in screening for ascending thoracic and abdominal aortic aneurysm, respectively (67). These modalities benefit from portability, widespread availability, and lack of ionizing radiation. The drawbacks include inability to image through bone and air (prohibiting comprehensive evaluation of thoracic aorta); operator dependence; and difficult tissue characterization, as fibrosis, false lumen, and hematoma all appear echolucent and may be difficult to differentiate (58,68). Vascular ultrasonography findings may be useful for the diagnosis of extracranial giant cell arteritis, Takayasu arteritis, and idiopathic aortitis variants with periaortitis. Classic giant cell arteritis may be diagnosed by a “halo” sign in the temporal arteries (16); furthermore, the extracranial “halo” sign seen in the aorta, subclavian, axillary, and iliac arteries corresponds with fluorine-18-fluorodeoxyglucose uptake on PET in these regions of affected giant cell arteritis patients (69). Takayasu arteritis can present with more pronounced and extensive concentric thickening of affected aorta and/or branch vessels, with a more heterogeneous and often brighter appearance (known as the “macaroni” sign) when compared with the “halo” of giant cell arteritis (33) (Fig. 14). Idiopathic aortitis variants present as mural thickening with an echolucent periaortic



Figure 18. TEE of Staphylococcus Aureus Aortitis With Pseudoaneurysm Incidental finding in the setting of bacteremia and valvular endocarditis. (A) Lower esophageal long-axis view of the abdominal aorta demonstrates aortic lumen (Lum) and cavity (Cav) separated by a neck (white arrow). (B) Lower esophageal shortaxis view of the abdominal aorta demonstrates the “double barrel” appearance of aortic lumen and cavity. (C) Lower esophageal short-axis view of the abdominal aorta with color Doppler showing bidirectional flow in the neck (green arrow). TEE ¼ transesophageal echocardiography.

mass, which may be difficult to differentiate from dissection or hematoma (44). A proposed aneurysm screening method of abdominal ultrasound, chest radiography, and TTE has been proposed as an alternative to CT/CTA in order to limit radiation exposure (22). Aortic root inflammation can cause mural thickening, dilation, valvulitis, and aortic valve insufficiency as seen on TTE (Figs. 15 and 16) in a variety of infectious and noninfectious aortitides (2,44). Specific echocardiographic findings have been described, such as a nodular appearance of the aortic valve with ankylosing spondylitis-related valvulitis

(60) and redundant aortic valve cusps with prolapse, vegetation-like masses, and echolucencies with Behcet’s valvulitis (70). These considerations may be of paramount importance, such as in the case of Behcet’s valvulitis, in which prosthetic aortic valve replacements often dehisce if no pre-operative immunosuppression is provided, and total root replacement, with a homograft or conduit, may provide more durable results (70). In other cases, pre-operative TEE may demonstrate aortic valve insufficiency due to commissural separation from aortic root dilation rather than valvulitis, which may improve with root replacement or aortic valve repair, thus avoiding prosthetic aortic valve replacement. TEE may be especially helpful in the diagnosis of infectious aortitis (Fig. 17). An atherosclerotic nidus is often identified, and aortic mural thickening with fusiform aneurysms, saccular aneurysms, and ulceration with pseudoaneurysm and thrombus have been described. One or more focal echolucencies may represent abscess cavities, in which the shortaxis views demonstrate a “double barrel” appearance of the cavity adjacent to the true aortic lumen, and the long-axis views may demonstrate a patent “neck” connecting the true lumen to the cavity, as seen by color Doppler (71) (Fig. 18). TEE is also the gold standard for imaging endocarditis and preoperative aortic valve, aortic root, and ascending aortic morphology for pre-operative planning in those with infectious aortitis (72,73). Summary

Multiple modalities provide different and often complementary imaging findings among a wide array of aortitis presentations and potential complications. PET is the most sensitive test for early vessel inflammation; however, it requires CT or MR imaging for anatomic localization. CT provides excellent anatomical characterization of structural aortic changes, but is limited in its assessment of early disease activity. MR provides characterization of both early inflammatory vessel changes and late structural changes, as well as dedicated cardiac and valvular assessment. Ultrasound and echocardiography provide both anatomical and physiologic information regarding vessel and valvular abnormalities. Reprint requests and correspondence: Dr. Gregory R. Hartlage, Department of Medicine, Division of Cardiology, Emory University School of Medicine, 335 Southerland Terrace, Atlanta, Georgia 30307. E-mail: [email protected].

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Key Words: aortic aneurysm aortitis - arteritis - computed tomography - echocardiography magnetic resonance - positron emmision tomography - vascular ultrasound.

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