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Case 59 - Neointimal calcifications mimicking displaced intimal calcifications on unenhanced CT
- from Section 7 - Acute aorta and aortic aneurysms
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- By Saurabh Jha, Hospital of the University of Pennsylvania
- Edited by Stefan L. Zimmerman, Elliot K. Fishman
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- Book:
- Pearls and Pitfalls in Cardiovascular Imaging
- Published online:
- 05 June 2015
- Print publication:
- 21 May 2015, pp 189-192
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Summary
Imaging description
The aortic wall comprises three layers: intima, media, and adventitia. The wall is imperceptible and inferred on contrast-enhanced CT by a boundary separating two tissues of contrasting attenuations: arterial lumen and the periarterial soft tissue. Processes such as intramural hematoma (IMH) that thicken the media expand the wall and displace the intimal layer inwards toward the lumen.
Aortic calcifications are usually centered on the intima and are, therefore, peripherally located (Figure 59.1). A process in the media that displaces the intima renders the calcifications non-peripheral (Figures 59.2A and 59.3).
However, non-peripheral calcifications can also be dystrophic calcifications of the mural thrombus, also known as neointimal calcifications (Figures 59.2B, 59.4, and 59.5).
How can the distinction be made on unenhanced CT?
Neointimal calcifications are chunky and random, since any part of the thrombus can calcify (Figure 59.2B). Intimal calcifications are thin, linear, and circumferentially configured (Figure 59.2A).
Neointimal calcifications may co-exist with intimal calcifications, in which case there are calcifications peripheral to neointimal calcifications (Figure 59.4).
Mural thrombus is of a lower attenuation (< 30 HU) than acute intramural hematoma (50–80 HU) and blood pool (40–50 HU).
Importance
Distinguishing between neointimal calcifications and displaced intimal calcifications is important because the latter reflects acute aortic pathology such as IMH and dissection. Dystrophic calcifications of the mural thrombus reflect an indolent process. The pitfall can result in incorrect diagnosis of acute aortic syndrome.
Case 38 - Giant coronary artery aneurysms
- from Section 4 - Coronary arteries
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- By Mark Stellingworth, University of South Carolina Medical School, Saurabh Jha, Hospital of the University of Pennsylvania, Koteswara Pothineni, Louisiana State University School of Medicine, Stefan L. Zimmerman, Johns Hopkins University School of Medicine
- Edited by Stefan L. Zimmerman, Elliot K. Fishman
-
- Book:
- Pearls and Pitfalls in Cardiovascular Imaging
- Published online:
- 05 June 2015
- Print publication:
- 21 May 2015, pp 120-123
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Summary
Imaging description
Coronary artery aneurysms are defined as localized vessel dilatation exceeding 50% of the adjacent normal coronary artery diameter. A precise definition of the threshold between aneurysm and “giant” aneurysm is not well established, but some authors have suggested that aneurysms > 20 mm meet this criteria. Giant coronary artery aneurysms are identified by the presence of a round or ovoid structure on the epicardial surface of the heart in the typical location for coronary arteries. Often discovered incidentally on echocardiogram, they will appear as a paracardiac mass with varying degrees of flow on Doppler interrogation depending on presence of thrombus. On non-contrast CT, they are low- attenuation, rounded masses that may have peripheral calcifications related to atherosclerosis. After contrast administration, lesions will enhance similar to blood pool, although varying degrees of thrombosis may be present (Figure 38.1). Large aneurysms can erroneously appear thrombosed on cardiac CT due to incomplete filling at the time of arterial phase acquisition (Figure 38.2). Delayed venous images will demon- strate further fill-in of the aneurysm. Cardiovascular magnetic resonance (CMR) imaging will typically show low signal on dark blood images due to flow (Figure 38.1). Steady-state free precession (SSFP) and contrast injections with gadolinium will confirm high signal in the structure due to blood and may show evidence of thrombus (Figures 38.1 and 38.2).
Importance
Patients with giant coronary aneurysms may present with life-threatening tamponade due to rupture. Thrombosis, fistulization to cardiac chambers, and embolization have also been noted in the literature. Giant coronary artery aneurysms can be misinterpreted as cardiac tumors, particularly if only limited imaging is available. The distinction between tumor and aneurysm could have significant impact on treatment.
Typical clinical scenario
Coronary artery aneurysms more commonly affect males and have an incidence between 0.3% and 5%. Coronary aneurysms greater than 20 mm are extremely rare and in one series represented only 0.02% of patients undergoing cardiac surgery. They are more likely to involve the right coronary artery.
Case 61 - Shearing of branch arteries in intramural hematoma: a mimic of active extravasation
- from Section 7 - Acute aorta and aortic aneurysms
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- By Saurabh Jha, Hospital of the University of Pennsylvania
- Edited by Stefan L. Zimmerman, Elliot K. Fishman
-
- Book:
- Pearls and Pitfalls in Cardiovascular Imaging
- Published online:
- 05 June 2015
- Print publication:
- 21 May 2015, pp 197-199
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Summary
Imaging description
The medial layer of the aorta expands in intramural hematoma (IMH) due to the accumulation of subacute blood products. The expansion can shear the wall of exiting arteries such as the intercostal and lumbar arteries.
Contrast collects between the sheared wall of the intercostal artery and the medial layer of the aorta. The contrast collection is beyond the confines of the arterial lumen but the pooled contrast is well localized (Figures 61.1 and 61. 2).
The shearing of the intercostal arteries is also called the “Chinese Ring Sword Sign”.
Importance
This entity can be confused for active extravasation.
In vascular imaging, active extravasation of contrast has important connotations. It means that there is active bleeding. The use of the present participle (bleeding) as opposed to the past tense (bled) elevates the clinical severity and urgency of the vascular process and the promptness with which corrective action is required. Both inappropriate usage and inappropriate non-usage of this term by imagers can have negative consequences.
Typical clinical scenario
Patient presents with chest or back pain with suspicion of an acute aortic syndrome.
Differential diagnosis
Active extravasation is inferred when there is contrast outside the confines of a vascular structure; the contrast outline does not conform to the shape of an arterial branch of venous tributary. Typically the contrast progressively pools in the arterial and venous phases of acquisition.
The pooled contrast can mimic false lumen of a dissection. It can also mimic a penetrating atherosclerotic ulcer.
Teaching point
Mistaking the pooled contrast from sheared vessels for active bleeding can lead to inappropriate operative intervention. IMH of the descending aorta is typically managed medically.
Case 60 - The value of non-contrast CT in vascular imaging
- from Section 7 - Acute aorta and aortic aneurysms
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- By Saurabh Jha, Hospital of the University of Pennsylvania, Benoit Desjardins, Hospital of the University of Pennsylvania
- Edited by Stefan L. Zimmerman, Elliot K. Fishman
-
- Book:
- Pearls and Pitfalls in Cardiovascular Imaging
- Published online:
- 05 June 2015
- Print publication:
- 21 May 2015, pp 193-196
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Summary
Imaging description
The attenuation of blood depends on the hematocrit but is usually 20–35 HU. Subacute blood has a higher attenuation (50–80 HU) than flowing blood. This is because of a reduction of water content, which raises the concentration of hemoglobin. This property makes it possible to identify a vascular process such as an aortic rupture (Figure 60.1), aortic injury (Figure 60.2), acute thrombus (Figure 60.3), intramural hematoma or instability of aneurysm on non-contrast CT, by the “hyperattenuating sign.”
Hyperattenuating sign can be unmasked by using narrow windows and comparing diseased vessel to normal vessel.
Importance
Understanding the value of non-contrast CT in vascular imaging is important because sometimes iodinated contrast cannot be administered.
Typical clinical scenario
Unenhanced CT is almost routinely obtained in vascular imaging. This is to prevent mistaking inherently high-attenuation material for iodinated contrast (Figure 60.4). Additionally, after the administration of iodinated contrast the subacute hematoma in the vessel wall or thrombus becomes less apparent.
In certain circumstances iodinated contrast cannot be administered, such as impaired renal function, allergy to iodinated contrast or difficult venous access. The vascular imager, in these situations, should not write off the study because no contrast is in the arteries, as much information can still be gleaned.
Unenhanced CT may be obtained for a suspected nonvascular medical emergency such as renal stone or pancreatitis. It is important to look for an acute vascular process, which is in the differential diagnosis for renal colic and back pain.
Differential diagnosis
Aortic rupture, intramural hematoma, unstable thrombus, calcification, and periaortic hypercellular tumor.
Teaching point
Sometimes only non-contrast CT is available. The imagers should be aware that valuable information about the acuity of a vascular process can still be obtained without iodinated contrast.
Case 72 - Post-operative air in the aorta: when is it of concern?
- from Section 8 - Post-operative aorta
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- By Saurabh Jha, Hospital of the University of Pennsylvania
- Edited by Stefan L. Zimmerman, Elliot K. Fishman
-
- Book:
- Pearls and Pitfalls in Cardiovascular Imaging
- Published online:
- 05 June 2015
- Print publication:
- 21 May 2015, pp 231-233
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Summary
Imaging description
The presence of air in the abdominal aorta raises the possibility of recent surgery, instrumentation, infection (Figure 72.1) or aortoenteric fistula (AEF) (Figure 72.2).
Imaging features favoring post-surgical air include a fat plane between the aorta and bowel and no tethering of the bowel. The presence of a fat plane essentially rules out AEF (Figure 72.3).
Importance
Air in the abdominal aorta may be a sign of important pathology or may be innocuous. Findings on imaging alone may not distinguish between the two. Specific inquiry should be made of the timing of intervention. Air is not atypical in the first 10 days after intervention.
Infection should be considered in a patient with fever and positive blood culture.
AEF is a surgical emergency and untreated can have a near- certain mortality. AEF can be clinically silent and imaging may provide the life-saving clues.
Typical clinical scenario
The patient is post-open or has a stent graft repair of abdominal aortic aneurysm. CT is obtained for surveillance or symptoms. Patients with AEF fistula may present with hematemesis, melena, sepsis, and abdominal pain. Air may be detected incidentally.
Differential diagnosis
The differential diagnosis for air in the aorta includes infection, aortoduodenal fistula, or instrumentation. Infection may lead to an aortoduodenal fistula and vice versa.
Teaching point
The presence of air in the abdominal aorta is both reflective of serious pathology and an expected finding post-intervention. Imagers should be aware of the bandwidth of possibilities and use findings on imaging and pertinent clinical information.