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Pathogenesis in Acute Aortic Syndromes: Aortic Dissection, Intramural Hematoma, and Penetrating Atherosclerotic Aortic Ulcer

¹ All authors: The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins Medical Institutions, 600 N. Wolfe St., Baltimore, MD 21287-0750.

View larger version (107K): [in a new window]   Fig. 1. —Diagram shows three layers of normal aortic wall, from inner to outer: intima (I), media (M), and adventitia (A).

View larger version (84K): [in a new window]   Fig. 2. —Diagram illustrates events leading to aortic dissection from formation of entrance tear and exit tear of intima to splitting of aortic media and formation of intimomedial flap. Blood under pressure dissects media longitudinally, and double-channel aorta is formed with blood filling both true and false lumens.

View larger version (121K): [in a new window]   Fig. 3A. —46-year-old man with concurrent intramural hematoma involving ascending aorta and communicating dissection involving descending aorta. Axial unenhanced CT scan shows hyperdense crescentic hematoma in wall of ascending aorta (white arrow) with eccentric narrowing of lumen, type A intramural hematoma. Small intramural hematoma (arrowhead) is also noted at left lateral aspect of proximal descending aorta. High-attenuation dissection flap (black arrow) is seen in descending aorta.

View larger version (111K): [in a new window]   Fig. 3B. —46-year-old man with concurrent intramural hematoma involving ascending aorta and communicating dissection involving descending aorta. Axial contrast-enhanced CT scan obtained at same level as A shows wall thickening in ascending and descending aorta, but high-attenuation intramural hematoma is less obvious. Classic intimomedial flap (arrow) dividing true and false lumens in descending aorta is more conspicuous after contrast administration. Note irregular margin of flap on false lumen side. Intramural hematoma (arrowhead) is seen along lateral wall of false lumen.

View larger version (119K): [in a new window]   Fig. 4A. —Axial double-inversion-recovery MR images (TR/TE, 1875/18; inversion time, 150 msec) of 37-year-old man with Marfan syndrome. Image shows classic aortic dissection with double-channel aorta. True lumen (straight arrow) is smaller than false lumen (curved arrow). High-velocity flow in true lumen causes signal void. Slower flow with higher signal can be seen in false lumen.

View larger version (122K): [in a new window]   Fig. 4B. —Axial double-inversion-recovery MR images (TR/TE, 1875/18; inversion time, 150 msec) of 37-year-old man with Marfan syndrome. Image shows swirling flow pattern in false lumen (curved arrow). True lumen (straight arrow) is significantly narrowed but patent.

View larger version (113K): [in a new window]   Fig. 5A. —68-year-old man with aberrant right subclavian artery and horseshoe kidney. Axial contrast-enhanced CT scan obtained at level of origin of aberrant right subclavian artery shows aberrant vessel (arrow) crossing midline behind trachea and esophagus.

View larger version (100K): [in a new window]   Fig. 5B. —68-year-old man with aberrant right subclavian artery and horseshoe kidney. Axial contrast-enhanced CT scan shows dissection involving aortic arch with calcifications within intimomedial flap and different attenuation of enhanced blood within true and false (arrow) lumens. Intimal tears leading to dissection frequently form in areas of elevated hydraulic stress, such as region of aberrant vessel origin.

View larger version (112K): [in a new window]   Fig. 5C. —68-year-old man with aberrant right subclavian artery and horseshoe kidney. Anteroposterior volume-rendered CT image of origin of aberrant subclavian artery depicts aberrant vessel course (arrow) better than axial scans A and B.

View larger version (121K): [in a new window]   Fig. 6A. —61-year-old man with symptoms of right hemispheric stroke who was found to have marked blood pressure discrepancy between arms and hypertension. Urgent CT scan (not shown) revealed type A aortic dissection. Patient went into asystole and died 15 hr after imaging. Axial contrast-enhanced CT scan obtained at level of aortic arch shows complex dissection with intimomedial flap involving arch and brachiocephalic artery (arrow). Dissection extended into left common carotid artery (arrowhead) and into left subclavian artery (not shown).

View larger version (114K): [in a new window]   Fig. 6B. —61-year-old man with symptoms of right hemispheric stroke who was found to have marked blood pressure discrepancy between arms and hypertension. Urgent CT scan (not shown) revealed type A aortic dissection. Patient went into asystole and died 15 hr after imaging. Axial CT scan shows irregular dissection flap within lumen of ascending and descending aorta (arrows).

View larger version (132K): [in a new window]   Fig. 6C. —61-year-old man with symptoms of right hemispheric stroke who was found to have marked blood pressure discrepancy between arms and hypertension. Urgent CT scan (not shown) revealed type A aortic dissection. Patient went into asystole and died 15 hr after imaging. Axial CT scan shows hemopericardium (arrow) that was confirmed at echocardiography (not shown) as large circumferential hyperechoic pericardial effusion with evidence of right ventricle compression.

View larger version (132K): [in a new window]   Fig. 6D. —61-year-old man with symptoms of right hemispheric stroke who was found to have marked blood pressure discrepancy between arms and hypertension. Urgent CT scan (not shown) revealed type A aortic dissection. Patient went into asystole and died 15 hr after imaging. Axial CT scan shows dissection continuing along right wall of abdominal aorta (arrow). No enhancement of right kidney parenchyma was present.

View larger version (133K): [in a new window]   Fig. 7A. —82-year-old man with thoracic aortic aneurysm type B and thoracoabdominal aortic dissection extending from just distal to left subclavian artery to proximal right common iliac artery. Patient was first diagnosed with aortic dissection 12 years ago. For more than 10 years, symmetric perfusion of kidneys was seen, until recently when CT showed hypoperfusion of right kidney. Contrast-enhanced CT scan shows both true and false (arrow) lumens to be well opacified with contrast material. There is minimal delay in enhancement and thinning of cortex of right kidney.

View larger version (123K): [in a new window]   Fig. 7B. —82-year-old man with thoracic aortic aneurysm type B and thoracoabdominal aortic dissection extending from just distal to left subclavian artery to proximal right common iliac artery. Patient was first diagnosed with aortic dissection 12 years ago. For more than 10 years, symmetric perfusion of kidneys was seen, until recently when CT showed hypoperfusion of right kidney. CT scan obtained 1 year after A shows decrease in attenuation of contrast-enhanced blood in false lumen (arrow) when compared with true lumen. Enhancement of right kidney is markedly diminished, which is compatible with progressive hypoperfusion.

View larger version (145K): [in a new window]   Fig. 7C. —82-year-old man with thoracic aortic aneurysm type B and thoracoabdominal aortic dissection extending from just distal to left subclavian artery to proximal right common iliac artery. Patient was first diagnosed with aortic dissection 12 years ago. For more than 10 years, symmetric perfusion of kidneys was seen, until recently when CT showed hypoperfusion of right kidney. Anteroposterior volume-rendered CT image shows right renal artery (open white arrow) originating from false lumen (solid white arrow). Left renal artery (open black arrow) originates from true lumen. Note dissection flap with calcifications (solid black arrow) that separates true and false lumens.

View larger version (85K): [in a new window]   Fig. 8. —Diagram shows events leading to intramural hematoma, from rupture of vasa vasorum feeding aortic media to creation of intramedial hematoma with intact intimal layer.

View larger version (93K): [in a new window]   Fig. 9A. —Axial double-inversion-recovery MR images (TR/TE, 1690/29; inversion time, 150 msec) of 76-year-old man with progression of intramural hematoma to overt dissection in ascending aorta within 6 days. Image shows high-signal-intensity crescentic intramural collection in ascending aorta (arrow), consistent with early subacute type A intramural hematoma.

View larger version (104K): [in a new window]   Fig. 9B. —Axial double-inversion-recovery MR images (TR/TE, 1690/29; inversion time, 150 msec) of 76-year-old man with progression of intramural hematoma to overt dissection in ascending aorta within 6 days. Image obtained 6 days after A shows that intramural hematoma progressed to type A aortic dissection within 6 days. Note signal intensity difference between true and false lumens. Signal void within true lumen reflects high-velocity blood flow, whereas higher signal within false lumen is related to slower, turbulent flow. Also note defect in intimomedial flap (arrow) representing intimal tear.

View larger version (70K): [in a new window]   Fig. 10. —Diagram shows events leading to penetrating aortic ulcer from formation of extensive aortic atheroma confined to intimal layer, through lesion progression to deep ulceration of plaque with penetration into media, to entrance of blood from aortic lumen into media and splitting of media with intramural hematoma. Hematoma formation may extend along media, resulting in long-segment intramural hematoma.

View larger version (144K): [in a new window]   Fig. 11A. —58-year-old woman presenting with severe back pain and penetrating atherosclerotic ulcer of aorta. Unenhanced CT scan shows crescentic high-attenuation intramural hematoma (arrow) at distal thoracic aorta.

View larger version (146K): [in a new window]   Fig. 11B. —58-year-old woman presenting with severe back pain and penetrating atherosclerotic ulcer of aorta. Contrast-enhanced CT scan obtained at level corresponding to A shows ulcer (arrow) filling with contrast material. Note that intramural hematoma presents as eccentric low-attenuation thickening of aortic wall.

View larger version (82K): [in a new window]   Fig. 11C. —58-year-old woman presenting with severe back pain and penetrating atherosclerotic ulcer of aorta. Lateral angiogram of distal thoracic aorta shows anterior ulcerlike aortic lesion (arrow) filling with contrast material above level of celiac axis.

View larger version (100K): [in a new window]   Fig. 11D. —58-year-old woman presenting with severe back pain and penetrating atherosclerotic ulcer of aorta. Multiplanar reformatted CT scan in sagittal view shows ulcer crater (open arrow) and long-segment intramural hematoma (solid arrows) in descending aorta.

View larger version (152K): [in a new window]   Fig. 12A. —48-year-old man with penetrating atherosclerotic ulcer. Axial double-inversion-recovery MR image (TR/TE, 1017/20; inversion time, 150 msec) shows intermediate-signal-intensity eccentric intramural hematoma in distal thoracic aorta (arrow).

View larger version (156K): [in a new window]   Fig. 12B. —48-year-old man with penetrating atherosclerotic ulcer. Axial double-inversion-recovery MR image (1017/20; inversion time, 150 msec) shows distinct ulcer crater with signal void (arrow).

View larger version (123K): [in a new window]   Fig. 12C. —48-year-old man with penetrating atherosclerotic ulcer. Contrast-enhanced spoiled gradient-refocused echo source MR image (3.7/1.3; flip angle, 30°) shows ulcer crater (arrow) filling with contrast material.

View larger version (145K): [in a new window]   Fig. 12D. —48-year-old man with penetrating atherosclerotic ulcer. Multiplanar reformatted MR scan in oblique sagittal view shows ulcer crater (arrow).

View larger version (114K): [in a new window]   Fig. 12E. —48-year-old man with penetrating atherosclerotic ulcer. Contrast-enhanced CT scan shows small focal contrast-filled outpouching (arrow) in distal thoracic aorta.

View larger version (112K): [in a new window]   Fig. 12F. —48-year-old man with penetrating atherosclerotic ulcer. Axial CT scan obtained below ulcer crater level shows intramural hematoma (arrow), compatible with aggressive behavior of lesion.

View larger version (133K): [in a new window]   Fig. 13A. —83-year-old man with chronic obstructive pulmonary disease and hypertension. Contrast-enhanced CT scan shows calcified atheromatous plaque with focal ulceration (arrow) but without contrast extravasation beyond plaque.

View larger version (130K): [in a new window]   Fig. 13B. —83-year-old man with chronic obstructive pulmonary disease and hypertension. Axial CT scan shows plaque-related intraluminal irregularity (arrow), but no contrast material is extending beyond level of intima (marked with calcification) and no intramedial hematoma is present.

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