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Acute Aortic Syndrome

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Radiological evaluation & management of AAS - an overview.

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Acute Aortic Syndrome

  1. 1. ACUTE AORTIC SYNDROME Dr. Marianayagam Anton Suthaharan Registrar in Clinical Radiology, Sri lanka. 2015. Dr.M.A.Suthaharan.
  2. 2.  Introduction  Pathophysiology  Reporting Dr.M.A.Suthaharan.
  3. 3. Introduction - AAS  Acute aortic syndrome (AAS) is a constellation of potentially life-threatening acute aortic diseases.  It includes Aortic dissection, IMH,  Penetrating aortic ulcer,  Traumatic aortic rupture,  Suture dehiscence Unstable/ ruptured aneurysm.Dr.M.A.Suthaharan.
  4. 4. Diagram shows three layers of normal aortic wall, from inner to outer: intima (I), media (M), and adventitia (A).Dr.M.A.Suthaharan.
  5. 5. Imaging Protocol - CT  ECG gating  A non-enhanced scan of the thoracic aorta is included for the detection of an intramural hematoma (IMH).  Iodine 350mg/ml; 120ml _ 4ml/sec followed by 50ml saline chase  18 g peripheral canula; R/ arm  Bolus triggering -ROI indescending aorta , 150 HU; be prepared for manual staring with visual stimulus  arterial phase 20 sec, venous phase 60 secDr.M.A.Suthaharan.
  6. 6.  Contrast differences between arterial and venous phase can be helpful in differentiating true and false lumen.  The iliac tract is included for evaluation of endovascular treatment possibilities.  The branches of the arch are visualized to evaluate the extend of dissection and awareness of possible neurological complications.  Visceral perfusion in both phases Dr.M.A.Suthaharan.
  7. 7. Classification of AAS Dr.M.A.Suthaharan.
  8. 8. Stanford Classification of AAS • Stanford Type A lesions involve the ascending aorta and aortic arch and may or may not involve the descending aorta. • Stanford Type B lesions involve the thoracic aorta distal to the left subclavian artery. Dr.M.A.Suthaharan.
  9. 9. Aortic Dissection Dr.M.A.Suthaharan.
  10. 10. Over view  Most common non-traumatic acute aortic emergency  overall in-hospital mortality of 20–25%, which increases markedly in patients with complicated dissection.  Aetiology:  advancing age and hypertension.  Cystic medial degeneration in connective tissue disorders (Marfan’s syndrome and Ehlers–Danlos syndrome  coarctation,  bicuspid aortic valve,  aortitis,  pregnancy  blunt chest trauma. Dr.M.A.Suthaharan.
  11. 11. 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. Dr.M.A.Suthaharan.
  12. 12.  Aortic dissection is initiated by an intimal tear, which allows blood to penetrate into the medial layer,  Producing a cleavage plane (false lumen) between the inner two-thirds and outer one-third of media.  The true lumen is separated from the false lumen by an intimomedial flap.  The blood course through the medial layer can variably extend the dissection distal or proximal to the entry tear and  eventually rupture through the adventitia or  back through the intima into the true lumen, creating re-entry tears.  Branching vessels can be involved Dr.M.A.Suthaharan.
  13. 13.  The false lumen may thrombose completely or partially over time.  Reduction in the amount of elastic tissue within the wall of the false lumen may lead to subsequent aneurysmatic dilatation. Dr.M.A.Suthaharan.
  14. 14. Unenhanced CT may demonstrate internal displacement of intimal calcifications.Dr.M.A.Suthaharan.
  15. 15. Dr.M.A.Suthaharan.
  16. 16. True Lumen • Surrounded by calcifications (if present) • Smaller than false lumenDr.M.A.Suthaharan.
  17. 17. False lumen  Flow or occluded by thrombus (chronic).  Delayed enhancement  Wedges around true lumen (beak-sign)  Collageneous media-remnants (cobwebs)  Larger than true lumen  Circular configuration (persistent systolic pressure)  Outer curve of the arch  Surrounds true lumen in Type A dissection Dr.M.A.Suthaharan.
  18. 18. Dr.M.A.Suthaharan.
  19. 19. Investigstions  Aortography  TOE  IVUS  MRI  CT AORTOGRAM Dr.M.A.Suthaharan.
  20. 20. MRI  excellent sensitivity and specificity that approximate 100%.  In BBFSE sequences it appears linear inside the black vessel lumen  The false lumen can be differentiated from the true lumen by its higher signal intensity due to the slower flow  fast spin-echo sequence in the sagittal plane -to define the extension of the dissection in the thoracic and abdominal aorta, including the aortic arch branches .Dr.M.A.Suthaharan.
  21. 21.  accurate definition of the anatomical details of the dissection (extension, site of entry and re-entry tear, aortic branch relationships) relies on gadolinium-enhanced 3D MRA and its reformatted images  SSFP technique- high-contrast resolution between the aortic lumen and the wall that may be used for morphological (2D or 3D images) or functional (cine sequences) analysis Dr.M.A.Suthaharan.
  22. 22. Axial BBFSE image of chronic type B aortic dissection. The intimal flap is well depicted as a straight hyperintense line dividing the true and false lumen at the level of descending aorta.Dr.M.A.Suthaharan.
  23. 23. CT  unusual type of aortic dissection is the intimo-intimal intussusception produced by,circumferential dissection of the intimal layer, which subsequently invaginates like a wind sock. Dr.M.A.Suthaharan.
  24. 24. Dr.M.A.Suthaharan.
  25. 25. When there are 2 lumina, these will spiral around each other. Dr.M.A.Suthaharan.
  26. 26. Dr.M.A.Suthaharan.
  27. 27. Dissection into abdominal arteries  Impaired perfusion of end-organs can be due to 2 mechanisms: 1) static = continuing dissection in the feeding artery (usually treated by stenting) 2) dynamic = dissection flap hanging in front of ostium like a curtain (usually treated with fenestration).  This may be hard to discern, MPR's can be helpfull.  Look for the re-entry point, usually to be found in the iliac tract.  Provide information about tortuisity and calcifications of the iliac tract if endovascular procedures are being considered. Dr.M.A.Suthaharan.
  28. 28. Dr.M.A.Suthaharan.
  29. 29. Reporting  The following anatomical details need to be considered for planning of endovascular treatment of aortic dissection. • The distance between the proximal neck, the entry tear and the origin of the epiaortic vessels. • The origin of the visceral vessels in regard to the true or false lumen must be defined. Dr.M.A.Suthaharan.
  30. 30.  If one or more vessels arise from the false lumen, a re-entry tear ensuring vessel perfusion after stent- graft deployment has to be identified.  Careful evaluation of ascending aorta and aortic arch dimensions and degree of atheromatous wall changes are necessary.  Ascending aorta and archaneurysms may favour a retrograde extension of the dissection if the proximal end of the stent graft (free flow extremity) is positioned in the distal arch. Dr.M.A.Suthaharan.
  31. 31. INTRA MURAL HAEMATOMA Dr.M.A.Suthaharan.
  32. 32. Intra Mural Haematoma Dr.M.A.Suthaharan.
  33. 33.  Intramural hematoma is thought to begin with the rupture of the vasa vasorum, within the medial layer and eventually results in a circumferentially oriented blood collection.  The hematoma may propagate along the media layer of the aorta .  Itweakens the aorta and may progress either to outward rupture of the aortic wall or to inward disruption of the intima, the latter leading to communicating aortic dissection Dr.M.A.Suthaharan.
  34. 34.  Causes:  Spontaneous  PAU  trauma Dr.M.A.Suthaharan.
  35. 35. Note that the IMH does not spiral around the true lumen, like in classic AD, helping to differentiate both. Dr.M.A.Suthaharan.
  36. 36.  visualised by cross-sectional imaging as an aortic wall thickening, symmetric or asymmetric,  variable in thickness from 3 mm to more than 1 cm  it must be differentiated from mural thrombus or plaque.  Intimal displacement of calcification can aid in distinguishing  because the IMH is a subintimal lesion, with calcifications displaced on top of the lesion facing the lumen.  Acute IMH is hyperdense on unenhanced CT.  shape of the aortic wall thickening: in IMH the borders are generally smooth, while a thrombus or a plaque are typically characterised by irregular margins Dr.M.A.Suthaharan.
  37. 37.  In the suspecion of IMH it is important to perform unenhanced CT:  in the acute phase the haematoma appears as a crescent-like aortic wall thickening  typically hyperdense on unenhanced CT with respect to the aortic lumen,  while after enhancement the density of wall and lumen are reversed, with the IMH remaining unenhanced, unlike the false lumen in aortic dissection Dr.M.A.Suthaharan.
  38. 38.  The differentiation between IMH and a completely thrombosed false lumen may be very difficult  IMH maintains a constant circumferential relationship to the wall (subintimal lesion), while the thrombosed false lumen tends to longitudinally spiral around the aorta  IMH does not reduce the lumen, which maintains its regular shape, while the false lumen can variably compress the true lumen Dr.M.A.Suthaharan.
  39. 39. Dr.M.A.Suthaharan.
  40. 40. Dr.M.A.Suthaharan.
  41. 41.  The diagnosis of IMH is mainly based on axial images,  but 2D reformatted images may be useful to evaluate the extent of IMH and its relationships with aortic branches. Dr.M.A.Suthaharan.
  42. 42. Reporting  Type A or Type B  Regression to normal in 80% of patients  Predictors of mortality:  - Ascending Aorta > 5 cm  - IMH thickness > 2 cm  - Pericardial effusion (to less extend pleural effusion)  IMH may persist or evolve into aneurysm or PAU  Associated PAU - worse prognostic outcome Dr.M.A.Suthaharan.
  43. 43. Pre-op evaluation of AAS 1. confirm or exclude the presence of impending aortic rupture or 2. any other signs of severe instability that deserve immediate surgical or endovascular treatment, e.g. a visceral malperfusion in aortic dissection. 3. should define anatomical conditions allow an endovascular or surgical treatment of the disease. Dr.M.A.Suthaharan.
  44. 44. Aortic Aneurism Dr.M.A.Suthaharan.
  45. 45.  Aortic aneurysm is a localised or diffuse dilatation involving all layers of the aortic wall, exceeding the expected aortic diameter by a factor of 1.5 or more.  False aneurysm or pseudoaneurysm the wall is represented only by the adventitial layer.  false aneurysms result from a contained ruptureand should not be considered stable. Dr.M.A.Suthaharan.
  46. 46.  As many as 95% of atherosclerotic aneurysms affect the abdominal rather than the thoracic aorta  Natural history of aneurysms is progressive remodelling, expansion and eventual rupture. Dr.M.A.Suthaharan.
  47. 47. Inflammatory Aneurysms  defined as dilation of the aorta with a thickened aneurysm wall, marked perianeurysmal and retroperitoneal fibrosis, and dense adhesions to adjacent abdominal organs. Dr.M.A.Suthaharan.
  48. 48. Mycotic Aneurysms  Infection can cause thrombosis of the vasa vasorum with consequent destruction of the aortic intima and media. Dr.M.A.Suthaharan.
  49. 49. Rupture of Aortic Aneurism  Aortic rupture appears on CTA images as a Discontinuity of the aortic wall with contrast medium extravasation  it is typically associated with a large, periaortic haematoma  On unenhanced CT images the rupture can be suspected if there is a discontinuity of wall calcification.  Tangential calcium sign  Draped aorta Dr.M.A.Suthaharan.
  50. 50. Dr.M.A.Suthaharan.
  51. 51. LEFT: Subtle periaortic stranding, MIDDLE: Hemorrhage into posterior pararenal and perirenal compartment, RIGHT: Extravasation of iv. Contrast. Dr.M.A.Suthaharan.
  52. 52.  The intimal calcification points away from the aneurysm ( tangential calcium sign) and there is retroperitoneal leakage. Dr.M.A.Suthaharan.
  53. 53. Draped aorta A positive aortic drape sign is considered to be present when the following features are seen: • area in which the posterior aortic wall is unidentifiable as a distinct line. • the posterior aorta follows the contour of the spine on one or both sides. 2 weeks later Dr.M.A.Suthaharan.
  54. 54. Dr.M.A.Suthaharan.
  55. 55. Impending rupture  haemorrhagic pleural effusion,  periaortic, pericardial and/or mediastinal haematoma. Dr.M.A.Suthaharan.
  56. 56. Reporting  Size and extension of the aneurysm.  Adequate distance (>15 mm) between the proximal neck of the aneurysm and the origin of the epiaortic vessels  Distance of the peripheral neck of the aneurysm and its relationship to the origin of the visceral arteries (should be >15 mm)  Extent and type of wall alterations (e.g. amount of atheromatous material or calcium) at the proximal and distal neck  Diameter and condition of the abdominal aorta and vascular access (iliac and femoral arteries) and tortuosity of descending aorta which might preventpassage of the stent-graft delivery system. Dr.M.A.Suthaharan.
  57. 57.  Any evidence for the presence of a large radicular artery supplying the spinal cord that could be covered by a stent graft  Any other incidental findings in the chest, abdomen, or pelvis that should contraindicate the procedure (e.g. metastatic tumour spread) Dr.M.A.Suthaharan.
  58. 58. Conclusion  AAS are medical emergencies  Radiologist plays very important role in diagnosis, planning of management, endovascular interventions , post-op evaluation and follow up.  MDCT is investigation of choice; correct CT technique and systematic reporting are very important for management. Dr.M.A.Suthaharan.
  59. 59. THANK YOU Dr.M.A.Suthaharan.

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