Aortic Disssection. Dr Nikrish Hegde.
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Aortic dissection is a serious condition where the layers of the aorta separate. There are two main types - Stanford type A involves the ascending aorta and requires urgent surgery, while Stanford type B involves the descending aorta and is treated medically. Computed tomography is the main imaging method used to diagnose aortic dissection and distinguish the true and false lumens. Findings include the intimal flap, thrombus, and complications. Emergent surgery is needed if the patient is hemodynamically unstable or has uncontrolled hypertension.
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Aortic Disssection. Dr Nikrish Hegde.
- 1. AORTIC DISSECTION! Dr. Nikrish S Hegde
- 2. LEARNING OBJECTIVES! Identify the two types of aortic dissection and list the indications for treatment. Describe the imaging parameters and the typical and atypical imaging findings in aortic dissections. Discuss the imaging features of complications that can arise from aortic dissections.
- 3. IMPORTANCE! Most common Fatal outcome Prompt diagnosis and treatment.
- 4. AORTA made of three layers, called from the luminal side outward, the tunica intima, the tunica media and the tunica adventitia
- 5. What is aortic dissection? Dissection is the result of a spontaneous longitudinal separation of the aortic intima and adventitia caused by circulating blood gaining access to and splitting the media of the aortic wall
- 9. Type A dissections account for 60%–70% of cases and typically require urgent surgical intervention. Stanford type B dissection involves the descending thoracic aorta distal to the left subclavian artery and accounts for 30%– 40% of cases. Management takes the form of medical treatment of hypertension.
- 10. Indications for immediate surgery Hemodynamic instabilty. Uncontrolled HTN. Diameter > 6cm. Ischaemic Complications.
- 11. PRESENTATION. CHEST PAIN SYNCOPE RIGHT HYPOCHONDRIAL PAIN ..ABNORMAL LFT OLIGURIA ..ANURIA ..ABNORMAL RFT NAUSEA ..VOMITING..PAIN ABDOMEN..BLOODY DIARRHOEA.. LOWER LIMB ISCHAEMIA
- 12. ACUTE VS CHRONIC The dissection is termed acute when it is diagnosed within 14 days after the first symptoms appear. It is termed chronic when it is diagnosed later .
- 13. HELICAL CT AND AORTIC DISSECTION. Aortography. Shorter acquisition time, wide availability, and high diagnostic accuracy and has, therefore, classically been the modality of choice for the evaluation of aortic dissection. The intimal flap, type and extent of dissection ,presence of thrombus and the presence of associated complications and follow up changes.
- 14. TECHNIQUE The examination begins with conventional unenhanced CT. Coverage begins 2 cm above the aortic arch and continues to the superior aspect of the femoral head. We then inject 100 mL of nonionic at a rate of 2 mL/sec through a 20-gauge catheter positioned in the right arm. Helical CT is performed 30 seconds after administration of contrast
- 16. TYPICAL AORTIC DISSECTION The classic feature of aortic dissection is a partition between the true and false channels. Secondary findings include internal displacement of intimal calcifications or a hyperattenuating intima; delayed enhancement of the false lumen; widening of the aorta; and mediastinal, pleural, or pericardial hematoma .
- 19. STANDFORD TYPE A
- 21. STANFORD B
- 22. How do we distinguish false lumen from the true lumen?? SIZE POSITION-False channel usually arises anterior in the ascending aorta and spirals to posterior and left lateral in descending aorta. FLOW SECONDARY CHANGES – THROMBOSIS BEAK’S SIGN
- 23. BEAK’S SIGN
- 25. ATYPICAL AORTIC DISSECTION INTRAMURAL HEMATOMA: Unenhanced CT shows a cuff or crescent of high attenuation and displacement of intimal calcifications. On enhanced CT scans, a smooth region of low attenuation can be seen
- 29. Penetrating atherosclerotic ulcer is defined as an atherosclerotic lesion with ulceration that penetrates the internal elastic lamina; such penetration facilitates hematoma formation within the media of the aortic wall
- 32. Ruptured Type B Dissection
- 34. Atypical Configuration of the Intimal Flap circumferential intimal flap
- 35. filiform
- 47. PITFALLS The CT appearances of several entities can cause them to be mistaken for atypical AAD.
- 49. CT scan shows an atheromatous thrombus with an irregular internal border in the thoracic descending. A thrombosed aortic dissection usually demonstrates a smooth internal border.
- 51. N
- 52. Perivenous streaks combination of beam hardening and motion orientation of such streaks typically varies from section to section and extends beyond the confines of the aortic wall minimize perivenous streaks by performing bolus injection into the right arm at a rate of 2 mL/sec
- 53. Aortic motion artifact ascending aorta and is related to movement of the aortic wall artifact is seen at the left anterior and right posterior margins of the aortic circumference a serrated appearance of the left anterior ascending aorta on two- or threedimensional reconstruction images
- 55. BRANCH VESSEL OCCLUSION There are two types of branch-vessel occlusion. 1)STATIC 2)DYNAMIC
- 56. STATIC the intimal flap intersects or enters the branch-vessel origin. Static obstruction is treated locally with an intravascular stent
- 59. DYNAMIC the intimal flap spares the branch-vessel wall but prolapses across the branchvessel origin and covers it like a curtain . Dynamic obstruction is treated with a fenestration procedure
- 63. Transesophageal echocardiography secondary signs of an aortic dissection such as aortic root dilatation, aortic regurgitation, coronary ostial patency, pericardial effusions, or regional abnormal wall motion can be diagnosed. TEE can be performed in the emergency department at the bedside of unstable patients.
- 67. MR angiography suitable for the investigation of aortic dissection in medically stable patients or those with chronic dissections including lack of nonionizing radiation, multiplanar evaluation, and greater vessel coverage at high resolution with fewer sections. It cannot be performed in unstable patients due to longer acquisition time and difficulty in monitoring, and it is not appropriate for patients with implanted electronic devices
- 68. TRIPLE-RULE-OUT -CT Assess the aorta, coronary arteries, and pulmonary arteries and the middle and lower portions of the lungs during a single scan with use of several optimally timed boluses of contrast material and ECG gating. Biphasic injection of iodinated contrast material (≤100 mL)
Editor's Notes
- Stanford type B aortic dissection. Contrast-enhanced CT scans obtained at different levels show a thrombosed false lumen (circle in a). Arrow in a indicates a small residual flow channel in the false lumen.
- these features are difficult to differentiate from those of an acutely thrombosed false lumen. An observation that may help one differentiate intramural hematoma from the thrombosed false lumen of classic intimal dissection is that the latter entity tends to spiral longitudinally around the aorta, whereas the former entity tends to maintain a constant circumferential relationship with the aortic wall (
- In an open dissection, these features are difficult to differentiate from those of an acutely thrombosed false lumen. An observation that may help one differentiate intramural hematoma from the thrombosed false lumen of classic intimal dissection is that the latter entity tends to spiral longitudinally around the aorta, whereas the former entity tends to maintain a constant circumferential relationship with the aortic wal
- Typically, penetrating atherosclerotic ulcer occurs in the middle or distal third of the thoracic aorta; CT features include a focal ulcer with adjacent subintimal hematoma (15) (Fig 8). Penetrating atherosclerotic ulcer can be differentiated from aortic dissection by means of (a) the extensive atherosclerotic disease and ectasia in penetrating atherosclerotic ulcer and (b) the lack of compression of the aortic lumen in elderly persons with penetrating atherosclerotic ulcer.