Diagnostic Imaging Pathways - Aortic Dissection (Spontaneous)
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This pathway provides guidance for imaging adult patients with suspected non-traumatic aortic dissection.
Date reviewed: July 2018
Date of next review: July 2021
Published: March 2019
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The relative radiation level (RRL) of each imaging investigation is displayed in the pop up box.
| SYMBOL | RRL | EFFECTIVE DOSE RANGE |
 | None | 0 |
 | Minimal | < 1 millisieverts |
 | Low | 1-5 mSv |
 | Medium | 5-10 mSv |
 | High | >10 mSv |
Images
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| 1 |  |
Aortic Dissection - Type A Image 1 (CT Angiography): Stanford type A Aortic Dissection involving the ascending and descending thoracic aorta (arrows). |
Teaching Points
Teaching Points
- CTA is the investigation of choice to evaluate suspected aortic dissection
- A chest radiograph is useful in excluding other causes of chest pain and can be performed if readily available, but it should not delay obtaining a CT. A normal chest radiograph does not exclude aortic dissection and further imaging should still be pursued
- TOE provides immediate information with comparable accuracy to CTA and can be useful in haemodynamically unstable patients if an experienced operator is readily available. TOE does not visualise the distal extension of a descending dissection
- MRI/MRA also has high diagnostic accuracy and does not require iodinated contrast so can be considered for haemodynamically stable patients in whom contrast is contraindicated. Long examination times and limited availability can potentially delay diagnosis so MRI is not widely used
- Stanford classification of aortic dissection:
- Type A dissection includes the ascending aorta
- Type B dissection does not involve the ascending aorta (i.e. distal to left subclavian artery)
aort_d
Aortic Dissection
- Predisposing factors for spontaneous aortic dissection include
- Systemic hypertension
- Bicuspid aortic valve
- Coarctation of the aorta
- Marfan's syndrome
- Marfan's syndrome
- Turner syndrome
- Giant cell arteritis
- Third trimester pregnancy
- Cocaine abuse
- Stanford classification of aortic dissection:
- Type A dissection includes the ascending aorta
- Type B dissection does not involve the ascending aorta (i.e. distal to left subclavian artery)
- Type A dissections are usually surgical emergencies owing to the high risk of acute aortic regurgitation, occlusion of coronary arteries and pericardial rupture
cxr
Chest Radiography
- A chest radiograph is useful in excluding other causes of chest pain and can be performed if readily available, but it should not delay obtaining a CTA if there is high suspicion of dissection. A normal chest radiograph does not exclude aortic dissection and further imaging should still be pursued if there is ongoing clinical concern 1
- Radiographic abnormalities that may suggest aortic dissection include
- Widened mediastinum and widening of the aortic contour, 2 although these can be difficult to accurately assess on portable AP views 1
- Difference in the diameter between the ascending and descending aorta
- Blurring of the aortic margin secondary to local extravasation of blood
- Unilateral / bilateral pleural effusion
- Separation of intimal calcification
- A literature review reported the accuracy of various radiological abnormalities in the detection of spontaneous aortic dissection 3
- Abnormal aortic contour - sensitivity 61% (95% CI 56-85)
- Pleural effusion - sensitivity 16% (95% CI 12-21)
- Displaced intimal calcification - sensitivity 9% (95% CI 6-13)
- Widened mediastinum - sensitivity 64% (95% CI 44-80)
- However, the review consisted mainly of retrospective studies, which may have biased the results and over predicted the usefulness of chest radiography in diagnosis of spontaneous aortic dissection
cta
Computed Tomography Angiography (CTA)
- CTA chest and abdomen is the investigation of choice for the evaluation of suspected spontaneous aortic dissection 1, 4, 5
- CT technology has undergone rapid improvements allowing higher resolution, faster acquisition times and better reconstructions, so there are no recent studies reflecting the accuracy of current technology. 1 A meta-analysis including studies of older helical CT scanners found CT, MRI and TOE to have comparable sensitivity approaching 100% and high specificity 95-98% 6
- The diagnosis is based on the demonstration of an intimal flap or intramural thrombus, which separates the true from the false channel. Intramural thrombus appears as eccentric mural thickening with Hounsfield units of 40-60 on non-contrast or post-contrast imaging. CTA also demonstrates the extent of dissection, involvement of vital vasculature, 7 and end organ ischaemia 1
- Advantages 1, 4
- Non-invasive, rapid test
- Widely available
- Allows distinction of type A from type B aortic dissection
- Allows imaging of the entire aorta and demonstrates the extent of involvement and organ ischaemia, including assessment of coronary arteries
- Permits follow-up of aortic dissection, aneurysm or intramural haematoma
- Can identify alternate causes of chest pain in 21% of cases 8
- Disadvantages
- Exposure to ionising radiation
- Use of iodinated contrast material
toe
Transoesophageal Echocardiography (TOE)
- Comparable accuracy to that of CT for detection of aortic dissection with sensitivity and specificity approaching 100% 6
- Advantages 1, 4, 9-12
- Can be performed at the bedside of critically ill patients
- Allows functional cardiac assessment
- Permits detection of coronary artery involvement
- Limitations
- Invasive
- Limited by availability and/or expertise
- Obscuring of the proximal aortic arch by interference from air within the trachea
- Lack of visualisation of the abdominal aorta (the distal extent of the dissection may not be seen if it involves the abdominal aorta)
mri
Magnetic Resonance Imaging/Angiography (MRI/MRA)
- Can be considered for haemodynamically stable patients in whom contrast is contraindicated 1, 4
- Long examination times and limited availability can potentially delay diagnosis so MRI is not widely used
- Comparable accuracy to that of CT and transoesophageal echocardiography with sensitivity and specificity approaching 100% 6
- MRI has advantages over CT for following up medically-managed patients with Type B dissection, who are often young and require repeat imaging. MRI may have the advantage of visualising false lumen thrombosis and identifying patients at risk of rupture 13, 14
- Advantages 1, 4, 9, 10
- Provides excellent visualisation of tear localisation, aortic regurgitation, side branch involvement and complications
- No exposure to ionising radiation
- Can be performed without intravenous contrast
- Non-invasive
- Limitations 2, 4
- Expensive
- Limited availability
- Long examination time
- Difficulty of monitoring haemodynamically unstable patients (limited access to the patient)
- Contraindicated in patients with ferromagnetic prostheses
tte
Transthoracic Echocardiography (TTE)
- Older studies report the sensitivity and specificity of TTE for aortic dissection are 80% and 93-96% respectively. 15-17 TTE has a lower sensitivity for detecting distal dissection. 18 There is a lack of more recent data on the accuracy of TTE, even though ultrasound technology has improved significantly in this time
- The main limitations of TTE include not being able to fully visualise the descending thoracic aorta and being limited by the narrow acoustic window between bones and lungs. 19 Reverberation artefacts can also mimic dissection flaps in TTE and TOE. 18 TTE is not recommended to rule out aortic dissection
- However, TTE is portable and may be useful in an emergent situation to assess: 19
- for pericardial and pleural effusion
- heart valves
- cardiac function
- aortic root and ascending aorta
References
References
References are graded from Level I to V according to the Oxford Centre for Evidence-Based Medicine, Levels of Evidence. Download the document
- American College of Radiology. ACR appropriateness criteria. Acute chest pain - suspected aortic dissection. (Guideline).View the reference
- McMahon MA, Squirrell CA. Multidetector CT of aortic dissection: a pictorial review. Radiographics. 2010;30(2):445-60. (Review article).View the reference
- Klompas M. Does this patient have an acute thoracic aortic dissection? JAMA. 2002;287(17):2262-72. (Review article). View the reference
- Erbel R, Aboyans V, Boileau C, Bossone E, Bartolomeo RD, Eggebrecht H, et al. 2014 ESC Guidelines on the diagnosis and treatment of aortic diseases: Document covering acute and chronic aortic diseases of the thoracic and abdominal aorta of the adult. The Task Force for the Diagnosis and Treatment of Aortic Diseases of the European Society of Cardiology (ESC). Eur Heart J. 2014;35(41):2873-926. (Guideline). View the reference
- Moore AG, Eagle KA, Bruckman D, Moon BS, Malouf JF, Fattori R, et al. Choice of computed tomography, transesophageal echocardiography, magnetic resonance imaging, and aortography in acute aortic dissection: International Registry of Acute Aortic Dissection (IRAD). Am J Cardiol. 2002;89(10):1235-8. (Level III evidence). View the reference
- Shiga T, Wajima Z, Apfel CC, Inoue T, Ohe Y Diagnostic accuracy of transesophageal echocardiography, helical computed tomography, and magnetic resonance imaging for suspected thoracic aortic dissection: systematic review and meta-analysis. Arch Intern Med. 2006;166(13):1350-6. (Level I-II evidence). View the reference
- LePage MA, Quint LE, Sonnad SS, Deeb GM, Williams DM Aortic dissection: CT features that distinguish true lumen from false lumen. AJR Am J Roentgenol. 2001;177(1):207-11. (Level III evidence). View the reference
- Thoongsuwan N, Stern EJ. Chest CT scanning for clinical suspected thoracic aortic dissection: beware the alternate diagnosis. Emergency radiology. 2002;9(5):257-61. (Level II evidence). View the reference
- Sommer T, Fehske W, Holzknecht N, Smekal AV, Keller E, Lutterbey G, et al. Aortic dissection: a comparative study of diagnosis with spiral CT, multiplanar transesophageal echocardiography, and MR imaging. Radiology. 1996;199(2):347-52. (Level II-III evidence). View the reference
- Nienaber CA, von Kodolitsch Y, Nicolas V, Siglow V, Piepho A, Brockhoff C, et al. The diagnosis of thoracic aortic dissection by noninvasive imaging procedures. N Engl J Med. 1993;328(1):1-9. (Level II evidence). View the reference
- Keren A, Kim CB, Hu BS, Eyngorina I, Billingham ME, Mitchell RS, et al. Accuracy of biplane and multiplane transesophageal echocardiography in diagnosis of typical acute aortic dissection and intramural hematoma. J Am Coll Cardiol. 1996;28(3):627-36. (Level II evidence). View the reference
- Meredith EL, Masani ND. Echocardiography in the emergency assessment of acute aortic syndromes. Eur J Echocardiogr. 2009;10(1):i31-9. (Review article). View the reference
- Clough RE, Hussain T, Uribe S, Greil GF, Razavi R, Taylor PR, et al. A new method for quantification of false lumen thrombosis in aortic dissection using magnetic resonance imaging and a blood pool contrast agent. J Vasc Surg. 2011;54(5):1251-8. (Level III evidence). View the reference
- Clough RE, Waltham M, Giese D, Taylor PR, Schaeffter T. A new imaging method for assessment of aortic dissection using four-dimensional phase contrast magnetic resonance imaging. J Vasc Surg. 2012;55(4):914-23. (Level III evidence). View the reference
- Mintz GS, Kotler MN, Segal BL, Parry WR. Two dimensional echocardiographic recognition of the descending thoracic aorta. Am J Cardiol. 1979;44(2):232-8. (Level III evidence). View the reference
- Khandheria BK, Tajik AJ, Taylor CL, Safford RE, Miller FA, Jr., Stanson AW, et al. Aortic dissection: review of value and limitations of two-dimensional echocardiography in a six-year experience. J Am Soc Echocardiogr. 1989;2(1):17-24. (Level II-III evidence). View the reference
- Iliceto S, Ettorre G, Francioso G, Antonelli G, Biasco G, Rizzon P. Diagnosis of aneurysm of the thoracic aorta. Comparison between two non invasive techniques: two-dimensional echocardiography and computed tomography. Eur Heart J. 1984;5(7):545-55. (Level IIII evidence). View the reference
- Hiratzka LF, Bakris GL, Beckman JA, Bersin RM, Carr VF, Casey DE, et al. 2010 ACCF/AHA/AATS/ACR/ASA/SCA/SCAI/SIR/STS/SVM Guidelines for the diagnosis and management of patients With thoracic aortic disease. A Report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines, American Association for Thoracic Surgery, American College of Radiology, American Stroke Association, Society of Cardiovascular Anesthesiologists, Society for Cardiovascular Angiography and Interventions, Society of Interventional Radiology, Society of Thoracic Surgeons, and Society for Vascular Medicine. 2010;121(13):e266-e369. (Guideline). View the reference
- Fukui T. Management of acute aortic dissection and thoracic aortic rupture. Journal of Intensive Care. 2018;6:15. (Review article). View the reference
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