Imaging Pearls ❯ Chest ❯ Thoracic Aneurysms and Dissection
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- • Repair of sporadic aortic root and ascending aortic aneurysms when they reach a maximum diameter of 5.5 cm is strongly recommended (SR; nonrandomized studies [NR]); it is reasonable to repair at a diameter of 5.0 cm when care can occur at a high-volume center with management by a multidisciplinary aortic team (MR; NR). It is reasonable to repair the aorta in patients at increased risk of adverse aortic events, and some genetic aortopathies at even lower thresholds (MR; LD).
• All patients with dilated thoracic aorta or thoracic aortic aneurysm (TAA) should have transthoracic echocardiography (TTE) at the time of diagnosis to assess aortic valve anatomy and function (SR; LD).
Diagnosis and Management of Aortic Diseases.
ltenburg MM, Davis AM, DeCara JM.
JAMA. 2024 Jan 23;331(4):352-353. - “A multidisciplinary team should determine the most appropriate type of intervention for patients with acute aortic disease requiring urgent repair(strong recommendation SR; benefit much greater than risk]; expert opinion [EO]). Patients with asymptomatic extensive disease, multiple comorbidities, or who may require complex repairs may be referred to centers with higher case volumes( 30-40cases/y)and a multidisciplinary aortic team(moderatere commendation [MR; benefit greater than risk]; limited data [LD]).”
Diagnosis and Management of Aortic Diseases.
ltenburg MM, Davis AM, DeCara JM.
JAMA. 2024 Jan 23;331(4):352-353. - In a major change, the guideline suggests that it is reasonable to repair sporadic aneurysms of the aortic root or ascending aorta in select patients with low surgical risk when the aneurysm reaches 5.0cm, provided management is at a high-volume center by experienced surgeons as part of a multidisciplinary aortic team. This suggestion is based on observational data from the Multi-Ethnic Study of Atherosclerosis database, which modeled risk of dissection at various aortic diameters relative to 3.4 cm or smaller: aorta diameters were less than 3.5 cm in 79.2%, 3.5 to 3.9 cm in 18.0%, 4.0 to 4.4 cm in 2.6%, and 4.5 cm or greater in 0.22%. Individuals with an aorta larger than 4.5 cm were 6305 times more likely to have aortic dissection than those with an aorta smaller than 3.5 cm. The prior cutoff of 5.5 cm for surgery was based on natural history studies that examined aortic diameter at the time of an adverse event, and supported a strong recommendation to repair aortic root aneurysms or TAAs greater than 5.5 cm in asymptomatic patients.
Diagnosis and Management of Aortic Diseases.
ltenburg MM, Davis AM, DeCara JM.
JAMA. 2024 Jan 23;331(4):352-353. - “Individuals with an aorta larger than 4.5 cm were 6305 times more likely to have aortic dissection than those with an aorta smaller than 3.5 cm. The prior cutoff of 5.5 cm for surgery was based on natural history studies that examined aortic diameter at the time of an adverse event, and supported a strong recommendation to repair aortic root aneurysms or TAAs greater than 5.5 cm in asymptomatic patients.”
Diagnosis and Management of Aortic Diseases.
ltenburg MM, Davis AM, DeCara JM.
JAMA. 2024 Jan 23;331(4):352-353. - “The benefits and harms of these recommendations balance operative risk with risk of spontaneous aortic dissection or rupture. Lower aortic dimension thresholds for surgery will increase the number of and cost associated with surgeries and may raise the risk of additional complications, including coronary artery bypass graft surgery, pacemaker implantation, mechanical circulatory support, and death. The guideline’s focus on higher risk types for screening and management is a potentially significant advance. For example, most genetic aortopathies are currently underdiagnosed and are recognized only after rupture.”
Diagnosis and Management of Aortic Diseases.
ltenburg MM, Davis AM, DeCara JM.
JAMA. 2024 Jan 23;331(4):352-353. - “There commendation for exercise limits deserves additional supportive evidence, as it is not clear to what degree aortic dissections are precipitated by increased wall stress or decreased wall strength. The recommendation of referrals to high-volume centers for certain complex asymptomatic patients may face insurance and travel barriers. Studies are needed to better stratify which patients merit travel to high-volume centers. Similarly, prospective studies show that despite a lower overall incidence, women appear to have a 2- to 3-fold increased risk of fatal aortic rupture relative to men (hazard ratio, 2.60; 95%CI, 1.58-4.29; P < .001). Determining sex specific surgical thresholds for aneurysms of the aortic root and TAA are a high priority for future investigation.”
Diagnosis and Management of Aortic Diseases.
ltenburg MM, Davis AM, DeCara JM.
JAMA. 2024 Jan 23;331(4):352-353.
- “Type A aortic dissection is a surgical emergency occurring when an intimal tear in the aorta creates a false lumen in the ascending aorta. Prompt diagnosis and surgical treatment are imperative to optimize outcomes. Surgical repair requires replacement of the ascending aorta with or without aortic root or aortic arch replacement. Surgical outcomes for this highly lethal diagnosis have improved, with contemporary survival to discharge at Centers of Excellence of 85% to 90%. Survival is related to prompt treatment, preexisting medical comorbidities, presence or absence of end organ malperfusion, extent of aortic repair required, and the development of postoperative complications.”
Acute Type A Aortic Dissection.
Elsayed RS1, Cohen RG1, Fleischman F1, Bowdish ME2.
Cardiol Clin. 2017 Aug;35(3):331-345 - “The aorta is a conduit that extends from the left ventricle that delivers pulsatile blood distally to organs and tissue beds. Acute dissection of the ascending aorta is a lethal disease that requires prompt diagnosis and surgical intervention. Once almost exclusively a postmortem diagnosis, improvements in the accuracy of diagnostic modalities, anesthetic techniques, extracorporeal perfusion, methods of end organ protection during aortic replacement, types of prosthetic grafts, surgical techniques, and critical care have markedly improved outcomes over the last 40 years.”
Acute Type A Aortic Dissection.
Elsayed RS1, Cohen RG1, Fleischman F1, Bowdish ME2.
Cardiol Clin. 2017 Aug;35(3):331-345 - “If the dissection involves the ascending aorta, it is a Stanford type A. If the ascending aorta proximal to the innominate artery is not involved in the process, the dissection is called a Stanford type B. The less commonly used DeBakey classification system was initially proposed in 1955 and then modified in 1965 and 1982 to correspond more closely with the Stanford classification system based on whether the ascending aorta was involved regardless of the site of the intimal tear or distal extent of the dissection.DeBakey type I and II dissections both involve the ascending aorta; however, a type I extends beyond the innominate artery, whereas a type II is confined to the ascending aorta. DeBakey type I and II dissections both correspond to a Stanford type A dissection. A DeBakey type III dissection corresponds to a Stanford type B dissection, where the ascending aorta proximal to the innominate artery is not involved.”
Acute Type A Aortic Dissection.
Elsayed RS1, Cohen RG1, Fleischman F1, Bowdish ME2.
Cardiol Clin. 2017 Aug;35(3):331-345 - “Aortic dissection is the most common and disastrous event to affect the aorta. It occurs nearly 3 times as frequently as rupture of abdominal aortic aneurysms in the United States.Studies of acute aortic syndromes recorded at tertiary care centers suggest that type A aortic dissection remains the most frequently transferred emergency through regional rapid transport systems.It occurs with a greater frequency than type B aortic dissections, while both types occur more frequently in men in the sixth decade of life. Women with aortic dissection are more likely to present at an older age than men and to have atypical symptoms, which often delays the diagnosis and subsequent treatment, leading to higher mortality in some studies.”
Acute Type A Aortic Dissection.
Elsayed RS1, Cohen RG1, Fleischman F1, Bowdish ME2.
Cardiol Clin. 2017 Aug;35(3):331-345 - “Aortic dissection is the most common and disastrous event to affect the aorta. It occurs nearly 3 times as frequently as rupture of abdominal aortic aneurysms in the United States.Studies of acute aortic syndromes recorded at tertiary care centers suggest that type A aortic dissection remains the most frequently transferred emergency through regional rapid transport systems.It occurs with a greater frequency than type B aortic dissections, while both types occur more frequently in men in the sixth decade of life.”
Acute Type A Aortic Dissection.
Elsayed RS1, Cohen RG1, Fleischman F1, Bowdish ME2.
Cardiol Clin. 2017 Aug;35(3):331-345 
- Risk factors for aortic dissection
Lifestyle and cardiovascular risk factors
• Long-term hypertension
• Old age
• Dyslipidemia
• Pregnancy-induced hypervolemia
• Weight-lifting
• Smoking
• Cocaine abuse - Risk factors for aortic dissection
Congenital and connective tissue disorders
• Bicuspid aortic valve
• Marfan syndrome
• Loeys-Dietz syndrome
• Ehlers-Danlos syndrome
• Turner syndrome - Risk factors for aortic dissection
Trauma-Aortic transection
• Motor vehicle deceleration injury
• Falling from height - Risk factors for aortic dissection
Iatrogenic
• Cardiac catheterization
• Arterial cannulation for cardiopulmonary bypass
• Aortic cross-clamping during valvular or aortic surgery
• Intra-aortic balloon pumps - Risk factors for aortic dissection
Vascular inflammation
Autoimmune disease
• Giant cell arteritis
• Takayasu arteritis
• Bechet disease - Risk factors for aortic dissection
Infectious disease
• Syphilis
• Tuberculosis
- TEVAR
- Thoracic endovascular aortic repair
- First reported in 1994 @ Stanford
- Favorable outcomes and reduced complications compared to open repair
- Between 1998 and 2007: 60% rise in thoracic aortic repair concomitant with 6-fold increase in TEVAR - Thoracic Aortic Segments
1. Ascending thoracic aorta can be stented in select patients
- Nonsurgical candidates
- Experienced centers
2. Arch coverage is complicated
- Arch curvature, branches
- Fenestrated, branched grafts
3. Descending thoracic aorta (DTA) - Left Subclavian Coverage
- Occlusion of the left subclavian artery may result in left upper extremity ischemia, stroke or paraplegia
- Branches of the left vertebral artery perfuse the anterior spinal artery
- Preoperative LSA bypass
- Varying practice - Descending Thoracic Aorta
1. Celiac artery coverage if aortic pathology involves abdominal aorta.
- Need preliminary arteriography to confirm patency of the gastroduodenal artery, which provides collateral flow from the superior mesenteric artery after celiac occlusion.
2. SMA stenosis may dictate SMA stent - Role of Radiologist
1. Critical pre-procedural analyses
- Location and extent of the pathology
- Requirement for branch vessel occlusion
- Risk of spinal cord ischemia
2. Identify risk factors for deployment failure and endoleak
- Angulation, tortuousity, calcification, caliber
3. Provide information to guide stent selection
4. Post-stent imaging - CT Post-TEVAR
1. Confirm stent positioning
2. Confirm exclusion of aortic pathology
3. Identify potential complications
- endoleak
- arterial branch occlusion
- stent collapse
- migration - Endoleaks
1. 3-29%
2. Risk factors include
- Aortic morphology
- Length of proximal landing zone
- Patient age
- Type of stent graft - Endoleaks
1. Type I: proximal or distal end of stent
- typically enhance on the arterial phase
2. Type II: perfusion of left subclavian (IIs) or intercostal or bronchial branch (IIo)
- seen on arterial and venous phase
3. Type III is a defect in the graft material or at the junction of overlapping grafts - Other Complications
1. Migration occurs in 3% at 12 months
2. Endograft infection is rare
- may necessitate surgical intervention
- high risk of mortality
3. Stent collapse
4. Retrograde type A dissection of ascending aorta proximal to the stent
5. Aneurysm formation distal to descending aortic dissection
- “ In the setting of undifferentiated chest pain, CT Angiography (CTA) with its high sensitivity and specificity can be considered the modality of choice to diagnose suspected PE or aortic pathology such as aortic dissection or aneurysm.”
ACR Appropriateness Criteria Acute Chest Pain-Low Probability of Coronary Artery Disease
Hoffman U et al.
J Am Coll Radiol 2012;9:745-750 - “ Most important, in this low-risk population, cardiac CTA has nearly perfect negative predictive value to rule out significant CAD. Multidetector CT is also the primary method for diagnosing coronary anomalies, a rare cause of acute chest pain.”
ACR Appropriateness Criteria Acute Chest Pain-Low Probability of Coronary Artery Disease
Hoffman U et al.
J Am Coll Radiol 2012;9:745-750 - “ With advanced CT technology, it is possible to perform a single phase triple rule out examination allowing comprehensive assessment of CAD, aortic dissection, and PE. However, its efficiency or effectiveness has not been demonstrated.”
ACR Appropriateness Criteria Acute Chest Pain-Low Probability of Coronary Artery Disease
Hoffman U et al.
J Am Coll Radiol 2012;9:745-750
- Ductus Aneurysm: Facts
- Most common mechanism is failure of closure of the aortic side of the ductus arteriosus
- In adults may present with cough, dyspnea, or dysphonia
- Can be confused with traumatic aneurysm of the aorta but that is usually located in the posterior part of the arch distal to the origin of the left subclavian artery
- Calcifications are not uncommon in ductus aneurysms - “Aneurysm of the ductus arteriosus is a very rare congenital lesion in adults that can be associated with thromboembolism, rupture, and death. Its detection in a silent clinical phase is very important for planning appropriate treatment and avoiding potentially fatal complications.”
Incidental detection of a giant ductus arteriosus aneurysm by low-dose multidetector computed tomography in an asymptomatic adult
Pontone G et al.
J Vasc Surg Vol 5;5 pg 1260-1264 May 2010
"Most IBPs show complete resorption over time (32 of 56 957%) or have incmplete resorption (16 of 56 (29%) during a median follow-up of 33.8 months: the presence of IBP was not associated with poor prognosis."
Intramural Blood Pools Accompanying Aortic Intramural hematoma: CT Appearance and Natural Course
Wu MT et al.
Radiology 2011;258:705-713"IBP is an intramural contrast medium filled pool with a tiny intimal orifice and/or a connection with an intercostal or lumbar artery in a IMH: IBP is morphologically distinct from an ulcerlike projection (ULP) which has a wider intimal opening to the lumen."
Intramural Blood Pools Accompanying Aortic Intramural hematoma: CT Appearance and Natural Course
Wu MT et al.
Radiology 2011;258:705-713"In patients with aortic IMH, IBP is not an uncommom finding: IBP is associated with a relatively benign clinical course that shows complete resorption or stability in most patients (86%)."
Intramural Blood Pools Accompanying Aortic Intramural hematoma: CT Appearance and Natural Course
Wu MT et al.
Radiology 2011;258:705-713" Intramural blood pools (IBP) are frequently observed at multidetector CT in patients with intramural hematoma (IMH). They may resolve over time or appear during follow-up. These findings are not associated with a poor prognosis, and IBPs should be distinguished from ulcerlike projections."
Intramural Blood Pools Accompanying Aortic Intramural hematoma: CT Appearance and Natural Course
Wu MT et al.
Radiology 2011;258:705-713"A total of 65.9% of patients had both normal aortic arch branching patterns and normal venous anatomy. Variants in the aortic arch branching pattern were present in 32.4% and anomalies in 1.5%. Venous anomalies were present in 0.7%."
Variants and Anomalies of Thoracic Vasculature on Computed Tomographic Angiography in Adults
Berko NS et al.
J Comput Assist Tomogr 2009;33: 523-528- Aortic Arch Vessel Mapping
- Normal arch branching seen in 65% of cases ( separate origins of brachiocephalic, left common carotid, left subclavian)
- Bovine arch branching is seen in 27% of cases (common origin of brachiocephalic and left carotid artery)
- Other variations are seen in 8% of cases and include left vertebral artery off the arch, right aortic arch, aberrant right subclavian artery) - Maximum Aortic Diameter
Segment Size Ascending 4 Descending 3 Abdominal 2 - Aortic Arch Anatomy: Variations
- 3 branches; right innominate, left carotid, left subclavian (70% of patients)
- 2 branches; right innominate and left subclavian arise from a common trunk, left suclavian (30%)
- Left vertebral aa arises off arch between left carotid and left subclavian (5%) - Stanford Type B Dissection
- Involves the descending aorta distal to the left subclavian artery
- Accounts for 30-40% of cases
- Usually managed conservatively
- Surgery required including ruptured aorta, aneurysm over 6 cm, poor perfusion of mesenteric vessels or renal arteries, distal embolization - Stanford Type A Dissection
- Involves ascending aorta and may extend into the descending aorta
- Account for 60-70% of cases
- Requires surgical intervention
- Mortality rate of up to 50% at 48 hours if untreated "Multidetector CT allows the early recognition and characterization of aortic dissection as well as determination of the presence of any associated complications, findings that are essential for optimizing treatment and improving clinical outcomes."
Multidetector CT of Aortic Dissection: A Pictorial Review
McMahon MA, Squirrell CA
RadioGraphics 2010; 30:445-460- Why do we gate evaluation of the thoracic aorta?
- Quality evaluation of the entire thoracic aorta including the aortic sinus and aortic valve
- Definition of the coronary arteries especially in the proximal portions of the coronaary vessels "Optimal image quality for either technique is obtained with a relatively slow heart rate, which may require beta-blocker medication."
Prospective and Retrospective ECG Gating for Thoracic CT Angiography: A Comparitive Study
Wu W et al.
AJR 2009;193:955-963"Compared with retrospective ECG-gated thoracic CT angiography, prospective ECG-gated thoracic CT angiography was associated with a lower radiation dose, slightly increased contrast load, increased aortic attenuation values, and equivalent image quality."
Prospective and Retrospective ECG Gating for Thoracic CT Angiography: A Comparitive Study
Wu W et al.
AJR 2009;193:955-963- When do you electively operate on thoracic aortic aneuysms?
- Ascending aorta exceeding 5.5 cm
- Descending aorta exceeding 6.5 cm
- Increase in aneurysm size of greater than 1 cm in one year
- Dilated Sinus of Valsalva: Differential Dx
- Marfan’s syndrome (most common)
- Homocystinuria
- Ehlers-Danlos syndrome
- Osteogenic imperfecta
- Idiopathic
"Although the aortic diameter increases slightly with age, the normal diameter of the midascending aorta should always be less than 4 cm, and that of the descending aorta no more than 3 cm."
Multidetector CT of Thoracic Aortic Aneurysms
Agarwal PP,Chughtai A, Matzinger FRK, Kazerooni EA
RadioGraphics 2009; 29:537-552"Multidetector CT angiography is routinely used to evaluate the spectrum of thoracic aortic aneurysms. Knowledge of the causes, significance, imaging appearances, and potential complications of both common and uncommon aortic aneurysms is essential for prompt and accurate diagnosis."
Multidetector CT of Thoracic Aortic Aneurysms
Agarwal PP,Chughtai A, Matzinger FRK, Kazerooni EA
RadioGraphics 2009; 29:537-552"Aortic valve area on CT strongly correlates with echocardiography and has excellent sensitivity and specificity to detect severe stenosis."
Aortic Valve Area on 64-MDCT Correlates with Transesophageal Echocardiography in Aortic StenosisLaBounty TM et al.AJR 2008; 191:1652-1658"Aortic valve area on CT strongly correlates with echocardiography and has excellent sensitivity and specificity to detect severe stenosis. Valve calcification has fair agreement between studies. Valve area and calcification should be reported on CT Angiography in patients with AS."
Aortic Valve Area on 64-MDCT Correlates with Transesophageal Echocardiography in Aortic StenosisLaBounty TM et al.AJR 2008; 191:1652-1658- "Endovascular stent graft repair is less invasive in patients with chronic and acute descending thoracic aortic aneurysm and dissection."
Descending Thoracic Aortic Diseases: Stent-Graft Repair Fattori R et al.
Radiology 2003; 229:176-183 - Stent-Graft Placement in the Thoracic Aorta: Indications
- Descending thoracic aneurysms
- Dissection of descending aorta
- Ulcers in descending aorta
- Repair mycotic aneurysm
- Post-traumatic aortic ruptur - "Multidetector row CT allows reliable assessment of anatomic relationships between the lesion and the aortic branches as well as evaluation of the iliac and femoral arteries (diameter,tortuosity) for vascular access."
Stent-Graft Placement for the Treatment of Thoracic Aortic Disease
Therasse E et al.
RadioGraphicss 2005; 25:157-173 - Thoracic Aorta: Pitfalls in CT Scanning
- False positive dissection due to motion (cardiac and/or respiratory) or streak artifact of SVC
- Aortic root
- Ascending aorta
- Aortic arch - CT of the Thoracic Aorta: Clinical Applications
- Suspected aneurysm or dissection
- Thoracic trauma
- Vasculitis
- Congenital disease (i.e. COA)
- Pre-operative stent planning
- Follow up of stent placement - Scanning Parameters
Scanner type 16 slice MDCT 64 slice MDCT
kVp 120 120
mAs 150-180 130-180
Scan collimati on .75 mm .6
Slice thickness .75 mm .75
Interscan spacing .5 mm .5