Imaging Pearls ❯ Chest ❯ Aorta and Anatomy
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- Upper limits of normal aortic diameter by segment: aortic root 4.0 cm, ascending aorta 4.0 cm or less than 1.5 times the descending aortic diameter, aortic arch 3.5 cm, descending aorta 3.0 cm. The new classification for aortic dissection from 2020 describes the entry tear zone, which determines the dissection type A/B, followed by the subscripts that denote the proximal and distal extensions according to the involved aortic zones. Although penetrating aortic ulcer (PAU) is categorized as part of the acute aortic syndrome , the vast majority of PAUs are asymptomatic. Symptomatic PAU is often associated with aortic wall hemorrhage. Ascending aortic dilation ranges from 4.0 to 4.4 cm, with an aneurysm defined at 4.5 cm.
Preoperative Imaging of the Thoracic Aorta
Zehavit E. Kirshenboim et al.
Radiol Clin N Am - (2024) in press - Aortic diameters vary by age and gender. For simplicity, the following upper limits of normal can be used: aortic root 4.0 cm, ascending aorta 4.0 cm or less than 1.5 times the descending aortic diameter, aortic arch 3.5 cm, descending aorta 3.0 cm. The normal ascending aortic wall thickness is approximately 2 mm.
Preoperative Imaging of the Thoracic Aorta
Zehavit E. Kirshenboim et al.
Radiol Clin N Am - (2024) in press - The aorta dilates with aging at a rate of approximately 0.7 mm per decade in women and 0.9 mm per decade in men. Thickening of the aortic wall and degeneration of the collagen and elastic components lead to aortic dilation, elongation, and tortuosity with advancing age, a process known as arteriosclerosis. Repeated pulsatile stress causes fragmentation of the elastic components in the proximal aorta, replacement by fibrotic tissue, and resultant aortic wall stiffening and increased pulse pressure, increasing the left ventricular workload.
Preoperative Imaging of the Thoracic Aorta
Zehavit E. Kirshenboim et al.
Radiol Clin N Am - (2024) in press - Acute IMH is contained hemorrhage within the aortic media, which can be attributed to PAU, trauma, or thrombosed dissected false lumen with microscopic tears in the intima. IMH accounts for 5% to 15% of AAS cases and occurs more frequently in older patients (60–80 years of age) compared to those with aortic dissection. Other risk factors include hypertension and aortic dilation, with commonly found concomitant abdominal aortic aneurysm. IMH is classified similarly to aortic dissection, with most cases (58%) being a type B.
Preoperative Imaging of the Thoracic Aorta
Zehavit E. Kirshenboim et al.
Radiol Clin N Am - (2024) in press - The two most common forms of inflammatory (noninfectious) aortitis are Takayasu arteritis and giant cell arteritis (GCA). Takayasu (necrotizing) arteritis typically affects females under 40 year old and usually manifests as panaortitis with granulomatous inflammation which may cause stenosis of the inflamed vessels, particularly the arch branches. GCA is more common in patients over 50 year old, is associated with temporal arteritis and polymyalgia rheumatica, syphilis (known as luetic aortopathy), mycobacterium tuberculosis infection, and human immunodeficiency virus. Contrast-enhanced CT is typically the preferred imaging modality for diagnosis, with key radiological findings including aortic wall thickening, periaortic fluid or soft tissue, rapid development of saccular aneurysms, and occasionally, the presence of air within the aortic wall. The term “mycotic aneurysm” refers to aneurysms caused by an infection, which are characterized by a mushroom-shaped appearance, and does not indicates fungal infection.
Preoperative Imaging of the Thoracic
Aorta Zehavit E. Kirshenboim et al.
Radiol Clin N Am - (2024) in press
- Calcific AS is characterized by aortic valve leaflet lipid infiltration and inflammation with subsequent fibrosis and calcification. Symptoms due to severe AS, such as exercise intolerance, exertional dyspnea, and syncope, are associated with a 1-year mortality rate of up to 50% without aortic valve replacement. Echocardiography can detect AS and measure the severity of aortic valve dysfunction. Although progression rates vary, once aortic velocity is higher than 2m/s, progression to severe AS occurs typically within 10 years. Severe AS is defined by an aortic velocity 4m/s or higher, a mean gradient 40mmHg or higher, or a valve area less than or equal to 1.0 cm2. Management of mild to moderate AS andasymptomatic severe AS consists of patient education about the typical progression of disease; clinical and echocardiographic surveillance at intervals of 3 to 5 years for mild AS, 1 to 2 years for moderate AS, and 6 to 12 months for severe AS; and treatment of hypertension, hyperlipidemia, and cigarette smoking as indicated.
Calcific Aortic Stenosis: A Review
Catherine M. Otto, David E. Newby, Graham S. Hillis
JAMA. 2024;332(23):2014-2026. doi:10.1001/jama.2024.16477 - When a patient with severe AS develops symptoms, surgical aortic valve replacement (SAVR) or transcatheter aortic valve implantation (TAVI) is recommended, which restores an average life expectancy; in patients aged older than 70 years with a low surgical risk, 10-year all-cause mortality was 62.7%with TAVI and 64.0% with SAVR. TAVI is associated with decreased length of hospitalization, more rapid return to normal activities, and less pain compared with SAVR. However, evidence supporting TAVI for patients aged younger than 65 years and long-term outcomes of TAVI are less well defined than for SAVR. For patients with symptomatic severe AS, the 2020 American College of Cardiology/American Heart Association guideline recommends SAVR for individuals aged 65 years and younger, SAVR or TAVI for those aged 66 to 79 years, and TAVI for individuals aged 80 years and older or those with an estimated surgical mortality of 8%or higher.
- “Aortic stenosis (AS), defined as valve leaflet disease with left ventricular (LV) outflow obstruction, is most commonly caused by calcification of a congenital bicuspid or normal trileaflet valve, although AS due to rheumatic heart disease occurs in areas of the world where rheumatic fever is endemic. Diagnosing AS may be challenging because symptoms of exercise intolerance, dyspnea on exertion, and dizziness occur late in the disease course and may be caused by other cardiac diseases, such as heart failure, or by pulmonary conditions, such as asthma or chronic obstructive pulmonary disease (COPD). Physical examination is not reliable for detection of Asor evaluation of Asseverity. Once patients develop symptoms, severe AS is associated with an annual mortality rate as high as 50% if not treated promptly with valve replacement.”
Calcific Aortic Stenosis: A Review
Catherine M. Otto, David E. Newby, Graham S. Hillis
JAMA. 2024;332(23):2014-2026. doi:10.1001/jama.2024.16477 - Current American College of Cardiology/American Heart Association (ACC/AHA) and European Society of Cardiology (ESC) guidelines strongly recommend prompt SAVR or TAVI in adults with symptoms due to severe AS (Figure 3). This recommendation is based on the high mortality rate associated with severe symptomatic AS, which was 50.7%at 1 year with standard medical care vs 30.7% with TAVI in the PARTNER RCT of 358 patients with AS who were not candidates for aortic valve surgery (HR [death with TAVI vs medical care], 0.55 [95%CI, 0.40-0.74]; P < .001). However, a palliative care approach may be more appropriate for patients with limited life expectancy (defined as less than 1 year) or those whose quality of life is unlikely to improve even after valve replacement, such as those with severe dementia or other substantial comorbidities.
Calcific Aortic Stenosis: A Review
Catherine M. Otto, David E. Newby, Graham S. Hillis
JAMA. 2024;332(23):2014-2026. doi:10.1001/jama.2024.16477 - “Calcific AS is a common chronic progressive condition among adults older than 65 years and is diagnosed via echocardiography. Symptomatic patients with severe AS have a mortality rate of up to 50% after 1 year, but treatment with SAVR or TAVI reduces mortality to that of age-matched control patients. The type and timing of valve replacement should be built on evidence-based professional society guidelines, shared decision-making, and involvement of a multidisciplinary heart valve team.”
Calcific Aortic Stenosis: A Review
Catherine M. Otto, David E. Newby, Graham S. Hillis
JAMA. 2024;332(23):2014-2026. doi:10.1001/jama.2024.16477
- “The IMA is an elastic artery which arises from the subclavian artery. In adults the diameter of the IMA varies from 1.9 to 2.6 mm, with a wall thickness of 180 to 430 microns. The intima consists of endothelium with some neointima, which is seen in up to 50% of cases and rarely (13%) is there a substantial neointima which is greater than the medial thickness. The media consists of discreet lamellae of collagen and smooth muscle cells (SMCs) that are located between the elastic layers and are aligned circumferentially. The number of elastic layers varies from 7 to 11, depending upon the thickness of the wall of the IMA. The adventitia has been shown to possess very few vasa vasorum.”
Why is the mammary artery so special and what protects it from atherosclerosis?
Fumiyuki Otsuka, Kazuyuki Yahagi, Kenichi Sakakura, Renu Virmani
Ann Cardiothorac Surg 2013;2(4):519-526
- “The IMA is an elastic artery which arises from the subclavian artery. In adults the diameter of the IMA varies from 1.9 to 2.6 mm, with a wall thickness of 180 to 430 microns. The intima consists of endothelium with some neointima, which is seen in up to 50% of cases and rarely (13%) is there a substantial neointima which is greater than the medial thickness. The media consists of discreet lamellae of collagen and smooth muscle cells (SMCs) that are located between the elastic layers and are aligned circumferentially. The number of elastic layers varies from 7 to 11, depending upon the thickness of the wall of the IMA. The adventitia has been shown to possess very few vasa vasorum.”
Why is the mammary artery so special and what protects it from atherosclerosis?
Fumiyuki Otsuka, Kazuyuki Yahagi, Kenichi Sakakura, Renu Virmani
Ann Cardiothorac Surg 2013;2(4):519-526
- “Thoracic endovascular aortic repair (TEVAR) has evolved as an alternative to open repair for a range of aortic pathology. The earliest endovascular repairs were limited to descending thoracic aortic pathology, but growing experience has resulted in the use of stents in the ascending aorta and aortic arch. This review presents the current literature pertaining to thoracic endoluminal stent repair, with emphasis on the role of intravenous contrast-enhanced multidetector computed tomography, the primary cross-sectional imaging modality used in these patients. Radiologists play an integral role in patient selection, procedural planning, and postprocedural follow-up.”
Thoracic endovascular aortic repair: literature review with emphasis on the role of multidetector computed tomography
Johnson PT, Black JH, Zimmerman SL, Fishman EK
Semin Ultrasound CT MR 2012 Jun; 33(3):247-64 - “This review presents the current literature pertaining to thoracic endoluminal stent repair, with emphasis on the role of intravenous contrast-enhanced multidetector computed tomography, the primary cross-sectional imaging modality used in these patients. Radiologists play an integral role in patient selection, procedural planning, and postprocedural follow-up.”
Thoracic endovascular aortic repair: literature review with emphasis on the role of multidetector computed tomography
Johnson PT, Black JH, Zimmerman SL, Fishman EK
Semin Ultrasound CT MR 2012 Jun; 33(3):247-64
- “C” - Double aortic arch
- Rare anomaly caused by persistence (to varying degree) of the fetal double aortic arch system.
- The ascending aorta divides into two arches that pass to either side of the esophagus and trachea and reunite to form the descending aorta.
- Form of complete vascular ring, resulting in noncardiac morbidity, but rarely associated with intracardiac defects.
- The descending aorta is usually on the left side.
- Most commonly, one arch is dominant, whereas the other may be of small caliber or represented by a fibrous band - “A” - Right AA with mirror image branching
The mirror-image type of the right aortic arch (left brachiocephalic trunk, right common carotid and subclavian arteries) is almost always associated with congenital heart disease, especially the cyanotic type. - “B” - Right AA with aberrant left subclavian artery
- Right aortic arch is an uncommon anatomical anomaly that occurs in <0.1% of the population.
- The most common type is the right aortic arch with an aberrant left subclavian artery
- The vessels originate in the following order: left common carotid, right common carotid, right subclavian, and left subclavian artery.
- Symptoms may arise from vascular ring formation as congenital heart disease is rare in this variant. - “D” - Left AA with aberrant right subclavian artery
- The right subclavian artery is the last branch of the aortic arch in l% of individuals.
- It courses to the right behind the esophagus in 80% of these cases, between the esophagus
and trachea in 15%, and anterior to the trachea or mainstem bronchus in 5%.
- A retroesophageal course may be the cause of so-called dysphagia lusoria.
- Another variant - aberrant right brachiocephalic artery is rare - Vascular Ring Hierarchy
- If abnormal combination of derivatives of the aortic arch system results in encirclement of
the trachea and the esophagus it is often referred to as “vascular ring”.
- International Congeital Heart Surgery Nomenclature And Database Committee
Classification:
- Double aortic arch
- Right arch dominant
- Left arch dominant
- Balanced arches
- Right aortic arch–left ligamentum
- Mirror-image branching
- Retroesophageal left subclavian artery
- Circumflex aorta
- Pulmonary artery sling - Normal Anatomy
- Predominant human anatomy is a left aortic arch with three great vessels; first, the
brachiocephalic trunk, then the left common carotid artery and finally the subclavian artery.
This pattern occurs in 65-80% of the cases.
- A common brachiocephalic trunk, so-called “bovine trunk”, in which both common carotid
arteries and the right subclavian artery arise from a single trunk off the arch, occurs in 10 to
22% of individuals and accounts for more than two thirds of all arch vessel anomalies. - Double Aortic Arch: Facts
- Most common symptomatic vascular aortic arch
- The right arch is larger , posterior, ad more cephalad than the left arch in two thirds of patients and the descending aorta is usually contralateral to the dominant arch
- Trachea compression is common
- Descending aortic diverticulum (Kommerell) is not uncommon - Aberrant left subclavian artery: facts
- Left subclavian arise as last arch vessel and crosses right to left (patient has right sided arch) and posterior to the esophagus
- Bulblike dilatation of abberrant subclavian can occur and is called diverticulum of Kommerell
- When large the diverticulum of Kommerell can cause symptoms of dysphagia - Aortic Arch Anomalies
- Aberrant left subclavian artery
- Mirror image branching
- Right aortic arch with left descending aorta
- Right aortic arch with aberrant branchiocephalic artery
- Right aortic arch with isolated left subclavian artery
- Double aortic arch
- Cervical aortic arch - Anomalies of the Aortic Arch: facts
- Frequency ranges from 0.5% to 3%
- Most patients asymptomatic though others may have dysphagia, dyspnea, hypertension or congestive heart failure
- Right aortic arch occurs in 0.1% of adults
- There are 6 paired arteries arising from the aortic sac during embryogenesis with the fourth left arch forming the aortic arch - CT of the Bronchial Arteries
- The bronchial arteries arise directly from the descending aorta and supply blood to the airways, esophagus and lymph nodes
- The left bronchial arteries arise from the anterior surface of the aorta or the concavity of the arch
- The right bronchial arteries arise from the posterolateral aspect of the thoracic aorta - Massive Hemoptysis: Common Etiologies
- Pulmonary TB
- Bronchogenic carcinoma
- Cystic fibrosis
- Aspergillosis Lung abscess
- Pneumonia
- Pulmonary artery aneurysm