Thoracic Aortic Aneurysms

Overview

Definitions

Thoracic aortic aneurysm (TAA)

• Dilation of the thoracic aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy by > 50% of its normal diameter
• Diameter affected by age, sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria, and body surface area
• Ascending aortic aneurysm: approximately > 5 cm
• Descending aortic aneurysm: approximately > 4 cm

Types

• True aneurysm: dilation of the aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy by > 50% of normal diameter, involving all 3 layers (intima, media, adventitia)
  • Fusiform-shaped: bulges on all sides of the aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy (more common)
  • Saccular-shaped: bulges on one side 
• Pseudoaneurysm:
  • Dilation caused by a disruption of the aortic wall
  • Extravasated blood contained by periarterial connective tissue Connective tissue Connective tissues originate from embryonic mesenchyme and are present throughout the body except inside the brain and spinal cord. The main function of connective tissues is to provide structural support to organs. Connective tissues consist of cells and an extracellular matrix. Connective Tissue: Histology, not by all wall layers
  • Extravascular hematoma Hematoma A collection of blood outside the blood vessels. Hematoma can be localized in an organ, space, or tissue. Intussusception communicates with intravascular space.

Location

• Ascending aorta Ascending aorta Mediastinum and Great Vessels: Anatomy: area from aortic annulus to the innominate artery/brachiocephalic trunk 
• Aortic arch Aortic arch Mediastinum and Great Vessels: Anatomy: area where innominate artery, left carotid, and left subclavian artery originate
• Descending aorta Descending aorta Mediastinum and Great Vessels: Anatomy: beyond left subclavian artery
• Thoracoabdominal aortic aneurysms: most descending TAAs are contiguous with abdominal aortic aneurysms (AAAs).

Epidemiology

• TAA: 15th-leading cause of death for patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship > 65 years old
• TAAs are less common than AAAs.
• 60% of TAAs are localized in the ascending aorta Ascending aorta Mediastinum and Great Vessels: Anatomy
• Majority of TAAs are degenerative, so risk factors include smoking Smoking Willful or deliberate act of inhaling and exhaling smoke from burning substances or agents held by hand. Interstitial Lung Diseases, hypertension Hypertension Hypertension, or high blood pressure, is a common disease that manifests as elevated systemic arterial pressures. Hypertension is most often asymptomatic and is found incidentally as part of a routine physical examination or during triage for an unrelated medical encounter. Hypertension, and hypercholesterolemia Hypercholesterolemia A condition with abnormally high levels of cholesterol in the blood. It is defined as a cholesterol value exceeding the 95th percentile for the population. Lipid Disorders.
• More common in men and in those of advanced age

Etiology

• Degenerative disorders:
  • Most common cause of AAA AAA An aortic aneurysm is the abnormal dilation of a segment of the aorta. Abdominal aortic aneurysm is the most common aortic aneurysm, occurring frequently in the infrarenal area. Most aneurysms are asymptomatic, but can cause compression of surrounding structures or rupture, which is a life-threatening emergency. Abdominal Aortic Aneurysms and TAA
  • Risk factors:
    • Atherosclerosis Atherosclerosis Atherosclerosis is a common form of arterial disease in which lipid deposition forms a plaque in the blood vessel walls. Atherosclerosis is an incurable disease, for which there are clearly defined risk factors that often can be reduced through a change in lifestyle and behavior of the patient. Atherosclerosis
    • Hypertension Hypertension Hypertension, or high blood pressure, is a common disease that manifests as elevated systemic arterial pressures. Hypertension is most often asymptomatic and is found incidentally as part of a routine physical examination or during triage for an unrelated medical encounter. Hypertension
    • Advanced age
    • Hypercholesterolemia Hypercholesterolemia A condition with abnormally high levels of cholesterol in the blood. It is defined as a cholesterol value exceeding the 95th percentile for the population. Lipid Disorders
    • Cigarette smoking Smoking Willful or deliberate act of inhaling and exhaling smoke from burning substances or agents held by hand. Interstitial Lung Diseases
• Genetic or developmental disorders:
  • Most common cause of TAA in patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship < 65 years old
  • Disorders:
    • Marfan’s syndrome
    • Turner’s syndrome
    • Ehlers-Danlos syndrome Ehlers-Danlos syndrome Ehlers-Danlos syndrome (EDS) is a heterogeneous group of inherited connective tissue disorders that are characterized by hyperextensible skin, hypermobile joints, and fragility of the skin and connective tissue. Ehlers-Danlos Syndrome
    • Bicuspid aortic valve Aortic valve The valve between the left ventricle and the ascending aorta which prevents backflow into the left ventricle. Heart: Anatomy
    • Loeys-Dietz syndrome
    • Familial thoracic aortic aneurysm and dissection (TAAD) 
• Vasculitis Vasculitis Inflammation of any one of the blood vessels, including the arteries; veins; and rest of the vasculature system in the body. Systemic Lupus Erythematosus
  • Giant cell arteritis Giant Cell Arteritis Giant cell arteritis (GCA), also known as temporal arteritis, is a type of large-vessel vasculitis that predominantly affects the aorta and its major branches, with a predilection for the branches of the carotid (including the temporal artery). Giant cell arteritis is defined by inflammatory leukocytes in the vessel walls leading to reactive damage, ischemia, and necrosis. Giant Cell Arteritis (most common inflammatory cause of TAA)
  • Takayasu’s arteritis Takayasu’s arteritis A chronic inflammatory process that affects the aorta and its primary branches, such as the brachiocephalic artery (brachiocephalic trunk) and carotid arteries. It results in progressive arterial stenosis, occlusion, and aneurysm formation. The pulse in the arm is hard to detect. Patients with aortitis syndrome often exhibit retinopathy. Vasculitides
  • Rheumatoid arthritis Arthritis Acute or chronic inflammation of joints. Osteoarthritis
  • Spondyloarthritides
  • Behcet’s disease
• Infection
  • Syphilis Syphilis Syphilis is a bacterial infection caused by the spirochete Treponema pallidum pallidum (T. p. pallidum), which is usually spread through sexual contact. Syphilis has 4 clinical stages: primary, secondary, latent, and tertiary. Syphilis (tertiary)
  • Tuberculosis Tuberculosis Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis complex bacteria. The bacteria usually attack the lungs but can also damage other parts of the body. Approximately 30% of people around the world are infected with this pathogen, with the majority harboring a latent infection. Tuberculosis spreads through the air when a person with active pulmonary infection coughs or sneezes. Tuberculosis
  • Mycotic aneurysm Mycotic aneurysm Aspergillus/Aspergillosis ( Salmonella Salmonella Salmonellae are gram-negative bacilli of the family Enterobacteriaceae. Salmonellae are flagellated, non-lactose-fermenting, and hydrogen sulfide-producing microbes. Salmonella enterica, the most common disease-causing species in humans, is further classified based on serotype as typhoidal (S. typhi and paratyphi) and nontyphoidal (S. enteritidis and typhimurium). Salmonella, staphylococcal, streptococcal, fungal infection)
• Trauma

Pathophysiology

Contributing factors

• Embryology:
  • Embryologic origin can affect response of aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy to stimuli (growth factors and cytokines Cytokines Non-antibody proteins secreted by inflammatory leukocytes and some non-leukocytic cells, that act as intercellular mediators. They differ from classical hormones in that they are produced by a number of tissue or cell types rather than by specialized glands. They generally act locally in a paracrine or autocrine rather than endocrine manner. Adaptive Immune Response).
  • Ascending aorta Ascending aorta Mediastinum and Great Vessels: Anatomy and aortic arch Aortic arch Mediastinum and Great Vessels: Anatomy: derived from neural crest cells Neural crest cells Gastrulation and Neurulation
  • Descending aorta Descending aorta Mediastinum and Great Vessels: Anatomy: derived from mesoderm Mesoderm The middle germ layer of an embryo derived from three paired mesenchymal aggregates along the neural tube. Gastrulation and Neurulation
• Genetics Genetics Genetics is the study of genes and their functions and behaviors. Basic Terms of Genetics:
  • 20% from genetic syndromes (Marfan’s syndrome, Ehlers-Danlos syndrome Ehlers-Danlos syndrome Ehlers-Danlos syndrome (EDS) is a heterogeneous group of inherited connective tissue disorders that are characterized by hyperextensible skin, hypermobile joints, and fragility of the skin and connective tissue. Ehlers-Danlos Syndrome)
• Structure and growth of artery:
  • Wall thickness of aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy decreases from the thoracic area to the distal aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy
  • Thoracic aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy:
    • Greater elastin and collagen Collagen A polypeptide substance comprising about one third of the total protein in mammalian organisms. It is the main constituent of skin; connective tissue; and the organic substance of bones (bone and bones) and teeth (tooth). Connective Tissue: Histology content than AAA AAA An aortic aneurysm is the abnormal dilation of a segment of the aorta. Abdominal aortic aneurysm is the most common aortic aneurysm, occurring frequently in the infrarenal area. Most aneurysms are asymptomatic, but can cause compression of surrounding structures or rupture, which is a life-threatening emergency. Abdominal Aortic Aneurysms
    • Has avascular Avascular Corneal Abrasions, Erosion, and Ulcers and vascular zones in media
    • Grows by ↑ number of lamellar units (elastin, collagen Collagen A polypeptide substance comprising about one third of the total protein in mammalian organisms. It is the main constituent of skin; connective tissue; and the organic substance of bones (bone and bones) and teeth (tooth). Connective Tissue: Histology, vascular smooth muscle cells): more lamellar units
• Atherosclerosis Atherosclerosis Atherosclerosis is a common form of arterial disease in which lipid deposition forms a plaque in the blood vessel walls. Atherosclerosis is an incurable disease, for which there are clearly defined risk factors that often can be reduced through a change in lifestyle and behavior of the patient. Atherosclerosis:
  • TAA can occur without plaque Plaque Primary Skin Lesions deposition.
  • In TAA: low likelihood of progression of fatty streak to atheroma
• Inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation:
  • Affects both TAA and AAA AAA An aortic aneurysm is the abnormal dilation of a segment of the aorta. Abdominal aortic aneurysm is the most common aortic aneurysm, occurring frequently in the infrarenal area. Most aneurysms are asymptomatic, but can cause compression of surrounding structures or rupture, which is a life-threatening emergency. Abdominal Aortic Aneurysms
  • Predominantly T cells T cells Lymphocytes responsible for cell-mediated immunity. Two types have been identified – cytotoxic (t-lymphocytes, cytotoxic) and helper T-lymphocytes (t-lymphocytes, helper-inducer). They are formed when lymphocytes circulate through the thymus gland and differentiate to thymocytes. When exposed to an antigen, they divide rapidly and produce large numbers of new T cells sensitized to that antigen. T cells: Types and Functions and macrophages Macrophages The relatively long-lived phagocytic cell of mammalian tissues that are derived from blood monocytes. Main types are peritoneal macrophages; alveolar macrophages; histiocytes; kupffer cells of the liver; and osteoclasts. They may further differentiate within chronic inflammatory lesions to epithelioid cells or may fuse to form foreign body giant cells or langhans giant cells. Innate Immunity: Phagocytes and Antigen Presentation; TAA noted to have proinflammatory cytokines Proinflammatory Cytokines Metabolic Syndrome
• Proteolysis by matrix metalloproteinases Matrix metalloproteinases A family of zinc-dependent metalloendopeptidases that is involved in the degradation of extracellular matrix components. Hypertrophic and Keloid Scars (MMPs):
  • ↑ Breakdown of extracellular matrix Extracellular matrix A meshwork-like substance found within the extracellular space and in association with the basement membrane of the cell surface. It promotes cellular proliferation and provides a supporting structure to which cells or cell lysates in culture dishes adhere. Hypertrophic and Keloid Scars
  • In TAA: MMP-9 (from fibroblasts Fibroblasts Connective tissue cells which secrete an extracellular matrix rich in collagen and other macromolecules. Sarcoidosis and smooth muscle cells)

Pathogenesis

• Regular Regular Insulin vascular remodeling Vascular remodeling The active alterations of vascular wall structures, often leading to elevated vascular resistance. It is associated with aging; atherosclerosis; diabetes mellitus; hypertension; pregnancy; pulmonary hypertension; and stroke, but is also a normal part of embryogenesis. Cor Pulmonale ( synthesis Synthesis Polymerase Chain Reaction (PCR), degradation, and repair) of extracellular matrix Extracellular matrix A meshwork-like substance found within the extracellular space and in association with the basement membrane of the cell surface. It promotes cellular proliferation and provides a supporting structure to which cells or cell lysates in culture dishes adhere. Hypertrophic and Keloid Scars (ECM) components maintain the functional and structural integrity of the artery.
• Above factors, in combination with age and environment (i.e., smoking Smoking Willful or deliberate act of inhaling and exhaling smoke from burning substances or agents held by hand. Interstitial Lung Diseases, infection, trauma) → result in breakdown of ECM → arterial medial degeneration → weakened vascular wall → dilation
• The dilation + rapid expansion of aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy: ↑ risk of rupture or aortic dissection Aortic dissection Aortic dissection occurs due to shearing stress from pulsatile pressure causing a tear in the tunica intima of the aortic wall. This tear allows blood to flow into the media, creating a “false lumen.” Aortic dissection is most commonly caused by uncontrolled hypertension. Aortic Dissection
• Widening of the vessel disrupts laminar blood flow Blood flow Blood flow refers to the movement of a certain volume of blood through the vasculature over a given unit of time (e.g., mL per minute). Vascular Resistance, Flow, and Mean Arterial Pressure → turbulence + inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation→ possible thrombus formation within the vessel (with risk of embolism)

Clinical Presentation

Symptoms

• Commonly asymptomatic (due to slow expansion rate)
• Often discovered on echocardiography Echocardiography Ultrasonic recording of the size, motion, and composition of the heart and surrounding tissues. The standard approach is transthoracic. Tricuspid Valve Atresia (TVA) or computed tomography (CT) scan
• Symptoms indicate expansion of the aneurysm → ↑ rupture or dissection risk
• Ascending aortic aneurysm:
  • Left recurrent laryngeal nerve compression Nerve Compression Brachial Plexus Injuries: hoarse voice
  • Phrenic nerve compression Nerve Compression Brachial Plexus Injuries: hemidiaphragmatic paralysis → shortness of breath Shortness of breath Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea 
  • Tracheobronchial tree compression Compression Blunt Chest Trauma: cough, wheezing Wheezing Wheezing is an abnormal breath sound characterized by a whistling noise that can be relatively high-pitched and shrill (more common) or coarse. Wheezing is produced by the movement of air through narrowed or compressed small (intrathoracic) airways. Wheezing, dyspnea Dyspnea Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea, and hemoptysis Hemoptysis Hemoptysis is defined as the expectoration of blood originating in the lower respiratory tract. Hemoptysis is a consequence of another disease process and can be classified as either life threatening or non-life threatening. Hemoptysis can result in significant morbidity and mortality due to both drowning (reduced gas exchange as the lungs fill with blood) and hemorrhagic shock. Hemoptysis
  • Esophageal compression Compression Blunt Chest Trauma: dysphagia Dysphagia Dysphagia is the subjective sensation of difficulty swallowing. Symptoms can range from a complete inability to swallow, to the sensation of solids or liquids becoming “stuck.” Dysphagia is classified as either oropharyngeal or esophageal, with esophageal dysphagia having 2 sub-types: functional and mechanical. Dysphagia
  • Compression Compression Blunt Chest Trauma of central veins Central Veins Central Venous Catheter or superior vena cava Superior vena cava The venous trunk which returns blood from the head, neck, upper extremities and chest. Mediastinum and Great Vessels: Anatomy (SVC): thromboembolism Thromboembolism Obstruction of a blood vessel (embolism) by a blood clot (thrombus) in the blood stream. Systemic Lupus Erythematosus or SVC syndrome 
  • Aortic regurgitation Regurgitation Gastroesophageal Reflux Disease (GERD) due to aortic root dilatation, annulus distortion Distortion Defense Mechanisms: heart failure Heart Failure A heterogeneous condition in which the heart is unable to pump out sufficient blood to meet the metabolic need of the body. Heart failure can be caused by structural defects, functional abnormalities (ventricular dysfunction), or a sudden overload beyond its capacity. Chronic heart failure is more common than acute heart failure which results from sudden insult to cardiac function, such as myocardial infarction. Total Anomalous Pulmonary Venous Return (TAPVR)
  • Coronary compression Compression Blunt Chest Trauma: chest pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways ( myocardial infarction Myocardial infarction MI is ischemia and death of an area of myocardial tissue due to insufficient blood flow and oxygenation, usually from thrombus formation on a ruptured atherosclerotic plaque in the epicardial arteries. Clinical presentation is most commonly with chest pain, but women and patients with diabetes may have atypical symptoms. Myocardial Infarction)
  • Aortic arch Aortic arch Mediastinum and Great Vessels: Anatomy branch vessel compression Compression Blunt Chest Trauma: neurologic symptoms from cerebrovascular thromboembolism Thromboembolism Obstruction of a blood vessel (embolism) by a blood clot (thrombus) in the blood stream. Systemic Lupus Erythematosus 
• Descending aortic aneurysm:
  • Symptoms occur when dilation is large.
  • Erosion Erosion Partial-thickness loss of the epidermis Generalized and Localized Rashes of the spine Spine The human spine, or vertebral column, is the most important anatomical and functional axis of the human body. It consists of 7 cervical vertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae and is limited cranially by the skull and caudally by the sacrum. Vertebral Column: Anatomy: upper back pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways 
  • Dissection of aneurysm: back pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways or epigastric pain Epigastric pain Mallory-Weiss Syndrome (Mallory-Weiss Tear)
• Aneurysmal rupture:
  • Life-threatening emergency!
  • TAA rupture, often into left chest or pericardium Pericardium A conical fibroserous sac surrounding the heart and the roots of the great vessels (aorta; venae cavae; pulmonary artery). Pericardium consists of two sacs: the outer fibrous pericardium and the inner serous pericardium. The latter consists of an outer parietal layer facing the fibrous pericardium, and an inner visceral layer (epicardium) resting next to the heart, and a pericardial cavity between these two layers. Heart: Anatomy: severe chest pain Severe Chest Pain Flail Chest, hypotension Hypotension Hypotension is defined as low blood pressure, specifically < 90/60 mm Hg, and is most commonly a physiologic response. Hypotension may be mild, serious, or life threatening, depending on the cause. Hypotension, shock Shock Shock is a life-threatening condition associated with impaired circulation that results in tissue hypoxia. The different types of shock are based on the underlying cause: distributive (↑ cardiac output (CO), ↓ systemic vascular resistance (SVR)), cardiogenic (↓ CO, ↑ SVR), hypovolemic (↓ CO, ↑ SVR), obstructive (↓ CO), and mixed. Types of Shock

Signs

• Vital signs:
  • Normal blood pressure if TAA not enlarged
  • Tachycardia Tachycardia Abnormally rapid heartbeat, usually with a heart rate above 100 beats per minute for adults. Tachycardia accompanied by disturbance in the cardiac depolarization (cardiac arrhythmia) is called tachyarrhythmia. Sepsis in Children, hypotension Hypotension Hypotension is defined as low blood pressure, specifically < 90/60 mm Hg, and is most commonly a physiologic response. Hypotension may be mild, serious, or life threatening, depending on the cause. Hypotension in rupture or dissection
• SVC syndrome: facial, neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess, or upper extremity swelling Swelling Inflammation (for vein distention)
• Can have aortic regurgitation Regurgitation Gastroesophageal Reflux Disease (GERD) murmur (early diastolic decrescendo murmur)
• Pulse deficit; peripheral pulses diminished in aneurysmal rupture
• Focal neurologic deficits Neurologic Deficits High-Risk Headaches in cerebrovascular thromboembolic event

Diagnosis

History

• Family history Family History Adult Health Maintenance of aortic pathology
• Risk factors ( hypertension Hypertension Hypertension, or high blood pressure, is a common disease that manifests as elevated systemic arterial pressures. Hypertension is most often asymptomatic and is found incidentally as part of a routine physical examination or during triage for an unrelated medical encounter. Hypertension, smoking Smoking Willful or deliberate act of inhaling and exhaling smoke from burning substances or agents held by hand. Interstitial Lung Diseases, hypercholesterolemia Hypercholesterolemia A condition with abnormally high levels of cholesterol in the blood. It is defined as a cholesterol value exceeding the 95th percentile for the population. Lipid Disorders)
• Known history of aneurysm in other areas (e.g., cerebral aneurysm Cerebral aneurysm Brain aneurysms, also known as intracranial or cerebral aneurysms, are dilations of the arteries along points of weakness in the brain. The majority of the aneurysms are berry (saccular) in nature and located within the anterior circulation of the circle of Willis. Brain Aneurysms)
• Prior aortic dissection Aortic dissection Aortic dissection occurs due to shearing stress from pulsatile pressure causing a tear in the tunica intima of the aortic wall. This tear allows blood to flow into the media, creating a “false lumen.” Aortic dissection is most commonly caused by uncontrolled hypertension. Aortic Dissection
• Aortic valve Aortic valve The valve between the left ventricle and the ascending aorta which prevents backflow into the left ventricle. Heart: Anatomy disease, bicuspid aortic valve Aortic valve The valve between the left ventricle and the ascending aorta which prevents backflow into the left ventricle. Heart: Anatomy
• Other conditions: Marfan’s syndrome, Loeys-Dietz syndrome, Ehlers-Danlos syndrome Ehlers-Danlos syndrome Ehlers-Danlos syndrome (EDS) is a heterogeneous group of inherited connective tissue disorders that are characterized by hyperextensible skin, hypermobile joints, and fragility of the skin and connective tissue. Ehlers-Danlos Syndrome, and other connective tissue Connective tissue Connective tissues originate from embryonic mesenchyme and are present throughout the body except inside the brain and spinal cord. The main function of connective tissues is to provide structural support to organs. Connective tissues consist of cells and an extracellular matrix. Connective Tissue: Histology disease
• Chest trauma

Diagnostic tests Diagnostic tests Diagnostic tests are important aspects in making a diagnosis. Some of the most important epidemiological values of diagnostic tests include sensitivity and specificity, false positives and false negatives, positive and negative predictive values, likelihood ratios, and pre-test and post-test probabilities. Epidemiological Values of Diagnostic Tests

• Chest X-ray X-ray Penetrating electromagnetic radiation emitted when the inner orbital electrons of an atom are excited and release radiant energy. X-ray wavelengths range from 1 pm to 10 nm. Hard x-rays are the higher energy, shorter wavelength x-rays. Soft x-rays or grenz rays are less energetic and longer in wavelength. The short wavelength end of the x-ray spectrum overlaps the gamma rays wavelength range. The distinction between gamma rays and x-rays is based on their radiation source. Pulmonary Function Tests:
  • Widened mediastinum Widened Mediastinum Imaging of the Mediastinum
  • Large aortic knob
  • Deviation or compression Compression Blunt Chest Trauma of trachea Trachea The trachea is a tubular structure that forms part of the lower respiratory tract. The trachea is continuous superiorly with the larynx and inferiorly becomes the bronchial tree within the lungs. The trachea consists of a support frame of semicircular, or C-shaped, rings made out of hyaline cartilage and reinforced by collagenous connective tissue. Trachea: Anatomy or left mainstem bronchus
  • Note: cannot distinguish TAA from a tortuous aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy
• CT or magnetic resonance angiography Angiography Radiography of blood vessels after injection of a contrast medium. Cardiac Surgery ( CTA CTA A non-invasive method that uses a ct scanner for capturing images of blood vessels and tissues. A contrast material is injected, which helps produce detailed images that aid in diagnosing vascular diseases. Pulmonary Function Tests/ MRA MRA Imaging of the Heart and Great Vessels):
  • CT: most widely used test for TAA
  • For diagnosis and preoperative planning
  • Detects aortic diameter, vessel anatomy, dissection, rupture, thrombus
  • In acutely symptomatic patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship, CT is used.
  • MRA MRA Imaging of the Heart and Great Vessels: no ionizing radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma and contrast, but not readily available in some centers
• Transesophageal ( TEE TEE Ultrasonic recording of the size, motion, and composition of the heart and surrounding tissues using a transducer placed in the esophagus. Imaging of the Heart and Great Vessels) or transthoracic echocardiography Transthoracic Echocardiography Imaging of the Heart and Great Vessels ( TTE TTE Imaging of the Heart and Great Vessels):
  • Evaluates aortic valve Aortic valve The valve between the left ventricle and the ascending aorta which prevents backflow into the left ventricle. Heart: Anatomy/other cardiac disease as cardiac motion affects CT/ MRA MRA Imaging of the Heart and Great Vessels
  • TTE TTE Imaging of the Heart and Great Vessels for initial study but TEE TEE Ultrasonic recording of the size, motion, and composition of the heart and surrounding tissues using a transducer placed in the esophagus. Imaging of the Heart and Great Vessels preferred in acute symptoms with hypotension Hypotension Hypotension is defined as low blood pressure, specifically < 90/60 mm Hg, and is most commonly a physiologic response. Hypotension may be mild, serious, or life threatening, depending on the cause. Hypotension
• Arteriography:
  • Shows extent and branch involvement of aneurysm; cannot define size
  • Has risk of contrast adverse reaction/s and radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma

Management

Non-surgical management of aortic aneurysms

• Reduce cardiovascular risk:
  • Smoking Smoking Willful or deliberate act of inhaling and exhaling smoke from burning substances or agents held by hand. Interstitial Lung Diseases cessation
  • Hypertension Hypertension Hypertension, or high blood pressure, is a common disease that manifests as elevated systemic arterial pressures. Hypertension is most often asymptomatic and is found incidentally as part of a routine physical examination or during triage for an unrelated medical encounter. Hypertension control:
    • Blood pressure control recommended in all aortic aneurysms
    • In TAA: beta blockers/angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor Receptor Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors blockers ( ARBs ARBs Agents that antagonize angiotensin receptors. Many drugs in this class specifically target the angiotensin type 1 receptor. Heart Failure and Angina Medication)
    • In Marfan’s syndrome:
      • Should be on beta blockers (to ↓ aortic root dilatation) unless contraindicated 
      • Other option: ARBs ARBs Agents that antagonize angiotensin receptors. Many drugs in this class specifically target the angiotensin type 1 receptor. Heart Failure and Angina Medication 
  • Lipid control with statins Statins Statins are competitive inhibitors of HMG-CoA reductase in the liver. HMG-CoA reductase is the rate-limiting step in cholesterol synthesis. Inhibition results in lowered intrahepatocytic cholesterol formation, resulting in up-regulation of LDL receptors and, ultimately, lowering levels of serum LDL and triglycerides. Statins (target low-density lipoproteins Lipoproteins Lipid-protein complexes involved in the transportation and metabolism of lipids in the body. They are spherical particles consisting of a hydrophobic core of triglycerides and cholesterol esters surrounded by a layer of hydrophilic free cholesterol; phospholipids; and apolipoproteins. Lipoproteins are classified by their varying buoyant density and sizes. Lipid Metabolism (LDL) < 70 mg/dL)
• Avoid fluoroquinolones Fluoroquinolones Fluoroquinolones are a group of broad-spectrum, bactericidal antibiotics inhibiting bacterial DNA replication. Fluoroquinolones cover gram-negative, anaerobic, and atypical organisms, as well as some gram-positive and multidrug-resistant (MDR) organisms. Fluoroquinolones (may ↑ risk of dissection or rupture)
• Surveillance Surveillance Developmental Milestones and Normal Growth (see table)
  • TAA: asymptomatic ascending aortic aneurysm < 5.5 cm or descending aortic aneurysm < 6 cm: aortic imaging ( CTA CTA A non-invasive method that uses a ct scanner for capturing images of blood vessels and tissues. A contrast material is injected, which helps produce detailed images that aid in diagnosing vascular diseases. Pulmonary Function Tests/ MRA MRA Imaging of the Heart and Great Vessels) periodically

Surgical management

Indications for operative repair

• TAA rupture: emergency repair
• Symptomatic TAA
• Asymptomatic ascending TAA
  • Aortic (ascending and aortic arch Aortic arch Mediastinum and Great Vessels: Anatomy) diameter is ≥ 5.5 cm
  • Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship undergoing aortic valve Aortic valve The valve between the left ventricle and the ascending aorta which prevents backflow into the left ventricle. Heart: Anatomy repair/replacement or coronary artery Coronary Artery Truncus Arteriosus bypass: aortic diameter > 4.5 cm
  • Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with Marfan’s syndrome or other genetically mediated disorders with ascending TAA 4–5 cm (depending on condition) should undergo elective operation.
• Asymptomatic descending TAA:
  • TEVAR should be considered when surgically possible. 
  • When diameter is ≥ 5.5 cm, TEVAR is considered.
  •  If TEVAR not possible, open surgery considered when diameter is ≥ 6 cm
  • When intervention is indicated in cases of Marfan’s syndrome or other elastopathies (4–6 cm depending on condition), open surgery is considered.
• Aneurysm growth rate of > 0.5 cm/year, in an aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy < 5 cm

Operative options

• Open surgical repair:
  • Surgery depends on location (ascending TAA involves full cardiopulmonary bypass and cardioplegia) 
  • General indications:
    • Genetically mediated syndromes
    • Aneurysms in aortic arch Aortic arch Mediastinum and Great Vessels: Anatomy and ascending aorta Ascending aorta Mediastinum and Great Vessels: Anatomy; chronic dissection/ intramural hematoma Intramural hematoma Dissection of the Carotid and Vertebral Arteries in ascending aorta Ascending aorta Mediastinum and Great Vessels: Anatomy
    • Bicuspid aortic valve Aortic valve The valve between the left ventricle and the ascending aorta which prevents backflow into the left ventricle. Heart: Anatomy
    • For descending aortic aneurysms when TEVAR is not technically possible
  • Not for patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with high operative risk
  • Complications: postoperative bleeding, reduced perfusion (stroke, paraplegia/ paresis Paresis A general term referring to a mild to moderate degree of muscular weakness, occasionally used as a synonym for paralysis (severe or complete loss of motor function). In the older literature, paresis often referred specifically to paretic neurosyphilis. ‘general paresis’ and ‘general paralysis’ may still carry that connotation. Bilateral lower extremity paresis is referred to as paraparesis. Spinal Disk Herniation, visceral/renal/limb ischemia Ischemia A hypoperfusion of the blood through an organ or tissue caused by a pathologic constriction or obstruction of its blood vessels, or an absence of blood circulation. Ischemic Cell Damage)
  • Surveillance Surveillance Developmental Milestones and Normal Growth: before discharge, obtain CTA CTA A non-invasive method that uses a ct scanner for capturing images of blood vessels and tissues. A contrast material is injected, which helps produce detailed images that aid in diagnosing vascular diseases. Pulmonary Function Tests/ MRA MRA Imaging of the Heart and Great Vessels; repeat at 1-, 6-, and 12-month intervals
• TEVAR:
  • Placement of graft Graft A piece of living tissue that is surgically transplanted Organ Transplantation via iliac or femoral arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries: Histology
  • Requires normal aortic areas for graft Graft A piece of living tissue that is surgically transplanted Organ Transplantation attachment (proximal and distal landing zones for the stent graft Graft A piece of living tissue that is surgically transplanted Organ Transplantation) 
  • Indication(s): degenerative descending aortic aneurysm; also for blunt thoracic aortic injury, aortic dissection Aortic dissection Aortic dissection occurs due to shearing stress from pulsatile pressure causing a tear in the tunica intima of the aortic wall. This tear allows blood to flow into the media, creating a “false lumen.” Aortic dissection is most commonly caused by uncontrolled hypertension. Aortic Dissection, penetrating ulcer
  • Lower perioperative morbidity Morbidity The proportion of patients with a particular disease during a given year per given unit of population. Measures of Health Status and mortality Mortality All deaths reported in a given population. Measures of Health Status; majority discharged 24 hours post-surgery
  • Possible complications:
    • Spinal/cerebral/limb/visceral ischemia Ischemia A hypoperfusion of the blood through an organ or tissue caused by a pathologic constriction or obstruction of its blood vessels, or an absence of blood circulation. Ischemic Cell Damage 
    • Late outcomes related to the device (endoleak, migration, malposition, injury to other structures)
  • Requires endograft surveillance Surveillance Developmental Milestones and Normal Growth ( CTA CTA A non-invasive method that uses a ct scanner for capturing images of blood vessels and tissues. A contrast material is injected, which helps produce detailed images that aid in diagnosing vascular diseases. Pulmonary Function Tests) at 1 month, 6 months post-surgery, then annually (more frequently as indicated)

Differential Diagnosis

Differential diagnoses of TAA include the following conditions:

• Aortic dissection Aortic dissection Aortic dissection occurs due to shearing stress from pulsatile pressure causing a tear in the tunica intima of the aortic wall. This tear allows blood to flow into the media, creating a “false lumen.” Aortic dissection is most commonly caused by uncontrolled hypertension. Aortic Dissection: occurs when the inner coat ( tunica intima Tunica intima The innermost layer of an artery or vein, made up of one layer of endothelial cells and supported by an internal elastic lamina. Arteries: Histology) of the aortic wall develops a fissure Fissure A crack or split that extends into the dermis Generalized and Localized Rashes that causes blood to enter the media layer of the wall to form a channel of blood. The pressure causes the layers to be forced apart and causes severe pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways, characteristically known as a tearing pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways. Computed tomography angiogram will differentiate dissection from rupture of the aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy.
• Acute pericarditis Acute pericarditis Pericarditis: an inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation of the pericardium Pericardium A conical fibroserous sac surrounding the heart and the roots of the great vessels (aorta; venae cavae; pulmonary artery). Pericardium consists of two sacs: the outer fibrous pericardium and the inner serous pericardium. The latter consists of an outer parietal layer facing the fibrous pericardium, and an inner visceral layer (epicardium) resting next to the heart, and a pericardial cavity between these two layers. Heart: Anatomy that may be idiopathic Idiopathic Dermatomyositis or caused by infection, autoimmune disease, radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma, surgery, myocardial infarction Myocardial infarction MI is ischemia and death of an area of myocardial tissue due to insufficient blood flow and oxygenation, usually from thrombus formation on a ruptured atherosclerotic plaque in the epicardial arteries. Clinical presentation is most commonly with chest pain, but women and patients with diabetes may have atypical symptoms. Myocardial Infarction, neoplasms Neoplasms New abnormal growth of tissue. Malignant neoplasms show a greater degree of anaplasia and have the properties of invasion and metastasis, compared to benign neoplasms. Benign Bone Tumors, or drugs. Acute pericarditis Acute pericarditis Pericarditis is the most common type and manifests as fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, pleuritic chest pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways that increases with lying supine, and an audible pericardial rub.
• Heart failure Heart Failure A heterogeneous condition in which the heart is unable to pump out sufficient blood to meet the metabolic need of the body. Heart failure can be caused by structural defects, functional abnormalities (ventricular dysfunction), or a sudden overload beyond its capacity. Chronic heart failure is more common than acute heart failure which results from sudden insult to cardiac function, such as myocardial infarction. Total Anomalous Pulmonary Venous Return (TAPVR): the inability of the heart to supply the body with normal cardiac output Cardiac output The volume of blood passing through the heart per unit of time. It is usually expressed as liters (volume) per minute so as not to be confused with stroke volume (volume per beat). Cardiac Mechanics to meet metabolic needs. Risk factors include hypertension Hypertension Hypertension, or high blood pressure, is a common disease that manifests as elevated systemic arterial pressures. Hypertension is most often asymptomatic and is found incidentally as part of a routine physical examination or during triage for an unrelated medical encounter. Hypertension, diabetes Diabetes Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus mellitus, and coronary artery Coronary Artery Truncus Arteriosus disease. Echocardiography Echocardiography Ultrasonic recording of the size, motion, and composition of the heart and surrounding tissues. The standard approach is transthoracic. Tricuspid Valve Atresia (TVA) can confirm the reduced ejection fraction Ejection fraction Cardiac Cycle ( EF EF Cardiac Cycle). 
• Infective endocarditis Infective endocarditis Infective endocarditis (IE) is caused by infection or inflammation of the inner lining of the heart (endocardium), most commonly affecting the heart valves. Endocarditis: an inflammatory disease of the interior heart lining usually caused by Staphylococci, Streptococci, and Enterococci. Most commonly affects the cardiac valves. Diagnosis is by history, blood cultures, and echocardiography Echocardiography Ultrasonic recording of the size, motion, and composition of the heart and surrounding tissues. The standard approach is transthoracic. Tricuspid Valve Atresia (TVA).
• Myocardial infarction Myocardial infarction MI is ischemia and death of an area of myocardial tissue due to insufficient blood flow and oxygenation, usually from thrombus formation on a ruptured atherosclerotic plaque in the epicardial arteries. Clinical presentation is most commonly with chest pain, but women and patients with diabetes may have atypical symptoms. Myocardial Infarction: ischemia Ischemia A hypoperfusion of the blood through an organ or tissue caused by a pathologic constriction or obstruction of its blood vessels, or an absence of blood circulation. Ischemic Cell Damage of the myocardial tissue due to a complete obstruction or drastic constriction of the coronary artery Coronary Artery Truncus Arteriosus. This is usually accompanied by an increase in cardiac enzymes Enzymes Enzymes are complex protein biocatalysts that accelerate chemical reactions without being consumed by them. Due to the body’s constant metabolic needs, the absence of enzymes would make life unsustainable, as reactions would occur too slowly without these molecules. Basics of Enzymes, typical electrocardiogram Electrocardiogram An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Electrocardiogram (ECG) ( ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Electrocardiogram (ECG)) changes, and chest pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways. 
• Pulmonary embolism Pulmonary Embolism Pulmonary embolism (PE) is a potentially fatal condition that occurs as a result of intraluminal obstruction of the main pulmonary artery or its branches. The causative factors include thrombi, air, amniotic fluid, and fat. In PE, gas exchange is impaired due to the decreased return of deoxygenated blood to the lungs. Pulmonary Embolism: a potentially fatal clinical condition that occurs as a result of mechanical obstruction Mechanical Obstruction Any impairment, arrest, or reversal of the normal flow of intestinal contents toward the anal canal. Imaging of the Intestines of the pulmonary artery Pulmonary artery The short wide vessel arising from the conus arteriosus of the right ventricle and conveying unaerated blood to the lungs. Lungs: Anatomy or its branches by a thrombus, air, or fat. Diagnosis established by CT pulmonary angiogram CT pulmonary angiogram Pulmonary Function Tests.
• SVC syndrome: a condition caused by the obstruction of blood flow Blood flow Blood flow refers to the movement of a certain volume of blood through the vasculature over a given unit of time (e.g., mL per minute). Vascular Resistance, Flow, and Mean Arterial Pressure through the SVC. Most often manifests in patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with a thoracic malignancy Malignancy Hemothorax that produces compression Compression Blunt Chest Trauma over the vessel or a thrombus.