Transposition of the Great Arteries

Overview

Definition

Transposition of the great 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 (TGA) is the switching of the origins of the great vessels whereby the aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy arises from the right ventricle and 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 arises from the left ventricle.

Epidemiology

• 3% of all cases of congenital heart disease and 20% of cyanotic congenital heart disease
• Prevalence Prevalence The total number of cases of a given disease in a specified population at a designated time. It is differentiated from incidence, which refers to the number of new cases in the population at a given time. Measures of Disease Frequency: approximately 4 in 10,000 live births
• Associated cardiac anomalies:
  • Ventricular septal defect Ventricular Septal Defect Tetralogy of Fallot (VSD): in 50% of cases
  • Left ventricle outflow tract obstruction:
    • Noted in 25% of cases
    • Pulmonary stenosis Stenosis Hypoplastic Left Heart Syndrome (HLHS), especially if a VSD is present
  • Coronary 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: variable Variable Variables represent information about something that can change. The design of the measurement scales, or of the methods for obtaining information, will determine the data gathered and the characteristics of that data. As a result, a variable can be qualitative or quantitative, and may be further classified into subgroups. Types of Variables origins and short course
  • Mitral or tricuspid valve Tricuspid valve The valve consisting of three cusps situated between the right atrium and right ventricle of the heart. Heart: Anatomy abnormalities

Etiology

• Not completely delineated
• Attributed to:
  •  Failed growth of the subpulmonary conus 
  •  Failure of absorption Absorption Absorption involves the uptake of nutrient molecules and their transfer from the lumen of the GI tract across the enterocytes and into the interstitial space, where they can be taken up in the venous or lymphatic circulation. Digestion and Absorption at the subaortic conus
• Increased risk in diabetic mothers
• No strong genetic component, may be seen in some cases of DiGeorge syndrome DiGeorge syndrome DiGeorge syndrome (DGS) is a condition caused by a microdeletion at location q11.2 of chromosome 22 (thus also called 22q11.2 syndrome). There is a defective development of the third and fourth pharyngeal pouches, leading to thymic and parathyroid hypoplasia (causing T-cell immunodeficiency and hypocalcemia, respectively). DiGeorge Syndrome

Pathophysiology and Clinical Presentation

Pathophysiology

• 2 parallel circuits:
  • Deoxygenated blood returns to the right ventricle and is pumped back into the systemic circulation Circulation The movement of the blood as it is pumped through the cardiovascular system. ABCDE Assessment by the misplaced aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy.
  • Oxygenated blood returns to the left ventricle and is pumped into the pulmonary circulation Circulation The movement of the blood as it is pumped through the cardiovascular system. ABCDE Assessment by the misplaced pulmonary vein Pulmonary Vein Total Anomalous Pulmonary Venous Return (TAPVR).
• Tolerated well in utero:
  • Oxygenated blood from umbilical vein umbilical vein Venous vessels in the umbilical cord. They carry oxygenated, nutrient-rich blood from the mother to the fetus via the placenta. In humans, there is normally one umbilical vein. Prenatal and Postnatal Physiology of the Neonate → right atrium
  • Right atrium → fossa ovalis Fossa ovalis Prenatal and Postnatal Physiology of the Neonate → left atrium → left ventricle→ 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→ ductus arteriosus Ductus arteriosus A fetal blood vessel connecting the pulmonary artery with the descending aorta. Patent Ductus Arteriosus (PDA)→ aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy
• After birth, complete separation of the circuits is not compatible with life.
• Viability depends on the intercirculatory mixing of blood:
  • Intracardiac Intracardiac Total Anomalous Pulmonary Venous Return (TAPVR):
    • Patent foramen ovale Foramen ovale An opening in the wall between the right and the left upper chambers (heart atria) of a fetal heart. Oval foramen normally closes soon after birth; when it fails to close the condition is called patent oval foramen. Patent Foramen Ovale ( PFO PFO A patent foramen ovale (PFO) is an abnormal communication between the atria that persists after birth. The condition results from incomplete closure of the foramen ovale. Small, isolated, and asymptomatic pfos are a common incidental finding on echocardiography and require no treatment. Patent Foramen Ovale)
    • Atrial septal defect Atrial Septal Defect Atrial septal defects (ASDs) are benign acyanotic congenital heart defects characterized by an opening in the interatrial septum that causes blood to flow from the left atrium (LA) to the right atrium (RA) (left-to-right shunt). Atrial Septal Defect (ASD) ( ASD ASD Autism spectrum disorder (ASD) is a neurodevelopmental disorder marked by poor social skills, restricted interests/social interactions, and repetitive/stereotyped behaviors. The condition is termed a “spectrum” because of the wide variability in the severity of symptoms exhibited. Autism Spectrum Disorder)
    • VSD
  • Extracardiac: patent ductus arteriosus Ductus arteriosus A fetal blood vessel connecting the pulmonary artery with the descending aorta. Patent Ductus Arteriosus (PDA) ( PDA PDA The ductus arteriosus (DA) allows blood to bypass pulmonary circulation. After birth, the DA remains open for up to 72 hours and then constricts and involutes, becoming the ligamentum arteriosum. Failure of this process to occur results in patent ductus arteriosus (PDA), a condition that causes up to 10% of congenital heart defects. Patent Ductus Arteriosus (PDA))
• Mixing of blood:
  • Reduced concentration of oxygen in the systemic circulation Circulation The movement of the blood as it is pumped through the cardiovascular system. ABCDE Assessment causing cyanosis Cyanosis A bluish or purplish discoloration of the skin and mucous membranes due to an increase in the amount of deoxygenated hemoglobin in the blood or a structural defect in the hemoglobin molecule. Pulmonary Examination
  • Effective: between atria because of low-pressure gradient
  • Less effective: VSD or PDA PDA The ductus arteriosus (DA) allows blood to bypass pulmonary circulation. After birth, the DA remains open for up to 72 hours and then constricts and involutes, becoming the ligamentum arteriosum. Failure of this process to occur results in patent ductus arteriosus (PDA), a condition that causes up to 10% of congenital heart defects. Patent Ductus Arteriosus (PDA)—blood is preferentially shunted in 1 direction because of pressure gradient Pressure gradient Vascular Resistance, Flow, and Mean Arterial Pressure
• Preferential shunting in 1 direction → clinical deterioration:
  • Worsening hypoxemia Hypoxemia Neonatal Respiratory Distress Syndrome/ cyanosis Cyanosis A bluish or purplish discoloration of the skin and mucous membranes due to an increase in the amount of deoxygenated hemoglobin in the blood or a structural defect in the hemoglobin molecule. Pulmonary Examination
  • 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)

Clinical presentation

• Apparent in the neonatal phase (1st 30 days of life)
• Cyanosis Cyanosis A bluish or purplish discoloration of the skin and mucous membranes due to an increase in the amount of deoxygenated hemoglobin in the blood or a structural defect in the hemoglobin molecule. Pulmonary Examination:
  • Severe, with intact ventricular septum
  • Mild, with ASD ASD Autism spectrum disorder (ASD) is a neurodevelopmental disorder marked by poor social skills, restricted interests/social interactions, and repetitive/stereotyped behaviors. The condition is termed a “spectrum” because of the wide variability in the severity of symptoms exhibited. Autism Spectrum Disorder, PFO PFO A patent foramen ovale (PFO) is an abnormal communication between the atria that persists after birth. The condition results from incomplete closure of the foramen ovale. Small, isolated, and asymptomatic pfos are a common incidental finding on echocardiography and require no treatment. Patent Foramen Ovale, or large VSD Large VSD Ventricular Septal Defect (VSD)
  • Not responsive to supplemental oxygen Supplemental Oxygen Respiratory Failure
  • Not affected by feeding/crying
  • Reverse differential cyanosis Cyanosis A bluish or purplish discoloration of the skin and mucous membranes due to an increase in the amount of deoxygenated hemoglobin in the blood or a structural defect in the hemoglobin molecule. Pulmonary Examination:
    • Higher post-ductal than pre-ductal saturations
    • If aortic coarctation, interrupted aortic arch Aortic arch Mediastinum and Great Vessels: Anatomy, or pulmonary hypertension Pulmonary Hypertension Pulmonary hypertension (PH) or pulmonary arterial hypertension (PAH) is characterized by elevated pulmonary arterial pressure, which can lead to chronic progressive right heart failure. Pulmonary hypertension is grouped into 5 categories based on etiology, which include primary PAH, and PH due to cardiac disease, lung or hypoxic disease, chronic thromboembolic disease, and multifactorial or unclear etiologies. Pulmonary Hypertension are also present with TGA
• Tachypnea Tachypnea Increased respiratory rate. Pulmonary Examination
• 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):
  • Usually if there is a concomitant large VSD Large VSD Ventricular Septal Defect (VSD)
  • Respiratory distress by 3–4 weeks of life

Diagnosis

Physical examination

• Visible cyanosis Cyanosis A bluish or purplish discoloration of the skin and mucous membranes due to an increase in the amount of deoxygenated hemoglobin in the blood or a structural defect in the hemoglobin molecule. Pulmonary Examination 
• Respiratory rate Respiratory rate The number of times an organism breathes with the lungs (respiration) per unit time, usually per minute. Pulmonary Examination > 60/min
• Failed pulse oximetry screening Screening Preoperative Care test
• Murmurs:
  • Pansystolic murmur of VSD 
  • Systolic ejection murmur if left ventricular outlet obstruction is present
• Diminished femoral pulses: if there is also aortic coarctation or arch interruption

Imaging

• Echocardiogram:
  • Prenatal: not always diagnostic
  • Postnatal echocardiogram is a main confirmatory test:
    • Evaluate the degree of atrial mixing.
    • VSD
    • Valve abnormalities
    • PDA PDA The ductus arteriosus (DA) allows blood to bypass pulmonary circulation. After birth, the DA remains open for up to 72 hours and then constricts and involutes, becoming the ligamentum arteriosum. Failure of this process to occur results in patent ductus arteriosus (PDA), a condition that causes up to 10% of congenital heart defects. Patent Ductus Arteriosus (PDA)
    • Coronary artery Coronary Artery Truncus Arteriosus anatomy
• Chest X ray: classic “egg on a string” appearance

Other tests

• 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):
  • Generally not diagnostic
  • May show right axis deviation and right ventricular hypertrophy Right Ventricular Hypertrophy Tetralogy of Fallot
• Cardiac catheterization Cardiac Catheterization Procedures in which placement of cardiac catheters is performed for therapeutic or diagnostic procedures. Cardiac Surgery (angiogram):
  • Can help assess origins/anatomy of coronary 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 prior to surgery
  • Can be therapeutic: balloon atrial septostomy Atrial Septostomy Tricuspid Valve Atresia (TVA) to increase blood mixing

Management and Prognosis

Management

Medical:

• For initial stabilization and optimization prior to surgery
• Intravenous prostaglandin infusion to keep PDA PDA The ductus arteriosus (DA) allows blood to bypass pulmonary circulation. After birth, the DA remains open for up to 72 hours and then constricts and involutes, becoming the ligamentum arteriosum. Failure of this process to occur results in patent ductus arteriosus (PDA), a condition that causes up to 10% of congenital heart defects. Patent Ductus Arteriosus (PDA) open
• Balloon atrial septostomy Atrial Septostomy Tricuspid Valve Atresia (TVA) (with cardiac catheterization Cardiac Catheterization Procedures in which placement of cardiac catheters is performed for therapeutic or diagnostic procedures. Cardiac Surgery)

Surgery:

• Definitive management
• Performed within 1st 2 weeks of life
• Most common:
  • Arterial switch operation (ASO) + VSD repair if necessary
  • Rastelli procedure if left ventricular outflow obstruction Ventricular Outflow Obstruction Occlusion of the outflow tract in either the left ventricle or the right ventricle of the heart. This may result from congenital heart defects, predisposing heart diseases, complications of surgery, or heart neoplasms. Tetralogy of Fallot is also present
• Post-surgical complications that require regular Regular Insulin screening Screening Preoperative Care include:
  • Coronary artery Coronary Artery Truncus Arteriosus stenosis Stenosis Hypoplastic Left Heart Syndrome (HLHS), or insufficiency
  • 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 stenosis Stenosis Hypoplastic Left Heart Syndrome (HLHS)
  • Aortic root dilation Aortic root dilation Aortic Regurgitation
  • Right ventricular failure
  • Arrhythmias (e.g., atrial flutter Atrial flutter Atrial flutter is a regular supraventricular tachycardia characterized by an atrial heart rate between 240/min and 340/min (typically 300/min), atrioventricular (AV) node conduction block, and a “sawtooth” pattern on an electrocardiogram (ECG). Atrial Flutter and fibrillation)

Prognosis Prognosis A prediction of the probable outcome of a disease based on a individual’s condition and the usual course of the disease as seen in similar situations. Non-Hodgkin Lymphomas

• If not treated:
  • 90% of patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship will die within the 1st year.
  • 30% of patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship will die within the 1st week.
• If treated, high morbidity Morbidity The proportion of patients with a particular disease during a given year per given unit of population. Measures of Health Status with continuous follow-up and decreased exercise capacity
• Higher chance of neurodevelopmental delay in infants

Differential Diagnosis

• Tetralogy of Fallot Tetralogy of Fallot Tetralogy of Fallot is the most common cyanotic congenital heart disease. The disease is the confluence of 4 pathologic cardiac features: overriding aorta, ventricular septal defect, right ventricular outflow obstruction, and right ventricular hypertrophy. Tetralogy of Fallot: a congenital heart disease characterized by the occurrence of 4 key cardinal  features: overriding aorta Overriding Aorta Tetralogy of Fallot, VSD, RVOT obstruction, and right ventricular hypertrophy Right Ventricular Hypertrophy Tetralogy of Fallot. Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship present with cyanosis Cyanosis A bluish or purplish discoloration of the skin and mucous membranes due to an increase in the amount of deoxygenated hemoglobin in the blood or a structural defect in the hemoglobin molecule. Pulmonary Examination and a history of tet spells Tet Spells Tetralogy of Fallot. Diagnosis is confirmed by an echocardiogram and patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship are surgically managed.
• Tricuspid atresia Atresia Hypoplastic Left Heart Syndrome (HLHS): congenital heart disease characterized by the lack of development of the tricuspid valve Tricuspid valve The valve consisting of three cusps situated between the right atrium and right ventricle of the heart. Heart: Anatomy. Presents with cyanosis Cyanosis A bluish or purplish discoloration of the skin and mucous membranes due to an increase in the amount of deoxygenated hemoglobin in the blood or a structural defect in the hemoglobin molecule. Pulmonary Examination, labored breathing, and hypoxic spells. Holosystolic murmur Holosystolic Murmur Tricuspid Valve Atresia (TVA) and single S2 S2 Heart Sounds are present on exam. Diagnosis is made by echocardiogram and 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).
• Truncus arteriosus Truncus arteriosus Truncus arteriosus (TA) is a congenital heart defect characterized by the persistence of a common cardiac arterial trunk tract that fails to divide into the pulmonary artery and aorta during embryonic development. Truncus arteriosus is a rare congenital malformation with a high mortality rate within the 1st 5 weeks of life if not managed promptly. Truncus Arteriosus: emergence of aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy and 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 from a common trunk overriding a VSD. Symptomatic from the 1st days of life, including cyanosis Cyanosis A bluish or purplish discoloration of the skin and mucous membranes due to an increase in the amount of deoxygenated hemoglobin in the blood or a structural defect in the hemoglobin molecule. Pulmonary Examination, respiratory distress, 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), poor feeding, and excessive sweating. Diagnosed by echocardiogram.
• Total anomalous pulmonary venous return: rare congenital cardiopathy in which pulmonary veins Pulmonary veins The veins that return the oxygenated blood from the lungs to the left atrium of the heart. Lungs: Anatomy drain to sites other than the left atrium. Presents with cyanosis Cyanosis A bluish or purplish discoloration of the skin and mucous membranes due to an increase in the amount of deoxygenated hemoglobin in the blood or a structural defect in the hemoglobin molecule. Pulmonary Examination from birth, 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), and respiratory distress. Characterized by wide-split S2 S2 Heart Sounds.
• Ebstein anomaly: congenital heart defect in which there is downward displacement Displacement The process by which an emotional or behavioral response that is appropriate for one situation appears in another situation for which it is inappropriate. Defense Mechanisms of the tricuspid valve Tricuspid valve The valve consisting of three cusps situated between the right atrium and right ventricle of the heart. Heart: Anatomy leaflets causing RVOT obstruction. Presents with cyanosis Cyanosis A bluish or purplish discoloration of the skin and mucous membranes due to an increase in the amount of deoxygenated hemoglobin in the blood or a structural defect in the hemoglobin molecule. Pulmonary Examination, arrhythmias, and failure to thrive Failure to Thrive Failure to thrive (FTT), or faltering growth, describes suboptimal weight gain and growth in children. The majority of cases are due to inadequate caloric intake; however, genetic, infectious, and oncological etiologies are also common. Failure to Thrive. Diagnosed by echocardiogram.