Development of the Heart

Derivatives of the Cardiac Tube

• First 3 weeks: primitive heart develops as a straight tube
  • 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 → ascending aorta Ascending aorta Mediastinum and Great Vessels: Anatomy and pulmonary trunk Pulmonary Trunk Truncus Arteriosus
  • Bulbus cordis
    • Proximal 3rd of bulbus cordis → muscular right ventricle
    • Conus cordis → smooth outflow portions of right and left ventricles
  • Endocardial cushion → atrial septum, membranous interventricular septum Interventricular Septum Ventricular Septal Defect (VSD), atrioventricular (AV) valves, and semilunar valves
    • Derived from neural crest cells Neural crest cells Gastrulation and Neurulation
    • Endocardial cushion defects: common in Down syndrome Down syndrome Down syndrome, or trisomy 21, is the most common chromosomal aberration and the most frequent genetic cause of developmental delay. Both boys and girls are affected and have characteristic craniofacial and musculoskeletal features, as well as multiple medical anomalies involving the cardiac, gastrointestinal, ocular, and auditory systems. Down syndrome (Trisomy 21) 
  • Posterior, subcardinal, supracardinal veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology → inferior vena cava Inferior vena cava The venous trunk which receives blood from the lower extremities and from the pelvic and abdominal organs. Mediastinum and Great Vessels: Anatomy ( IVC IVC The venous trunk which receives blood from the lower extremities and from the pelvic and abdominal organs. Mediastinum and Great Vessels: Anatomy)
  • Primitive atrium → trabeculated parts of the left and right atria
  • Primitive pulmonary vein Pulmonary Vein Total Anomalous Pulmonary Venous Return (TAPVR) → smooth left atrium
  • Primitive ventricle → trabeculated parts of the left and right ventricles
  • Right common cardinal vein (RCCV) and right anterior cardinal vein (RACV) → 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)
  • Left horn of sinus venosus Sinus Venosus Atrial Septal Defect (ASD) → coronary sinus Coronary Sinus A short vein that collects about two thirds of the venous blood from the myocardium and drains into the right atrium. Coronary sinus, normally located between the left atrium and left ventricle on the posterior surface of the heart, can serve as an anatomical reference for cardiac procedures. Atrial Septal Defect (ASD)
  • Right horn of sinus venosus Sinus Venosus Atrial Septal Defect (ASD) → posterior part of the right atrium (sinus venarum) with a relatively smooth surface
• Smooth portions are found in the areas where the heart connects with the vessels (e.g., below the pulmonic valve).
• Cardinal veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology:
  • Form superior and inferior venae cavae Venae Cavae The inferior and superior venae cavae. Veins: Histology (that connect to the right atrium (RA))
  • RCCV + RACV = SVC
  • Posterior vein + subcardinal vein + supracardinal vein = IVC IVC The venous trunk which receives blood from the lower extremities and from the pelvic and abdominal organs. Mediastinum and Great Vessels: Anatomy

Cardiac Looping

• Begins in 4th week: goal is to establish left-right polarity
• Cranial end bends ventrally and caudally.
• Then, rotates over to the right (24 days)
• Atrial end shifts dorso-cranially (posteriorly and cranially) and moves to the left (35 days).
• Requires cilia and dynein Dynein A family of multisubunit cytoskeletal motor proteins that use the energy of ATP hydrolysis, generated by a ring of aaa ATPases in the dynein heavy chain, to power a variety of cellular functions. Dyneins fall into two major classes based upon structural and functional criteria. The Cell: Cytosol and Cytoskeleton involvement
• Defect in dynein Dynein A family of multisubunit cytoskeletal motor proteins that use the energy of ATP hydrolysis, generated by a ring of aaa ATPases in the dynein heavy chain, to power a variety of cellular functions. Dyneins fall into two major classes based upon structural and functional criteria. The Cell: Cytosol and Cytoskeleton function → dextrocardia (heart on the right side, seen in Kartagener’s syndrome (primary ciliary dyskinesia Ciliary dyskinesia Primary Ciliary Dyskinesia))

Cardiac Septation

Atrial septum

The atrial septum begins with endocardial cushions at the base of the atrial chamber and septum primum.

• Septum primum
  • Grows toward the endocardial cushions
  • Foramen (ostium) primum narrows → replaced by foramen (ostium) secundum (which forms in the septum primum as the ostium primum Ostium Primum Atrial Septal Defect (ASD) regresses)
  • Oxygenated blood enters RA from IVC IVC The venous trunk which receives blood from the lower extremities and from the pelvic and abdominal organs. Mediastinum and Great Vessels: Anatomy → passes into left atrium (LA) (through foramen secundum) → passes into developing ventricle
  • Poorly oxygenated blood from SVC will be directed to the bulbus cordis (RV).
  • Prenatal and postnatal physiology Postnatal physiology Neonatal physiology during prenatal life differs significantly from that during postnatal life. Postnatally, the fetal circulatory system and organ systems adapt to the extrauterine environment. Placental blood supply is cut off, causing the neonate to make adaptive changes. Prenatal and Postnatal Physiology of the Neonate
• Septum secundum
  • Develops on the right side of septum primum
  • Foramen (ostium) secundum maintains right-to-left shunt.
  • Expands and covers most of foramen (ostium) secundum → residual opening is the  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
  • RA gets larger → pulls sinus venosus Sinus Venosus Atrial Septal Defect (ASD) into its wall → moves SVC and IVC IVC The venous trunk which receives blood from the lower extremities and from the pelvic and abdominal organs. Mediastinum and Great Vessels: Anatomy closer → one opening formed
• 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
  • Opening between septum primum and septum secundum (shunt between right and left atria)
  • Blood continues to flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure right to left, due to ↑↑ pressure in RA
  • After birth: ↑↑ pressure in LA and decreased pressure in RA → septum primum pushed against septum secundum → 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 closed
    • Usually fused shut during infancy/early childhood, but in 20%–25% of the population it remains open as a small defect (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).

Ventricular septum

• Muscular interventricular septum Interventricular Septum Ventricular Septal Defect (VSD) forms (growing from base of ventricle toward endocardial cushions).
• Aorticopulmonary septum rotates and fuses with the muscular ventricular septum to form the membranous interventricular septum Interventricular Septum Ventricular Septal Defect (VSD) (closing the interventricular foramen Interventricular foramen Ventricular System: Anatomy).
• Growth of endocardial cushions separates atria from ventricles → contributes to atrial septation and membranous portion of interventricular septum Interventricular Septum Ventricular Septal Defect (VSD).
• Defect → membranous/muscular ventricular septal defect Ventricular Septal Defect Tetralogy of Fallot (VSD)
  • Most common congenital cardiac defect
  • Usually a defect in the membranous portion of the interventricular septum Interventricular Septum Ventricular Septal Defect (VSD)

Aorticopulmonary septum

• Spiral Spiral Computed tomography where there is continuous x-ray exposure to the patient while being transported in a spiral or helical pattern through the beam of irradiation. This provides improved three-dimensional contrast and spatial resolution compared to conventional computed tomography, where data is obtained and computed from individual sequential exposures. Computed Tomography (CT) septum that divides the aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy from 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 → forms outflow tract
• Neural crest cells Neural crest cells Gastrulation and Neurulation migrate to truncal and bulbar ridges that spiral Spiral Computed tomography where there is continuous x-ray exposure to the patient while being transported in a spiral or helical pattern through the beam of irradiation. This provides improved three-dimensional contrast and spatial resolution compared to conventional computed tomography, where data is obtained and computed from individual sequential exposures. Computed Tomography (CT) and fuse to form aorticopulmonary septum → forming ascending aorta Ascending aorta Mediastinum and Great Vessels: Anatomy and pulmonary trunk Pulmonary Trunk Truncus Arteriosus
• Also fuses with muscular portion of ventricular septum → forms membranous interventricular septum Interventricular Septum Ventricular Septal Defect (VSD)
• Defect (due to failure of migration of neural crest cells Neural crest cells Gastrulation and Neurulation):
  • Transposition of great vessels (TGV)
  • 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
  • Persistent 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

Valve development

• Semilunar (aortic/pulmonic) valves: derived from endocardial cushions of outflow tract
• AV (mitral/tricuspid) valves: derived from fused endocardial cushions of AV canal
• Defects lead to stenotic, regurgitant, atretic (e.g., tricuspid atresia Atresia Hypoplastic Left Heart Syndrome (HLHS)), or displaced (e.g., Ebstein anomaly) valves

Fetal Circulation

• Placenta Placenta A highly vascularized mammalian fetal-maternal organ and major site of transport of oxygen, nutrients, and fetal waste products. It includes a fetal portion (chorionic villi) derived from trophoblasts and a maternal portion (decidua) derived from the uterine endometrium. The placenta produces an array of steroid, protein and peptide hormones (placental hormones). Placenta, Umbilical Cord, and Amniotic Cavity brings blood through the 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 (80% oxygen saturation Oxygen Saturation Basic Procedures and PO₂ of approximately 30 mm Hg)
  • Umbilical 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 have low oxygen saturation Oxygen Saturation Basic Procedures
• Ductus venosus:
  • Allows blood to bypass the liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy
  • Transports blood to IVC IVC The venous trunk which receives blood from the lower extremities and from the pelvic and abdominal organs. Mediastinum and Great Vessels: Anatomy from the 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
  • Blood is slightly deoxygenated due to mixing
• Pathway of oxygenated blood from IVC IVC The venous trunk which receives blood from the lower extremities and from the pelvic and abdominal organs. Mediastinum and Great Vessels: Anatomy back to placenta Placenta A highly vascularized mammalian fetal-maternal organ and major site of transport of oxygen, nutrients, and fetal waste products. It includes a fetal portion (chorionic villi) derived from trophoblasts and a maternal portion (decidua) derived from the uterine endometrium. The placenta produces an array of steroid, protein and peptide hormones (placental hormones). Placenta, Umbilical Cord, and Amniotic Cavity:
  • Blood hits atrial septum → pushes the valve of the 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 (2/3 to LA, 1/3 to lungs Lungs Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. Lungs: Anatomy) → LA → LV → aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy → common iliac 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 → umbilical 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 → placenta Placenta A highly vascularized mammalian fetal-maternal organ and major site of transport of oxygen, nutrients, and fetal waste products. It includes a fetal portion (chorionic villi) derived from trophoblasts and a maternal portion (decidua) derived from the uterine endometrium. The placenta produces an array of steroid, protein and peptide hormones (placental hormones). Placenta, Umbilical Cord, and Amniotic Cavity
  • Mnemonic: Remember O for Oxygenated blood as well as for Ovale.
• Pathway of deoxygenated blood from SVC: 
  • SVC → RA → RV → pulmonary trunk Pulmonary Trunk Truncus Arteriosus → ductus arteriosus Ductus arteriosus A fetal blood vessel connecting the pulmonary artery with the descending aorta. Patent Ductus Arteriosus (PDA) → descending aorta Descending aorta Mediastinum and Great Vessels: Anatomy → common iliac 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 → umbilical 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 → placenta Placenta A highly vascularized mammalian fetal-maternal organ and major site of transport of oxygen, nutrients, and fetal waste products. It includes a fetal portion (chorionic villi) derived from trophoblasts and a maternal portion (decidua) derived from the uterine endometrium. The placenta produces an array of steroid, protein and peptide hormones (placental hormones). Placenta, Umbilical Cord, and Amniotic Cavity
  • This shunt is due to high fetal pulmonary arterial resistance Resistance Physiologically, the opposition to flow of air caused by the forces of friction. As a part of pulmonary function testing, it is the ratio of driving pressure to the rate of air flow. Ventilation: Mechanics of Breathing (partly because of low oxygen tension).
  • Mnemonic: Remember D for deoxygenated blood as well as for Ductus arteriosus and Descending aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy.
• Transition from fetal to adult circulation Circulation The movement of the blood as it is pumped through the cardiovascular system. ABCDE Assessment:
  • At birth, infant takes first breath → decreased resistance Resistance Physiologically, the opposition to flow of air caused by the forces of friction. As a part of pulmonary function testing, it is the ratio of driving pressure to the rate of air flow. Ventilation: Mechanics of Breathing in pulmonary vasculature → increased left atrial pressure in relation to right atrial pressure, leading to the closing of the 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 (becomes the fossa ovalis Fossa ovalis Prenatal and Postnatal Physiology of the Neonate)
  • ↑ In oxygen (from respiration Respiration The act of breathing with the lungs, consisting of inhalation, or the taking into the lungs of the ambient air, and of exhalation, or the expelling of the modified air which contains more carbon dioxide than the air taken in. Nose Anatomy (External & Internal)) and ↓ in prostaglandins Prostaglandins A group of compounds derived from unsaturated 20-carbon fatty acids, primarily arachidonic acid, via the cyclooxygenase pathway. They are extremely potent mediators of a diverse group of physiological processes. Eicosanoids (from placental separation) → closure of ductus arteriosus Ductus arteriosus A fetal blood vessel connecting the pulmonary artery with the descending aorta. Patent Ductus Arteriosus (PDA)
• Fetal-postnatal derivatives:
  • 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 → ligamentum teres Ligamentum teres A cord-like remnant structure formed from the closed left fetal umbilical vein. It is located along the lower edge of the falciform ligament. Liver: Anatomy hepatis ( round ligament Round ligament A fibromuscular band that attaches to the uterus and then passes along the broad ligament, out through the inguinal ring, and into the labium majus. Uterus, Cervix, and Fallopian Tubes: Anatomy – contained in falciform ligament Falciform Ligament Liver: Anatomy)
  • Umbilical 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 → medial umbilical ligaments
  • Ductus venosus → ligamentum venosum Ligamentum Venosum Liver: Anatomy
  • Ductus arteriosus Ductus arteriosus A fetal blood vessel connecting the pulmonary artery with the descending aorta. Patent Ductus Arteriosus (PDA) → ligamentum arteriosum Ligamentum arteriosum Prenatal and Postnatal Physiology of the Neonate (near left recurrent laryngeal nerve)
  • 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 → Fossa ovalis Fossa ovalis Prenatal and Postnatal Physiology of the Neonate

Mnemonics

1. Indomethacin helps close the patent ductus arteriosus → ligamentum arteriosum (remnant of ductus arteriosus) → remember: “Come In and close the Door!”
2. “Prostaglandins E₁ and E₂ kEEp PDA open!”

Congenital Abnormalities

Right-to-left shunts (cyanotic lesions)

• 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: A single large vessel arises from both ventricles due to failure of formation of the aorticopulmonary septum to divide into the pulmonary trunk Pulmonary Trunk Truncus Arteriosus and aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy. Usually, it is accompanied by a VSD. Danger of irreversible 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. 
• TGV: Failure of the aorticopulmonary septum to spiral Spiral Computed tomography where there is continuous x-ray exposure to the patient while being transported in a spiral or helical pattern through the beam of irradiation. This provides improved three-dimensional contrast and spatial resolution compared to conventional computed tomography, where data is obtained and computed from individual sequential exposures. Computed Tomography (CT). 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 LV (posterior), whereas the aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy comes out from the RV (anterior). Unsuitable for life without a shunt. In 65% of cases, TGV is accompanied by patent ductus arteriosus Ductus arteriosus A fetal blood vessel connecting the pulmonary artery with the descending aorta. Patent Ductus Arteriosus (PDA) or 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. In 35% of cases, it is accompanied by a ventricular septal defect Ventricular Septal Defect Tetralogy of Fallot. Radiologically will have an “egg on string” appearance on 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 due to narrowed mediastinum Mediastinum The mediastinum is the thoracic area between the 2 pleural cavities. The mediastinum contains vital structures of the circulatory, respiratory, digestive, and nervous systems including the heart and esophagus, and major thoracic vessels. Mediastinum and Great Vessels: Anatomy and globular heart outline. Surgical intervention is needed, otherwise most infants die within the first few months of life.
• Tricuspid atresia Atresia Hypoplastic Left Heart Syndrome (HLHS): The tricuspid valve Tricuspid valve The valve consisting of three cusps situated between the right atrium and right ventricle of the heart. Heart: Anatomy is absent, which impedes the development of the right ventricle, leading to a hypoplastic right ventricle. Requires 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) and VSD for viability. Blood will flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure from the RA to the LA through the 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) or the 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. To get to the lungs Lungs Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. Lungs: Anatomy, blood will flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure from the RA to the LA through the 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, and then from the LV to the RV through the ventricular septal defect Ventricular Septal Defect Tetralogy of Fallot. 
• 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: Most common cause of early childhood 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. Accompanied by pulmonary stenosis Stenosis Hypoplastic Left Heart Syndrome (HLHS), right ventricular hypertrophy Right Ventricular Hypertrophy Tetralogy of Fallot, overriding aorta Overriding Aorta Tetralogy of Fallot, and a ventricular septal defect Ventricular Septal Defect Tetralogy of Fallot. 
• Total anomalous pulmonary venous return (TAPVR): All pulmonary veins Pulmonary veins The veins that return the oxygenated blood from the lungs to the left atrium of the heart. Lungs: Anatomy drain into the right heart circulation Circulation The movement of the blood as it is pumped through the cardiovascular system. ABCDE Assessment (SVC, coronary sinus Coronary Sinus A short vein that collects about two thirds of the venous blood from the myocardium and drains into the right atrium. Coronary sinus, normally located between the left atrium and left ventricle on the posterior surface of the heart, can serve as an anatomical reference for cardiac procedures. Atrial Septal Defect (ASD), etc ETC The electron transport chain (ETC) sends electrons through a series of proteins, which generate an electrochemical proton gradient that produces energy in the form of adenosine triphosphate (ATP). Electron Transport Chain (ETC).). The defect is similar to the shunt from the LA to the RA. The RA and the RV cause oxygenated blood to mix with deoxygenated blood and spread throughout the body. Associated with an 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 and sometimes a 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) to allow for right-to-left shunting to maintain 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.

Mnemonic: right-to-left shunts (cyanotic lesions) (the 5 Ts):

• Truncus arteriosus: 1 vessel
• Transposition of the great vessels: 2 switched vessels
• Tricuspid atresia Atresia Hypoplastic Left Heart Syndrome (HLHS): 3 = tri
• Tetralogy of Fallot: 4 = tetra
• Total anomalous pulmonary venous return (TAPVR): 5 letters in the name

Left-to-right shunts ( acyanotic Acyanotic Tetralogy of Fallot)

• VSD: Most common congenital anomaly, associated with fetal alcohol syndrome Fetal alcohol syndrome An umbrella term used to describe a pattern of disabilities and abnormalities that result from fetal exposure to ethanol during pregnancy. It encompasses a phenotypic range that can vary greatly between individuals, but reliably includes one or more of the following: characteristic facial dysmorphism, fetal growth retardation, central nervous system abnormalities, cognitive and/or behavioral dysfunction, birth defects. The level of maternal alcohol consumption does not necessarily correlate directly with disease severity. Alcohol Use Disorder. The defect causes communication Communication The exchange or transmission of ideas, attitudes, or beliefs between individuals or groups. Decision-making Capacity and Legal Competence between LV and RV. Clinical presentation is harsh, holosystolic murmur Holosystolic Murmur Tricuspid Valve Atresia (TVA) that is heard best in the tricuspid area.
• 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:  Communication Communication The exchange or transmission of ideas, attitudes, or beliefs between individuals or groups. Decision-making Capacity and Legal Competence between LA and RA, can lead to 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. Clinically characterized by wide splitting Splitting Defense Mechanisms of S2 S2 Heart Sounds. There are 4 types of 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: primum, secundum, sinus venosus Sinus Venosus Atrial Septal Defect (ASD), and coronary sinus Coronary Sinus A short vein that collects about two thirds of the venous blood from the myocardium and drains into the right atrium. Coronary sinus, normally located between the left atrium and left ventricle on the posterior surface of the heart, can serve as an anatomical reference for cardiac procedures. Atrial Septal Defect (ASD), the most common being a secundum type of 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.
• 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)): Normally, ductus arteriosus Ductus arteriosus A fetal blood vessel connecting the pulmonary artery with the descending aorta. Patent Ductus Arteriosus (PDA) shunts blood from the left 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 to the aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy. This should stop after birth due to decreased levels of prostaglandin E2 Prostaglandin E2 The most common and most biologically active of the mammalian prostaglandins. It exhibits most biological activities characteristic of prostaglandins and has been used extensively as an oxytocic agent. The compound also displays a protective effect on the intestinal mucosa. Fever. Clinical presentation of 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) is a continuous machinery-like murmur on auscultation, blue toes and normal fingers, and a widened pulse pressure. 

Other congenital abnormalities Congenital Abnormalities Malformations of organs or body parts during development in utero. Omphalocele

• Coarctation of the aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy: The aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy narrows in the area around the ductus arteriosus Ductus arteriosus A fetal blood vessel connecting the pulmonary artery with the descending aorta. Patent Ductus Arteriosus (PDA) to a certain point and then widens to its normal diameter. Postductal coarctation (occurring after the ductus arteriosus Ductus arteriosus A fetal blood vessel connecting the pulmonary artery with the descending aorta. Patent Ductus Arteriosus (PDA)) is clinically silent and only present in adults. Preductal coarctation (occurring before the ductus arteriosus Ductus arteriosus A fetal blood vessel connecting the pulmonary artery with the descending aorta. Patent Ductus Arteriosus (PDA)) is an infantile type, where clinical presentation involves 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 in the toes. 
• 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): Present in 25% of adults. Failure of fusion of septum primum with septum secundum after increased left atrial pressure. Clinically detected with bubble test in evaluation of syncope Syncope Syncope is a short-term loss of consciousness and loss of postural stability followed by spontaneous return of consciousness to the previous neurologic baseline without the need for resuscitation. The condition is caused by transient interruption of cerebral blood flow that may be benign or related to a underlying life-threatening condition. Syncope and strokes. 
• Hypoplastic left heart syndrome: High-grade stenosis Stenosis Hypoplastic Left Heart Syndrome (HLHS) or atresia Atresia Hypoplastic Left Heart Syndrome (HLHS) of the aortic and/or mitral valve Mitral valve The valve between the left atrium and left ventricle of the heart. Heart: Anatomy in addition to severe hypoplasia Hypoplasia Hypoplastic Left Heart Syndrome (HLHS) of the left ventricle, ascending aorta Ascending aorta Mediastinum and Great Vessels: Anatomy, and aortic arch Aortic arch Mediastinum and Great Vessels: Anatomy.
• Ebstein anomaly: Defect 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, which is displaced toward the right ventricle. Tethering of septal leaflet causes tricuspid regurgitation Regurgitation Gastroesophageal Reflux Disease (GERD), which will result in right-sided heart failure Right-Sided Heart Failure Ebstein’s Anomaly. 
• Double aortic arch Aortic arch Mediastinum and Great Vessels: Anatomy: Embryonic vascular malformation resulting in a double aortic arch Aortic arch Mediastinum and Great Vessels: Anatomy. This can lead to subsequent constriction of the 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 and esophagus Esophagus The esophagus is a muscular tube-shaped organ of around 25 centimeters in length that connects the pharynx to the stomach. The organ extends from approximately the 6th cervical vertebra to the 11th thoracic vertebra and can be divided grossly into 3 parts: the cervical part, the thoracic part, and the abdominal part. Esophagus: Anatomy.
• Endocardial cushion defect: Defect of the atrioventricular valves as well as the atrial septum and/or ventricular septum. Can present as a complete form ( 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, and severe abnormalities in the AV valves, leading to severe mixing of blood) or a partial form (only 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 and minor AV valve abnormalities). Commonly seen in patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with Down syndrome Down syndrome Down syndrome, or trisomy 21, is the most common chromosomal aberration and the most frequent genetic cause of developmental delay. Both boys and girls are affected and have characteristic craniofacial and musculoskeletal features, as well as multiple medical anomalies involving the cardiac, gastrointestinal, ocular, and auditory systems. Down syndrome (Trisomy 21).