Large Ventricular Septal Defect with Irreversible Pulmonary Hypertension

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1 Week 20 Blue Is For Boys Tetralogy of Fallot Presenting Symptoms Child, 4 Cyanosis Exercise Tolerance Failure to thrive Clubbing Lower Sternal Heave Right ventricular hypertrophy Loud ejection systolic murmur at left sternal border Hx of Cardiac Surgery Cyanosis Blue coloration of the skin/mucous membranes Due to > 30g/L (~20%) deoxygenated haemoglobin in circulation Mechanism: Deoxygenated blood leaving the heart prior to reaching periphery, due to low oxygen saturation and/or abnormal haemoglobin Cardiac: mixing of venous + arterial blood = O2 sat Respiratory: V/Q mismatch or shunting of blood through lungs inadequate oxygenation = deoxygenated haemoglobin in pulmonary vein Congenital Heart Defects Shunt: portion of the blood going from R. L. side of the heart without an opportunity for exchange of oxygen and carbon dioxide Anatomic shunt: intracardiac septal defects, via pulmonary arteriovenous malformations + a % of venous return from cardiac and bronchial circulations directly emptying into L. Atrium Physiological Shunt: Blood entering the arterial system without passing through the ventilated areas of the lung causing po2 of arterial blood to be less than that of alveolar po2 3 major categories of CHDs 1. Left to Right Shunts After birth the pressure in the left side of the heart is greater than in the right side of the heart Shunts connecting the left side and right side lead to blood flowing back into the right side of the heart Causes: ventricular septal defect, atrial septal defect (not patent foramen ovale), patent ductus arteriosus, interventricular septal defect (common in Down syndrome patients) Consequences: increased pulmonary pressure, right ventricular hypertrophy (due to pressure) Not associated with cyanosis Atrial Septal Defect Ventricular Septal Defect Patent Ductus Arteriosus Complete Atrioventricular Canal Defect 2. Right to Left Shunts Blood flows from the right side of the heart to the left - resulting in less pulmonary bloodflow Causes: Tetralogy of Fallot, transposition of great vessels, persistent truncus arteriosus Consequences: The major effect is reduced pulmonary blood flow, leading to poor oxygenation of the blood (and therefore cyanosis (+ clubbing), also compensatory polycythaemia) 3. Obstruction Examples: Coarctation of the aorta; aortic or pulmonary valvular stenosis; tricuspid atresia Often, congenital heart defects occur in combinations (e.g. get septal defects + obstructive malformations) Congenital Malformations Critical Periods in Embryological Development PRE- EMBRYONIC (fertilization week 3): Processes of cleavage and blastocyst formation all of nothing response to teratogens Embryo will either die or it will not be affected EMBRYONIC PERIOD (weeks 3-8): Most susceptible/sensitive period (due to ORGANOGENESIS) Major structural abnormalities can occur FOETAL PERIOD (week 9 birth): Period of intense growth ( mass and length) Less susceptibility (but can still get more minor malformations, or functional defects eg. Mental retardation) Large Ventricular Septal Defect with Irreversible Pulmonary Hypertension TORCH infections associated with congenital malformations: T - toxoplasmosis O other infections (e.g. syphilis, varicella) R - rubella C - cytomegalovirus H herpes simplex

2 Tetralogy of Fallot Four heart defects that occur simultaneously UNTS (the Ts ) 1. Ventricular Septal Defect (VSD) underdevelopment of membranous septum mixing of deoxygenated blood from right heart with oxygenated blood from left heart 2. Pulmonary Infundibular Stenosis area just before pulmonary valve is stenosed impaired right ventricular outflow bloodflow to lungs right ventricular (RV) outflow tract obstruction (RVOTO) 3. Overriding Aorta Aortic dextroposition due to improper formation of the aorticopulmonary septum, the aorta is larger than the pulmonary trunk it straddles the IV septum and collects most of the bloodflow from both ventricles 4. Right Ventricular Hypertrophy A functional result of increased pressure in the right ventricle due to the infundibular Stenosis Normal Foetal Circulation Umbilical Arteries (arise from internal iliac arteries) PLACENTA Umbilical Vein (becomes ligamentum teres) Portal Sinus LIVER Systemic Arteries and Capillaries Normal Embryological Shunts Three normal shunts allow most blood to bypass the lungs and liver: Ductus venosus - allows oxygenated blood from the umbilical vein to bypass liver sinusoids and enter the inferior vena cava Foramen ovale - between the left and right atria, allows blood to bypass the lungs Ductus arteriosus - allows blood from the pulmonary trunk to bypass the lungs by flowing directly into the aorta Risk Factors for Tetralogy Of Fallot Maternal Rubella (or other viral illnesses during pregnancy) Poor prenatal nutrition, Maternal alcohol use, Maternal age older than 40 years, Maternal phenylketonuria (PKU) birth defects Maternal diabetes Heart Embryology The heart derives from the cardiogenic region, which is made up of splanchopleuric mesoderm (forming the myocardium and cardiac jelly). It is later invested with mesothelium (forming the endocardium). Two endocardial tubes fuse to form a primitive heart tube, which starts to beat at day 22 after conception. This heart tube then folds to form the basic shape of the heart. Four septation steps, occurring simultaneously, divide heart into its atria, ventricles and outflow vessels: Atrioventricular: Endothelial cushions invade the heart, leaving AV canals. Atrial: Septum primum (ostium primum/secondum) septum secondum (foramen ovale) Aorticopulmonary: Truncoconal swellings form the spiral- shaped aorticopulmonary septum. Interventricular: Muscular septum grows up, membranous septum grows down. Ductus Venosus Vaccination Viruses are a common risk factor for congenital conditions thus vaccination can reduce the incidence of congenital defects Vaccination involves injection of pathogen- specific antigens into the body in order to prime the adaptive immune system for an infection primary infection induces a much stronger secondary response Types of Vaccine 1. Live/attenuated virus the most immunogenic/effective but can cause symptoms 2. Killed/inactivated virus moderately immunogenic, not possible for all viruses 3. Viral subunits (protein subunit vaccines) safest but least immunogenic Herd Immunity Raising the overall level of immunity in the population to a point at which there are insufficient susceptible individuals to maintain effective transmission People who are not vaccinated reduce herd immunity Many people have never seen the effects of diseases like polio and diphtheria because of vaccination and so they think that since it isn t around they don t need to be vaccinated for it Systemic Veins Aorta Left Ventricle Left Atrium Foramen ovale Right Atrium IVC Ductus arteriosus Pulmonary Trunk Right Ventricle Lungs

3 Valvular Heart Disease Stenosis (narrowing) or regurgitation (insufficiency) of the heart valves - due to congenital defects or a variety of acquired diseases Pathophysiology Aetiology Consequences Heard as a Aortic Stenosis Narrowing of the aortic valve impaired left ventricular emptying stroke volume + end systolic volume end diastolic volume preload & force of contraction Calcification of the aortic cusps, congenitally bicuspid aortic valve (predisposes to calcification) Left ventricular hypertrophy, left ventricular failure Systolic murmur (lubwhistle-dup) Aortic Regurgitation Insufficiency of the aortic valve blood flow back into left ventricle during diastole end diastolic volume stroke volume & force of contraction Infective endocarditis, lupus Systolic ventricular failure Diastolic murmur (lubdup-swish) Mitral Stenosis Narrowing of the mitral valve impaired left ventricular filling end diastolic volume stroke volume cardiac output Compensatory mechanisms: vasoconstriction, HR, contractility, blood volume Calcification, rheumatic fever (fibrosis from rheumatic carditis) Left heart failure (pulmonary oedema), left atrial hypertrophy Diastolic murmur (lubdup-whistle) Mitral Regurgitation Insufficiency of the mitral valve blood flow back into left atrium during systole left atrial systolic pressure end diastolic volume + afterload Myxomatous degeneration (e.g. Marfan syndrome), infective endocarditis Systolic murmur (lupswish-dup) MANAGEMENT PLAN Protocol Blalock- Taussig Shunt Process Classic Blaclock- Taussig Shunt: Involves a direct anastomosis between the transected subclavian artery (or the innominate artery) and the pulmonary artery. Modified Blaclock- Taussig Shunt: An interposition polytetrafluoroethylene (PTFE, or Gore- Tex) graft between the subclavian artery and the pulmonary artery is used to prevent sacrificing the subclavian artery. Total Repair surgery Open the pulmonary stenosis, close the septal defect, reconstruct the pathway into the aorta successful surgery can increase life expectancy from 3-4 years to 50+.

4 PPH / PPD / Other Implications Vaccination Programs Ethical issues in immunization: Immunization is for the benefit of the individual, but also for the benefit of the whole population (herd immunity). Thus, the more individuals that refuse to be vaccinated, the higher the risk of disease to the whole population. Ethics of compulsory vaccination = informed consent of all risks necessary; do parents have right to withhold vaccination from their child (JW are not allowed to withhold blood transfusions...?); consequences of non- vaccination (include discrimination of that child, spread of disease, illness, etc). Reasons for no vaccination = access for rural people, education about necessity, costs of vaccinations, belief in myths (such as vaccination causes SIDS). Vaccination failure occurs because = vaccines never 100% effective; poor administration; missed / delayed doses. In Australia, a national immunization program gives free vaccination (Hep B, Diphtheria, Tetanus, Acellular Pertussis, Haemophilus influenzae type B, Oral poliomyelitis, Pneumococcal conjugate, Measles, Mumps, Rubella, Meningococcal C, Pneumococcal polysaccharide and Influenza). Congenital Malformations Congenital malformations are anatomical defects, chromosomal abnormalities or other genetic diseases that are present at birth. These include conditions which are genetic or caused by environmental factors. They can be either lethal, or just present defects (mild or severe) in the child). Congenital anomalies account for approx of all births. Women 40+yrs are twice as likely ( checking systems); congenital anomalies are higher in ATSI women. Most common = Hypospadias (23.8/10,000); Trisomy 21 (11.1/10,000); Neural tube defects (4.2/10,000). Prenatal screening (ultrasound or amniocentesis) has likelihood of detecting congenital malformations before birth. - Termination of pregnancy following the diagnosis of a congenital malformation is increasing, resulting in a decreased recorded incidence of some malformations. Newborn Screening Blood test that aims to detect certain rare, genetic and/or metabolic conditions that may be life- - threatening and/or cause intellectual disability prior to onset of symptoms, with the goal of reducing the effect of the condition on the child through earlier treatment Strategies to reduce Congenital defects There are many strategies that have been implemented, such as; Family planning services ( age related malfs) Screening programs amniocentesis for at risk groups Regulate good nutrition as much as possible (i.e. adding folate to bread products to NTDs) Control maternal diabetes Provide genetic counseling ( rate of genetic malfs) Educate to smoking and drinking during pregnancy Conditions screened for Australia wide: CF PKU Galactosaemia Primary congential hypothyroidism Rare metabolic conditions Criteria for Newborn Screening: 1. Benefit to the individual from early diagnosis 2. Benefit is cost- - effective 3. Reliable screening test available 4. System in place to deal with diagnostic testing, counseling, treatment & follow- - up of patients identified by test

5 Embryology of the Heart Fusion and Folding: Weeks 3 & 4 Cardiogenic Region Dorsal Aortae Truncus arteriosus Endocardial Tube Primordial Heart Tube Vitelloumbilical vein Bloodflow A B C D Day 15: The Cardiogenic Region (A) is derived from splanchopleuric mesoderm. Day 19: Two Endocardial Tubes (B) are formed by vasculogenesis. Day 20: The embryo folds, bringing the endocardial tubes closer together. Day 21: Endocardial tubes fuse to form a Primitive Heart Tube (C), with sulci separating it into chambers: Bulbus Cordis Forms smooth parts of left (conus arteriosus) and right (aortic vestibule) ventricles Primitive Ventricle Forms trabeculated (muscular) parts of the left and right ventricles Primitive Atrium Forms anterior parts of the left and right atria Sinus Venosus Forms the superior vena cava and part of the right atrium Day 22: The heart starts beating. The splanchnopleuric mesoderm already present in the tube derives into myocardium and cardiac jelly. Mesothelial cells enter into the tube and derive into endocardium. Day 23: Folding of the heart commences. The Bulbus Cordis moves inferiorly, anteriorly and to the right The Primitive Ventricle moves to the left side The Primitive Atrium and Sinus Venosus move superiorly and posteriorly Day 28: Folding is complete (D). Septation: Weeks 5 & 6 The Atrioventricular Septum Endocardial cushions form the septum intermedium, separating the atria and ventricles and leaving the left and right atrioventricular canals. Common atrium Atrioventricular canal Endocardial Cushion Common Ventricle Left & right atrioventricular canals

6 The Atrial Septum Septum primum Ostium secondum Septum secondum Foramen ovale Valve Fossa ovale Ostium primum The septum primum forms towards the endocardial cushions. The space between left during formation is the ostium primum. 2. As the ostium primum closes, a perforation forms in the septum primum the ostium secondum. 3. The septum secondum starts to form, leaving the foramen ovale. 4. In fetal circulation, the lungs are underdeveloped so there is increased resistance in the pulmonary circulation. Since the pressure in the right heart is higher than pressure in the left heart, blood flows from the right atrium through the foramen ovale and ostium secondum into the left atrium. 5. The ostium secondum enlarges, degrading the septum primum partly. What is left over is called the valve of the foramen ovale. 6. After birth, the pulmonary circulation begins to work properly, reversing the pressure difference between atria and thus closing off the valve of the foramen ovale. The valve and the foramen eventually fuse (by three weeks after birth) and leave behind the fossa ovale. The Aorticopulmonary Septum Truncoconal swellings Aorticopulmonary septum Truncoconal swellings, or masses of tissue, form on the sides of the truncus arteriosus. These swellings join to form the spiral-shaped aorticopulmonary septum. This septum grows down to form part of the membranous part of the ventricular septum. The Interventricular Septum The muscular intraventricular septum grows up from the ventricular floor, but doesn t completely separate the ventricles; The membranous intraventricular septum grows down from the septum intermedium and aorticopulmonary septum, to join the muscular septum.

7 Fetal Circulation Prenatal Circulation Postnatal Circulation Foramen ovale Ductus arteriosus Fossa ovalis Ligamentum arteriosum Ductus venosus Ligamentum venosum Umbilical vein Ligamentum teres Umbilical arteries Medial umbilical ligaments Transmission of blood supply to the fetus is by the umbilical vein from the placenta. Oxygen poor blood returns to the placenta through umbilical arteries. The lungs are filled with fluid, so the pulmonary circulation has high resistance this makes the pressure in the pulmonary circulation higher than that in the systemic circulation, so blood tends to flow into the systemic circulation (or left side of the heart). Shunts Three normal shunts allow most blood to bypass the lungs and liver: o Ductus venosus - allows oxygenated blood from the umbilical vein to bypass liver sinusoids and enter the inferior vena cava o Foramen ovale - between the left and right atria, allows blood to bypass the lungs o Ductus arteriosus - allows blood from the pulmonary trunk to bypass the lungs by flowing directly into the aorta After Birth After birth, several changes close these shunts and normal human circulation commences o Loss of placental circulation increases systemic circulation resistance while inflation of the lungs lowers pulmonary circulation resistance. This reversal of pressures switches the pressure gradient between atria and the foramen ovale is held closed ( fossa ovalis). o Reversal of pressure between the aorta and pulmonary trunk causes constriction and closure of the ductus arteriosus ( ligamentum arteriosum). o Clamping of the umbilical cord collapses the umbilical vessels (umbilical vein ligamentum teres) and ductus venosus ( ligamentum venosum).