Congenital Heart Disease and other Abnormalities Flashcards
What is the cardiac embryology?
- clusters of angiogenic cells from mesodermal cardiogenic plate arising from right and left endocardial tubes
- day 21: lateral folding brings tubes together forming primitive heart tube
- day 23: heart beats
- tube lengthens and folds further into bulboventricular loop
- day 28: septation of the atria, ventricles and outflow tract
- over 2nd and 3rd trimester: long periods and maturation
What does failure of the septation of the atria cause?
CHD
- early (AVSD from endocardial cushion)
- late (simple ASD or VSD)
What are the anatomical connections in fetal circulation?
- foramen ovale (bypasses pulmonary circulation)
- ductus arteriosus
- ductus venosus (1/3 of blood supply from umbilical vein)
What is the purpose of anatomical connections in fetal circulation?
- high resistance pulmonary circulation
- low resistance systemic circulation
What is the purpose of high pressure in fetal circulation?
High pressure pulmonary circulation forces most blood through ductus arteriosus into systemic circulation (diverts it from pulmonary circulation)
What closes during pregnancy?
- closure of ductus arteriosus
- closure of foramen ovale
- closure ductus venosus
What is the purpose of the ductus arteriosus closing?
- increased oxygen levels
- in utero ductus is kept open under PG E1 influence
What is the purpose of formen ovale closing?
- drop in pressure in pulmonary circulation/right side of heart
- shunting reversed and valve closes
What is the purpose of ductus venosus closure?
- decrease in blood flow in IVC
What is persistent pulmonary hypertension of the newborn?
- if problems with lungs (pneumonia, aspirate meconium(
- increased pressure in pulmonary artery keeping foramen ovale open
- shunting of deoxygenated blood into systemic circulation
- cyanotic baby
What is cyanosis?
- patient blue
- blue produced by amounts of deoxygenated Hb (g/l) not percentage saturation
- Hb>50g/l in capillaries OR 34/l in arterial blood
How does CHD present?
- normal alveolar gas exchange
- no dyspnoea
- normal pulmonary venous saturations
- results from shunting of deoxygenated blood from right to left
How does lung disease present?
- impaired alveolar gas exchange
- tachypnoea and recession
- reduced pulmonary venous saturations
- results from oxygen diffusion problems or ventilation-perfusion mismatch within the lung
What is the main difference between lung disease and CHD?
CHD - no problem with functioning of lungs so normal oxygenation
Lung disease - limited gas exchange so body not perfused
What occurs in transposition of great vessels?
- aorta connected to RV, pulmonary connected to LV forming 2 separate connections
- baby stays alive because of blood mixing in foramen ovale and ductus arteriosus
What is teratology of fallot?
- ventricular septal defect
- overriding aorta (aorta above septal defect)
- right ventricular hypertrophy
- stenosis of RV (narrow outflow)
What are other forms of CHD?
- tricuspid atresia (complete valve closure)
- pulmonary valve atresia
- critical pulmonary stenosis
- truncus arteriosus (single artery from heart, large ventricular septal defect below valve of trunk)
- total anomalous pulmonary venous drainage (pulmonary veins not connected to LA but to one of veins draining back to RA)
Define acyanotic?
Patient pink
What are the 2 major groups of acyanotic congenital problems?
- left to right shunts: increase pulmonary blood flow = pulmonary oedema/hypertension
- left heart outflow tract obstruction: pulmonary oedema/impaired tissue perfusion/lactic acidosis (increased back pressure on pulmonary veins -> pulmonary circulation)
How can cyanosis occur as a secondary feature of acyanosis?
- pulmonary oedema impairs gas exchange
- pulmonary hypertension causes right to left shunting as there is higher pressure on right side = Eisenmenger shunt
- dangerous = if closed will develop right heart failure
What is ventricular septal defect?
- pressure in left ventricle is higher than right -> shunt
What is preductal coarctation of the aorta?
- causes pulmonary oedema as increased pulmonary pressure
- preductal: before ductus arteriosus
What are other forms of cyanotic CHD?
- atrial septal defect
- atrioventricular septal defect
- critical aortic stenosis
- patent ductus arteriosus
What are the main complex mixed presentations?
Hypoplastic left heart
Double outlet right ventricle (aorta connects to right ventricle instead of left)
What is hypoplastic left heart?
- no blood flow through left ventricle to aorta
- patient reliant on fetal circulation to stay alive
- blood flows through foramen ovale into right ventricle -> pumped to rest of body
How may ductus arteriosus and foramen ovale delayed presentation/treatment?
- bypass obstruction (teratology of fallot, pulmonary atresia, coarctation, hypoplastic left heart)
- allow mixing (transposition)
- both delay presentation as mild cyanosis easily missed and only get symptoms once ductus closes
- reopen ductus with PG E/enlarge foramen ovale with balloon septostomy transposition
How do you treat CHD?
- depends on condition
- monitoring
- diuretics for pulmonary oedema
- re-open ductus arteriosus with PG E
- surgery and catheter procedures
Symptoms of acyanotic CHD?
- expectant small vascular VSDs PDA and ASD/PFO may close spontaneously
- diuretics and prostaglandins
What would definitely correct acyanotic CHD?
- percutaneous catheter closure of PDA
- balloon dilatation of valvular stenosis
- repair of coarctation
- open heart surgery for VSD/ASD
What are the limiting factors in treatment of CHD?
- anatomical@ disuse atrophy (cannot grow new ventricles)
- functional: chronically elevated pulmonary blood flow (irreversible pulmonary hypertension)
What neural tube defects are there?
- failure of normal zipping of neural tube
- spina bifida occulta (failure of one or more vertebrae in spine to form properly)
- meningocoele (meninges protrude form spinal column)
- encephalocoele (protrusion of neural tissue from head)
- anencephaly (absence of major portion of brain, skull and scalp)
What is the most serious form of spina bifida occulta?
- myelonmengocoele: neural tissue exposed on babies back
How is myelomeningocele treated?
- closure reduces risk of infection but does not restore neural function
- closure may lead to hydrocephalus (plastic catheter through valve running under skin into peritoneal cavity to be rapidly absorbed into circulation)
What are the neurological consequences of lumbar myelomeningocele?
- mixed sensory, motor and autonomic problems (dependent on level of lesions and degree of neural disruption)
- loss of bladder control, faecal incontinence and loss of sensation in legs
What are the abdominal wall defects?
Gastroschisis
Exomphalos
What are the features of gastrochisis?
- full thickness small defect in abdominal wall lateral to umbilicus (bowel free within abdominal cavity)
- surgical closure possible
- bowel may take 1-3 months to start functioning normally
What is exomphalos?
- wide based defect
- membrane covers herniated viscera
- may be associated with other abnormalities/genetic disorders
What is cleft lip?
- common defect where maxilla fail to fuse with frontonasal process
- complete surgical correction possible
- can affect eustachian tube function (risk of conductive hearing loss)
What is cleft palate?
- common defect
- failure of secondary palate to fuse
- philtrum formed
- tongue too large and stops plated from turning horizontally
- general failure of rotation
- can affect eustachian tube function (risk of conductive hearing loss)
