35. Congenital Heart Disease and Other Abnormalities Flashcards
Breifly describe the development of the heart.
What are the 3 unique anatomical connections of foetal circulation?
How do systemic and pulmonary pressures change from foetal to transitional circulation?
Clusters of angiogenic cells -> mesodermal cardiogenic plate -> R/L endocardial tubes fuse = single cardiac tube, beating by 23d -> fold into bulboventricular loop -> atrial, ventricular and outflow tract septation (28d).
Foramen ovale, ductus arteriosus (pulm artery + aorta), ductus venosis (umbilical vein -> IVC, bypasses liver).
Foetal: high resistance pulmonary circulation and low resistance systemic circulation = avoids lungs. Transitional: drop in pulmonary vascular resistance so systemic pressure > pulmonary, shunting across ductus arteriosis and foramen ovale reverses (pic), circ for first 12h of life.
What is persistent pulmonary hypertension of the newborn?
Differentiate between cyanosis due to congenital heart disease and due to lung disease (incl. pulmonary oedema).
Describe transposition of the great arteries/vessels,
Failure in systemic circulation and pulmonary circulation to convert from antenatal circulation pattern to normal pattern. Happens if e.g. meconium aspiration -> inflammation, or infection with GBS.
CHD: normal alveolar gas exchange, no dyspnoea, normal pulmonary venous saturations, results from shunting of deO2 blood from R->L. LD: impaired alveolar gas exchange, tachypnoea and recession, reduced pulmonary venous saturations, results from O2 diffusion problems or V/Q mismatch in lung.
Aorta connected to R ventricle and pulmonary artery connected to L ventricle, so O2 blood back from lungs to LA -> LV -> lungs again. Stays alive due to mixing of blood through FO and DA. Cyanosis.
What 4 abnormalities comprise Tetralogy of Fallot?
What are some other forms of cyanotic heart disease (apart from ToF and TOGV)?
1) VSD allows blood to mix between R and L ventricles.
2) Overriding aorta sits astride ventricular septum so deO2 blood can enter it.
3) Pulmonary setenosis - muscle below pulmonary valve narrows R ventricular outflow tract so hard for blood to enter pulmonary artery.
4) (secondary to 1-3) R ventricle becomes hypertrophied. Blood shunts R->L = cyanosis.
Tricuspid/pulmonary valve atresia (valve not developed so blocks blood flow, survival via FO and DA). Critical pulmonary stenosis. Truncus arteriosus (aorta and pulmonary artery not seperated = common outflow tract). Total anamalous pulmonary venous drainage (TAPVD)(pulmonary vein comes back to R atrium).
What are the 2 major groups of acyanotic congenital heart disease?
How can acyanotic congenital heart disease cause secondary cyanosis?
Describe VSD.
1) L->R shunts which increase pulmonary blood flow (-> pulmonary oedema/hypertension).
2) L heart outflow tract obstruction (-> pulmonary oedema, impaired tissue perfusion, lactic acidosis (b/c not enough blood to organs)).
Pulmonary oedema impairs gas exchange -> dyspnoeic -> cyanosis OR pulmonary hypertension causese R->L shunting (Eisenmenger shunt).
Ventricular septal defect: acyanotic, pressure higher on LV than RV so blood shunted L->R. Too much blood going to the lungs.
What effect to L->R VSD shunts have on the ratio of pulmonary to systemic blood flow?
What are some other types of acyanotic heart disease?
What are some complex mixed presentations?
Twice as much blood going through the lungs -> pulmonary oedema. Abnormal loop of blood flow joining normal systemic blood flow (pic).
Atrial/atrioventricular septal defect (AVSD due to endocardial cushions - VSD, ASD, abnormal AV valve), patent ductus arteriosus, A-V malformations (liver, brain) - abnormal connection between arteries and veins, bypassing the capillary system, critical aortic stenosis.
Hypoplastic L heart, double outlet right ventricle.
Describe predictal coarctation of the aorta - LV outflow tract obstruction.
Why might presentation be delayed?
What is the initial treatment?
Acyanotic CHD. Narrowing in aorta, blood backs up into lungs -> pulmonary oedema and lactic acidosis due to poor blood flow to rest of the body. Pt says well in first few days due to DA.
DA and FO may bypass obstruction (ToF, pulmonary atresia, coarctation, hypoplastic L heart), or allow mixing (TOGV). Only obvious once DA closes in first few days of life.
Reopening the DA with prostaglandin E, or enlarging the FO (balloon septostomy for transposition) can be acutely life-saving.
Describe hypoplastic left heart.
How is cyanotic CHD treated?
How is acyanotic CHD treated?
Aortic valve blocked so no blood through L ventricle, so it hasn’t developed properly in foetal life. Uses DA to get blood from pulmonary artery -> aorta, and blood back to lungs needs to go through the FO.
Establish adequate pulmonary blood flow (prostaglandin E, laser + balloon valvotomy for pulmonary atresia, modified Blalock-Taussig shunt). Definitive correction of anatomical abnormality (arterial switch for transposition, valvotomy, closure of VSD/ASD).
Symptomatic: small muscular VSD, PDA and ASD/PFO may close spontaneously. Diuretics +/- ACE-I for L->R shunts to treat pulmonary oedema. Prostaglandin E for LV outflow tract obstruction. Can correct with: percutaneous catheter closure of PDA, ballon dilation of valvular stenosis, repair of coarctation, open heart sugery for VSD/ASD.
What are some limiting factors in treatment of CHD?
Describe the following neural tube defects (failure of normal ‘zipping up’ of neural tube by 28d):
a) spina bifida occulta
b) meningocoele
c) myelomeningocoele (spina bifida)
d) encephalocoele
e) anencephaly
Anatomical - disuse atrophy: can’t grow new ventricles so univentricular anatomy may be best, pulmonary arteries may be too small. Fuctional: chronically elevated pulmonary blood flow -> irreversible pulmonary hypetension.
a) Small defect in vertebral arch, neural tissue OK, neves normal.
b) Protrusion of the meninges through gap in spine, neural tissue may be ok.
c) Meninges and neural tissue exposed at skin level. Often neurological deficits.
d) Brain tissue and overlying meninges herniate out through a defect in the cranium.
e) Absence of a major portion of the brain, skull, and scalp. Incompatible with life.
How is myelomeningocoele and hydrocephalus (CSF accumulates in brain) treated?
What are some neurological consequences of lumbar myelomeningocoele?
Describe the following abdominal wall defects:
a) gastroschisis
b) exomphalos
Closure reduces risk of infection but doesn’t restore normal neural function. Hydrocephalus common and needs V-P shunt (fluid from ventricle -> peritoneal cavity).
Mixed sensory, motor and autonomic problems, faecal/urinary incontinence +/- retention, paralysis and loss of leg sensation.
a) full thickness small defect in abdo wall lateral to umbilicus, bowel free in amniotic cavity, surgical closure. No overlying sac.
b) Membrane covers herniated viscera, may be associated with other abnormalities and genetic disorders.
What causes a cleft lip and palate?
Failure of fusion of maxillary and frontonasal processes. Complete surgical correction possible. Minor abnormalities of palatal control may persist. Risk of conductive hearing loss.
