Paeds cardio Flashcards
Location and function of foramen ovale
Shunt between the atria.
Allows blood in R.atrium to bypass the RV and pulm. circulation.
Becomes fossa ovalis a few weeks after birth.
Where do the pulmonary veins drain into?
Carry ox. blood into L atrium
What do the pulmonary arteries do?
Carry deoxy. blood from RV to lungs
Location and function of ductus arteriosus
Shunt connecting the pulmonary artery with the aorta, bypasses pulm. circulation.
Becomes ligamentum arteriosus when prostaglandins drop.
Ductus venosus
Shunt connects the umbilical vein to the inferior vena cava, to bypass the liver.
Becomes ligamentum venosum when cord is clamped.
Pathophysiology of patent ductus arteriosus
Pressure in aorta > pulmonary arteries. Get a L to R shunt. Increased pressure in pulmonary arteries causes pulmonary hypertension, R sided strain and RVH.
Greater flow through pulmonary circulation leads to LVH.
RF for patent ductus arteriosus
Rubella
Prematurity
Sx of PDA
sob
difficulty feeding
poor weight gain
LRTI
Murmur heard in PDA
If small, murmur may not be present.
Continuous crescendo-decrescendo machinery murmur, can continue through second heart sound, making it difficult to hear.
What investigation should be ordered if PDA is suspected?
Echo
PDA prognosis/mx
Small PDAs can be asymptomatic and close spontaneously.
Unless symptomatic, generally monitor with echos until age 1. Beyond 1, it’s unlikely to close spontaneously so will require trans-catheter or surgical closure.
Pathophysiology of transposition of great arteries
Attachments of aorta and pulmonary arteries are switched, resulting in two separate circulations that don’t mix. The R side is systemic only. The L side is pulmonary only.
Normal development during pregnancy due to placenta. Following birth, the baby becomes cyanosed and requires a systemic-pulmonary shunt for immediate survival. This shunt may be a PDA, ASD or VSD.
How is transposition diagnosed? What arrangements should be made?
Antenatal US.
Requires close monitoring through pregnancy and arranging the birth at a hospital that’s capable of managing the condition.
What conditions is transposition associated with?
Coarctation of aorta
VSD
Pulmonary stenosis
How does transposition present?
Cyanosis at birth or within a few weeks. A shunt will initially provide some compensation, but within a few weeks baby will develop respiratory distress, tachycardia, poor feeding, poor weight gain, sweating.
How is transposition managed?
Definitive management is open heart surgery within a few days using a cardiac bypass machine.
Time can be bought through using a prostaglandin infusion to maintain the DA, or through balloon septostomy.
RF for tetralogy of fallot
Rubella
Mum = diabetic/over 40/drinking during pregnancy
What are the 4 coexisting pathologies of tetralogy of fallot?
VSD
Overriding aorta (positioned further to the right, more deoxy. enters when the heart contracts)
Pulmonary valve stenosis
RVH
Why does RVH occur in tetralogy of fallot?
Increased resistance from p.stenosis and from LV due to VSD.
Why does a R to L shunt occur in tetralogy?
Pulmonary stenosis creates greater resistance for RV, so blood is encouraged to flow through the VSD.
Overriding aorta is positioned more to the right, so more deoxy. enters the aorta from the R.
What is the impact of the R to L shunt in tetralogy?
Blood bypasses the lungs, travels to the body deoxygenated, causing cyanosis.
How is tetralogy diagnosed?
Antenatal scans- echo with doppler flow studies to assess severity of shunt.
Ejection systolic murmur during baby checks.
Can present as heart failure as the child ages.
Signs and symptoms of tetralogy of fallot
Cyanosis Clubbing Poor feeding Poor weight gain Ejection systolic murmur, loudest over pulmonary area. "Tet spells"
Pathology of “Tet spells” in tetralogy
R to L shunt is intermittently, temporarily worsened, precipitating a cyanotic episode. This occurs either when 1) pulmonary resistance increases 2) systemic resistance decreases.
When a child physically exerts itself, more CO2 is produced, which is a vasodilator. Systemic vasodilation reduces systemic resistance, so blood takes the easier path from RV to aorta instead of the lungs.
When may “tet spells” occur + how do they present?
Can be precipitated by waking, crying, physical exertion.
Become irritable, cyanosed, reduced consciousness, seizures, potential death.
How can tet spells be treated?
Squatting in older kids/knees to chest in younger- increases systemic resistance.
Medical mx: involve senior paed. Think of breathing, increasing resistance and relaxation.
- O2
- Sodium bicarb if met.acid.
- Morphine to reduce resp.drive
- IV fluids to increase preload, more reaches pulm.
- Beta blockers to reduce RV
- Phenylephrine to increase systemic resistance
Mx of tetralogy
Definitive mx = open heart surgery.
Prostaglandin infusion can be used to maintain the DA so blood can shunt back from the aorta - pulmonary arteries.
Valves on L side of heart
M
A
Valves on R side of heart
T
P
