State eight functions of the placenta
- foetal homeostasis
- gas exchange
- acid base balance
- nutrient transport to foetus
- waste transport from foetus
- hormone production
- transport of IgG
- PGE2
How can the foetal lungs be described prior to birth?
Unexpanded & filled with fluid
Describe foetal blood supply
From the placenta oxygenated blood comes through the umbilical vein and leaves through the umbilical arteries which arise from the descending aorta
Name the structure that connects the umbilical vein to the IVC
Ductus venosus
What is the function of the ductus venosus?
Allows blood with nutrients to come from the placenta without being processed by the liver
Name the opening in the atrial septum
foramen ovale - connects RA to LA
What is the function of the foramen ovale?
The oxygenated blood enters LA then LV and flows to ascending aorta & carotids
What is the function of the ductus arteriosus?
connects the pulmonary bifurcation to the descending aorta - only 7% of blood flows to foetal lungs
How is the ductus arteriosus kept open?
prostaglandin E2 produced by the placenta
What type of drugs inhibit prostaglandin E2?
NSAIDs - contraindicated in pregnancy
What happens to the lungs after the baby is born?
They inflate and fill will oxygen, the baby turns from blue to pink, pulmonary vascular resistance decreases
What is the result of circulating oxygen increase?
It is a vasodilator therefore decreases resistance
At what age will pulmonary resistance reach adult levels?
2-3 months
What happens to systemic vascular resistance?
When the cord is cut it increases as more cardiac output goes to the lungs
After birth what happens to the foramen ovale?
It closes so there is no flow between the atria (this mechanism fails in 20% of the population)
What happens to the ductus arteriosus after birth?
Constricts due to increased oxygen and reduced prostaglandins, ends up as fibrous ligament - ligamentum arteriosum
What are oxygen sats when a baby is born?
60-70%
Describe failure of ductus arteriosus closure
High incidence in premature babies, causes extra blood to flow to the lungs, increasing pulmonary BP leading to SOB and cardiac arrest
Why is there increased blood flow to the lungs?
Blood shunts from the aorta to the pulmonary bifurcation
When is persistent pulmonary hypertension common?
- sepsis
- hypoxic ischaemic insult
- meconium aspiration syndrome
- cold stress
- prematurity
What are the signs of PPH?
The baby will remain blue after birth and oxygen sats will be higher in the upper body compared to lower
State the two management aims in babies with PPH
- reduce pulmonary resistance
- increase systemic resistance
How can pulmonary resistance be reduced?
- ventilation & oxygenation
- sedation
- thermoregulation
- correction of acidosis
- treat sepsis
- inhaled NO
How can systemic resistance be increased?
- increase BP
- inotropes
- support other organ function
- heart bypass
Describe the spectrum of severity
Mild - asymptomatic
Moderate - requires specialist intervention
Severe - presents severely unwell
Major - needs surgery within first year of life
State the six different time periods for screening
- Antenatal
- Newborn (24 hours old)
- Day 1-2
- Day 3-7
- 4-6 weeks
- 6-8 weeks
Describe antenatal screening
18-22 weeks gestation scan
What are the management options if congenital heart disease is detected on an antenatal scan?
Prostaglandin E2 infusion, palliative care, termination
What signs may present 1-2 days post birth?
murmurs, abnormal pulses, cyanosis, ductual sats
What may present 3-7 weeks after birth?
sudden circulatory collapse, shock, cyanotic death
How will 4-6 week year old babies with CHD present?
cardiac failure, reduced feeding, failure to thrive, SOB, sweating
What is the most common congenital defect? How will it present?
Muscular ventricular septal defect - a murmur can be heard early in life due to blood shunting from left to right
What causes cyanosis?
any condition that causes blood that is deoxygenated to pass the lungs and enter the systemic circulation
What is the most common cause of cyanosis?
Transposition of the great arteries e.g the aorta arises from the RV
What is the differential diagnosis for a baby with cyanosis?
- cardiac disease (blue with no resp distress)
- respiratory disease (increased work of breathing & x ray changes)
- PPHN (very ill baby)
State two reasons for collapse at the time of duct closure
- duct dependent systemic circulation
- duct dependent pulmonary circulation
What may cause duct dependent systemic circulation?
- hypoplastic left heart syndrome
- coarctation of the aorta
- aortic stenosis
- interruption of aortic arch
What may cause duct dependent pulmonary circulation?
- pulmonary atresia (valve not working )
- pulmonary stenosis
What are the signs of a baby that has collapsed due to duct closure?
- pallor
- prolonged CRT
- poor pulses
- crepitations
What is the differential diagnosis for a baby collapsed due to duct closure?
sepsis, metabolic disease
What is the treatment for a baby collapsed due to duct closure?
ABC, prostaglandin E2, specialist support
Why is a baby likely to present with cardiac failure?
Large left to right shunt increases pulmonary and ventricular flow, a few weeks later pulmonary pressure drops and blood moves right to left (shunt reverses)
What are the clinical signs of VSD?
- failure to thrive
- slow/reduced feeding
- SOB
- sweatiness
- hepatomegaly
- crepitations
How can a patent ductus arteriosus be repaired?
Catheter procedure which does not require bypass - insertion of a closure device
How can VSD be repaired?
Involves closure with a patch that required bypass, thoracotomy and follow up through childhood
Why is hypo plastic left heart syndrome repair difficult?
It is a three stage operation & is only palliative, transplant is eventually required as it involved the RV supplying the systemic circulation but this fails over time