Congenital Abnormalities of the Cardiovascular System

Congenital heart disease (CHD) is a structural abnormality of the heart or great vessels present at birth. Defects alter pulmonary blood flow, systemic blood flow, mixing or cardiac workload. Critical CHD requires catheter or surgical intervention in early life and may first appear when the ductus arteriosus closes.

Suspect critical CHD in unexplained central cyanosis, shock, weak/absent femoral pulses, differential upper/lower limb saturation, severe tachypnoea without marked lung findings, hepatomegaly, poor feeding/sweating, metabolic acidosis or sudden collapse in the first days of life. A murmur may be absent.

Fetal Circulation and Transition

Before birth the placenta oxygenates blood, and the foramen ovale and ductus arteriosus bypass the lungs. After birth lung expansion lowers pulmonary resistance, cord clamping raises systemic resistance, the foramen ovale functionally closes and the ductus constricts. Duct-dependent lesions deteriorate when this pathway closes; prostaglandin E1 can temporarily maintain ductal patency under specialist care.

Classification by Physiology

Group	Examples	Main effect
Left-to-right shunt	VSD, ASD, patent ductus arteriosus, AV septal defect	Excess pulmonary flow and heart failure; usually no early cyanosis
Obstructive	Coarctation, aortic stenosis, pulmonary stenosis	Restricted ventricular/systemic or pulmonary outflow
Cyanotic/mixing	Tetralogy of Fallot, transposition, truncus, total anomalous pulmonary venous return	Deoxygenated blood enters systemic circulation
Duct-dependent systemic flow	Hypoplastic left heart, critical aortic stenosis, severe coarctation	Shock when duct closes
Duct-dependent pulmonary flow	Pulmonary atresia, critical pulmonary stenosis, some severe TOF	Profound cyanosis when duct closes

Acyanotic Shunt Lesions

Ventricular Septal Defect

A VSD is an opening between ventricles. Small defects may cause a loud murmur but little illness and may close spontaneously. Large defects produce increasing tachypnoea, sweating with feeds, poor weight gain, recurrent chest infections and hepatomegaly as pulmonary resistance falls over weeks. Echocardiography defines size and pressure effects. Treat heart failure with specialist-directed diuretics/nutritional support; close by catheter or surgery when large, symptomatic, causing poor growth or pulmonary hypertension.

Atrial Septal Defect and AV Septal Defect

ASD causes left-to-right atrial shunting and may be asymptomatic in infancy; significant defects are closed later by device/surgery. AV septal defect involves atrial/ventricular septa and AV valves and is strongly associated with Down syndrome. Large defects cause early heart failure and require nutritional/medical stabilisation followed by surgical repair.

Patent Ductus Arteriosus

Persistent ductus creates a left-to-right shunt after pulmonary resistance falls. Premature infants may develop bounding pulses, wide pulse pressure, murmur, ventilator difficulty or systemic “steal.” Management depends on gestation, haemodynamic significance and local protocol: observation/fluid strategy, selected pharmacological closure (ibuprofen/indomethacin or paracetamol under neonatal supervision), catheter closure or surgery. These drugs have renal, bleeding and gastrointestinal precautions and are not given simply for every murmur.

Obstructive and Duct-Dependent Lesions

Coarctation of the Aorta

Narrowing of the aorta may cause weak/delayed femoral pulses, upper-limb hypertension, lower-limb poor perfusion or collapse when the duct closes. Measure right-arm and leg BP/saturation where possible, but normal pulse oximetry does not exclude coarctation. In critical disease stabilise shock, commence prostaglandin E1 under specialist protocol, correct acidosis and transfer for surgery/catheter intervention.

Hypoplastic Left Heart Syndrome

Left-sided structures cannot support systemic circulation. As the duct closes, the newborn develops pallor, cool extremities, weak pulses, tachypnoea, acidosis and shock. Maintain ductal patency with prostaglandin, balance ventilation/oxygen carefully, support circulation and urgently transfer to congenital-cardiac care for staged palliation, transplant evaluation or family-centred palliative planning.

Cyanotic Congenital Heart Disease

Tetralogy of Fallot

TOF comprises VSD, right-ventricular outflow obstruction, overriding aorta and right-ventricular hypertrophy. Cyanosis varies with obstruction. Hypercyanotic spells cause sudden deep cyanosis, rapid breathing, irritability or syncope. Place infant in knee-chest position, keep calm, give oxygen, obtain urgent help and administer prescribed morphine/IV fluid/beta-blocker according to specialist protocol; severe obstruction may require prostaglandin and urgent intervention. Definitive repair closes VSD and relieves obstruction.

Transposition of the Great Arteries

Aorta arises from right ventricle and pulmonary artery from left, creating parallel circuits. Survival requires mixing through ASD/VSD/PDA. Severe cyanosis appears soon after birth, often with limited respiratory distress. Give prostaglandin to maintain ductus and urgently transfer. Balloon atrial septostomy improves mixing when needed; arterial switch is definitive surgery.

Pulmonary Atresia, Truncus and Total Anomalous Pulmonary Venous Return

Pulmonary atresia blocks flow from right ventricle to lungs and is often duct-dependent. Truncus arteriosus has one arterial trunk causing mixing and pulmonary overcirculation. Obstructed total anomalous pulmonary venous return causes severe cyanosis, respiratory distress and pulmonary oedema and requires emergency surgery. Stabilisation is physiology-specific; do not assume oxygen alone will correct cyanosis.

Recognition, Screening and Investigations

History: antenatal scan, maternal diabetes/infection/medicines, family CHD, feeding time, sweating, cyanosis, growth and recurrent respiratory illness.
Examination: central colour in tongue/mucosa, respiratory effort, pulses in all limbs, capillary refill, precordium, heart sounds/murmur, liver size, oedema and dysmorphism.
Pulse oximetry screening: use current approved newborn algorithm with right hand (preductal) and one foot (postductal) after the recommended age. A failed screen requires clinical evaluation for CHD and other hypoxaemic illness; a pass does not exclude every CHD.
Hyperoxia assessment: specialist interpretation may help distinguish cardiac from pulmonary causes but must not delay echocardiography/transfer.
Tests: echocardiography is diagnostic; ECG, chest radiograph, blood gas/lactate, glucose, FBC, electrolytes/renal/liver tests and cultures help assess physiology and differentials.

Emergency Management of Suspected Critical CHD

ABCDE, warmth, glucose, continuous ECG/saturation and IV/umbilical access; call neonatal/cardiology/transfer team.
Support airway/ventilation without causing excessive hypocapnia or hyperoxia in lesions needing balanced circulations; follow specialist targets.
Treat shock with cautious protocol-based fluid boluses and reassessment because excessive fluid worsens heart failure.
If duct-dependent disease is suspected, commence weight-based prostaglandin E1 infusion under specialist protocol. Prepare for apnoea, hypotension and fever; airway-skilled staff and ventilation must be available.
Treat sepsis concurrently until excluded when presentation is indistinguishable. Correct acidosis, hypoglycaemia, anaemia and electrolyte disturbance.
Transfer urgently with full handover, infusions secured and resuscitation equipment available.

Heart Failure and Ongoing Medical Care

Goals are adequate systemic oxygen delivery, reduced congestion/workload and sufficient growth for intervention. Diuretics such as furosemide are prescribed for congestion with monitoring of weight, urine, sodium, potassium and renal function. ACE inhibitors are selected for specific lesions and require BP/renal/potassium monitoring. Digoxin is not universal and requires weight-based dosing, renal assessment and toxicity monitoring. Concentrated breast milk or fortified feeds may reduce feeding effort; NG feeding is used when oral work is unsafe/excessive.

Nursing Management

Priority	Intervention	Rationale
Oxygen delivery	Monitor pre/postductal saturation, colour, respiratory pattern, perfusion, lactate/mental state; use prescribed oxygen target.	Both hypoxaemia and inappropriate excess oxygen can disturb ductal/balanced physiology.
Cardiac output	Trend HR, pulses, four-limb BP when indicated, capillary refill, temperature gradient, urine output and hepatomegaly.	Detects ductal closure, obstruction and heart failure before arrest.
Feeding/growth	Assess respiratory stability, limit exhausting feeds, give smaller frequent/concentrated or NG feeds as prescribed; daily weight.	Cardiac infants expend high energy but may not tolerate volume or prolonged sucking.
Medicines	Use exact weight/dose/pump; monitor prostaglandin apnoea/hypotension, diuretic electrolytes, ACE-inhibitor BP/renal function and digoxin toxicity.	Cardiac medicines have narrow physiological margins.
Energy conservation	Cluster care, minimise crying, maintain warmth and provide rest.	Reduces oxygen consumption and cardiac workload.
Family education	Teach medicines, feeding, saturation plan if applicable, dental/endocarditis advice, immunisation and danger signs.	Supports lifelong CHD care and early recognition of deterioration.

Complications and Follow-up

Heart failure, shock, arrhythmia, pulmonary hypertension, stroke/brain injury and infective endocarditis.
Growth failure, feeding/oral aversion and developmental delay.
Postoperative bleeding, low cardiac output, infection, residual shunt/obstruction and thrombosis.
Many repaired patients require lifelong congenital-cardiology follow-up for valves, rhythm, ventricular function, exercise, pregnancy and re-intervention.

Revision Questions

Classify CHD by physiology and explain the clinical implications.
Describe recognition and emergency management of duct-dependent CHD.
Compare VSD, TOF, transposition and coarctation.
Explain pulse-oximetry screening and its limitations.
Develop nursing care for an infant with heart failure.

References

Prostaglandin, fluids, oxygen targets and cardiac medicines must be prescribed and monitored by trained neonatal/cardiac teams using current local protocols.