Introduction

At birth there are changes in two major shunts in the circulation:

i) Ductus arteriosus:

– In the fetus, this connects the pulmonary artery to the aorta to allow bypassing of the foetal lungs

– After birth, drop in maternal prostaglandins causes it to close

ii) Foramen Ovale:

– In the fetus, left atrium pressure is low as little blood returns from the lungs

– Right atrium pressure is higher as it receives all the systemic venous return (including blood from the placenta)

– Therefore, the flap valve of the foramen ovale is held open and blood flows from RA to LA

After birth, when the baby starts to breathe, resistance to pulmonary blood flow falls

– The volume of blood flowing through the lungs increases, causing a rise in left atrial pressure

– The volume of blood returning to the right atrium falls as the placenta is excluded from the circulation

– This change in pressure gradient causes the flap valve of the foramen ovale to close

Heart Defects

Heart defects arise in embryogenesis during the first trimester can lead to blood mixing between sides of the circulation:

Right-to-left shunting:

– This gives cyanosis soon after birth.

Left-to-right shunting:

This is often asymptomatic at birth.

– However, the increased flow through pulmonary circulation causes pulmonary hypertrophy and hypertension.

– This gives right ventricle hypertrophy

– This leads to eventual reversal of the shunting causing late cyanosis (Eisenmenger syndrome) 

Heart Murmurs

Many of the paediatric heart conditions produce a murmur, due to the interrupted flow of blood.

– However, many children who present with a murmur have a normal heart, hence these are called Innocent Murmurs.

– Murmurs may also be heard during a febrile illness or anaemia due to increased cardiac output

Features of an innocent murmur include the 4S’s:

– Asymptomatic

– Soft blowing murmur

– Systolic only (never diastolic)

– Heard along the left Sternal edge

– These murmurs will also have no added sounds like thrills or clicks, no radiation and may vary with posture 

Heart Failure

This is defined as a cardiac output which is inadequate for the body’s requirements.

– In children, the causes of HF are significantly different from adults and many cases are due to congenital malformations which usually result in high output cardiac failure

– The causes in children usually differ according to the age group.

Causes:

Neonates (immediately after birth):

– Due to conditions which impair outflow from the heart

– e.g., Severe aortic stenosis, interrupted aortic arch, transposition of the great arteries

Infants (1st year of life):

– Due to conditions which lead to mixing between circulations

– e.g. large patent ductus arteriosus, VSD

Older children:

– More due to acquired conditions

– e.g. Rheumatic fever, cardiomyopathy, Eisenmenger syndrome

Symptoms:

– Shortness of breath

– Inability to gain weight/poor growth

– Predisposition to recurrent chest infections

– Hepatomegaly

– Signs of specific cause –> e.g., murmur, cardiomegaly, cyanosis

Tests:

– Chest X-ray –> may show cardiomegaly

– ECG –> can show ischaemic changes as well as congenital arrythmias

– Echocardiogram –> this is used to diagnose structural disease

Management:

– Treat the underlying cause of the heart failure

– Medical management can be used to reduce afterload of the heart reducing the work the heart has to do

– If unresolving –> consider need for heart transplant