These conditions lead to the mixing of deoxygenated blood from the right side of the circulation and oxygenated blood in the left side of the circulation.

– This leads to cyanosis, which can be divided into two types:

i) Peripheral cyanosis:

– This occurs in the extremities such as feet and hands, is very common in the first 24 hours of life

– It can also occur when the child is crying or unwell from any cause, and so is less serious

ii) Central cyanosis:

– This is seen when the concentration of reduced haemoglobin in the blood exceeds 5g/dl

– This is serious as it indicates an oxygen deprived state, which can be fatal

Tetralogy of Fallot (TOF)

This is the most common cyanotic congenital heart disorder made of 4 problems:

– Aorta overriding the VSD (accepting right heart blood)

– Right ventricular hypertrophy

– Pulmonary outflow stenosis

– Ventricular septal defect

Symptoms:

– Cyanosis –> this occurs around 1-2 months after birth

– Toddlers squat –> this increases peripheral vascular resistance, decreasing right-to-left shunt allowing more blood to reach the lungs and get oxygenated

– Tet spells –> spells of cyanosis and loss of consciousness which occur when babies cry or have bowel movements

– Clubbing

– Harsh ejection systolic murmur at the left sternal edge (due to pulmonary stenosis)

– If left untreated leads to heart failure –> dyspnea, poor growth, poor feeding, chest infections

Diagnosis:

– Echocardiogram is diagnostic

– Chest X-ray –> Gives classic Boot shaped heart on x-ray and small heart

– ECG –> normal at birth, but right ventricular hypertrophy when older

Management:

– If acute cyanosis at birth, treat with oxygen and prostaglandin infusion

– Medical management –> Tet spells can be treated with beta blockers

– Total surgical repair is curative –> this is usually done after 6 months of age

Transposition of great arteries (TGA)

This is a condition where the pulmonary artery arises from left ventricle and the aorta from right.

– This means that oxygenated blood is a closed loop between the heart and the lungs, and deoxygenated blood is a closed loop between the body and the heart

– This means that there are 2 parallel circulations which do not mix

– Unless there is mixing of blood between them, the condition is incompatible with life and the child will die

– Fortunately, TGA often occurs in association with anomalies that allows this mixing such as a VSD/ASD/PDA

Symptoms:

– Cyanosis shortly after birth e.g., on day 2 when ductus arteriosus closes

– The more mixing of blood there is, the less severe the presentation

– Gives a loud single S2 but no murmur

– If left untreated, leads to heart failure and mortality

Diagnosis:

– Echocardiogram is the investigation of choice

– Pulse oximetry –> shows reverse differential cyanosis (SpO₂ in legs > SpO₂ in arms), as the legs can receive some oxygenated blood through the PDA. In

contrast, the branches to the arms occur before the PDA so they only get deoxygenated blood.

– CXR –> shows narrow upper mediastinum with an ‘egg on side’ appearance of the cardiac shadow

Management:

– Prostaglandin infusion (5mg/kg/min) and oxygen to manage acute cyanosis

– Surgical correction –> arterial switch procedure is the definitive treatment