Congenital heart diseases (CHDs) are structural abnormalities of the heart and intrathoracic great vessels that arise during fetal development.
CHDs are the most common congenital disorders, and the most common cause of death in children with congenital malformations.
They occur in 8 – 9 per 1000 live births.
Classification according to ductal dependence
| Classification | Description | Examples |
|---|---|---|
| Systemic ductal dependence | These are left-sided obstructive lesions that cause systemic hypoperfusion when the ductus arteriosus closes. They require PGE1 to maintain the ductus arteriosus until surgery | Critical aortic stenosis, coarctation of the aorta (CoA), interrupted aortic arch (IAA), hypoplastic left heart syndrome (HLHS) |
| Pulmonary ductal dependence | These are right-sided obstructive lesions that cause severe cyanosis when the ductus arteriosus closes. They require PGE1 to maintain the ductus arteriosus until surgery | Critical pulmonary stenosis, pulmonary atresia (with or without VSD), tricuspid atresia (with pulmonary obstruction), tetralogy of Fallot (TOF) with pulmonary atresia, Ebstein’s anomaly (with functional pulmonary atresia) |
| Mixing lesions | These defects depend on the ductus arteriosus or other shunts to allow mixing of oxygenated and deoxygenated blood. They may require maintenance of the ductus arteriousus or balloon-atrial septostomy before definitive surgery | Transposition of great arteries (TGA), Total anomalous pulmonary venous return (TAPVR) |
Classification based on cyanosis
| Classification | Description |
|---|---|
| Acyanotic CHDs | Involves shunting of blood from the left to the right, obstructive or stenotic lesions, and regurgitant lesions. These are less severe and present during childhood or adulthood. |
| Cyanotic CHDs | Involves shunting of blood from the right to the left, or severe stenosis or atresia. These are more severe and tend to present in infancy or early childhood. Surgery is always needed for cyanotic heart diseases |
Subtypes of acyanotic CHDs
| Subtype | Examples |
|---|---|
| Left-to-right shunt | Atrial septal defect (ASD), Ventricular septal defect (VSD), endocardial cushion defects (ECD), Patent ductus arteriosus (PDA) |
| Obstructive | Pulmonary stenosis, Aortic stenosis, Coarctation of the aorta, Mitral stenosis |
| Regurgitant | Pulmonary insufficiency, Mitral regurgitation (MR), mitral valve prolapse (MVP), tricuspid regurgitation (TR), aortic regurgitation (AR) |
Subtypes of cyanotic CHDs
| Subtype | Examples | Nota bene |
|---|---|---|
| Right heart obstructive | Pulmonary atresia, tricuspid atresia, tetralogy of Fallot, and critical pulmonary stenosis | Presents with severe cyanosis |
| Left heart obstructive | Hypoplastic left heart syndrome, coarctation of the aorta, interrupted aortic arch, and critical aortic stenosis | Has differential cyanosis and weak femoral pulses |
| Mixing lesions | Transposition of the great arteries, total anomalous pulmonary venous return, and truncus arteriosus | Often ductal-independent |
Conditions and their associated cardiac lesions
| Condition | Cardiac lesion |
|---|---|
| Congenital rubella | Patent ductus arteriosus (PDA), pulmonary stenosis |
| Infant of a diabetic mother | Cardiomyopathy, transposition of great arteries (TGA), ventricular septal defect (VSD), patent ductus arteriosus (PDA) |
| Maternal SLE | Congenital heart block |
| Maternal phenylketonuria | Ventricular septal defect (VSD), Atrial septal defect (ASD), Patent ductus arteriosus (PDA), coarctation of the aorta (CoA) |
Effects of teratogens on the foetal heart
| Teratogen | Effect on the heart |
|---|---|
| Alcohol | Ventricular septal defect, atrial septal defect, patent ductus arteriosus, and tetralogy of Fallot |
| Retinoic acid | Conotruncal anomalies, e.g. truncus arteriosus |
| Phenytoin | Pulmonary stenosis, aortic stenosis, and coarctation of the aorta |
| Valproate | Coarctation of the aorta, hypoplastic left heart syndrome, atrial septal defect |
| Warfarin | Ventricular septal defect |
- Mnemonic for Cyanotic CHDs (5 T’s with 1 – 5)
- Truncus arteriosus – vessels join to make (1)
- Transposition of great vessels – (2) major vessels switched
- Tricuspid atresia – (3) tricuspid
- Tetralogy of Fallot – (4) defects
- Total anomalous pulmonary venous return – (5) letters in TAPVR
- Risk factors
- Genetic associations
- Trisomy 13
- Trisomy 18
- Trisomy 21
- Turner syndrome
- Maternal risk factors
- Diabetes
- SLE
- Phenylketonuria
- Teratogens
- Infections
- Genetic associations
- Pathophysiology
- Oxygenation in utero occurs in the placenta
- Key shunts in the foetal circulation include:
- Ductus venosus → bypasses the liver
- Foramen ovale → shunts blood from the right atrium to the left atrium
- Ductus arteriosus → shunts blood from the pulmonary artery to the aorta
- This results in parallel circulation, with the lung largely bypassed
- At birth:
- The first breath reduces PVR, causing increased pulmonary blood flow
- Increased left atrial pressure closes the foramen ovale
- Increased oxygen delivery decreases prostaglandins, leading to closure of the ductus arteriosus
- This causes a transition to a series circulation
- Many cyanotic congenital heart diseases appear after ductal closure
- Mechanisms of cyanosis
- Right-to-left shunting causes deoxygenated blood to bypass the lung and enter systemic circulation
- Right-sided obstructive lesions reduced pulmonary blood flow
- Left-sided obstructive lesions reduced systemic perfusions
- Mixing lesions mix oxygenated and deoxygenated blood before entering systemic circulation
- Role of ductal-dependence
- Pulmonary flow-dependent lesions require the ductus arteriosus to divert blood from the aorta to the pulmonary artery
- Systemic flow-dependent lesions require the ductus arteriosus to divert blood from the pulmonary artery to the aorta
- Mixing-dependent lesions require the ductus arteriosus to maintain adequate oxygenation
- Secondary physiologic effects
- Chronic hypoxemia → polycythemia and hyperviscosity (stroke risk)
- Pulmonary overcirculation → heart failure and pulmonary hypertension
- Eisenmenger syndrome in uncorrected left-to-right shunts
- Patient history
- Preterm
- Small for gestational age
- Slow weight gain
- Failure to thrive
- Syndromic baby
- Recurrent respiratory infections
- Pulmonary hypertension
- Family history of CHDs or sudden deaths
- Signs and symptoms
- Poor feeding
- Diaphoresis
- Failure to thrive
- Tachypnoea
- Irritability
- Cyanosis
- Exercise intolerance in older children
- Murmur
- Note that an innocent murmur occurs in a small area, is sensitive (changes with position), short, single, soft, sweet, and systolic
- Hepatomegaly
- Weak femoral pulses in left-sided lesions
- Signs of shock
- Differentials for cyanosis
- Pulmonary disease
- Persistent pulmonary hypertension of the newborn (PPHN0
- Sepsis
- Inborn errors of metabolism
- Haemoglobinopathies, e.g., methemoglobinaemia
- Investigations
- Pulse oximetry screening – This is done ≥ 24 hours of life. The right hand is preductal while the foot is postductal. The test is positive if:
- < 90% oxygen saturation
- < 95% oxygen saturation in both (3 readings)
- 3% difference between preductal and postductal readings
- Hyperoxia test: This is done by giving 100% oxygen for 10 minutes
- PaO2 < 100 mmHg → cardiac cause of cyanosis
- PaO2 ≥ 100 mmHg → pulmonary cause of cyanosis
- Echocardiography: This is the best initial and definitive diagnostic test
- Chest radiograph
- Electrocardiography
- Axis deviation
- Hypertrophy
- Pulse oximetry screening – This is done ≥ 24 hours of life. The right hand is preductal while the foot is postductal. The test is positive if: