Congenital heart disease covers a wide spectrum from small defects, which may be totally asymptomatic and compatible with a normal lifespan, to more severe forms which require urgent intervention. Many defects are possible but most defects either obstruct flow of blood in the heart or in vessels near to it or cause blood to take an abnormal route through the heart. More rarely only one ventricle may be present, or the right or left side of the heart has failed to form properly (hypoplastic heart). Significant amounts of blood shunting from right to left without traversing the lungs causes cyanotic congenital heart disease.
The management of congenital heart disease has improved so much over the years that many affected children are now adults. See separate Congenital Heart Disease in Adults article.
Classification into five groups based on pathophysiology has been suggested as it would be helpful in planning management.However, for ease of understanding, congenital heart disease is best classified into two groups - namely:
- Ventricular septal defect (VSD).
- Atrial septal defect (ASD).
- Patent ductus arteriosus (PDA).
- Aortic stenosis.
- Pulmonic stenosis.
- Coarctation of the aorta.
- Atrioventricular canal defect (endocardial cushion defect): variable severity of defects involving the atrial septum, ventricular septum and one or both of the atrioventricular valves.
- Fallot's tetralogy.
- Transposition of the great arteries.
- Tricuspid atresia: complete absence of the tricuspid valve; an ASD must be present to maintain blood flow.
- Total anomalous pulmonary venous return: all four pulmonary veins are malpositioned and make anomalous connections to the systemic venous circulation.
- Persistent truncus arteriosus.
- Hypoplastic left heart: the left side of the heart is severely underdeveloped.
- Pulmonary atresia: the pulmonary valve is completely closed and the only source of pulmonary blood flow is a PDA.
- Ebstein's anomaly.
- The reported total birth prevalence of congenital heart disease in Europe is 8.2 per thousand live births which is higher than reported birth prevalence in the USA (6.9 per thousand live births). The highest birth prevalence of congenital heart disease (9.3 per thousand) is reported from Asia.
- Congenital heart disease accounts for nearly one third of all major congenital anomalies and is the most common congenital condition diagnosed in newborns.
- The prevalence of adult congenital heart disease is increasing at a rapid pace and currently there are twice as many adults with congenital heart disease as compared with children.
- The relative risk of recurrence of congenital heart disease increases if a first-degree relative has a congenital heart disease. While the overall relative risk for all congenital heart disease is estimated to be 3, it is much higher for certain congenital heart diseases such as heterotaxia (relative risk 80). Other congenital heart disease with significantly high recurrence risk are atrioventricular septal defects and left and right ventricular outflow obstructive lesions.
- Risk of congenital heart disease is increased in consanguineous unions, especially at first cousin level; this needs to be taken into account at time of genetic counselling.
- A fetus may be affected during cardiac development by intrauterine infection such as rubella, or drugs and toxins taken by the mother, including lithium and alcohol.
- Some genetic conditions are associated with a higher incidence of congenital heart disease, including Down's syndrome, DiGeorge's syndrome, Williams' syndrome, Noonan's syndrome and Turner syndrome.
- Maternal diabetes mellitus is associated with an increased incidence (8.5 per hundred live births) of congenital heart disease.
- Lack of folic acid during the first trimester is associated with neural tube defects but a link with congenital heart disease has not been established.
The cardiovascular system is complex, as the circulation changes from fetal to infant and there may be transient problems such as PDA or patent foramen ovale, especially in premature babies.
- Many congenital heart anomalies are now diagnosed before delivery, by detailed antenatal scans.
- Congenital heart disease can also be suspected and diagnosed in asymptomatic neonates during the neonatal screening examination which includes checking femoral pulses and auscultation for heart murmurs. See also separate Neonatal Examination article.
- Introduction of pulse oximetry as a screening test in neonates has helped in earlier detection of congenital heart disease. Although this is currently not universal practice, it is being introduced in many units in the UK.
- Babies born with complex congenital heart disease, where either the systemic or pulmonary circulation is dependent on the arterial duct remaining patent (Duct-dependent congenital heart disease), presently acutely in the first week or two of life.Two presentations are described:
- In those with severe left-sided obstructive lesions: systemic blood flow is dependent on right-to-left blood flow through a PDA. Closure of the duct soon after birth causes acute, severe cardiovascular collapse requiring immediate cardiovascular resuscitation and prostaglandin infusion. Examples of left-sided ductus-dependent congenital heart disease include hypoplastic left heart syndrome, critical aortic stenosis, coarctation of aorta and interrupted aortic arch.
- In those with severe right-sided duct-dependent lesions, closure of the ductus causes increasing hypoxia and cyanosis. Examples include pulmonary atresia, severe tetralogy of Fallot, tricuspid atresia and Ebstein's anomaly. Transposition of great arteries also presents as a blue baby. Urgent cardiovascular resuscitation and prostaglandin infusion are the mainstay of treatment.
- Babies with significant left-to-right shunts (VSD, ASD, PDA, aorto-pulmonary window) are asymptomatic at birth but can present with signs of heart failure and faltering growth in early infancy.
- Others are diagnosed at various ages subsequent to the detection of a heart murmur as part of routine screening or during clinical examination for intercurrent illness.
- Heart murmurs. See also separate Heart Murmurs in Children article:
- Not all murmurs are pathological.
- Murmurs heard in the first week to months of life are more likely to be due to congenital heart disease than those discovered in later childhood years. Although it remains controversial, some experts are recommending echocardiography for all neonates with heart murmurs.
- Murmurs may not appear until an infant has left hospital, as the pulmonary vascular resistance changes with the closure of the ductus arteriosus. Hence, a child with a VSD may have no signs for the first 24 hours and a child with a hypoplastic left heart may appear healthy until the ductus closes.
- Routine child health surveillance in the UK and in other developed countries has ensured that the majority of children with significant disease are diagnosed at an early stage.
Investigation should be preceded by a thorough health and development history of the infant or child as well as a history of the pregnancy, including the mother's health and drug use during the pregnancy, and a family history of cardiac abnormalities.
- Babies developing severe cardiovascular and respiratory distress/collapse require urgent hospital admission, CXR, blood gases, assessment of renal function and electrolytes and assessment of other possible causes of cardiovascular collapse - eg, full infection screen. Clinical assessment should include checking for femoral pulses and measurement of pre- and post-ductal saturations.
- Murmurs arising during the first days or weeks of life should be referred to a paediatrician for assessment.
- The initial investigation of choice is echocardiography. It is non-invasive. It can elucidate both anatomy and flow and will give a conclusive diagnosis in most cases.
- Cardiac catheterisation may be required in more severe cases to assess the extent of the problem and to prepare for correction of the problem.
- Some children with congenital heart disease will require no specific treatment but may be at risk of infective endocarditis. See separate Prevention of Infective Endocarditis article.
- Acute severe presentations may require:
- Immediate resuscitation.
- Urgent hospital treatment, including prostaglandin infusion for ductus-dependent lesions.
- If the disorder is severe enough to compromise the circulation and the oxygenation of the blood, or to put a strain on the heart or lungs, surgical correction or non-surgical intervention, such as balloon valvotomy, may be required.
- In the most severe cases (for example, hypoplastic heart), multiple palliative surgical procedures or a heart transplant may be required.
- The type and extent of the correction required will depend on the underlying anomaly.
- All forms of congenital heart disease, apart from ASD, carry a risk of infective endocarditis.
- There may be failure to thrive or just difficulty in joining in with games and sports with other children.
- A right-to-left shunt can permit paradoxical embolism that may present with a systemic embolism such as a stroke.
- A left-to-right shunt does not cause cyanosis but the high volume pumped by the right side may result in pulmonary hypertension and, if this builds up and exceeds systemic pressure, the shunt may reverse from right to left. This is called Eisenmenger's complex and it may not develop until the child is an adolescent or adult.
- Cyanosis results in polycythaemia; a haemoglobin value as high as 20 g/dL may cause additional difficulty as the blood is so viscous.
- The prognosis for children with congenital heart disease has improved dramatically over the last few decades. However, children who have undergone surgery for congenital heart disease still have impaired survival compared to the general population and often need new operations or catheter-based procedures.
- The long-term outcome is exceptionally good for some conditions such as surgically corrected isolated VSDs, with no excess mortality compared to the general population.
- Although many forms of congenital heart disease are not currently preventable, the avoidance of known risk factors such as drugs and alcohol during pregnancy will help to reduce the risk.
- Vaccination against rubella has reduced the number of children born with rubella syndrome. Reduced uptake of the measles, mumps and rubella (MMR) vaccine could allow the incidence of congenital rubella to increase again.
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