Congenital Heart Defect
A congenital heart defect (CHD), also known as congenital heart anomaly or congenital heart disease, is a defect in the structure of the heart or great vessels present at birth. These defects are the most common type of birth defect, affecting millions globally. The causes are often unknown, but risk factors include certain infections during pregnancy, use of specific medications, and genetic conditions.
Signs and Symptoms
The signs and symptoms of CHD depend on the type and severity of the defect. Some individuals may be asymptomatic, while others exhibit rapid breathing, bluish skin (cyanosis), poor weight gain, and feeling tired. Other signs can include shortness of breath, fainting, heart murmurs, under-development of limbs and muscles, poor feeding, and respiratory infections.
Associated Conditions
CHD is often associated with other medical conditions, collectively known as the VACTERL association, which includes vertebral anomalies, anal atresia, cardiovascular anomalies, tracheoesophageal fistula, esophageal atresia, renal anomalies, and limb defects. Common congenital defects in this association include ventricular septal defect (VSD), atrial septal defects (ASD), and tetralogy of Fallot (ToF).
Causes
Genetic
Genetic mutations, often sporadic, are a significant cause of congenital heart defects. Specific gene mutations related to heart development, such as MYH6, GATA4, NKX2-5, and TBX5, are associated with various heart defects. Mutation in the notch signalling pathway and the Ras/MAPK pathway are also implicated in CHD.
Environmental
Environmental factors such as maternal infections (e.g., rubella), exposure to certain drugs (alcohol, hydantoin, lithium, thalidomide), and maternal illnesses (diabetes, phenylketonuria) can contribute to CHD. Maternal obesity and poor nutritional status are additional risk factors.
Mechanism
The development of the heart begins around day 15 of embryogenesis, with significant structural formation occurring between days 19 and 28. Any disruption during these phases can result in congenital heart defects. The heart initially forms as a simple tube, which then folds and divides into the four chambers and the great vessels. Failures in this process can lead to septal defects, outflow tract abnormalities, and other structural issues.
Diagnosis
Many CHDs can be diagnosed prenatally using foetal echocardiography during the second trimester. Postnatally, cyanotic heart diseases are often identified shortly after birth due to visible cyanosis. Other defects may manifest later in life.
Classification
Hypoplasia
Hypoplasia refers to the underdevelopment of the heart's ventricles, leading to conditions such as hypoplastic left heart syndrome and hypoplastic right heart syndrome, which are severe and typically cyanotic.
Obstructive Defects
Obstructive defects involve narrowing or blockage of heart valves, arteries, or veins, such as in pulmonic stenosis, aortic stenosis, and coarctation of the aorta, leading to heart enlargement or hypertension.
Septal Defects
Septal defects include atrial septal defects (ASD) and ventricular septal defects (VSD), allowing blood to flow between the left and right sides of the heart, reducing efficiency.
Cyanotic Defects
Cyanotic heart defects, such as tetralogy of Fallot, transposition of the great vessels, and tricuspid atresia, cause a bluish discolouration due to insufficient oxygenation.
Treatment
Treatment for CHD may involve medications like diuretics and digoxin, catheter-based procedures, or heart surgery. Some defects may require multiple surgeries or even heart transplantation. Minimally invasive procedures, such as the Melody Transcatheter Pulmonary Valve (TPV), offer alternatives to surgery.
Mental Health
Supporting the mental health of individuals with CHD is very important, as they may face challenges related to their condition, such as reduced quality of life, difficulty finding employment, and clinical depression. Psychotherapy can be beneficial, though more research is needed to optimise treatment approaches.
Epidemiology
Heart defects occur in 1% of live births, with 34.3 million people affected globally in 2013. The recurrence risk of CHD in offspring is 3–5%, higher in certain conditions.
Self-assessment MCQs (single best answer)
Which of the following is the most common type of birth defect?
Which gene mutation is NOT associated with congenital heart defects?
Which of these symptoms is NOT typically associated with congenital heart defects?
Which condition is NOT part of the VACTERL association?
Which environmental factor is NOT known to contribute to congenital heart defects?
During which days of embryogenesis does significant structural formation of the heart occur?
Which type of congenital heart defect is characterised by underdevelopment of the heart's ventricles?
Which cyanotic defect is characterised by a combination of four heart malformations?
Which diagnostic tool is commonly used prenatally to identify congenital heart defects?
Which of the following treatments is NOT typically used for congenital heart defects?
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