Abstract

Congenital heart defects (CHDs) are the most prevalent birth anomalies, affecting approximately 1% of live births globally and representing a leading cause of infant morbidity and mortality. CHDs range from minor defects with spontaneous resolution to complex malformations requiring urgent intervention. Epidemiological data reveal that around 25% of cases are classified as critical CHDs, demanding surgical or catheter-based correction within the first year of life. While the etiology is multifactorial, involving genetic mutations, chromosomal syndromes, and environmental factors, many cases are sporadic. Diagnosis can occur prenatally via fetal echocardiography or postnatally through clinical evaluation, pulse oximetry, and imaging modalities such as echocardiography and cardiac MRI. Management is tailored to defect severity and includes medical therapy, interventional cardiology, and surgical repair, with staged procedures reserved for complex defects like hypoplastic left heart syndrome. Advances in diagnosis and treatment have markedly improved survival, underscoring the importance of early detection and lifelong follow-up in affected individuals.

Introduction

Congenital heart defects (CHDs) are structural anomalies of the heart or great vessels present at birth. They represent the most common type of birth defect, affecting approximately 1% of live births worldwide, and account for significant morbidity and mortality in infancy and childhood  . CHDs encompass a broad spectrum—from minor lesions that may resolve spontaneously to complex malformations requiring urgent intervention. Advances in prenatal diagnosis, surgical and catheter-based therapies, and long-term follow-up have dramatically improved survival and quality of life for affected children.

Epidemiology

• Global Prevalence

CHDs occur in about 9 to 10 per 1,000 live births globally, with variation by region and surveillance method  .

• Critical CHDs

Approximately 25% of infants with CHDs have a critical congenital heart defect (CCHD)—a lesion necessitating surgery or catheter intervention within the first year of life  .

• Survival Trends

One-year survival for infants with non-critical CHDs exceeds 95%, while for critical defects it has improved from roughly 67% in 1979–1993 to about 83% in 1994–2005  . Survival into adulthood now exceeds 80% overall, underscoring the need for lifelong care  

Etiology and Risk Factors

Congenital heart defects (CHDs) arise from abnormal development of the heart or major blood vessels during early embryogenesis—typically between the 3rd and 8th weeks of gestation. Their etiology is multifactorial, involving both genetic and environmental influences, though in many cases the exact cause remains unknown.

1. Genetic Causes

a. Chromosomal Abnormalities

• Account for 10–15% of CHD cases.

• Common syndromes include:

o Down Syndrome (Trisomy 21): Associated with atrioventricular septal defects (AVSD), VSD, ASD.

o DiGeorge Syndrome (22q11.2 deletion): Conotruncal defects like tetralogy of Fallot, interrupted aortic arch.

o Turner Syndrome (45,XO): Commonly associated with coarctation of the aorta and bicuspid aortic valve.

o Trisomy 13 and 18: Often linked with multiple complex CHDs.

b. Single-Gene Mutations

• Account for 3–5% of cases.

• Involve mutations in genes important for heart development (e.g., NKX2-5, GATA4, TBX1).

• Inherited in autosomal dominant, autosomal recessive, or X-linked patterns.

c. Familial CHDs

• A child with a sibling or parent who has a CHD has a 3–10 times higher risk of developing a CHD.

• Recurrence risk is higher in first-degree relatives and with specific defect types.

3. Assisted Reproductive Technologies (ART)

• Use of ART (e.g., IVF) is associated with a slightly increased risk of CHDs.

• May be related to underlying subfertility, embryo manipulation, or multiple pregnancies.

4. Environmental Exposures

• Radiation: High-dose radiation in early pregnancy (rare).

• Industrial chemicals or pollutants: Limited evidence but suspected based on animal studies (e.g., dioxins, heavy metals).

• Pesticides and solvents: Some studies show a potential link.

5. Multifactorial Inheritance

• In 80–85% of cases, CHDs result from a complex interplay of genetic susceptibility and environmental exposures.

• Often referred to as “sporadic” due to the absence of a clear inheritance pattern.

Classification and Types 

Congenital heart defects (CHDs) are classified based on anatomical, physiological, and clinical features. They can range from simple lesions that may resolve spontaneously to complex anomalies requiring surgical intervention.

II. Classification Based on Clinical Severity

1. Simple CHDs (often asymptomatic or corrected easily):

• Small VSD or ASD

• Isolated PDA

• Mild valve stenosis

2. Moderate CHDs:

• Larger septal defects

• AVSD

• Coarctation of the aorta

• TOF (repaired)

3. Complex CHDs:

• Unrepaired TOF

• TGA

• HLHS

• Single ventricle physiology

Clinical Presentation

• Infants may show:

o Cyanosis or pallor, especially with feeding or crying

o Tachypnea, grunting, poor feeding, and failure to thrive

o Hepatomegaly and peripheral edema in heart failure

• Older Children often present with:

o Exercise intolerance, fatigue, or syncope

o Recurrent respiratory infections

o Growth delays or clubbing in chronic cyanosis  .

Diagnosis

Early and accurate diagnosis of congenital heart defects is essential for timely management and improving outcomes. CHDs can be diagnosed before birth (prenatally), after birth (neonatally), or later in childhood or adulthood, depending on the severity and type of defect.

1. Prenatal Diagnosis

a. Fetal Ultrasound (Anomaly Scan)

• Typically done at 18–22 weeks gestation.

• May show structural abnormalities (e.g., abnormal heart chambers or outflow tracts).

• Indications include increased nuchal translucency, abnormal four-chamber view, or associated extracardiac anomalies.

b. Fetal Echocardiography

• Gold standard for prenatal CHD diagnosis.

• Performed between 18–24 weeks in high-risk pregnancies.

• Assesses cardiac structure, flow, rhythm, and function.

• Indicated in cases with family history of CHD, maternal diabetes, infections, or genetic syndromes.

2. Postnatal Diagnosis (After Birth)

a. Clinical Examination

• Auscultation: Heart murmur (most common early finding).

• Signs of heart failure: Tachypnea, poor feeding, sweating during feeds, failure to thrive.

• Cyanosis: Indicates right-to-left shunting or mixing of blood.

• Clubbing: Seen in chronic hypoxemia (later stages).

b. Pulse Oximetry Screening

• Non-invasive bedside test done within 24–48 hours of birth.

• Detects critical CHDs by measuring oxygen saturation in right hand and either foot.

• A saturation < 95% or a difference >3% between extremities is suspicious.

3. Imaging and Diagnostic Tools

a. Echocardiography (Transthoracic Echo)

• Primary diagnostic tool postnatally.

• Non-invasive, real-time imaging of heart chambers, valves, septa, and great vessels.

• Color Doppler assesses blood flow direction and velocity.

b. Chest X-ray

• Provides general information:

o Cardiomegaly (enlarged heart).

o Pulmonary vascular markings (increased in L-to-R shunts, decreased in TOF).

o Abnormal heart silhouettes (e.g., “egg on a string” in TGA).

c. Electrocardiogram (ECG)

• Evaluates electrical activity and rhythm.

• Can suggest chamber enlargement or conduction abnormalities.

d. Cardiac MRI/CT Scan

• Useful for complex CHDs or unclear anatomy.

• MRI is excellent for visualizing blood flow and vessel relationships without radiation.

• CT angiography is rapid and detailed (often used before surgery).

Management and Treatment 

The management of congenital heart defects (CHDs) is highly individualized and depends on the type, severity, and presence of symptoms or complications. Treatment may range from observation to life-saving surgical interventions, often involving a multidisciplinary team of pediatric cardiologists, surgeons, and intensivists.

1. General Principles of Management

• Initial stabilization is crucial for critically ill newborns (e.g., maintaining oxygenation and perfusion).

• Definitive therapy may include medical management, catheter-based procedures, or surgery.

• Lifelong follow-up is often necessary due to residual defects, arrhythmias, or need for re-intervention.

2. Medical Management

Used for symptom control, stabilization, and sometimes as primary or temporary therapy

a. Medications

Medication Indication

Prostaglandin E1 (PGE1) Keeps ductus arteriosus open in duct-dependent CHDs (e.g., TGA, HLHS, Pulmonary atresia)

Diuretics (e.g., furosemide) Treat heart failure by reducing fluid overload

ACE inhibitors (e.g., captopril) Lower afterload, improve cardiac output

Beta-blockers Manage arrhythmias or cardiomyopathy

Inotropes (e.g., dopamine, milrinone) Support in severe heart failure

Antibiotics (prophylactic) For prevention of infective endocarditis in high-risk cases

b. Nutritional Support

• High-calorie feeds or tube feeding may be needed due to poor feeding and increased energy expenditure in infants.

3. Catheter-Based Interventions (Interventional Cardiology)

Minimally invasive procedures performed via cardiac catheterization:

Procedure Indication

Balloon atrial septostomy TGA to allow mixing of oxygenated and deoxygenated blood

Balloon valvuloplasty Pulmonary or aortic stenosis

Device closure ASD, VSD, or PDA (if suitable size and anatomy)

Coil embolization To close abnormal vessels (e.g., arteriovenous malformations)

Stent placement Coarctation of the aorta or other obstructive lesions

4. Surgical Management

Surgery is often required for moderate to complex CHDs, especially those incompatible with life without intervention.

a. Corrective Surgery(restores normal anatomy):

• VSD/ASD closure

• PDA ligation

• TOF repair

• TGA arterial switch operation (Jatene procedure)

b. Palliative Surgery(temporizes or partially corrects):

• Blalock–Taussig shunt: Connects subclavian artery to pulmonary artery in TOF or pulmonary atresia.

• Pulmonary artery banding: Reduces pulmonary overcirculation in large VSDs.

c. Staged Surgical Approaches (for complex CHDs like HLHS or single ventricle physiology):

1. Norwood Procedure – within the first week of life

2. Glenn Procedure – around 4–6 months

3. Fontan Procedure – around 2–4 years

References

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2020 ACC/AHA Guidelines for the Management of Adults With Congenital Heart Disease.

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