1. Overview of Congenital Heart Disease

1.1 Definition and Embryogenesis

• Congenital heart defects arise during embryogenesis, typically between weeks 3 and 8 of gestation.
• Occur in approximately 1% of live births.
• Often sporadic in origin but can be part of genetic syndromes (e.g., Down syndrome).

1.2 Classification: Cyanotic vs. Non-Cyanotic

• Cyanotic: Inadequate oxygen saturation due to right-to-left shunting or mixing of oxygenated and deoxygenated blood in a single chamber (e.g., Tetralogy of Fallot, Transposition of the Great Vessels). Presents with blue discoloration shortly after birth.
• Non-Cyanotic: Blood is adequately oxygenated, but structural defects cause left-to-right shunting or obstructive lesions (e.g., Atrial Septal Defect, Ventricular Septal Defect, Patent Ductus Arteriosus, Aortic Stenosis, Coarctation of the Aorta).

A summary of key lesions:

1.3 Left-to-Right vs. Right-to-Left Shunts

• Left-to-Right Shunts (e.g., ASD, VSD, PDA):
  • Often relatively asymptomatic at birth, but can lead to excess pulmonary flow, progressive pulmonary hypertension, and potential reversal of flow (Eisenmenger syndrome).
  • Eisenmenger Syndrome: Prolonged high pulmonary pressures cause the right-sided pressures to exceed left-sided pressures, reversing the shunt from right-to-left and leading to late cyanosis, right ventricular hypertrophy, polycythemia, and clubbing.
• Right-to-Left Shunts: Typically present with early cyanosis (e.g., Tetralogy of Fallot, Transposition of the Great Vessels).

1.4 Advances in Management

• Many adults live with non-cyanotic congenital conditions (e.g., ASDs, bicuspid aortic valves) that have relatively good prognoses.
• Modern treatments and surgical interventions have greatly improved survival, often extending it into adulthood, even for complex lesions.

2. Atrial Septal Defect (ASD)

2.1 Definition

• An ASD is a hole in the interatrial septum allowing abnormal blood flow from the left atrium (higher pressure) to the right atrium (lower pressure), resulting in left-to-right shunting.

2.2 Types of ASD

1. Ostium Secundum (≈ 90% of cases)
   • Arises from deficiency, perforation, or absence of the septum primum in the region of the fossa ovalis.
   • Commonly presents in adulthood; may remain undiagnosed if asymptomatic.
2. Ostium Primum
   • Associated with Down syndrome.
   • Involves the lower part of the atrial septum near the atrioventricular valves (endocardial cushion region).
   • May present earlier in childhood (e.g., failure to thrive).

2.3 Epidemiology

• Accounts for 10% of all congenital heart disease.
• Female predominance (2:1 female-to-male ratio).
• In adults, ASDs are among the most common congenital lesions, often diagnosed incidentally.

2.4 Pathophysiology

• Left-to-right shunt from the higher-pressure left atrium to the right atrium → extra blood volume through the right ventricle and pulmonary circulation.
• Chronic excess flow to the right side can lead to right atrial and right ventricular dilation, potentially precipitating right-sided heart failure over time.
• While pulmonary hypertension may develop, it is not usually severe unless the defect is large or long-standing.

2.5 Clinical Features

• Many patients are asymptomatic for years, leading to later-life diagnosis.
• When present, symptoms may include:
  • Failure to thrive in early childhood (often ostium primum).
  • Exertional dyspnoea or fatigue if significant shunting.
  • Signs of right heart failure (raised jugular venous pressure, peripheral oedema) in middle age.
  • Atrial fibrillation can occur due to atrial enlargement.
• Physical Exam:
  • Fixed split S2 (due to delayed closure of the pulmonic valve from increased right-sided volume).
  • Possible right ventricular heave if pulmonary pressures rise.
  • Murmurs: Not always prominent, but a systolic ejection murmur may occur across the pulmonic valve due to increased flow.

Paradoxical Emboli

• An important complication of ASD; an embolus from the venous system can cross the atrial septum and enter systemic circulation, potentially causing a stroke.

2.6 Diagnosis

1. Electrocardiography (ECG)
   • Right bundle branch block (common in both primum and secundum ASDs).
   • Axis deviation differs by type:
     • Ostium primum → left axis deviation
     • Ostium secundum → right axis deviation
2. Chest X-Ray
   • Enlarged right atrium and right ventricle (cardiomegaly).
   • Pulmonary plethora (increased vascular markings) if shunt is significant.
3. Echocardiography
   • Transthoracic echo can detect many ASDs in children.
   • Transoesophageal echo (TEE/TOE) is often required in adults to visualize the interatrial septum definitively and distinguish an ASD from a patent foramen ovale (PFO).
4. Cardiac Catheterisation
   • Sometimes necessary for quantification of the shunt (right-to-left vs. left-to-right) or when planning interventional closure.

2.7 Management

• Small ASDs: May be left untreated if clinically insignificant, with no signs of right heart volume overload.
• Moderate to Large ASDs or those causing symptoms:
  • Closure is recommended, typically in childhood or early adulthood, to prevent right ventricular failure, pulmonary hypertension, and arrhythmias.
  • Methods:
    • Percutaneous device closure (via catheter) for suitable defects.
    • Surgical repair for larger or more complex defects.
• Long-term:
  • Excellent prognosis post-closure; normal life expectancy is common.
  • However, risk of atrial arrhythmias (e.g., AF) may persist due to prior atrial dilation.

3. Key Takeaways

• Eisenmenger Syndrome can theoretically develop in large, uncorrected left-to-right shunts, reversing flow to right-to-left and causing late cyanosis and potential complications.
• Congenital Heart Disease spans a wide spectrum of cyanotic and non-cyanotic lesions, with ASD being a classic left-to-right shunt in the non-cyanotic category.
• ASD Subtypes: Ostium secundum (~90%) vs. Ostium primum (often linked to Down syndrome).
• Clinical Importance: ASDs can remain asymptomatic into adulthood; may present with fixed split S2, paradoxical emboli, and eventual right-sided volume overload.
• Diagnosis relies on echocardiography (particularly transoesophageal in adults).
• Definitive Treatment involves device or surgical closure, offering excellent outcomes if done early.

3. Ventricular Septal Defect (VSD)

3.1 Definition

• A Ventricular Septal Defect is a defect in the interventricular septum separating the right and left ventricles.
• Can be congenital (present at birth) or acquired (e.g., post-myocardial infarction necrosis).
• Congenital VSDs represent ~20% of all congenital cardiac anomalies and are often cited as the most common congenital heart defect.

3.2 Epidemiology

• Incidence: Occurs in approximately 2–7 neonates per 1000 live births.
• Association with Fetal Alcohol Syndrome: VSDs have been noted in children with this condition.

3.3 Aetiology

• Result from an embryological abnormality during the first trimester.
• May occur in isolation or with other lesions (e.g., Tetralogy of Fallot, Patent Ductus Arteriosus).
• Acquired VSD can form when the septum ruptures after a large myocardial infarction.

3.4 Pathophysiology

1. Left-to-Right Shunt
   • Blood moves from higher-pressure left ventricle to lower-pressure right ventricle.
   • The degree of shunting depends on VSD size and pulmonary vascular resistance.
2. Small VSDs
   • Often asymptomatic; the only sign may be a pansystolic murmur along the left sternal border.
   • Normal ECG and chest X-ray are common.
3. Large VSDs
   • Significant left-to-right shunt, leading to volume overload of the left ventricle and excess pulmonary blood flow.
   • Presents in neonates with heart failure signs (rapid breathing, difficulty feeding, poor weight gain, hepatomegaly).
   • Risk of pulmonary hypertension and Eisenmenger syndrome (shunt reversal to right-to-left with cyanosis) if uncorrected.

3.5 Clinical Features

• Symptoms:
  • Neonates (large VSD): Tachypnoea, feeding difficulties, failure to thrive, and other signs of heart failure.
  • Small VSDs: Often asymptomatic, discovered incidentally on routine exam.
• Signs:
  • Pansystolic (holosystolic) murmur best heard at the lower left sternal edge.
  • RV heave and displaced apex beat if significant volume overload.
  • Raised jugular venous pressure (JVP), peripheral oedema, and pulmonary congestion can occur when heart failure sets in.

Eisenmenger Syndrome

• In patients with a large, uncorrected VSD, prolonged left-to-right shunting can cause irreversible pulmonary vascular disease.
• As pulmonary pressures rise above systemic levels, the shunt reverses from right-to-left, resulting in cyanosisand related complications.

3.6 Diagnostic Approach

1. Electrocardiography (ECG)
   • Small VSD: Often normal.
   • Large VSD: May show signs of left or right ventricular hypertrophy (axis deviation).
2. Chest X-ray
   • Small VSD: Generally normal.
   • Large VSD: May show biventricular enlargement and features of cardiac failure.
3. Echocardiography
   • Mainstay for diagnosing VSD; shows the defect’s location and shunt flow.
4. Cardiac Catheterisation
   • Measures shunt magnitude and precise anatomy; less necessary if echo findings are clear.

3.7 Management

1. Spontaneous Closure
   • Occurs in 30–50% of congenital VSDs, especially small ones.
   • Observation is often sufficient if the child is asymptomatic with no signs of volume overload.
2. Medical Therapy
   • Diuretics can relieve symptoms in infants with large VSDs who develop heart failure.
   • Temporary measure until spontaneous closure or surgical correction can be pursued.
3. Surgical/Interventional Closure
   • Indications: Failure to thrive, significant left-sided volume overload, or refractory heart failure.
   • Procedures: Patching or device closure, often with a <2% mortality rate.
   • Early repair helps prevent pulmonary hypertension and Eisenmenger syndrome.

3.8 Prognosis

• Delayed intervention in large VSDs can lead to pulmonary hypertension, Eisenmenger syndrome, and more complicated clinical outcomes.
• If a small VSD closes spontaneously or a larger defect is surgically corrected early, patients usually lead normal, active lives with normal life expectancy.

4. Patent Ductus Arteriosus (PDA)

4.1 Definition

• Patent Ductus Arteriosus is a condition in which the ductus arteriosus—a normal fetal blood vessel connecting the pulmonary artery to the descending aorta—fails to close after birth.
• Postnatally, this results in a left-to-right shunt (higher-pressure aorta → lower-pressure pulmonary artery).

4.2 Epidemiology

• Accounts for 5–10% of congenital heart lesions.
• Overall incidence in neonates is ~0.08%.
• More common in preterm infants.
• Associated with congenital rubella in some cases.

4.3 Pathophysiology

• Normal Fetal Circulation: The ductus arteriosus shunts blood away from the fetal lungs, which are not yet in use.
• Postnatal Closure: Typically closes spontaneously in the first month of life.
• Persistent Patency (PDA):
  • The aortic pressure exceeds pulmonary artery pressure, causing left-to-right shunting of blood.
  • The volume overload in the pulmonary circulation may lead to increased work for the left ventricle if the shunt is large.
  • Chronic significant shunting can cause pulmonary hypertension and potential Eisenmenger syndrome(reversal of shunt to right-to-left, leading to differential cyanosis, especially in the lower extremities).

4.4 Clinical Features

1. Asymptomatic Presentations
   • Many PDAs are discovered incidentally on routine newborn exams when auscultating the heart or checking peripheral pulses.
2. Symptomatic Presentations
   • Large shunts behave similarly to a VSD, causing signs of left-to-right volume overload such as heart failure in infancy (feeding difficulties, failure to thrive, tachypnoea).
   • With long-standing or significant PDAs, patients can develop pulmonary hypertension and potential Eisenmenger syndrome, which leads to late cyanosis in the lower extremities.
3. Characteristic Murmur
   • Continuous, machinery-like murmur heard best in the pulmonary area (left infraclavicular region).
   • A palpable thrill may be present if the shunt is large.
   • A collapsing (bounding) pulse with a wide pulse pressure may be observed in significant PDAs.

4.5 Diagnostic Approach

1. Clinical Examination
   • Newborn screening (‘baby check’) typically includes auscultation of the heart and assessment of pulses, which can identify a PDA early.
2. Echocardiography
   • Investigation of choice: Visualizes the patent ductus, assesses flow, and can estimate pulmonary pressures.
3. Magnetic Resonance Imaging (MRI)
   • Occasionally used to define the anatomical defect if echo windows are poor or for surgical planning.

4.6 Management

1. Observation / Spontaneous Closure
   • The ductus can still close spontaneously up to 6 months of life in some infants, especially if small.
2. Medical Therapy
   • Indomethacin or other NSAIDs (e.g., ibuprofen) inhibit prostaglandin synthesis, promoting closure in the immediate neonatal period.
   • Prostaglandin (PGE) normally keeps the ductus open in utero, so blocking it helps facilitate closure.
3. Interventional / Surgical Closure
   • Indicated if there is significant shunt, risk of heart failure, or failure to thrive.
   • Closure can be accomplished via catheter-based device or surgical ligation.
   • Prompt intervention helps prevent complications such as pulmonary hypertension.

4.7 Prognosis

• Excellent if the PDA is closed before irreversible pulmonary vascular changes develop.
• Patients can expect a normal life provided no severe complications (e.g., Eisenmenger syndrome, heart failure) arise.
• Untreated large PDAs may lead to pulmonary hypertension, Eisenmenger syndrome, and potential lower extremity cyanosis.

5. Tetralogy of Fallot

5.1 Definition

• Tetralogy of Fallot (TOF) is the most common cyanotic congenital heart defect, comprising four key features:
  1. Pulmonary stenosis (right ventricular outflow tract obstruction)
  2. Ventricular septal defect (VSD)
  3. Overriding aorta (the aorta overrides the VSD)
  4. Right ventricular hypertrophy

5.2 Epidemiology

• Accounts for 10% of all congenital heart disease.
• Incidence is 3–6 per 10,000 live births.
• Slightly more common in males than females.

5.3 Aetiology

• During embryonic heart development, the bulbus cordis fails to rotate correctly.
• This results in anterior and superior displacement of the infundibular (conal) septum, leading to pulmonary stenosis, a VSD beneath the aortic valve, and right ventricular hypertrophy.
• Some patients have pulmonary atresia or critical pulmonary stenosis, in which case blood flow to the lungs may depend on a patent ductus arteriosus (PDA).

5.4 Pathophysiology

• The VSD is large, typically at the infundibular septum, and the right and left ventricles share nearly the same systemic pressure.
• Right-to-left shunting occurs due to the pulmonary stenosis (increased resistance to right ventricular outflow), causing deoxygenated blood to enter the overriding aorta and leading to cyanosis.
• Other associated anomalies may include a hypoplastic left pulmonary artery, an atrial septal defect (ASD), or a right-sided aortic arch.

5.5 Clinical Features

1. Age of Presentation
   • Typically presents around 3 months of age. Neonates can appear normal initially and not be obviously cyanosed at birth.
2. Cyanotic Episodes
   • Known as “Tet spells” or “blue spells,” which commonly occur with stress (e.g., during feeding or crying).
   • Squatting is a compensatory mechanism in older children, as it increases systemic vascular resistance, reducing the right-to-left shunt and improving oxygenation.
3. Signs on Examination
   • Clubbing of fingers can develop with prolonged cyanosis, though earlier diagnosis and surgical repair make this less common nowadays.
   • Right Ventricular (RV) Heave due to RV hypertrophy.
   • Systolic Murmur from pulmonary stenosis and the VSD.
   • Polycythaemia may occur from chronic hypoxia.
4. Additional Clues
   • Parents or caregivers may report episodes of increased irritability, crying, and bluish discolorationrelieved by squatting in older children.

5.6 Diagnostic Approach

1. Electrocardiography (ECG)
   • Shows right ventricular hypertrophy (RVH) and right axis deviation.
2. Chest X-Ray
   • Classically described as a “boot-shaped” heart (coeur en sabot) due to the RV enlargement and upturned cardiac apex.
3. Echocardiography
   • Confirmatory test that visualises the VSD, overriding aorta, degree of pulmonary stenosis, and RV hypertrophy.
4. Cardiac MRI
   • Provides detailed anatomical information, useful for surgical planning.

5.7 Management

1. Definitive Surgical Repair
   • Ideally performed by 1 year of age.
   • Involves closing the VSD, relieving the pulmonary stenosis, and addressing the overriding aorta.
2. Staged Palliative Shunts
   • In severely cyanotic infants with inadequate pulmonary blood flow, a Blalock–Taussig shunt (subclavian artery to pulmonary artery) or a Waterston shunt (ascending aorta to right pulmonary artery) may be created before 3 months of age.
   • Complete repair is then typically done by age 2 years.
3. Medical Management
   • Supportive care (e.g., ensuring adequate oxygenation, treating heart failure symptoms if present).
   • Counseling: Families often become highly knowledgeable (“professional patients”) about the condition and its management.

5.8 Prognosis

• Long-term survival is favorable with surgical correction: more than 85% survive beyond 30 years post-repair.
• Pulmonary regurgitation may develop over time after repair (due to the relief of pulmonary stenosis), leading to potential late complications that may require further intervention.

6. Transposition of the Great Arteries (TGA)

6.1 Definition and Subtypes

• Transposition of the Great Arteries describes a situation where the pulmonary artery and aorta are switched from their normal ventricular connections.
• Two main forms:
  1. Complete TGA (d-TGA)
     • The aorta arises from the right ventricle, and the pulmonary artery arises from the left ventricle, creating two separate (non-communicating) circulatory loops—one pulmonary and one systemic.
  2. Congenitally Corrected TGA (l-TGA)
     • The ventricles themselves are ‘inverted’, so the right ventricle receives blood from the left atrium and pumps to the aorta, while the left ventricle receives blood from the right atrium and pumps to the pulmonary artery.
     • Despite the ‘switch,’ overall circulation can remain physiologically correct (systemic blood goes to the body, pulmonary blood goes to the lungs), but the right ventricle is functioning as the systemic ventricle.

6.2 Epidemiology

1. Complete TGA
   • Accounts for 5–7% of all congenital heart defects.
   • Incidence: 2–3 per 10,000 live births.
   • Most common congenital lesion presenting with cyanosis at birth.
   • Associated with maternal diabetes in some cases.
2. Congenitally Corrected TGA
   • Also rare, but exact incidence is lower than complete TGA.
   • Offspring of mothers with l-TGA have a ~6% risk of congenital heart disease.

6.3 Pathogenesis

6.3.1 Complete TGA

• The aorta and pulmonary artery each arise from the inappropriate ventricle, forming two separate loops:
  1. Systemic loop: Right ventricle → Aorta → Body → Right atrium → Right ventricle (deoxygenated blood never reaches the lungs)
  2. Pulmonary loop: Left ventricle → Pulmonary artery → Lungs → Left atrium → Left ventricle (oxygenated blood never reaches the body)
• Survival depends on the presence of a shunt (ASD, VSD, or PDA), which allows mixing of oxygenated and deoxygenated blood.
• Often associated with VSD or PDA, which can be lifesaving but may still provide insufficient mixing for full oxygenation.

6.3.2 Congenitally Corrected TGA

• The right ventricle is anatomically on the left side but pumps blood to the body, while the left ventricle is on the right side pumping to the lungs.
• Circulation can remain physiologically normal, but the right ventricle (not suited for high systemic pressures) must work as the main systemic pump, leading to potential complications over time.
• Commonly associated with other anomalies:
  • VSD (80%)
  • Pulmonary stenosis (40%)
  • Aortic regurgitation
  • Heart block (conduction system anomalies are frequent)

6.4 Clinical Features

6.4.1 Complete TGA

• Early Cyanosis: Presents at or shortly after birth; intensifies as the PDA (if present) begins to close.
• Progressive Heart Failure if not corrected.
• Murmurs: May be absent or faint unless there is an associated lesion (e.g., VSD).
• Hyperdynamic Circulation might be noted.
• Without intervention, mortality is high:
  • ~30% by 1 week, 50% by 1 month, 90% by 1 year.

6.4.2 Congenitally Corrected TGA

• Patients may be asymptomatic early, but over time can develop:
  • Systemic ventricular failure (the RV working at systemic pressures)
  • Arrhythmias (e.g., complete heart block or supraventricular tachycardias)
  • Dizziness or syncope due to conduction issues
• Clinical signs often reflect the associated lesions (e.g., pulmonary stenosis murmur, aortic regurgitation findings).

6.5 Diagnostic Approach

1. ECG
   • Right axis deviation, right ventricular hypertrophy, or conduction blocks (particularly in corrected TGA).
2. Chest X-Ray
   • Complete TGA: Classic “egg on its side” appearance.
   • Corrected TGA: May show an unusual cardiac silhouette (“duck’s back”) and signs of associated lesions.
3. Echocardiography
   • Definitive for visualizing arterial-ventricular connections and intracardiac anatomy.
4. Cardiac MRI
   • Provides detailed anatomical information when planning intervention.

6.6 Management

6.6.1 Complete TGA

• Neonatal Period:
  • IV Prostaglandin (PGE) infusion to keep the ductus arteriosus patent, maintaining some degree of mixing of oxygenated and deoxygenated blood.
  • Balloon Atrial Septostomy: An urgent procedure to enlarge an atrial opening (e.g., foramen ovale), increasing mixing and stabilizing the infant.
• Definitive Surgical Correction:
  • Arterial switch operation (anatomic correction), typically performed in early infancy.
  • Prognosis after successful repair is excellent, with ~97% survival at 25 years.

6.6.2 Congenitally Corrected TGA

• Usually managed in specialist centers due to complexity.
• Medical therapy for heart failure if the RV fails as the systemic ventricle.
• Pacemaker insertion for high-degree AV block; ablation for supraventricular tachyarrhythmias.
• Surgical interventions:
  • Closure of an associated VSD or repair of valvular lesions (e.g., pulmonary stenosis, regurgitant valves).

6.7 Prognosis

• Complete TGA:
  • Without surgical correction, mortality approaches 90% by 1 year of life.
  • With timely intervention, long-term survival is excellent (97% at 25 years).
• Congenitally Corrected TGA:
  • Variable outcome; depends on associated lesions and the function of the systemic RV.
  • Patients remain at risk for arrhythmias, valve problems, and RV failure over time.

7. Coarctation of the Aorta

7.1 Definition

• Coarctation of the aorta is a congenital condition characterized by a focal narrowing of the aorta, typically near the origin of the left subclavian artery (aortic isthmus).
• Results in high blood pressure proximal to the lesion (upper body) and reduced blood flow distal to the lesion (lower body).

7.2 Epidemiology

• Accounts for 5–8% of congenital heart defects in the UK.
• Often presents either neonatally (infantile form) or in adulthood (adult form).

7.3 Types and Aetiology

1. Infantile Form (‘Preductal’ Coarctation)
   • Narrowing is proximal to a Patent Ductus Arteriosus (PDA) but distal to the aortic arch vessels.
   • Often presents soon after birth with features of lower-body hypoperfusion and may be associated with Turner syndrome.
   • Can cause lower extremity cyanosis if the PDA allows right-to-left shunting.
2. Adult Form (‘Postductal’ Coarctation)
   • Narrowing lies distal to the aortic arch branches and is not associated with a PDA.
   • Typically presents later in life with hypertension in upper extremities and weak or delayed pulses in the lower extremities (radiofemoral delay).
   • Frequently associated with a bicuspid aortic valve and other structural anomalies.

Pathogenesis

• In both forms, the lesion arises during embryonic development of the aortic arch.
• The infantile variant is typically due to hypoplasia of the aortic isthmus, whereas the adult form tends to have a progressive narrowing that becomes symptomatic later.

7.4 Clinical Features

1. Infants (Infantile Coarctation)
   • Heart failure and failure to thrive in neonates.
   • If a PDA is present, there can be differential cyanosis (lower limbs more cyanotic than upper limbs).
2. Older Children and Adults (Adult Coarctation)
   • Upper body hypertension leading to headaches, epistaxis, or asymptomatic detection during routine blood pressure checks.
   • Weak or delayed femoral pulses compared to brachial/radial pulses (radiofemoral delay).
   • Systolic murmur best heard under the left clavicle or on the back.
   • Rib notching on chest X-ray due to enlarged collateral intercostal arteries, which erode the inferior aspects of the ribs.
   • Many patients also have a bicuspid aortic valve or other aortopathies.

7.5 Diagnostic Approach

1. Physical Examination
   • Check blood pressure in both arms; note if it differs or if one arm is more proximal to the coarctation.
   • Palpate femoral pulses—commonly weak, delayed, or absent.
   • Listen for a systolic murmur on the back or infraclavicular area.
2. ECG
   • May show left ventricular hypertrophy due to chronic pressure overload.
   • Right bundle branch block (RBBB) or other conduction abnormalities can appear as secondary signs of hypertrophy.
3. Chest X-Ray
   • Infants: Often normal early on.
   • Older patients: May reveal rib notching and cardiomegaly (secondary to LVH).
4. Echocardiography
   • Investigation of choice to visualise the narrowing and assess the gradient across the coarctation site.
   • Can evaluate for bicuspid aortic valve or other associated lesions.
5. Cardiac MRI or CT Angiography
   • Provides detailed morphological assessment of the aorta, especially important for surgical or interventional planning.

7.6 Management

1. Infants
   • Corrective Surgery:
     • End-to-end anastomosis after resecting the narrowed segment.
     • Patch aortoplasty if anatomy is suitable.
   • If coarctation is critical, might require PGE (prostaglandin) infusion to keep ductus arteriosus open, ensuring distal perfusion until definitive repair.
2. Older Children / Adults
   • Balloon Angioplasty or Stenting of the coarctation site is often preferred for less invasive correction.
   • Open Aortic Surgery may be used if anatomy is complex or if stenting is not feasible.
3. Long-term Follow-up
   • Lifelong monitoring because of risks of:
     • Recurrent coarctation
     • Hypertension (may persist post-repair)
     • Aneurysm formation at the repair site

7.7 Prognosis

• Good once coarctation is successfully corrected, but patients require lifelong follow-up.
• Early repair in infancy can prevent complications like heart failure or severe lower-body hypoperfusion.
• Adults treated later in life may still develop residual hypertension, aneurysms, or recoarctation.

8. Truncus Arteriosus and Tricuspid Atresia

8.1 Truncus Arteriosus

Definition

• A single great vessel (the “truncus”) arises from the heart, receiving blood from both ventricles.
• Embryologically, this occurs when the truncus arteriosus fails to divide into the pulmonary artery and the aorta.

Pathophysiology

• Because the blood from the right ventricle (deoxygenated) mixes with blood from the left ventricle (oxygenated) before separating into systemic and pulmonary circulations, there is partial mixing of oxygenated and deoxygenated blood.
• This often leads to early cyanosis in neonates due to inadequate systemic oxygen saturation.

Clinical Features

• Early cyanosis: Mixed blood is delivered to both systemic and pulmonary circuits through the single vessel.
• The degree of cyanosis and associated symptoms depend on the relative blood flow to the lungs versus the body.
• A VSD is usually present beneath the truncus, as the single vessel overrides what would normally be two separate outflow tracts.

Management (General Principles)

• Surgical repair is required to separate the single vessel into distinct aortic and pulmonary outflows and to close any associated ventricular septal defect.
• Without correction, progressive heart failure and cyanosis lead to significant morbidity and mortality.

8.2 Tricuspid Atresia

Definition

• Tricuspid atresia is the absence (atresia) of the tricuspid valve orifice between the right atrium and right ventricle.
• Consequently, the right ventricle becomes hypoplastic because it does not receive direct blood flow from the right atrium.

Pathophysiology

• Because blood from the right atrium cannot enter the right ventricle, it must bypass the atretic valve area to reach the left side of the heart.
• In most cases, an atrial septal defect (ASD) is present, allowing venous blood from the right atrium to pass into the left atrium, resulting in a right-to-left shunt with deoxygenated blood entering systemic circulation.
• The reduced or absent flow into the right ventricle leads to inadequate pulmonary blood flow unless there is another connection (e.g., a ventricular septal defect or patent ductus arteriosus).

Clinical Features

• Early cyanosis: Deoxygenated blood from the right atrium moves to the left atrium (and subsequently systemic circulation).
• Hypoplastic right ventricle: The chamber is underdeveloped due to lack of inflow.
• If additional defects (like a VSD) are present, some blood may still reach the lungs for oxygenation.

Management (General Principles)

• Surgical palliation and eventual single-ventricle pathway approaches are typically required (e.g., Fontan procedure), ensuring that systemic venous return is directed to the lungs and the functional left ventricle supplies systemic output.
• Maintenance of adequate pulmonary blood flow (e.g., via a patent ductus arteriosus or a systemic-to-pulmonary shunt) may be necessary early on.