Classification of Congenital Heart Diseases

Topic Name Introduction Classification of CHDs Acyanotic CHDs Cyanotic CHDs

Introduction to Congenital Heart Diseases (CHDs)

Congenital heart diseases (CHDs) are structural abnormalities of the heart or great vessels that are present at birth. These defects occur due to abnormal formation of the heart during fetal development. CHDs affect approximately 1% of live births and are a significant cause of infant morbidity and mortality.

The severity of CHDs can range from minor defects that may resolve spontaneously to complex abnormalities requiring immediate intervention after birth. Understanding the classification and characteristics of different CHDs is crucial for proper diagnosis, management, and treatment planning.

Classification of Congenital Heart Diseases

CHDs can be classified in several ways, but the most common and clinically relevant classification is based on the presence or absence of cyanosis:

1. Acyanotic CHDs: These defects do not typically cause cyanosis (bluish discoloration of the skin due to decreased oxygen saturation in the blood).
2. Cyanotic CHDs: These defects usually result in cyanosis due to right-to-left shunting of deoxygenated blood.

Another classification system is based on the hemodynamic effects of the defects:

1. Left-to-right shunts: Blood flows from the left side of the heart to the right side, increasing pulmonary blood flow (e.g., Atrial Septal Defect, Ventricular Septal Defect).
2. Right-to-left shunts: Deoxygenated blood from the right side of the heart enters the systemic circulation (e.g., Tetralogy of Fallot, Transposition of Great Arteries).
3. Obstructive lesions: Narrowing or obstruction in the heart or great vessels (e.g., Coarctation of Aorta, Pulmonary Stenosis).
4. Complex lesions: Combination of multiple defects (e.g., Hypoplastic Left Heart Syndrome).

Acyanotic Congenital Heart Diseases

Acyanotic CHDs are characterized by the absence of cyanosis under normal conditions. These defects often involve left-to-right shunts or obstructive lesions. Common acyanotic CHDs include:

1. Atrial Septal Defect (ASD):
   • An opening in the interatrial septum allowing blood flow between atria.
   • Types: Ostium secundum (most common), ostium primum, sinus venosus, and coronary sinus defects.
   • Symptoms: Often asymptomatic in childhood; may cause fatigue, palpitations, or right heart failure in adulthood.
2. Ventricular Septal Defect (VSD):
   • An opening in the interventricular septum allowing blood flow between ventricles.
   • Types: Perimembranous (most common), muscular, inlet, and outlet defects.
   • Symptoms: Small VSDs may be asymptomatic; larger ones can cause failure to thrive, recurrent respiratory infections, and heart failure.
3. Patent Ductus Arteriosus (PDA):
   • Persistent patency of the ductus arteriosus after birth.
   • Causes left-to-right shunt from aorta to pulmonary artery.
   • Symptoms: Continuous "machinery" murmur, wide pulse pressure, and potentially heart failure.
4. Coarctation of the Aorta:
   • Narrowing of the aorta, typically just distal to the left subclavian artery.
   • Presents with upper body hypertension and weak femoral pulses.
   • Can lead to left ventricular hypertrophy and heart failure if untreated.
5. Pulmonary Valve Stenosis:
   • Narrowing of the pulmonary valve causing obstruction to right ventricular outflow.
   • Severity ranges from mild (asymptomatic) to severe (right ventricular failure).
   • Characterized by a systolic ejection murmur and potential right ventricular hypertrophy.

Cyanotic Congenital Heart Diseases

Cyanotic CHDs typically involve right-to-left shunting of deoxygenated blood, resulting in cyanosis. These defects often require early intervention. Common cyanotic CHDs include:

1. Tetralogy of Fallot (TOF):
   • Consists of four defects: VSD, overriding aorta, right ventricular outflow tract obstruction, and right ventricular hypertrophy.
   • Presents with cyanotic spells, difficulty feeding, and poor growth.
   • Characteristic "boot-shaped" heart on chest X-ray.
2. Transposition of the Great Arteries (TGA):
   • Aorta arises from the right ventricle, and pulmonary artery from the left ventricle.
   • Results in two parallel circulations, requiring mixing of blood for survival.
   • Presents with severe cyanosis shortly after birth.
3. Total Anomalous Pulmonary Venous Return (TAPVR):
   • All pulmonary veins drain into the right atrium or its tributaries instead of the left atrium.
   • Types: Supracardiac, cardiac, infracardiac, and mixed.
   • Presents with cyanosis and signs of pulmonary congestion.
4. Tricuspid Atresia:
   • Absence or underdevelopment of the tricuspid valve, preventing blood flow from right atrium to right ventricle.
   • Requires an ASD for survival and is often associated with other defects.
   • Presents with early cyanosis and signs of heart failure.
5. Truncus Arteriosus:
   • A single arterial trunk arising from the heart supplies both systemic and pulmonary circulation.
   • Always associated with a large VSD.
   • Presents with cyanosis, tachypnea, and signs of heart failure.

Objective QnA: 2. Classification of Congenital Heart Diseases

1. What are the two main categories of congenital heart diseases?
   Cyanotic and acyanotic
2. Which congenital heart defect is characterized by right ventricular outflow tract obstruction, ventricular septal defect, overriding aorta, and right ventricular hypertrophy?
   Tetralogy of Fallot
3. What is the most common cyanotic congenital heart defect?
   Tetralogy of Fallot
4. Which acyanotic congenital heart defect is characterized by a left-to-right shunt at the ventricular level?
   Ventricular septal defect (VSD)
5. What is the most common acyanotic congenital heart defect?
   Ventricular septal defect (VSD)
6. Which congenital heart defect involves complete mixing of systemic and pulmonary circulations?
   Total anomalous pulmonary venous return (TAPVR)
7. What is the defining feature of Eisenmenger syndrome?
   Reversal of shunt direction from left-to-right to right-to-left due to pulmonary hypertension
8. Which congenital heart defect is characterized by obstruction of the aortic arch?
   Coarctation of the aorta
9. What is the primary hemodynamic consequence of a large atrial septal defect (ASD)?
   Right heart volume overload
10. Which congenital heart defect is often referred to as "blue baby syndrome"?
    Transposition of the great arteries (TGA)
11. What is the hallmark of Ebstein's anomaly?
    Apical displacement of the septal and posterior leaflets of the tricuspid valve
12. Which congenital heart defect is characterized by a single ventricle pumping blood to both systemic and pulmonary circulations?
    Hypoplastic left heart syndrome (HLHS)
13. What is the primary physiological abnormality in patent ductus arteriosus (PDA)?
    Persistent communication between the aorta and pulmonary artery
14. Which congenital heart defect is associated with cyanosis and pulmonary oligemia?
    Tricuspid atresia
15. What is the most common cause of right ventricular outflow tract obstruction in infants?
    Pulmonary valve stenosis
16. Which congenital heart defect is characterized by underdevelopment of the left side of the heart?
    Hypoplastic left heart syndrome (HLHS)
17. What is the primary hemodynamic consequence of aortic stenosis?
    Left ventricular pressure overload
18. Which congenital heart defect involves abnormal connection of the great arteries to the ventricles?
    Double outlet right ventricle (DORV)
19. What is the defining feature of truncus arteriosus?
    A single arterial trunk arising from the heart, supplying systemic, pulmonary, and coronary circulations
20. Which congenital heart defect is characterized by absence of the pulmonary valve?
    Pulmonary atresia
21. What is the primary physiological abnormality in total anomalous pulmonary venous return (TAPVR)?
    All pulmonary veins drain into the right atrium or systemic veins
22. Which congenital heart defect is associated with DiGeorge syndrome?
    Interrupted aortic arch
23. What is the most common cause of left ventricular outflow tract obstruction in children?
    Subaortic stenosis
24. Which congenital heart defect is characterized by a hole in the muscular wall separating the left and right ventricles?
    Ventricular septal defect (VSD)
25. What is the primary hemodynamic consequence of a large patent ductus arteriosus (PDA)?
    Left heart volume overload
26. Which congenital heart defect is associated with heterotaxy syndrome?
    Atrioventricular septal defect (AVSD)
27. What is the defining feature of cor triatriatum?
    Division of the left atrium into two chambers by a fibromuscular membrane
28. Which congenital heart defect is characterized by narrowing of the aortic valve opening?
    Aortic stenosis
29. What is the primary physiological abnormality in pulmonary atresia with intact ventricular septum?
    Absence of communication between the right ventricle and pulmonary artery
30. Which congenital heart defect is associated with Turner syndrome?
    Coarctation of the aorta

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