Congenital heart disease is a cardiovascular malformation caused by certain internal or external factors during the embryonic development of the heart and blood vessels, and it is the leading cardiac condition in pediatrics. Its incidence accounts for 7–8% of live births, and without treatment, approximately one-third of affected infants die within the first month of life, and about half die within the first year. Pediatric pathological examinations reveal that 10–12% of cases involve congenital cardiovascular malformations. In recent years, due to advancements and widespread adoption of diagnostic and therapeutic techniques, most affected children can be diagnosed early. With timely surgical intervention, many cases can be completely cured, significantly improving the prognosis of congenital heart disease.

1. Embryonic development of the heart: The development of the heart begins in the third week of embryogenesis and is completed by the eighth week. Blood circulation starts in the fourth week, the atrial septum forms in the fifth week, and the ventricular septum forms by the eighth week, resulting in a four-chambered heart. Simultaneously, the truncus arteriosus is divided by the spiral aorticopulmonary septum, forming the aorta and pulmonary artery. During this period, exposure to certain factors can easily lead to cardiovascular developmental malformations.
2. Fetal circulation: After gas and nutrient exchange in the placenta, oxygen-rich blood enters the fetus via the umbilical vein. A portion of this blood flows directly into the inferior vena cava through the ductus venosus, while another portion (20–80%) enters the liver and merges with the portal vein before being transmitted to the hepatic veins, which also drain into the inferior vena cava. The highly oxygenated blood from the inferior vena cava enters the right atrium, with most of it flowing through the foramen ovale into the left atrium and then into the left ventricle, which pumps it into the aorta to supply the heart, head, and upper limbs. Venous blood from the superior vena cava enters the right atrium, with most of it flowing into the right ventricle and then into the pulmonary artery. A small amount of this blood reaches the lungs (which are non-functional for respiration) and returns to the left atrium via the pulmonary veins, while the majority flows from the pulmonary artery through the ductus arteriosus into the descending aorta to supply the lower body. This blood has lower oxygen levels than that in the aorta and returns to the placenta via the umbilical arteries for gas and nutrient exchange, after which it is transmitted back through the umbilical vein to repeat the cycle. (Figure 8-1)
   Characteristics of fetal circulation:
   1. Gas and nutrient exchange occurs via the placenta.
   2. Except for the umbilical vein, which carries oxygenated blood, all other vessels carry mixed blood.
   3. The foramen ovale and ductus arteriosus are normal pathways in fetal circulation.
   4. Both ventricles supply blood to the systemic circulation.
   5. The systemic circulation predominates; although the pulmonary circulation exists, no gas exchange occurs.
   6. Pulmonary artery pressure is higher than aortic pressure.
3. Postnatal circulatory changes: After birth, the umbilical cord is clamped, fetal circulation ceases, and respiration begins, with the alveoli expanding to initiate gas exchange. During inhalation, the negative intrathoracic pressure expands the lungs, increasing blood flow from the right ventricle into the pulmonary artery and subsequently into the pulmonary veins, which return more blood to the left atrium. As left atrial pressure rises above right atrial pressure, the valve-like membrane of the foramen ovale functionally closes, with anatomical closure occurring by 5–7 months of age, leaving behind the fossa ovalis. As pulmonary vascular resistance decreases and systemic pressure increases, the ductus arteriosus functionally closes when the pressures equalize. After birth, pulmonary respiration increases blood oxygen levels, and bradykinin inhibits prostaglandin E release, causing the ductus arteriosus to constrict. Later, thrombosis, organization, and intimal proliferation lead to ductal occlusion, with most cases forming the ligamentum arteriosum by 3–6 months of age. After umbilical cord clamping, fetal circulation ceases, and the umbilical vessels gradually obliterate: the umbilical arteries become the medial umbilical ligaments, the umbilical vein becomes the ligamentum teres hepatis, and the ductus venosus becomes the ligamentum venosum.

bubble_chart Etiology

Due to advances in genetics, embryology, pestilence studies, metabolic diseases, and microbiology, clues and directions have been provided for the disease causes of congenital heart disease. Many aspects remain unclear and require further research to develop effective prevention and treatment measures.

1. Infectious factors: During early embryonic stages, particularly within 3 to 8 cycles of day and night, maternal infection with the rubella virus increases the likelihood of fetal cardiovascular malformations. Other viruses (such as influenza, mumps, and Coxsackie) can also cause such anomalies.
2. Physical and chemical factors: Certain medications taken during early pregnancy, such as methotrexate, busulfan, cyclophosphamide, tolbutamide, and some sedatives, can lead to fetal heart malformations. Additionally, high-altitude environments, hypoxia, exposure to radioactive materials, and radiation therapy may also contribute.
3. Genetic factors and metabolic disorders: Chromosomal abnormalities such as trisomy 21 (Down syndrome), trisomy 18, trisomy 13, 4 or 5 short arm deletion syndromes, X0 syndrome, Marfan syndrome, and congenital osteogenesis imperfecta can be associated with heart malformations. Congenital metabolic disorders, such as type II glycogen storage disease, maternal diabetes, phenylketonuria, hypercalcemia, and folic acid deficiency, may also cause fetal heart abnormalities.
4. Other factors: A familial tendency may exist, with higher disease mechanisms observed among siblings, particularly monozygotic twins. Additionally, children born to older mothers have a higher incidence of congenital heart disease.

bubble_chart Pathological Changes

1. Stirred pulse, decreased blood oxygen saturation: occurs in right-to-left shunts and advanced stages of left-to-right shunts. Cyanosis appears when the reduced hemoglobin in capillaries exceeds 50g/L (5g/dl). Hypoxia can stimulate capillary dilation and connective tissue hyperplasia at the ends of fingers (toes), leading to clubbing and rounded convex fingernails (toenails). Hypoxia can also cause rapid and increased respiration, as well as stimulate bone marrow hematopoiesis, resulting in compensatory increases in red blood cells. Cerebral hypoxia can cause syncope. Hypoxic children instinctively reduce physical activity, adopting a protective squatting posture and remaining quiet and inactive.
2. Ventricular overload: Various malformations often lead to ventricular overload. This can be categorized into four types: left ventricular systolic overload (e.g., stirred pulse constriction), left ventricular diastolic overload (e.g., stirred pulse patent ductus arteriosus), right ventricular systolic overload (e.g., pulmonary stirred pulse valve stenosis), and right ventricular diastolic overload (e.g., atrial septal defect). Overloaded ventricles typically first develop hypertrophy, followed by heart failure or dilation.
3. Changes in circulating blood volume and ineffective circulation: In left-to-right shunts, systemic circulation volume decreases while pulmonary circulation volume increases, with some blood continuously recirculating in the pulmonary circulation, failing to serve its physiological role and increasing the pulmonary circulation load. This condition is called ineffective circulation, and the shunt volume (ineffective circulation volume) is significant for surgery and prognosis assessment. In right-to-left shunts, systemic circulation volume increases, with the additional portion being venous blood, which increases the workload of systemic circulation without delivering oxygen to the body. Pulmonary circulation volume decreases, impairing oxygen exchange in the lungs, thereby exacerbating the decrease in blood oxygen saturation and worsening cyanosis, leading to further hypoxia.
4. Pulmonary stirred pulse hypertension: Left-to-right shunts can cause pulmonary stirred pulse hypertension. In the early stages, increased blood flow in the pulmonary stirred pulse leads to dynamic pulmonary stirred pulse hypertension. In advanced stages, thickening and loss of elasticity in the small pulmonary stirred pulse membrane result in obstructive pulmonary stirred pulse hypertension.

〔Specific Discussions〕

1. Atrial Septal Defect

During the 4th to 6th a cycle of day and night of embryonic development, the first septum grows within the atria, dividing them into left and right atria. The primary foramen remains at the lower part of the first septum, while a secondary foramen forms at the upper part. Later, a second septum grows to the right of the first septum, fusing with it and covering the secondary foramen, leaving an oval opening called the foramen ovale. The left side of the first septum acts as a curtain membrane covering the foramen ovale, functioning as a valve to allow blood flow only from the right atrium to the left atrium. After birth, the foramen ovale closes, forming the fossa ovalis. If any of these openings fail to close during embryonic development, it is termed an atrial septal defect. These are classified as primary foramen (ostium primum) defects and secondary foramen (ostium secundum) defects, the latter being more common, accounting for about 70% of atrial septal defects, with defect diameters ranging from 1 to 3 cm. A patent foramen ovale without blood shunting has no clinical significance. An atrial septal defect accompanied by mitral stenosis is called Lutembacher syndrome. Generally, pediatric internal medicine diagnoses an atrial septal defect, but surgical intervention requires identifying whether it is a primary or secondary foramen defect and the size of the defect to facilitate the procedure.

Hemodynamic changes in atrial septal defect: Due to the higher pressure in the left atrium compared to the right atrium, blood flows from the left atrium through the defect into the right atrium and then into the right ventricle. As a result, the right atrium receives not only the normal blood returning from the superior and inferior vena cava but also the additional blood shunted from the left atrium. The amount of shunting primarily depends on the size of the defect and the pressure gradient between the left and right atria. Small shunts may have minimal impact, whereas large shunts can overload the right atrium and right ventricle during diastole, leading to enlargement of these chambers. The increased blood flow into the pulmonary circulation can cause dynamic pulmonary hypertension. In advanced stages, obstructive pulmonary hypertension may develop, raising the pressure in the right ventricle and right atrium. When the right atrial pressure exceeds that of the left atrium, blood flows into the left atrium, resulting in persistent cyanosis, at which point definitive surgical intervention is no longer advisable. Additionally, because blood is shunted from the left atrium to the right atrium, the volume entering the left ventricle and systemic circulation is reduced, which can impair the child's growth and development over time.

2. Ventricular Septal Defect

The ventricular septum forms during embryonic weeks 4–8. It originates from three sources:

1. The muscular portion is formed by the upward growth of muscle from the base of the ventricular wall.
2. The membranous portion arises from the fusion of endocardial cushions, which grow downward, and the membranous part of the bulbus cordis, merging with the muscular septum to close the interventricular foramen. If developmental disturbances occur, a ventricular septal defect (VSD) results.

1. Defects in the membranous septum are called high ventricular septal defects, which are more common, accounting for about 90%. The defect diameter ranges from 0.5 to 3 cm.
2. Defects in the muscular septum are called low ventricular septal defects, with diameters also ranging from 0.5 to 3 cm, also known as Roger’s disease.

Hemodynamic changes: Blood flows from the left ventricle through the defect into the right ventricle. The shunt volume depends on the pressure difference between the two ventricles and the size of the defect. Small shunts may be asymptomatic. Moderate defects result in shunt volumes 1–2 times the systemic circulation, while large defects can reach 3–5 times. The right ventricle, in addition to receiving normal blood flow from the right atrium, also receives a large amount of shunted blood. This increases the diastolic load on the right ventricle, leading to increased output and dynamic pulmonary hypertension. In advanced stages, obstructive pulmonary hypertension may develop, causing persistent cyanosis, known as Eisenmenger syndrome. The left atrium and ventricle may also enlarge.

3. Patent Ductus Arteriosus

The ductus arteriosus connects the pulmonary artery bifurcation to the descending aortic arch. It is classified into three types: tubular (most common), window-like, and funnel-like. It measures 0.7–1 cm in length and 0.5–1 cm in diameter.

Hemodynamic changes: Since aortic pressure exceeds pulmonary pressure, blood flows through the duct into the pulmonary artery. The shunt volume depends on the duct’s diameter, length, and the pressure gradient between the aorta and pulmonary artery. A large shunt to the pulmonary circulation returns to the left atrium and ventricle, chronically overloading the left ventricle during diastole, leading to left atrial and ventricular enlargement. Increased pulmonary circulation can, in advanced stages, cause obstructive pulmonary hypertension, overloading the right ventricle and resulting in right ventricular hypertrophy. When pulmonary pressure exceeds aortic pressure, venous blood from the pulmonary artery flows backward through the patent ductus arteriosus into the aorta, causing lower-body cyanosis, known as differential cyanosis.

4. Tetralogy of Fallot

Despite involving four pathological changes, the key hemodynamic alteration is pulmonary stenosis. This increases the systolic load on the right ventricle, leading to right ventricular hypertrophy and elevated pressure, followed by right atrial pressure rise and hypertrophy. When right ventricular pressure exceeds left ventricular pressure, blood shunts through the ventricular septal defect into the left ventricle and the overriding aorta, causing systemic persistent cyanosis. Pulmonary stenosis reduces blood flow for oxygenation in the lungs, worsening cyanosis. If pulmonary stenosis is mild and right ventricular pressure remains lower than left ventricular pressure, blood shunts left-to-right without cyanosis, termed "acyanotic tetralogy of Fallot." In infants under 3 months, the patent ductus arteriosus allows some blood to reach the lungs for oxygenation, making cyanosis less noticeable. As the duct closes, cyanosis worsens.

5. Trilogy of Fallot

Although there are three types of pathological changes, their pathophysiological and hemodynamic alterations, as well as clinical manifestations, are the same. The primary issue is the obstruction of blood ejection from the right ventricle, leading to an increased systolic load on the right ventricle. This results in elevated pressure and hypertrophy of the right ventricle, as well as increased pressure and hypertrophy of the right atrium, ultimately causing right heart failure. The amount of blood entering the pulmonary circulation is reduced, leading to decreased pulmonary artery pressure and reduced pulmonary blood flow. Consequently, the blood returning to the left heart and then to the systemic circulation is insufficient, often causing flusteredness and shortness of breath after physical exertion. When right atrial pressure increases, if accompanied by an atrial septal defect or patent foramen ovale, blood shunts from the right atrium to the left atrium, resulting in cyanosis. This condition is referred to as the trilogy of Fallot.

VI. Coarctation of the aorta

At the proximal end of the coarctation, the blood supply to the head and upper limbs is sufficient, with increased blood pressure. Distal to the coarctation, collateral circulation forms early. The superior intercostal branches of the subclavian artery anastomose with the first intercostal artery, the scapular branches of the subclavian artery anastomose with the intercostal arteries, and the internal mammary branches of the subclavian artery anastomose with the abdominal wall branches of the external iliac artery to supply blood to the lower body, but the blood volume is insufficient, and the blood pressure is lower than normal. Post-stenotic dilation may occur in the aorta distal to the coarctation.

bubble_chart Type

Most domestic classifications divide congenital heart diseases into three types based on the presence or absence of shunts between the left and right sides of the heart and major blood vessels, while a few classify them according to the presence or absence of cyanosis. This book adopts the former approach.

1. Left-to-right shunt type (latent cyanotic type or advanced stage cyanotic type): There is an abnormal pathway between the systemic and pulmonary circulations. Since the pressure on the left side is higher than that on the right, blood flows from left to right, generally without cyanosis. When the pressure on the right side exceeds that on the left—such as during crying, pneumonia, heart failure, or when pulmonary stirred pulse generates high pressure—a right-to-left shunt occurs, leading to cyanosis. When these causes are resolved, the cyanosis subsides. Common examples of this type include patent stirred pulse ductus arteriosus, atrial septal defect, and ventricular septal defect. In the advanced stage of the disease, when combined with obstructive pulmonary stirred pulse hypertension, persistent cyanosis occurs, known as Eisenmenger syndrome.
2. Right-to-left shunt type (cyanotic type or early cyanotic type): There is an abnormal pathway between the systemic and pulmonary circulations, and when pulmonary stirred pulse hypertension or right ventricular outflow tract stenosis is present, the pressure in the right ventricle exceeds that in the left ventricle. Blood then flows from the right ventricle to the left ventricle and into the systemic circulation, resulting in cyanosis. Additionally, abnormal origins of major blood vessels can cause venous blood to enter the systemic circulation, leading to persistent cyanosis. Examples include tetralogy of Fallot and transposition of the great arteries.
3. No shunt type (non-cyanotic type): There is no abnormal pathway between the systemic and pulmonary circulations, so cyanosis does not occur (except for cyanosis caused by venous blood entering the systemic circulation). Examples include pulmonary stirred pulse stenosis, coarctation of the aorta, and dextrocardia.

bubble_chart Diagnosis

1. Atrial Septal Defect

Symptoms: Vary depending on the size of the defect. Small defects often cause no obvious symptoms, while large defects lead to insufficient systemic circulation, manifesting as developmental delays, post-exertional flusteredness, shortness of breath, lack of strength, and profuse sweating. Due to pulmonary congestion, respiratory infections are common. Temporary cyanosis may occur when crying, during pneumonia, or heart failure, as right atrial pressure exceeds left atrial pressure.

Signs:

1. The precordial and xiphoid regions may show bulging with strong pulsations and palpable impulses; a few cases exhibit fine systolic tremors.
2. A grade II/6 to III/6 ejection systolic murmur is audible at the left sternal border (2nd–3rd intercostal space), caused by relative pulmonary valve stenosis rather than blood flow through the defect. The pulmonary component of the second heart sound (P2) is accentuated with fixed splitting. A diastolic intermediate-stage murmur may sometimes be heard at the tricuspid area due to relative tricuspid stenosis from increased blood flow from the right atrium to the right ventricle.

[Auxiliary Examinations]

1. X-ray: Small defects show a normal heart, while large defects reveal right atrial and ventricular enlargement with a prominent pulmonary artery segment. Pulsatile changes in hilar density ("hilar dance") may occur, and the main pulmonary artery shadow may shrink.
2. ECG: Right axis deviation, right atrial and ventricular hypertrophy, and complete or incomplete right bundle branch block may be present.
3. Echocardiography: M-mode shows increased right ventricular and atrial diameters with a smaller main pulmonary artery diameter. Two-dimensional ultrasound reveals an interrupted atrial septal echo. Color Doppler demonstrates blood shunting and defect size.
4. Cardiac catheterization: Right atrial oxygen saturation exceeds the average of superior and inferior vena cava by 1.9 vol%. The catheter may pass through the defect into the left atrium. Advanced cases may show elevated pulmonary artery, right ventricular, and right atrial pressures.

2. Ventricular Septal Defect

Symptoms: Small defects may remain asymptomatic for years, with only a systolic murmur at the left sternal border (3rd–4th intercostal space), often discovered incidentally during exams. Moderate to large defects with shunting exceeding twice systemic flow cause systemic hypoperfusion, presenting as growth retardation, emaciation, lack of strength, profuse sweating, and pale complexion. Exertional flusteredness and dyspnea are common, and pulmonary congestion predisposes to bronchitis, pneumonia, and heart failure. Subacute bacterial endocarditis is a frequent complication. Temporary cyanosis may occur with pulmonary hypertension; advanced cases develop Eisenmenger syndrome.

Signs: Precordial bulging, enlarged cardiac borders, and forceful apical and xiphoid pulsations. A loud, harsh, grade III/6 or higher pansystolic murmur is heard at the left sternal border (3rd–4th intercostal space), radiating widely with a systolic thrill. In advanced pulmonary hypertension with right-to-left shunting, the murmur may soften and shorten. Murmur intensity does not correlate with defect size, so clinical severity cannot be judged by loudness. P2 may be accentuated, occasionally split. A low-pitched, short diastolic rumble may be heard at the apex due to relative mitral stenosis.

[Auxiliary Examinations]

1. X-ray: Small shunts show no changes; large shunts reveal left ventricular and atrial enlargement, with right ventricular enlargement in advanced cases. The main pulmonary artery may widen, and the pulmonary segment may protrude. Hilar dance may appear.
2. ECG: About 1/3 are normal; findings may include left ventricular hypertrophy, left atrial hypertrophy, and right ventricular hypertrophy in advanced stages.
3. Echocardiography: Increased left atrial, left ventricular, and main pulmonary artery diameters. Two-dimensional ultrasound visualizes duct size, length, and position between the pulmonary artery and descending aorta. Color Doppler shows duct morphology and flow direction.
4. Right heart catheterization:
   1. Pulmonary artery stirred pulse Blood oxygen content > right ventricle 0.6vol%.
   2. Pulmonary artery stirred pulse and right ventricular pressure may increase.
   3. In some patients, right heart catheterization can pass through the patent stirred pulse duct into the descending aorta stirred pulse.

III. Patent stirred pulse duct

Symptoms: Those with small shunts are mostly asymptomatic, occasionally discovered during physical examination with a continuous murmur. Those with large shunts exhibit manifestations of insufficient systemic circulation blood supply, such as fatigue, weakness, pallor, profuse sweating, delayed development, slender physique, and susceptibility to respiratory infections. Occasionally, hoarseness may occur due to the enlarged pulmonary stirred pulse compressing the recurrent laryngeal nerve. In advanced stages, it is often complicated by heart failure, cyanosis, dyspnea, etc., and may also be complicated by subacute bacterial endocarditis. Signs:

1. Precordial prominence, enhanced apical impulse.
2. A continuous machinery-like murmur is heard at the second left intercostal space, predominantly during systole, and may radiate to the neck and back, caused by blood flow through the duct. During the cardiac cycle, the pressure difference between the aorta stirred pulse and pulmonary stirred pulse varies, resulting in changes in the murmur's intensity, being loudest near the second heart sound, often accompanied by fine tremors. In infancy, the systolic pressure difference between the aorta stirred pulse and pulmonary stirred pulse is large, but the diastolic pressure difference is minimal, hence only a systolic murmur is present. With age, both systolic and diastolic pressure differences increase, leading to the typical continuous machinery-like murmur. In advanced stages with pulmonary stirred pulse hypertension, the pressure difference between the aorta and pulmonary stirred pulse decreases again, resulting in only a systolic murmur without a diastolic murmur, losing its continuity. Therefore, the diagnosis is straightforward when typical murmurs are present, but early or advanced stages with atypical murmurs can lead to misdiagnosis.
3. A diastolic intermediate-stage [second stage] grade I rumbling murmur may sometimes be heard at the mitral area, caused by relative mitral stenosis.
4. The pulmonary stirred pulse valve area may have an accentuated second sound, sometimes split.
5. Peripheral vascular signs: Pulse pressure greater than 5.3 kPa (40 mmHg), with water-hammer pulse, capillary pulsation, and femoral stirred pulse pistol-shot sound.

[Auxiliary Examinations]

1. X-ray: Mild cases show normal heart, while severe cases exhibit enlargement of the left atrium, left ventricle, and right ventricle, dilated pulmonary stirred pulse with strong pulsation, possibly hilar dance, thickened and increased pulmonary vascular markings, and a smaller aortic shadow.
2. ECG: Small defects show normal findings; medium or larger defects may show left ventricular or biventricular hypertrophy patterns, with occasional bundle branch block and first- or second-degree atrioventricular block. Heart failure may show myocardial strain.
3. Echocardiography: M-mode ultrasound may show increased diameters of the left atrium, left ventricle, and right ventricle, with a smaller aortic diameter. Two-dimensional ultrasound may reveal an interrupted ventricular septal echo, and Doppler color ultrasound can visualize the shunt location and direction, aiding in definitive diagnosis.
4. Right heart catheterization: Right ventricular blood oxygen content exceeds that of the right atrium by 1.0 vol% or more, with elevated right ventricular and pulmonary stirred pulse pressures. Occasionally, the catheter may pass through the defect into the left ventricle.

IV. Tetralogy of Fallot

Symptoms:

1. Cyanosis: Skin and mucous membranes gradually develop cyanosis 2–3 months after birth, most noticeable in the extremities, lips, fingers, earlobes, and nasal tip. In severe cases, conjunctival congestion and cyanosis occur.
2. Dyspnea: Due to hypoxia, even mild physical activity, feeding, or crying can cause breathlessness, dyspnea, and worsening cyanosis.
3. Cerebral hypoxia: In children under 2–3 years old, severe hypoxia and cyanosis can lead to right ventricular outflow tract muscular spasm, sudden reduction in pulmonary blood flow, and a sharp drop in blood oxygen, resulting in impaired consciousness, syncope, spasms, hemiplegia, or even death.
4. Squatting phenomenon: Most children experience shortness of breath and worsening cyanosis during walking or activity, at which point they voluntarily squat to rest for a short while. This is a forced protective posture. When squatting, the resistance of the lower limbs to stirred pulse increases, raising left ventricular pressure, which enhances cerebral blood supply. At the same time, it reduces the volume of right-to-left shunting, thereby increasing pulmonary circulation and alleviating hypoxia.
5. A few children may experience symptoms such as dizziness, headache, or chest discomfort, all of which are related to hypoxia.

Sign:

1. Physical development is delayed, and in severe cases, intelligence may also be delayed.
2. The precordium is prominent, with a heaving apical impulse, more noticeable at the xiphoid process.
3. A grade II/6 or higher harsh systolic ejection murmur can be heard at the left sternal border in the 2nd to 4th intercostal spaces, radiating to the apex and subclavian area, often accompanied by a tremor. The main cause is pulmonary stenosis, but it can also result from a ventricular septal defect.
4. The second heart sound of the pulmonary artery is weakened, while the second heart sound of the aorta is enhanced.
5. Clubbing of fingers and toes: caused by chronic hypoxia, capillary dilation, and connective tissue hyperplasia.

[Auxiliary Examination]

1. Laboratory findings: Red blood cells may reach 5×1012/L (over 5 million/mm³), hemoglobin over 150 g/L (15 g/dL), and hematocrit between 60–80%.
2. X-ray: Due to right ventricular enlargement, the apex is upturned, the pulmonary artery segment is concave, and the pulmonary artery is narrowed, giving the heart a boot-shaped appearance. The lung fields are clear, the hilar shadow is small, and the aorta is widened.
3. Electrocardiogram: Right axis deviation, right ventricular hypertrophy and strain, and possibly right atrial hypertrophy.
4. Echocardiography: Right ventricular wall thickening and aortic root dilation. Two-dimensional ultrasound can reveal the degree of aortic override, ventricular septal defect, and right ventricular outflow tract stenosis. Doppler color ultrasound can identify the location and direction of blood flow shunting.
5. Right heart catheterization:
   1. Right ventricular pressure exceeds pulmonary artery pressure, and the type of pulmonary stenosis can be determined based on the pressure curve.
   2. The catheter may pass through the ventricular septal defect into the left ventricle or aorta.
   3. Aortic oxygen saturation is reduced.

V. Trilogy of Fallot

Symptoms: Depend on the degree of stenosis. Mild cases may be asymptomatic, with only a murmur detected during physical examination. Severe cases often present with weakness, flusteredness, shortness of breath, easy fatigue, and occasional chest discomfort or syncope. They are often complicated by bronchitis, pneumonia, or right heart failure.

Sign: Mild cases show normal development, while severe cases may exhibit a round face, flushed cheeks, precordial prominence, and a heaving apical impulse. A grade III/6 or higher systolic ejection murmur, harsh and widely transmitted, is heard at the left sternal border in the 2nd to 3rd intercostal spaces. The second heart sound of the pulmonary artery is diminished, often with splitting. Due to right ventricular hypertrophy, relative tricuspid insufficiency may cause a systolic murmur.

[Auxiliary Examination]

1. X-ray: Clear lung fields with reduced lung markings. In pulmonary valve stenosis, post-stenotic dilation of the pulmonary trunk may be visible. Right ventricular enlargement is prominent, and sometimes the right atrium is also enlarged. Mild cases may show no changes on X-ray.
2. Electrocardiogram: Right axis deviation, right ventricular hypertrophy and strain, incomplete right bundle branch block, and possibly right atrial enlargement.
3. Echocardiography: Right ventricular wall thickening and dilation. B-mode and Doppler color ultrasound can identify the site of pulmonary stenosis.
4. Right heart catheterization: Right ventricular pressure is 1.33–2.0 kPa (10–15 mmHg) higher than pulmonary artery pressure. The type of stenosis can be determined from the continuous pressure curve from the pulmonary artery to the right ventricle. Cardiac angiography can further clarify the type.

VI. Aortic Coarctation

1. The upper body is well-developed, while the lower body is thin, resulting in a broad-shouldered, narrow-hipped physique.
2. Symptoms of upper-body hypertension include dizziness, headache, flushed complexion, and epistaxis. Blood pressure in the upper limbs is elevated and higher than in the lower limbs. The cardiac border expands to the left and downward. A grade II/6 or higher systolic murmur is heard at the left sternal border in the 2nd to 3rd intercostal spaces, radiating to the back and left side of the spine.
3. Insufficient blood supply to the lower limbs, symptoms of low blood pressure, weakness in the lower limbs, numbness, soreness, coldness, and susceptibility to frostbite disease.
4. Manifestations of collateral circulation may include continuous vascular murmurs heard in the supraclavicular fossa, interscapular region, near the scapula, and axilla.
5. The radial pulse is strong, while the femoral pulse is weak.

[Auxiliary Examinations]

1. X-ray: Left ventricular enlargement, prominent main pulmonary artery, sometimes post-stenotic dilation may be observed, with notching of the lower rib margins due to intercostal artery impressions.
2. Electrocardiogram: Left ventricular hypertrophy with strain, high left ventricular voltage.
3. Echocardiography: Two-dimensional ultrasound can visualize the coarctation segment, and color Doppler may show the blood flow jet through the narrowed area.

[Diagnosis]

The diagnosis of congenital heart disease at the primary care level primarily relies on medical history, symptoms, physical examination, and X-ray findings to make a preliminary diagnosis. Further investigations may be conducted based on available resources for confirmation.

1. Medical history:
   1. Whether the mother had a history of viral infection during the first three months of pregnancy, exposure to radioactive materials, or took medications that might affect embryonic development.
   2. Onset before the age of 3 with murmurs, cyanosis, or heart failure is often indicative of congenital heart disease.
   3. Delayed growth, dyspnea, sweating, and recurrent respiratory infections.
   4. For those with cyanosis, note when it was first observed and its relation to crying or activity—whether it is transient, recurrent, or persistent. Also inquire about associated symptoms such as palpitations, syncope, or squatting.
2. Physical examination:
   1. Assess general growth and development, and check for other malformations or clubbing of fingers/toes.
   2. Cardiovascular examination should focus on precordial bulging, thrills, and murmurs. At the primary level, murmurs are often used for preliminary diagnosis—they are typically harsh, grade II/6 or higher in intensity during systole, and commonly located at the left sternal border in the 2nd to 4th intercostal spaces. Differentiate from functional murmurs; if uncertain, periodic follow-up is recommended.
3. Laboratory tests: Red blood cell count, hemoglobin, hematocrit, and blood oxygen saturation are diagnostically significant for cyanotic congenital heart disease.
4. X-ray: Fluoroscopy or radiography to evaluate cardiac silhouette, chamber sizes, vascular positioning, and pulmonary congestion (hilar or lung field).
5. Electrocardiogram: Provides supportive evidence. Echocardiography, cardiac catheterization, and heart blood vessel angiography often confirm the diagnosis of congenital heart disease.

bubble_chart Treatment Measures

1. Medical Therapy

The aim is to maintain the general health of the child, provide health guidance, conduct regular follow-ups, prevent and treat complications, and sustain the child until the appropriate age for surgery.

1. Prevention and treatment of heart failure: Limit physical activity under normal circumstances. Once heart failure occurs, administer digitalis-based medications to maintain cardiac function over an extended period. If heart failure recurs repeatedly, surgery should be performed promptly after stabilization (see Chapter 18, Section 1).
2. Management of arrhythmias: Refer to internal medicine.
3. Prevention and treatment of infections: Infections in congenital heart disease are a major cause of death. Prevent and treat conditions such as bronchitis and pneumonia. Other chronic infections should be addressed promptly to avoid subacute bacterial endocarditis. If it occurs, administer high-dose penicillin. For right-to-left shunt types, take care to prevent cerebral embolism and brain abscesses.
4. Pharmacotherapy: Use indomethacin to treat patent ductus arteriosus (PDA) in early neonates. In cases of pulmonary atresia, severe pulmonary stenosis in tetralogy of Fallot, or preductal coarctation of the aorta, the patency of the ductus arteriosus allows blood to enter the pulmonary artery to maintain oxygen exchange. Since the ductus arteriosus closes 3–6 months after birth, these patients struggle to survive. Prostaglandins can dilate the ductus arteriosus, so they are used to keep it open and sustain life until surgery can be performed when conditions permit.

2. Surgical Therapy

Most congenital heart defects can be treated with curative surgery, while a few require palliative surgery to prolong life until curative surgery becomes feasible. In recent years, non-thoracotomy treatments have also been developed, such as using specially designed micro-spring umbrella patches to repair atrial septal defects, foam-plastic plugs to occlude patent ductus arteriosus, and balloon catheter dilation to treat pulmonary valve stenosis, aortic valve stenosis, and aortic coarctation.

[Specific Conditions]

1. Atrial Septal Defect (ASD)

Atrial septal defect (ASD) is one of the common congenital heart diseases, classified as a left-to-right shunt type. It accounts for 20–30% of congenital heart diseases and is more prevalent in females than males. Up to 30% of cases close naturally within the first year of life, so a definitive diagnosis should not be made too early if ASD is suspected in infants under one year old; instead, regular follow-up is recommended.

﹝Treatment﹞

Prevent and treat respiratory infections and heart failure. Atrial septal repair surgery is typically performed at ages 4–6. Alternatively, a micro-spring umbrella patch can be deployed via cardiac catheterization to repair the defect.

2. Ventricular Septal Defect (VSD)

Ventricular septal defect (VSD) is a common congenital heart disease, classified as a left-to-right shunt type. It accounts for 20–25% of congenital heart diseases and is more common in males than females. Defects smaller than 0.5 cm are considered small, 0.5–1.0 cm medium, and larger than 1.0 cm large. Medium and small defects have a higher chance of natural closure, up to 50%.

﹝Treatment﹞

Prevent and treat complications. Due to the high natural closure rate, surgical decisions should be made cautiously. The optimal age for surgery is 4–5 years, with good outcomes for symptomatic patients without pulmonary hypertension.

3. Patent Ductus Arteriosus (PDA)

Patent ductus arteriosus (PDA) is one of the common congenital heart diseases, classified as a left-to-right shunt type. It accounts for 15–20% of congenital heart diseases and is about three times more common in females than males. The ductus arteriosus closes anatomically 3–6 months after birth. If it remains open, resulting in a left-to-right shunt, it is diagnosed as PDA.

﹝Treatment﹞

Spontaneous closure of this disease is rare, and surgery is recommended after diagnosis. Premature labor infants have a higher incidence of patent ductus arteriosus, which often closes spontaneously within 12 weeks. To prevent and treat patent ductus arteriosus in premature labor infants, indomethacin at a dose of 0.3–0.6 mg/kg per day divided into three doses can be administered within the first week after birth, and one day of treatment may suffice. Indomethacin reduces the synthesis of prostaglandin E, promoting the contraction of the ductus arteriosus smooth muscle and leading to closure. Recently, some have used a cardiac catheter to deliver a foam plug to the site of the patent ductus arteriosus, thereby occluding the ductus arteriosus and achieving the therapeutic goal.

IV. Tetralogy of Fallot

Tetralogy of Fallot refers to the combination of four pathological conditions: pulmonary stenosis, ventricular septal defect, overriding aorta, and right ventricular hypertrophy, forming a right-to-left shunt. It is the most common cyanotic congenital heart disease among surviving infants, accounting for 10–15% of all congenital heart diseases and about 70% of cyanotic types. If an atrial septal defect is also present, it is termed pentalogy of Fallot.

[Treatment]

Prevent and manage complications such as pneumonia, right heart failure, and subacute bacterial endocarditis. Severe symptoms accompanied by right heart enlargement and a right ventricular-to-pulmonary artery pressure gradient exceeding 5.33 kPa (40 mmHg) warrant early surgical intervention. For valvular stenosis, non-thoracotomy balloon catheter dilation can be used to expand the narrowed valve and achieve therapeutic goals.

V. Coarctation of the Aorta

Coarctation of the aorta is a relatively common non-shunt congenital heart disease, accounting for 7% of congenital heart diseases. It is more prevalent in males than females and is classified into two types:

1. Infantile type (preductal): The narrowing occurs in the aortic arch proximal to the ductus arteriosus opening. This type is rare. Prenatally, blood supply is maintained via the ductus arteriosus, and collateral circulation is not established. After birth, as the ductus arteriosus gradually closes and other anomalies are often present, most infants die within the first year of life.
2. Adult type (postductal): The coarctation is located distal to the ductus arteriosus opening. This type is more common, accounting for 90% of cases. The following descriptions pertain to the adult type.

[Treatment]

Prevent and manage complications. Surgical intervention is optimal between the ages of 4 and 8.

bubble_chart Complications

Subacute bacterial endocarditis is more common, and other complications may include pneumonia, pulmonary edema, and heart failure.

bubble_chart Differentiation

1. Differential diagnosis with other cyanotic heart diseases:

1. Transposition of the great vessels.
2. Eisenmenger syndrome.
3. Severe pulmonary stenosis.
4. Tricuspid atresia.

2. Pulmonary stenosis

Pulmonary stenosis can be classified into three types:

1. Pulmonary valve stenosis, accounting for 85–90% of cases.
2. Stenosis of the pulmonary trunk and its branches.
3. Stenosis of the right ventricular outflow tract (infundibular region). It is an acyanotic type, accounting for 10–20% of congenital heart diseases.

3. Auscultation

When a systolic murmur of grade II/6 or higher is heard at the left second intercostal space of the sternum, the following conditions may also be present:

1. High ventricular septal defect.
2. Pulmonary valve stenosis.
3. Patent ductus arteriosus before the appearance of the typical continuous murmur, when only a systolic murmur is present.
4. Tetralogy of Fallot with mild cyanosis.