| disease | Ventricular Septal Defect in Children |
| alias | Ventricular Septal Defect |
Ventricular septal defect (VSD) is the most common type of congenital heart disease. Most cases occur alone but can be associated with other malformations. The defect size typically ranges from 0.3 to 3 cm. Defects smaller than 0.5 cm are considered small and commonly found in the muscular portion; those between 0.5 and 1 cm are medium-sized; defects larger than 1 cm are classified as large, usually located higher and often seen in the membranous portion. Anatomically, VSD is broadly divided into four types: Type I, also known as supracristal defect or infundibular defect; Type II, membranous defect (also called subcristal defect), which is the most clinically prevalent, accounting for about 70% of cases; Type III, endocardial cushion defect; and Type IV, muscular defect (also referred to as sub-tricuspid defect).
bubble_chart Diagnosis
(1) Symptoms 1. Small defects: Growth and development are normal, and there may be no symptoms. They are often discovered incidentally during physical examinations. 2. Medium defects: Symptoms may appear during infancy, including rapid breathing during feeding, low body weight, recurrent respiratory infections that are difficult to control, and even heart failure within the first three months. As growth progresses, the defect may relatively shrink, the shunt volume decreases, and breathing difficulties lessen. At this stage, the general condition may improve. 3. Large defects: Symptoms may appear 2–3 weeks after birth, often involving membranous defects. Difficulties in feeding, labored breathing, recurrent lung infections, and even rapid breathing at rest may occur. Most cases show improvement after six months. 4. Large defects with increased pulmonary resistance: In the initial stage [first stage], there may be no cyanosis. As pulmonary vascular resistance continues to rise, leading to right-to-left shunting, obvious clinical cyanosis appears, activity may be restricted, and right heart failure gradually develops.
(2) Signs 1. Small defects: The heart may not be enlarged or may show grade I enlargement. In 90% of cases, a rough, holosystolic regurgitant murmur with systolic tremor is heard at the left sternal border in the 3rd–4th intercostal spaces (few at the 2nd–3rd). With small defects, the murmur occurs early in systole during the intermediate stage [second stage] and is softer. 2. Medium defects: The heart is enlarged. A rough, loud holosystolic regurgitant murmur with obvious tremor is heard at the left sternal border in the 3rd–4th intercostal spaces. A moderate-intensity diastolic filling murmur may also be heard at the apex, along with accentuated and split P2. 3. Large defects: The heart is significantly enlarged, with precordial bulging. A prominent holosystolic regurgitant murmur with systolic tremor is heard at the left sternal border in the 3rd–4th intercostal spaces, and a short, loud diastolic filling murmur is heard at the apex during the intermediate stage [second stage]. In cases with pulmonary hypertension, the murmur is often ejection-type, and P2 is loud. 4. Large defects with increased pulmonary resistance: Only a short systolic murmur is heard at the left sternal border in the 3rd–4th intercostal spaces, which is loud but with reduced splitting. If left-to-right shunting completely stops, no murmur is heard. Clubbing of fingers and toes may occur, along with precordial bulging. A high-pitched diastolic murmur may be heard at the left sternal border in the 2nd–3rd intercostal spaces.(2) X-ray Findings With small shunts: Grade I increased pulmonary blood flow, manifested as slightly increased and thickened pulmonary vascular markings. The pulmonary segment is usually not prominent or only grade I prominent. The cardiac border may show grade I enlargement, primarily in the left ventricle. With moderate to large left-to-right shunts: Pulmonary pressure is moderately or severely elevated, pulmonary markings are significantly thickened, and the pulmonary segment is prominently convex. Biventricular hypertrophy is present, predominantly in the left ventricle, and the left atrium may also enlarge. With grade III pulmonary hypertension: The pulmonary segment becomes more convex, and the hilar vessels dilate accordingly, sometimes appearing as "stump-like" with narrowed and twisted peripheral pulmonary vascular markings and reduced pulmonary blood flow.
(4) Echocardiography Two-dimensional four-chamber and left ventricular long-axis views show interrupted echoes at the ventricular septum, with left ventricular and right atrial enlargement and narrowing of the main pulmonary artery diameter. Pulsed Doppler detects a systolic turbulent spectrum at the site of echo interruption on the right ventricular side of the septum. Color Doppler reveals a multicolored blood flow jet from the left ventricle to the right ventricle during systole.
(5) Cardiac catheterization and angiography: In small defects, the shunt volume is minimal, and catheterization may sometimes fail to confirm the diagnosis. In moderate defects, if the oxygen content in the right ventricle exceeds the average oxygen content in the right atrium by 0.9% or 3% saturation, a left-to-right shunt at the ventricular level can be confirmed. The pressure in the right ventricle and pulmonary artery may be normal or mildly to moderately elevated (grade II). When accompanied by pulmonary vascular obstructive disease, catheterization can calculate pulmonary vascular resistance. If the resistance is significantly increased, a right-to-left shunt may occur. Occasionally, the catheter may pass through the ventricular septal defect and enter the left ventricle, confirming the diagnosis. In most cases, a correct diagnosis can be made non-invasively without the need for catheterization or angiography.
﹝Treatment﹞
The natural closure rate of ventricular septal defects can reach 30–50%, mostly involving small defects, though occasional closure of larger defects has been observed. Closure typically occurs before the age of 7, particularly within the first year of life. In some children, the defect may shrink with age, so if there are no clinical symptoms, no significant abnormalities on electrocardiogram or X-ray, and pulmonary artery pressure remains normal, immediate surgery is unnecessary, as spontaneous closure may still occur. Even if the defect does not close, the hemodynamic changes are usually mild and generally do not affect growth, development, or future work and life, though regular follow-up is required. Surgical intervention is indicated for children with clinical symptoms, significant hemodynamic changes, a Qp/Qs ratio >1.5:1, or increased pulmonary artery pressure with predominantly left-to-right shunting. The optimal age for surgery is 2–6 years. Large defects associated with heart failure or pulmonary artery pressure elevated to grade II or higher require surgery before the age of 2 to prevent progression to pulmonary vascular obstructive disease, which would render surgery ineffective. Children with Eisenmenger syndrome and significant right-to-left shunting due to elevated pulmonary vascular resistance are contraindicated for surgery. In recent years, surgical mortality has declined to below 1%, though it remains higher in infants with severe pulmonary hypertension, heart failure, or other intracardiac anomalies. Postoperative improvement is typically significant, with gradual reduction in heart size and pulmonary blood flow. Some children may still exhibit a grade 2–3 systolic murmur at the left sternal border (2nd–4th intercostal spaces), possibly due to tricuspid regurgitation, right ventricular outflow tract muscle hypertrophy, or residual shunting. Generally, minor residual shunts have no significant impact. However, if pulmonary vascular obstructive disease is already present preoperatively, pulmonary vascular resistance often fails to decrease postoperatively, resulting in a poorer prognosis.
