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Ventricular Septal Defect (VSD)

by Jeanne Marie Baffa, MD

A ventricular septal defect (VSD) is an opening in the interventricular septum, causing a shunt between ventricles. Large defects result in a significant left-to-right shunt and cause dyspnea with feeding and poor growth during infancy. A loud, harsh, holosystolic murmur at the lower left sternal border is common. Recurrent respiratory infections and heart failure may develop. Diagnosis is by echocardiography. Defects may close spontaneously during infancy or require surgical repair.

VSD (see Figure: Ventricular septal defect.) is the 2nd most common congenital heart anomaly after bicuspid aortic valve, accounting for 20% of all defects. It can occur alone or with other congenital anomalies (eg, tetralogy of Fallot, complete atrioventricular septal defects, transposition of the great arteries).

Ventricular septal defect.

Pulmonary blood flow and LA and LV volumes are increased. Atrial pressures are mean pressures. RV pressure and O 2 saturation are variably elevated, positively related to defect size.

AO = aorta; IVC = inferior vena cava; LA =left atrium; LV = left ventricle; PA = pulmonary artery; PV =pulmonary veins; RA = right atrium; RV = right ventricle; SVC =superior vena cava.

Classification

VSDs are classified by location:

  • Perimembranous

  • Trabecular muscular

  • Subpulmonary outlet (supracristal or doubly committed subarterial)

  • Inlet

Perimembranous defects (70 to 80%) are defects in the membranous septum adjacent to the tricuspid valve and they extend into a variable amount of surrounding muscular tissue; the most common type of this defect occurs immediately below the aortic valve.

Trabecular muscular defects (5 to 20%) are completely surrounded by muscular tissue and may occur anywhere in the septum.

Subpulmonary outlet defects (5 to 7% in the US; about 30% in Far Eastern countries) occur in the ventricular septum immediately under the pulmonary valve. These defects are often referred to as supracristal, conoseptal, or doubly committed subarterial defects and are frequently associated with aortic leaflet prolapse into the defect, causing aortic regurgitation.

Inlet defects (5 to 8%) are bordered superiorly by the tricuspid annulus and are located posterior to the membranous septum. These defects are sometimes referred to as atrioventricular septal-type defects.

Pathophysiology

The magnitude of the shunt depends on defect size and downstream resistance (ie, pulmonary outflow tract obstruction and pulmonary vascular resistance). Blood flows easily across larger defects, which are thus called nonrestrictive; pressure equalizes between the right and left ventricles and there is a large left-to-right shunt. Assuming there is no pulmonic stenosis, over time, a large shunt causes pulmonary artery hypertension, elevated pulmonary artery vascular resistance, right ventricular pressure overload, and right ventricular hypertrophy. Ultimately, the increased pulmonary vascular resistance causes shunt direction to reverse (from the right to the left ventricle), leading to Eisenmenger syndrome (see Eisenmenger Syndrome).

Smaller defects, also referred to as restrictive VSDs, limit the flow of blood and the transmission of high pressure to the right heart. These VSDs result in a relatively small left-to-right shunt, and pulmonary artery pressure is normal or minimally elevated. Heart failure (HF), pulmonary hypertension, and Eisenmenger syndrome do not develop.

Symptoms and Signs

Symptoms depend on defect size and magnitude of the left-to-right shunt. Children with a small VSD are typically asymptomatic and grow and develop normally. In children with a larger defect, symptoms of HF (eg, respiratory distress, poor weight gain, fatigue after feeding) appear at age 4 to 6 wk when pulmonary vascular resistance falls. Frequent lower respiratory tract infections may occur. Eventually, untreated patients may develop symptoms of Eisenmenger syndrome.

Auscultatory findings vary with the size of the defect. Small VSDs typically produce murmurs ranging from a grade 1 to 2/6 high-pitched, short systolic murmur (due to tiny defects that actually close during late systole) to a grade 3 to 4/6 holosystolic murmur (with or without thrill) at the lower left sternal border; this murmur is audible shortly after birth. The precordium is not hyperactive, and the 2nd heart sound (S 2 ) is normally split and has normal intensity.

Moderate to large VSDs produce a holosystolic murmur that is present by age 2 to 3 wk; S 2 is usually narrowly split with an accentuated pulmonary component. An apical diastolic rumble (due to increased flow through the mitral valve) and findings of HF (eg, tachypnea, dyspnea with feeding, failure to thrive, gallop, crackles, hepatomegaly) may be present. In moderate high-flow VSDs, the murmur is often very loud and accompanied by a thrill (grade 4 or 5 murmur). With large defects allowing equalization of left ventricular and right ventricular pressures, the systolic murmur is often attenuated.

Diagnosis

  • Chest x-ray and ECG

  • Echocardiography

Diagnosis is suggested by clinical examination, supported by chest x-ray and ECG, and established by echocardiography.

If the VSD is large, chest x-ray shows cardiomegaly and increased pulmonary vascular markings. ECG shows right ventricular hypertrophy or combined ventricular hypertrophy and, occasionally, left atrial enlargement. ECG and chest x-ray are typically normal if the VSD is small.

Two-dimensional echocardiography with color flow and Doppler studies establishes the diagnosis and can provide important anatomic and hemodynamic information, including the defect’s location and size and right ventricular pressure. Cardiac catheterization is rarely necessary.

Treatment

  • For HF, medical therapy (eg, diuretics, digoxin, ACE inhibitors)

  • Sometimes surgical repair

Small VSDs, particularly muscular septal defects, often close spontaneously during the first few years of life. A small defect that remains open does not require medical or surgical therapy. Larger defects are less likely to close spontaneously.

Diuretics, digoxin, and ACE inhibitors may be useful to control symptoms of HF before cardiac surgery or to temporize infants with moderate sized VSDs that seem likely to close spontaneously over time. If infants do not respond to medical treatment or have poor growth, surgical repair is often recommended during the first few months of life. Even in asymptomatic children large VSDs should be repaired, usually within the first year of life, to prevent later complications. Current surgical mortality rate is < 2%. Surgical complications may include residual ventricular shunt and/or complete heart block.

Endocarditis prophylaxis is not needed preoperatively and is required only for the first 6 mo after repair or if there is a residual defect adjacent to a surgical patch.

Key Points

  • A ventricular septal defect (VSD) is an opening in the interventricular septum, causing a left-to-right shunt.

  • Over time, large left-to-right shunts cause pulmonary artery hypertension, elevated pulmonary artery vascular resistance, right ventricular pressure overload, and right ventricular hypertrophy, which ultimately cause shunt direction to reverse, leading to Eisenmenger syndrome.

  • Larger defects cause symptoms of heart failure (HF) at age 4 to 6 wk.

  • Typically, a grade 3 to 4/6 holosystolic murmur at the lower left sternal border is audible shortly after birth.

  • Infants who do not respond to medical treatment of HF or have poor growth should have surgical repair during the first few months of life; even asymptomatic children should have repair during the first year of life.

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