Pediatric Cardiology: ASD and PDA

Congenital Heart Diseases

• Congenital heart disease occurs in 8 per 1,000 births, with a spectrum of lesions ranging from asymptomatic to fatal.
• Most cases of congenital heart disease are multifactorial, but some lesions are associated with chromosomal disorders, single gene defects, teratogens, or maternal metabolic disease.

Acyanotic Congenital Heart Defects

• Left-to-right shunts result in an increase in pulmonary blood flow, including:
  • Patent ductus arteriosus (PDA)
  • Ventricular septal defect (VSD)
  • Atrial septal defect (ASD)
• Obstructive lesions include:
  • Aortic stenosis
  • Pulmonary stenosis
  • Coarctation of the aorta
  • These lesions usually have normal pulmonary blood flow

Ventricular Septal Defect (VSD)

• VSD is the most common congenital heart defect, accounting for 25% of all congenital heart disease.
• The location of the VSD is important prognostically and in approach to repair.
• The amount of flow crossing a VSD depends on the size of the defect and the pulmonary vascular resistance.
• Large VSDs are not symptomatic at birth because the pulmonary vascular resistance is normally elevated at this time.
• As the pulmonary vascular resistance decreases over the first 6-8 weeks of life, the amount of shunt increases, and symptoms may develop.
• Small VSDs with little shunt are often asymptomatic but have a loud murmur.
• Moderate to large VSDs result in pulmonary overcirculation and heart failure.
• The typical physical finding with a VSD is a pansystolic murmur, usually heard best at the lower left sternal border.
• There may be a thrill.

Patent Ductus Arteriosus (PDA)

• The ductus arteriosus allows blood to flow from the pulmonary artery to the aorta during fetal life.
• Failure of the normal closure of this vessel results in a PDA.
• With falling pulmonary vascular resistance after birth, left-to-right shunting of blood and increased pulmonary blood flow occur.
• Excluding premature infants, PDAs represent approximately 5-10% of congenital heart disease.
• Symptoms depend on the amount of pulmonary blood flow.
• The magnitude of the shunt depends on the size of the PDA and the pulmonary vascular resistance.
• Small PDAs are asymptomatic; moderate to large shunts can produce the symptoms of heart failure as the pulmonary vascular resistance decreases.
• The physical examination findings depend on the size of the PDA.
• A continuous, machine-like murmur can be heard at the left infraclavicular area, radiating along the pulmonary arteries and often well heard over the left side of the back.

Pulmonary Stenosis

• Pulmonary stenosis accounts for approximately 10% of all congenital heart disease.
• It can be valvular, subvalvular, or supravalvular in nature.
• Symptoms depend on the degree of obstruction present.
• Mild pulmonary stenosis is asymptomatic.
• Moderate to severe stenosis results in exertional dyspnea and easy fatigability.
• Newborns with severe stenosis may be more symptomatic and even cyanotic because of right-to-left shunting at the atrial level.
• Pulmonary stenosis causes a systolic ejection murmur at the second left intercostal space, which radiates to the back.
• A thrill may be present.

Aortic Stenosis

• Aortic stenosis represents approximately 5% of all congenital heart disease.
• Lesions result from failure of development of the three leaflets or failure of resorption of tissue around the valve.
• Mild to moderate obstructions cause no symptoms.
• More severe stenosis results in easy fatigability, exertional chest pain, and syncope.
• Infants with critical aortic stenosis may present with symptoms of heart failure.
• A systolic ejection murmur is heard at the right second intercostal space along the sternum and radiating into the neck.

Coarctation of the Aorta

• Coarctation of the aorta represents a significant proportion of congenital heart disease.
• The ECG and chest x-ray show evidence of right ventricular enlargement and hypertrophy in infantile coarctation with marked cardiomegaly and pulmonary edema.
• Echocardiography shows the site of coarctation and associated lesions.
• In older children, the ECG and chest x-ray usually show left ventricular hypertrophy and a mildly enlarged heart.
• Echocardiography shows the site and degree of coarctation, the presence of left ventricular hypertrophy, and the aortic valve morphology and function.