Other Causes of Common Mixing

If the aorta and pulmonary artery do not divide, the child is born with a persistent truncus arteriosus or common arterial trunk. This is a single (or common) trunk arising from the base of heart and serves as both the aorta and the pulmonary artery. This one big artery has one large valve instead of there being pulmonary and aortic valves.

It is almost always associated with a large nonrestrictive VSD, and therefore mixed oxygenated and deoxygenated blood are carried both into the pulmonary and systemic circulation. When pulmonary vascular resistance drops after birth, more blood enters into the low-resistance pulmonary circuit, causing heart failure.

Presentation:

• Occurs in the newborn period
• CHF; massive pulmonary over-circulation with postnatal decrease in PVR
• Wide pulse pressure due to diastolic runoff of blood into the pulmonary vasculature
• Chest X-ray     Prominent cardiomegaly with increased pulmonary vascularity
• Consider truncus if right aortic arch is present
• “hilar comma” or “hilar waterfall” sign due to malposition of the pulmonary arteries; occur in older children
• Treatment is surgical repair using cardiopulmonary bypass support. Complete repair should be performed within the first weeks to months of life after CHF medical management is optimized.

5) Tricuspid Atresia

The third most common cause of cyanotic CHD

The most common cause of cyanosis with left ventricular hypertrophy

Agenesis or congenital absence of the tricuspid valve (No tricuspid valve)

Underdevelopment of the right ventricle and the pulmonary artery

Pulmonary blood flow decreased

No blood flow from right atrium to right ventricle, therefore a right to left shunt at the atrial level is essential for survival. When tricuspid atresia is associated with severe pulmonic stenosis or pulmonic atresia, it is a duct-dependent lesion.

The amount of cyanosis has inverse relationship with the amount of pulmonary blood flow.

Presentation:

• Cyanosis by the first days of life (50%)
• CHF within several weeks of life (30%)
• Single S2
• Systolic murmur due to VSD or continuous murmur due to PDA
• CHF: hepatomegaly
• EKG
• Superior QRS axis
• Right atrial hypertrophy, left atrial hypertrophy and left ventricle hypertrophy
• Chest Radiograph
• Normal to slight increase in heart size due to right atrial and left ventricular enlargement and LVH
• Decreased pulmonary vascular markings

Management

• Decreased pulmonary blood flow: PGE ₁ infusion to preserve ductus patency
• modified BT shunt
• CHF medical management
• Atrial septostomy to maintain an interatrial communication
• Fontan or Fontan-Kreutzer operation is the definitive procedure

6) Hypoplastic Left Heart Syndrome

• Rare; 1.2% to 1.5% of all CHD
• Up to 7% to 9% of CHD diagnosed before the age of 1 year
• The fourth most common CHD present in the first year of life
• This involves a severely hypoplastic left ventricle and hypoplasia of the ascending aorta and aortic arch. Therefore, the right ventricle becomes the default pumping chamber for both the lungs and the systemic circulation. The right heart structures (atrium, ventricle, pulmonary arteries) are significantly dilated.

In Utero:

• Pulmonary vascular resistance > systemic vascular resistance
• This helps the RV to maintain an adequate perfusion pressure in the systemic circulation. This flow is ductus dependent.
• After Birth: Systemic vascular resistance > Pulmonary vascular resistance
• As the ductus closes, cardiac output falls and aortic pressure drops (non-functional left heart)
• Increased pulmonary flow results in pulmonary edema

Presentation:

• Asymptomatic at birth
• Circulatory failure as the ductus closes within hours to days
• Listless, and dusky
• Single heart sound
• Systolic ejection murmur
• Diminished pulses
• EKG: Right atrial enlargement, right ventricular hypertrophy and peaked P waves

Chest Radiograph:

• Normal at birth
• Marked cardiomegaly and both increased pulmonary arterial flow and pulmonary venous congestion develop within 2 days

Management

The newborn is stabilized with prostaglandin to maintain ductal patency. A Norwood operation is performed in the first week of life. This consists of creating a neo-aorta using the native pulmonary valve and augmenting the hypoplastic arch. Pulmonary perfusion is achieved by inserting a modified Blalock-Taussig shunt from the innominate artery or a Sano shunt from the right ventricle. Survivors undergo a Glenn anastomosis (connecting SVC to the branch PA) at 4-6 months of age, and then a Fontan operation (connecting IVC to the branch PA) at 2-4 years of age. At that point, the pulmonary and systemic circulations are separated.

Coarctation of the aorta

Congenital narrowing of the aorta in the upper thoracic region of the ductus arteriosus

Presentation:

• Heart failure develops after a variable period of well-being
• Tachypnea, feeding problems, and sweating
• Gallop rhythm
• Systolic murmur along the left sternal edge and usually posteriorly over the coarctation site
• Femoral pulses are absent or reduced in volume and delayed compared with   radial or brachial pulses (difficult to detect in sick neonates)
• Higher Blood pressure in the arms than in the legs

EKG

RVH or RBBB

Chest Radiograph

Marked Cardiomegaly and pulmonary edema