Ventricular septal defects (VSDs) can occur anywhere in the ventricular septum. VSDs are the most common form of congenital heart disease (excluding bicuspid aortic valves). The physiologic effect of a VSD is determined by the size of the defect and the relative resistances of the systemic and pulmonary circulations. Small and moderate-sized VSDs often close spontaneously or get smaller over time. Even if a VSD remains small, it does not lead to congestive heart failure. Occasionally, small defects may be a nidus for infective endocarditis.

Large defects cause significant congestive heart failure, or “pulmonary overcirculation.” Generally the pulmonary vascular resistance drops in the first few weeks and months of life. As the pulmonary vascular resistance drops, more blood is shunted from left to right, resulting in pulmonary overcirculation and enlargement of the left side of the heart. Symptoms of congestive heart failure in infants are tachypnea, poor feeding, sweating with feeds, failure to thrive, and lethargy. The growth chart of such infants is an invaluable tool in assessing the overall physiologic effect of the VSD. On physical exam, these infants may appear small, and have hepatomegaly. It is uncommon to hear rales or crackles in small babies with VSDs and congestive heart failure.

Cardiac examination can reveal a hyperdynamic precordium. Initially a systolic ejection murmur is heard and as the pulmonary vascular resistance drops, a holosystolic murmurmay be heard. In very large defects, the murmur may remain systolic ejection in quality or not carry throughout systole, as there is little pressure difference between the two circulations. A diastolic rumble at the apex reflecting the large volume of shunted blood crossing the mitral valve as it is returned from the lungs may be heard in advanced congestive heart failure.

The CXR shows cardiomegaly and increased pulmonary vascular markings dilation of the pulmonary arteries. The electrocardiogram reflects left ventricular and atrial enlargement and sometimes left and right ventricular hypertrophy. Definitive diagnosis is made by transthoracic echocardiography.

The treatment of significant VSDs involves medical management initially before eventual surgical repair. Maximizing growth and feeding is an important initial step. Remember, feeding for any infant requires a lot of energy “relative” to an infant’s body size. Patients with significant congenital heart disease require more calories to grow. This, in combination with the fact that they may tire or take breaks with feeds because of the additional amount of work needed to feed results in failure to thrive. In addition, some babies with congenital heart disease have genetic defects and gastroesophageal reflux, which can result in feeding difficulties. Thus maximizing caloric intake (preferably by increasing caloric density and not overall fluid intake) is essential. In addition, some babies with congenital heart disease may require nasogastric feeding before or after surgery. Nasogastric feeds take away the extra effort and energy required during feeding in these infants.

Medical treatment includes:

By decreasing the systemic vascular resistance with ACE inhibitors, less blood is shunted to the pulmonary circulation, thus decreasing the extra blood flow to the lungs and heart.

Today, surgery in these infants is performed between 3 and 6 months of age routinely to prevent long standing pulmonary hypertension. Surgery beyond 2 years of age may increase the risk of pulmonary hypertension even after repair.

Like VSDs, atrial septal defects can occur anywhere in the atrial septum. The most common ASD is called a secundum ASD. The left-to-right shunt is mainly dependent on the differences between the compliance of the two ventricular ventricles. Because the compliance difference between the two ventricles is not of a high magnitude, these children are asymptomatic and not at risk for early pulmonary hypertension, despite the increased pulmonary blood flow. Also, unlike patients with VSDs and PDAs, the right side of the heart is enlarged. It is important to remember that the vast majority of patients with ASDs are asymptomatic in childhood. Only rarely do children with ASDs encounter problems early on in life, such as congestive heart failure or frequent lower respiratory tract infections.

Examination reveals a systolic ejection murmur in the pulmonary area, indicative of excessive flow across the pulmonary valve. A diastolic rumble may be heard at the right and left lower sternal border because of extra flow across the tricuspid valve. The hallmark of atrial septal defects is a fixed splitting of the second heart sound. Normally the right ventricle empties slightly later than the left ventricle, thus accounting for the pulmonary component (P2) of the second heart sound (S2) to come after the aortic component (A2). This split is increased in inspiration because of the increase in venous return to the right ventricle. In patients with ASDs, the right ventricle is always volume loaded, both in expiration and inspiration, thus leading to a fixed, split second heart sound that does not vary with respiration. The CXR shows cardiomegaly with increased pulmonary flow. The EKG shows an RSR’ pattern in VI, indicating right ventricular volume load. Transthoracic
echocardiography allows accurate delineation of the anatomy.

Medical therapy is almost never needed in childhood. The majority of secundum ASDs are closed in the catheterization laboratory electively between the ages of 3 and 5 years. A small minority of secundum ASDs (because of large size and/or proximity to other structures) in addition to other forms of ASDs are closed surgically. Left untreated, significant ASDs can lead to pulmonary hypertension much later on in life.

Atrioventricular canal defects (AV canal defects) are a heterogeneous group of defects that result from defects in the endocardial cushion development. There are numerous subtypes and classifications, the most common form being the complete AV canal defect. In this lesion, there is a primum ASD and inlet VSD, resulting in defects in the atrial and ventricular septums that are in continuity. It is important to remember that about 40% to 50% of patients with Down syndrome have congenital heart disease. Of those patients, 40% to 50% have AV canal defects.

Infants with complete AV canal defects have clinical presentations similar to that of infants with large VSDs. Likewise, the CXR is similar to that of infants with large VSDs. The electrocardiogram shows features of VSDs and ASDs. The classic eletcrocardiographic feature is left axis deviation and a frontal plane axis that is superiorly oriented. Diagnosis is made by echocardiography.

Medical therapy is similar to that for infants with large VSDs. Surgical repair is usually performed between 3 and 6 months of life. In addition to feeding difficulties encountered with this lesion, infants with Down syndrome may have more feeding difficulties.

Children with a patent ductus arteriosus (PDA) may present any time in life. Closure of PDAs in term newborns normally occurs soon after birth. PDAs are frequently encountered lesion in premature babies. In premature babies, initially there may be predominantly right-to-left shunting of blood. In these babies, the PDA acts as a “popoff” for the high resistance pulmonary circulation. PDAs in these circumstances should not be closed, as closure could result in a further increase in pulmonary hypertension, and an extra strain on the right ventricle. As the pulmonary vascular resistance falls, there is a predominant left-to-right shunt. The left side of the heart enlarges. Neonates become more tachypneic or if ventilated, their ventilatory support parameters increase, and hepatomegaly develops. There is a wide pulse pressure and the pulses are bounding because of the “runoff” in diastole in the aorta.

The cardiac exam reveals a hyperactive precordium. A continuous machinery-like murmur (systolic and diastolic component) is heard in the left infraclavicular region and throughout the precordium. The CXR shows cardiomegaly and the EKG is consistent with left ventricular and atrial volume overload. Echocardiography is diagnostic and provides accurate assessment of the degree of shunting in systole and diastole, and the relative resistances of the pulmonary and systemic circulations.

In premature babies, closure can be achieved with nonsteroidal anti-inflammatory medications (NSAIDs) such as indomethacin and ibuprofen. NSAIDs are contraindicated in neonates with severe thrombocytopenia and impaired renal function. Fluid restriction is also advantageous. If these measures fail, surgical ligation is indicated for clinically significant PDAs in the newborn period.

Infants and older children with PDAs are often asymptomatic and a PDA is only diagnosed upon hearing a murmur on routine physical exam. If the PDA is large, they may present with congestive heart failure and failure to thrive. The vast majority of these PDAs are closed in the catheterization laboratory with coils or devices.

Tetralogy of Fallot is the most common cause of cyanotic congenital heart disease. It is a conotruncal abnormality, and it is associated with DiGeorge syndrome. The four components of the defect are:

1. A VSD

2. An overriding aorta

3. Pulmonary stenosis (or right ventricular outflow tract obstruction at other levels)

4. Right ventricular hypertrophy

The clinical presentation is variable. Patients with minimal right ventricular outflow tract obstruction may only be detected upon auscultation of a murmur. Infants with severe right ventricular outflow tract obstruction are cyanotic.

Infants may be cyanotic or pink on exam, depending on the degree of obstruction to pulmonary blood flow. The cardiac examination reveals an increased right ventricular impulse. There is a harsh, high frequency systolic ejection murmur (from the right ventricular outflow tract obstruction) heard at the left middle and upper sternal border, which radiates to the lung fields and back. The CXR shows a “boot-shaped” heart (the hypertrophic right ventricle causes the apex to be “lifted up”) and decreased pulmonary vascular markings resulting from decreased pulmonary flow (Fig. 25.1). The electrocardiogram is consistent with right ventricular hypertrophy. Transthoracic echocardiography defines the precise anatomy of the components of the defect and other associated lesions.

Hypercyanotic episodes, or “Tet spells,” are also discussed in Chapter 24. These are bouts in which infants are
inconsolable and extremely cyanotic. The exact etiology of these spells is unknown, although various theories have been proposed. Treatment includes consoling the patient (handing the baby over to a parent), and assuming a kneechest position. The knee-chest position increases the systemic vascular resistance, thereby forcing more blood to flow to the lungs and less deoxygenated blood to flow to the systemic circulation. Oxygen, fluid resuscitation, administration of morphine, phenylephrine (increases systemic vascular resistance and forces more blood to the lungs), and beta-blockers (decreasing heart rate and thus potentially decreasing the obstruction to pulmonary blood flow) are options for medical therapy It is important to remember that the murmur during a “tet spell” is actually softer and not louder. This is because less blood flows across the right ventricular outflow tract (cause of the murmur) in a “tet spell.”