Pediatric

Usually encountered congenital heart defects are due to any deviation from the normal changes that accompany after birth. The common defects are divided into 2 main categories:

1. Acyanotic congenital heart disease
2. Cyanotic congenital heart disease

Acyanotic heart diseasecan be further subdivided into 2 categories: shunt lesions and nonshunt lesions. Shunt lesions such as ventricular septal defects (VSDs) allow oxygenated blood to bypass systemic circulation and reenter pulmonary circulation. On the other hand, nonshunt lesions mainly consist of valvular heart diseases and aortic arch anomalies.

Shunt lesions :

The main anomalies that fall under this category are:

1. Atrial Septal Defect (ASD)
2. Ventricular Septal Defect (VSD)
3. Common Atrioventricular Canal
4. Patent Ductus Arteriosus

Atrial Septal Defects (ASDs) constitute 5% to 10 % of all congenital heart defects and occur in approximately 1 in 1500 live births. Children with ASDs are usually asymptomatic unless the defect is very large. If symptoms occur, they usually are:

• Shortness of breath on exertion
• Fatigue
• Swollen legs, feet or abdomen
• Stroke
• Heart murmur

Ventricular Septal Defects constitute about 20% of all the congenital heart diseases and occur in 2-10 out of 1000 live births. If the defect is large enough to cause a significant shunt, the baby may show signs of congestive heart failure. These symptoms include:

• Sweating with feeds
• Poor weight gain
• Tachypnea (abnormally rapid breathing)
• Tachycardia (faster beating than normal)
• Hepatomegaly (increase in liver size)

Common atrioventricular canal also known as endocardial cushion defect or AV septal defect accounts for 4% to 5% of all congenital heart disease and 40% of heart disease in children with trisomy 21 (the most common form of Down's syndrome, caused by an extra copy of chromosome number 21). The common AV valve cannot separate into tricuspid and mitral valve because of the failure of the endocardial cushions to fuse. Infants with a complete AV canal have symptoms consistent with large VSDs. Incomplete AV canals develop symptoms more consistent with ASDs but can be compounded by symptomatology from left AV valve regurgitation. Transitional AV canal defects can vary in their presentation and symptoms depending on the size and level of restriction at the VSD and the amount of AV valve regurgitation.

Patent Ductus Arteriosus constitutes about 5% to 10% of all congenital heart diseases. In premature infants weighing less than 1750 grams, the incidence is much higher at about 40%. Failure of the closure of ductus results in a left-to-right shunt between the aorta and the pulmonary artery. The magnitude of the shunt depends on the size of the open ductus and pulmonary versus systemic vascular resistance. 

Infants with small Patent DuctusArteriosus are asymptomatic but those with larger Patent DuctusArteriosus can present with Congestive Heart Failure symptoms. 

Non shunt lesions

The main anomalies that come under this category are:

• Aortic valve disease
• Coarctation of the aorta
• Pulmonary valve disease
• Mitral valve disease
• Vascular ring

Aortic valve disease: Valvular aortic stenosis (AS) constitutes about 3% to 8% of congenital heart defectsor 4 in 100000 live births. The male predominance is significant with about 80% of the cases. Most infants are asymptomatic but those with severe obstruction children might present with chest pain on exercise, syncope, heart failure or sudden death.

Coarctation of the aorta is a discrete narrowing of the distal aortic arch opposite the entrance of the ductusarteriosus or the ligamentum (after ductal closure). In some rare instances, it can be a narrowing of the abdominal aorta. It constitutes about 8% of all congenital heart defects. Males are more affected up to 4 times than females. Coarctation is also frequently associated with left-sided lesions such as bicuspid aortic valve, aortic stenosis, mitral valve abnormalities and ventricular septal defects. It can also be associated with non-cardiac abnormalities such as intracranial aneurysms. In neonates with critical or severe coarctation, the clinical manifestation is usually shock. The usual findings in such patients are elevated systolic pressures in the upper extremities and lower systolic blood pressures in lower extremities. However, some infants may not have upper extremity hypertension but only have lower extremity hypotension and so blood pressures in all the 4 extremities should be measured because the blood pressure differential may vary in location based on the area of coarctation and the area of arch anatomy.

Pulmonary valve disease usually manifested as pulmonary stenosis constitutes about 8% of children with congenital heart disease or 7 in 100000 live births. Pulmonary stenosis (PS) can be valvular, subvalvular or supravalvular. Valvular PS is the most common and occurs in 90% of the cases. Infants and children with noncritical PS are rarely symptomatic. In more severe cases, children can have dyspnea with exertion and right-sided heart failure. Newborns with critical or severe PS present with cyanosis from right-to-left shunting through a patent foramen ovale, tachypnea, and poor feeding.

Mitral valve disease usually manifests as mitral stenosis (MS) is an uncommon isolated congenital heart defect but appears more commonly as a complication of rheumatic heart disease. Structural abnormalities that can cause MS include parachute mitral valve (a defect in the mitral valve in which there is only one papillary muscle present), mitral valve arcade (direct attachment of leaflets to the papillary muscles without intervening chordae and therefore absence of interchordal spaces), or a supramitral ring.

Vascular rings are anomalies of the aortic arch that can cause compression of the trachea, esophagus or both. Infants may present with noisy breathing or with stridor. Respiratory distress associated concomitant upper respiratory infections is common. Kids with the disease might present with swallowing difficulties. Double aortic arch and right aortic arch with a retroesophageal diverticulum of Kommerell are the two most common types of vascular rings. 

Cyanotic congenital heart disease encompasses cardiac lesions that result in a characteristic blue discoloration of the skin which is referred to as cyanosis. Cyanotic heart disease usually present in infancy. The conditions that fall under this category are:

• Transposition of great arteries
• Tetralogy of Fallot
• Double Outlet Right Ventricle with Pulmonic Stenosis
• Critical Pulmonic Stenosis
• Tricuspid atresia
• Pulmonary atresia
• Ebstein’s Anomaly of the Tricuspid Valve
• Total Anomalous Pulmonary Venous Connection
• Truncus Arteriosus Communis

Transposition of the great arteries means that the pulmonary artery arises above the left ventricle and the aorta above the right ventricle. It is the most common cardiac cause of cyanosis in the neonatal period (period immediately after the child is born) and is present in 2 to 4 in 10000 live births. The parallel flows of pulmonary and systemic circulations with minimal mixing leads to cyanosis. 

Tetralogy of Fallotis characterized by an abnormally small subpulmonaryconus or outflow tract, resulting in anterior and cephalad displacement of the infundibular (outflow tract) septum. This produces the four characteristic findings: 

• subvalvular pulmonic stenosis, 
• VSD caused by malalignment ofthe infundibular septum relative to the rest of the ventricular septum,
• “overriding aorta” (i.e., the aortic valve sits above both ventricles), and 
• right ventricular hypertrophy caused by pressure overload from the large VSD.

This condition occurs in 19 to 26 in 100000 live births and represents 8% of congenital cardiac lesions. Cyanosis in tetralogy of Fallot is variable, resulting from extensive systemic–pulmonary mixing and decreased pulmonary blood flow caused by the combination of subpulmonic stenosis and a large VSD.

Double outlet right ventricle with pulmonic stenosis has similar physiology to tetralogy of Fallot. The clinical presentation can be similar, with differentiation provided by echocardiography.

Tricuspid atresia is absence of communication between the right atrium and either ventricle. All blood returning to the right atrium flows across a patent foramen ovale or ASD to the left atrium, left ventricle, and usually through a VSD to the remnant of the right ventricle. In cases with normally aligned great arteries, the size of the VSD affects the amount of pulmonary blood flow and therefore the degree of cyanosis

Because all patients with tricuspid atresia, regardless of associated abnormalities, have a functional single ventricle, the ultimate treatment is a Fontan operation, in which all systemic venous return goes directly to the pulmonary arteries (without passing through a ventricle) and pulmonary venous return goes to the left atrium and left ventricle and out the aorta (normally aligned great arteries) or through the VSD to the right ventricular remnant to the aorta (transposition). Because the Fontan operation depends on low pulmonary resistance to allow systemic venous blood to flow without a pump into the pulmonary arteries, it cannot be carried out until the high pulmonary resistance of the normal newborn has resolved. An intermediary operation, superior cavopulmonary anastomosis (bidirectional Glenn or hemi-Fontan), is typically performed at 4 to 6 months of age. In this operation, the superior vena cava is connected to the right pulmonary artery so that all venous drainage from the upper body goes to the lungs but inferior vena caval blood mixes with pulmonary venous return and goes to the body. One or 2 years later, the inferior vena cava is connected to the pulmonary arteries by way of an intraatrial baffle or extracardiac conduit, completing the Fontan circuit

Infants with extreme narrowing of the pulmonic valve orifice (critical pulmonic stenosis) can present with hepatomegaly (abnormal increase in liver size) and cyanosis from right-to-left shunting across the foramen ovale because of right ventricular failure or low right ventricular compliance.

Pulmonary atresia with intact ventricular septum is a more severe form of critical pulmonary stenosis. This occurs in 7 in 100000 live births. Because the severe obstruction occurs during fetal development, the right ventricular hypertrophy causes poor compliance so that the right ventricle stops growing. Thus, patients have a small right ventricle. In many cases, they also have right ventricle-to-coronary artery fistulae. These may lead to perfusion defects of the left ventricle as coronary blood flow is forced retrograde into the aorta from a suprasystemic right ventricle.

Ebstein’s anomaly of the tricuspid valve is a rare anatomic abnormality characterized by displacement of the attachment of the septal and posterior leaflets of the tricuspid valve toward the apex of the right ventricle. The lesion constitutes fewer than 1% of congenital cardiac lesions, representing 5 in 1000000 live births. Children of mothers taking lithium have a higher incidence of Ebstein’s anomaly. No extracardiac syndromes are associated with it, but it is commonly associated with other cardiac lesions, including interatrial communication (ASD or patent foramen ovale) as well as VSDs, pulmonic stenosis or atresia, and L-transposition of the great arteries. Downward displacement of the tricuspid valve partitions the right ventricle into an apical right ventricular portion and a proximal atrialized right ventricle. The tricuspid valve anterior leaflet becomes large redundant and “sail-like” with variable tricuspid regurgitation. These patients have a high incidence (20%-30%) of preexcitation with accessory pathway. Hemodynamically, Ebstein’s anomaly has a wide range of possible physiologies, depending on the degree of regurgitation or stenosis of the tricuspid valve, the presence of atrial communication, and the degree of right ventricular dysfunction as a result of the dysplastic valve. Thus, patients can present with symptoms of cyanosis, heart failure, or atrial arrhythmias depending on the balance of the aforementioned factors.

Total anomalous pulmonary venous connection means connection of all pulmonary veins to somewhere other than the left atrium. Connections to the innominate vein, the portal system of the liver, and the coronary sinus are representative of the main categories noted below. This defect comprises 1% to 3% of congenital cardiac lesions. Anatomically, patients are divided among those whose pulmonary veins connect above the diaphragm (70%), below the diaphragm (25%), or in mixed fashion (i.e., to more than one connection; 5%). Those connecting above the diaphragm are further divided into those connecting to a vein, most often the innominate vein, and those connecting to the heart, either the coronary sinus or the right atrium. The majority of these are unobstructed. Connection below the diaphragm is almost always to the portal vein or one of its branches or to the ductusvenosus; hence, they become obstructed when the ductusvenosus closes in the first few days of life.

The degree of cyanosis depends on the amount of pulmonary venous obstruction. Patients with significant obstruction present with marked cyanosis from decreased pulmonary blood flow accentuated by pulmonary edema and pulmonary arterial hypertension; they also show tachypnea and respiratory distress. Patients without obstruction have high pulmonary blood flow and initially have minimal cyanosis, but they progress to congestive heart failure because of pulmonary overcirculation.

Truncusarteriosuscommunis denotes a single arterial trunk that serves as the common origin of the aorta, pulmonary artery, and coronary arteries. It comprises 2% to 2.8% of congenital cardiac lesions. This condition is almost always associated with a VSD. The truncus is fed by a single truncalvalve, most commonly with three cusps, but may have two to five cusps, often myxomatous and asymmetric. This truncal valve typically sits over the VSD but in rare cases arises predominantly above the right ventricle. Associated cardiac defects include right aortic arch (33%) and anomalous coronary artery origins. Extracardiac anomalies associated with truncus include 22q11 microdeletion. The physiology of truncus is usually that of high pulmonary blood flow with minimal cyanosis but commonly tachypnea and respiratory distress. Congestive heart failure is exaggerated by poor coronary perfusion secondary to low diastolic pressures from runoff into the pulmonary arteries.