Congenital Heart Disease

Author: Jason M Kendall, Robert Tulloh / Editor: Steve Fordham / Reviewer: Muhammad Waseem / Codes: PAP13 / Published: 17/06/2013 / Review Date: 17/06/2016

Introduction

Context

Congenital heart disease (CHD) accounts for 10% of all congenital anomalies. In the developed world, it is one of the most common causes of death in the first year of life. Usually, CHD is diagnosed in utero or in the newborn nursery, however, some critical lesions do not manifest until 1 to 2 weeks of life, when the ductus arteriosus closes.

Many of these conditions require immediate intervention. About 25% of children are born with critical and potentially fatal forms of congenital heart disease.

It should be notedthat even those who have undergone surgical corrections may have residual deficits making them susceptible to acute illness.

Typically, infants with previously undiagnosed structural CHD initially present in the emergency department (ED) with the following;

A) Cyanosis

B) Congestive heart failure (CHF)

C) Cardiogenic shock or circulatory collapse

A) Cyanotic or blue baby

These are referred to as the terrible T’s or the horrible H’s. Cyanosis results from decreased pulmonary perfusion, or from complete mixing of systemic and pulmonary venous return in the heart.

• Tetralogy of Fallot
• Transposition of great arteries (TGA)
• Total anomalous pulmonary venous return (TAPVR)
• Truncus arteriosus
• Tricuspid atresia
• Hypoplastic left heart syndrome
• Hypoplastic right heart conditions

B ) Congestive heart failure (CHF):

Usually, left-sided obstructive lesions present with shock as the ductus arteriosus closes and the blood supply to the systemic circulation diminishes. The examples are as follows:

• Coarctation of the aorta
• Congenital aortic stenosis
• Hypoplastic left heart syndrome
• Total anomalous pulmonary venous return with obstruction (resulting in volume overload of the right ventricle)

C) Cardiogenic shock or circulatory collapse

• Critical coarctation of the aorta
• Interrupted aortic arch
• Congenital aortic stenosis
• Hypoplastic left heart syndrome

For clinical purposes cyanotic lesions can be classified based on the pulmonary blood flow

I ) Decreased Pulmonary blood flow (Right to Left Shunting): associated with obstruction to pulmonary blood flow

• Tetralogy of Fallot
• Tricuspid Atresia
• Pulmonary Atresia

II) Increased Pulmonary blood flow (Intracardiac mixing): not associated with obstruction to pulmonary blood flow

• Total Anomalous Pulmonary Venous Return
• Truncus arteriosus
• Transposition of the Great Arteries
• Hypoplastic Left Heart Syndrome

Definition

CHD is defined as structural heart disease present at birth. It is relatively common and affects around 1% of all newborns (actual incidence of 8 per 1000 live births).

Potential outcome

The outcome for an infant with CHD depends on the type and severity of the defect as well as the presence of extra-cardiac malformations which are common in this group of children. The more complex, cyanotic defects generally have a worse prognosis. Without surgical intervention, many of these are associated with death in infancy without surgical treatment. Those who have successfully undergone surgery usually remain well through childhood; but the prognosis in adult life depends on the type and severity of the condition, as well as the magnitude of any residual lesions.

The role of the clinician

• Rapid and thorough assessment
• Consider alternate diagnoses: excluding non-cardiac causes such as sepsis, congenital adrenal hyperplasia etc.
• The first step in the evaluation is to determine whether the cyanosis is central or peripheral.
• If cyanosis is central perform hyperoxia test; since it helpsto distinguish cardiac from pulmonary causes of cyanosis
• Administer 100% oxygen for 10 minutes (hyperoxia), and then obtain a post-ductal blood sample for arterial blood gas analysis.
• Pa O₂ > 150 mm Hg is suggestive of a pulmonary cause
• Pa O₂ < 150 mm Hg then suspect a cardiac cause
• Chest Radiograph: Provides assessment of heart size, pulmonary vascular markings, and aortic arch-sidedness

Heart Size

• Increased heart size: left-sided obstructive lesions
• Congenital aortic stenosis
• Interrupted aortic arch
• Critical coarctation of the aorta

Pulmonary vascular marking

• “Black out” appearance: Decreased Pulmonary blood flow
• Tetralogy of Fallot
• Tricuspid Atresia
• Pulmonary Atresia
• “White out” appearance: Increased pulmonary blood flow or pulmonary venous obstruction
• Total Anomalous Pulmonary Venous Return
• Truncus arteriosus
• Transposition of the Great Arteries
• Hypoplastic Left Heart Syndrome

 

• TGA: egg-on-a-string appearance
• Tetralogy of Fallot: Boot-shaped heart
• Snowman appearance: TAPVR

Aortic arch sidedness

• Left-sided aortic arch: Normal
• Right-sided aortic arch: tetralogy of Fallot, TGA, and truncus arteriosus

Pathophysiology

i) Circulatory changes at birth:

During fetal life, the placenta serves as the site for oxygen exchange. The fetus receives blood with relatively higher oxygen saturation from the placenta via the umbilical vein

Fetal circulation differs from postnatal circulation in two important ways:

1. Oxygenated blood enters the circulation via placental transfer
2. Pulmonary blood flow accounts for less than 20% of total cardiac output due to high pulmonary vascular resistance

Starting at birth and continuing over the first few days of life, the cardiovascular system undergoes several physiological changes:

Drop in pulmonary vascular resistance

The lungs inflate causing a decrease in pulmonary vascular resistance allowing greater pulmonary blood flow and an increase in oxygen tension

Closure of shunts (between pulmonary and systemic circulation)

The ductus arteriosus (see Fig 1) closes soon after birth as the smooth muscle in the medial layer of the ductus constricts in response to increased oxygen tension and a fall in prostaglandins. Functional closure is complete within 60 hours in the majority of term newborns

The increased pulmonary blood flow and increased pulmonary venous return and subsequent increased systemic resistance lead to an increase in left atrial pressure. This causes the foramen ovale (see figure 1) to close; thereby separates the right and left atria

The ductus venosus closes as flow dwindles in the umbilical vein after the umbilical cord has been clamped

In certain CHD, closure of the ductus arteriosus can precipitate rapid clinical deterioration. These are referred to as duct-dependent lesions. Clinical problems may also occur when certain structures remain patent beyond the immediate postnatal period, for example patent ductus arteriosus.

Oxygenation of blood through the pulmonary system causes closure of umbilical vessels, the ductus arteriosus and the ductus venosus.

Figure 1: Structure of newborn heart

(ii) Classification:

CHD is broadly classified as acyanotic and cyanotic.

Acyanotic:left-to-right shunts, in which oxygenated blood is redirected toward the right heart containing deoxygenated blood.

Cyanotic: right-to-left shunts in which deoxygenated systemic venous blood is directed toward the left heart.

Acyanotic lesions account for approximately 75% of CHD and acyanotic CHD is associated volume or pressure overload (Figure 1).

Cyanotic lesions account for approximately 25% of CHD. Cyanotic lesions may be associated with decreased pulmonary blood flow (right-to-left shunts) or with increased pulmonary blood flow (intracardiac mixing). (Figure 2).

(iii) Etiology:

There are many genetic and environmental factors that increase the risk of CHD and these should be considered about when obtaining the history. Specific gene defects have been identified in 40-60% of CHD (Table 1). Maternal factors are also associated with certain forms of CHD (Table 2).

Table 1: Specific gene defects:

Table 2: Maternal factors:

 

Clinical Presentation

Common types of CHD

Table 1 provides a summary of the more common types of CHD and their presentations.

The following sections detail the various presentations of CHD in the ED and outline the defects, clinical features, investigations and management of the examples mentioned in Table 1.

Left to Right Shunts

(1) Atrial Septal Defect

There are two main types of ASD:

• Secundum ASD (80% of ASDs)
• Partial atrioventricular septal defect (primum ASD, pAVSD)

Both present with similar symptoms and signs, but their anatomy is quite different. The secundum ASD is a defect in the centre of the atrial septum involving the foramen ovale (Fig 1). Partial AVSD is a defect of the atrioventricular septum.

Fig 1: Secundum ASD

Clinical presentation

Symptoms

None (commonly) Recurrent chest infections/wheeze Arrhythmias (fourth decade onwards)

Physical Signs

An ejection systolic murmur best heard at the upper left sternal edge due to increased flow across the pulmonary valve because of the left-to-right shunt A fixed and widely split second heart sound (often difficult to hear) due to the right ventricular stroke volume being equal in both inspiration and expiration With a partial AVSD, an apical pansystolic murmur from atrioventricular valve regurgitation

Investigations

Chest radiograph	Cardiomegaly Enlarged pulmonary arteries Increased pulmonary vascular markings
ECG	Secundum ASD partial right bundle branch block is common (but may occur in normal children), right axis deviation due to right ventricular enlargement Partial AVSD a superior QRS axis (mainly negative in AVF). This occurs because there is a defect of the middle part of the heart where the atrioventricular node is. The displaced node then conducts to the ventricles superiorly giving the abnormal axis
Echocardiography	This will delineate the anatomy and is the mainstay of diagnostic investigations

Management

Children with significant ASD will require treatment. For secundum ASDs this is by cardiac catheterisation with insertion of an occlusion device but for partial AVSD surgical correction is required. Treatment is usually undertaken at about 3-5 years of age in order to prevent right heart failure and arrhythmias in later life.

(2) Ventricular Septal Defect

VSDs are common, accounting for 30% of all cases of congenital heart disease. There is a defect anywhere in the ventricular septum (Fig 2), perimembranous (adjacent to the tricuspid valve) or muscular (completely surrounded by muscle).

They can be classified according to the size and location of the VSD.

Small and large

Peri-membranous, outlet, inlet or muscular

Small VSDs are smaller than the aortic valve in diameter, perhaps up to 3 mm. Large VSDs and complete AVSDs are the same size or bigger than the aortic valve.

Fig 2: VSD

(i) Small VSD

Clinical presentation

Symptoms	Asymptomatic
Physical Signs	Loud pansystolic murmur at lower left sternal edge (loud murmur implies that it is not a large defect) Quiet pulmonary second sound (P2)

Investigations

Chest radiograph	Normal
ECG	Normal
Echocardiography	Demonstrates the precise anatomy of the defect. It is possible to assess its haemodynamic effects using Doppler echocardiography. There is no pulmonary hypertension.

Management

These lesions will close spontaneously. This is ascertained by the disappearance of the murmur with a normal ECG on follow-up by a paediatrician or paediatric cardiologist and by a normal echocardiogram. Whilst the VSD is present, prevention of bacterial endocarditis is attempted by maintaining good dental hygiene.

(ii) Large VSD

Clinical presentation

Symptoms	Heart failure with breathlessness and faltering growth after 1 week old Recurrent chest infections
Physical Signs	Tachypnoea, tachycardia and enlarged liver from heart failure Active precordium Soft pansystolic murmur or no murmur (implying large defect) Apical mid-diastolic murmur (from increased flow across the mitral valve after the blood has circulated through the lungs) Loud pulmonary second sound (P2) from raised pulmonary arterial pressure

Investigations

Chest radiograph	Cardiomegaly Enlarged pulmonary arteries Increased pulmonary vascular markings Pulmonary oedema
ECG	Biventricular hypertrophy by 2 months of age Superior axis in AVSD
Echocardiography	Demonstrates the anatomy of the defect, haemodynamic effects and pulmonary hypertension (due to high flow).

Management

The indications for surgical repair depend on the size of the VSD, degree of shunting, and associated lesions. Young infants with large VSDs, refractory heart failure, and large shunts should undergo surgical closure of the defects in infancy.

(3) Patent Ductus Arteriosus

The ductus arteriosus connects the pulmonary artery to the descending aorta. In term infants, it normally closes shortly after birth and is completely closed in most infants by 2 to 3 weeks of age.

When there is a failure of ductal constriction after birth, the ductus arteriosus remains patent. The flow of blood across a PDA is then from the aorta to the pulmonary artery (i.e. left to right Fig 3), following the fall in pulmonary vascular resistance after birth. In the preterm infant, the presence of a PDA is not from congenital heart disease but due to prematurity (since muscularization of the medial layer occurs primarily in the third trimester).

Fig 3: Patent ductus arteriosus

Clinical presentation

Symptoms

Usually asymptomatic When the duct is large there will be increased pulmonary blood flow with heart failure and pulmonary hypertension (i.e. breathlessness)

Physical signs

A continuous machinery murmur left upper sternal border Diastolic rumble: the murmur continues into diastole because the pressure in the pulmonary artery is lower than that in the aorta throughout the cardiac cycle. In premature infants, a large ductus may only present with a flow murmur, or frequently, with no murmur. The diagnosis is suspected due to the requirement of increasing respiratory support. The pulse pressure is increased, causing bounding pulses

Investigations

Chest radiograph	Usually normal Cardiomegaly and increased pulmonary vascular markings (Large PDA)
ECG	Left and right ventricular hypertrophy (Large PDA)
Echocardiography	The duct is readily identified on echocardiography

Management

Surgical closure is the gold standard when indicated in the newborn period.

Indomethacin may be considered; it does, however, have the potential to cause necrotizing enterocolitis, intracranial hemorrhage, and renal toxicity.

Summary of left-to-right shunts

Right to Left Shunts

(1) Tetralogy of Fallot

TOF is the most common cause of cyanotic CHD.

In tetralogy of Fallot, as implied by the name, there are four cardinal anatomical features (see Fig 1):

• A large VSD
• Overriding of the aorta
• Right ventricular outflow tract obstruction (pulmonary stenosis): this may be valvular, sub-valvular, and/or supra-valvular
• Right ventricular hypertrophy

The most common cause of cyanotic CHD.

Comprises up to 10% of all CHD.

The pathophysiology relates to shunting of desaturated, systemic venous blood through the VSD to mix with the systemic cardiac output.

The greater the degree of obstruction to pulmonary blood flow, the larger the right-to-left shunt and the worse the desaturation.

Time of manifestation depends on the severity of right ventricular outflow tract obstruction and thus the amount of pulmonary blood flow; severe obstruction results in cyanosis in the newborn period and presents in the first week of life with cyanosis or collapse.

Right ventricular outflow tract obstruction: determines the amount of cyanosis.

The direction of shunt depends on the extent of right ventricular outflow tract obstruction. The VSD is almost never restrictive in tetralogy of Fallot.

Fig 1: Tetralogy of Fallot

Clinical presentation

Symptoms	Most are diagnosed antenatally or following the identification of a murmur in the first month or two of life. The degree of RV outflow obstruction determines the age and symptoms at presentation Newborn: Cyanosis at this stage may not be obvious, although a few with severe RVOTO may present with severe cyanosis in the first few days of life (secondary to reduced pulmonary blood flow) Older Children: May present with pulmonary over-circulation and CHF (Net left-to-right flow through the VSD)- pink TOF (adequate pulmonary flow)
“Tet” spells Sudden hypoxic spells, characterized by tachypnea and hyperpnea, followed by worsening cyanosis. Occurs due to transient increase in right ventricular outflow tract obstruction that involvesnarrowing of the infundibulum (the sub-pulmonary outflow tract) Precipitating factors: Agitation and dehydration. Spells often are precipitated by crying The classical description of severe cyanosis, hypercyanotic spells and squatting on exercise, developing in late infancy. It is important to recognize hypercyanotic spells, as they may lead to cerebrovascular accidents and even death if left untreated. They are characterised by a rapid increase in cyanosis, usually associated with irritability or inconsolable crying because of severe hypoxia, and breathlessness and pallor due to tissue acidosis.
Physical Signs	Systolic thrill at the lower and middle left sternal border Loud single S2 Loud systolic ejection murmur at the lower left sternal border With increasing right ventricular outflow tract obstruction, the murmur softens and cyanosis increases. When the severity of obstruction worsens, more blood is shunted across the VSD. During a hypercyanotic spell, the murmur may be inaudible Clubbing of the fingers and toes may be present in older children

Investigations

Chest radiograph	Boot shaped heart (with elevation of the cardiac apex due to right ventricular hypertrophy) Normal heart size with decreased pulmonary vascular markings reflecting reduced pulmonary blood flow (may be normal or engorged in pink patients without significant PS)
ECG	Right axis deviation and Right ventricular hypertrophy
Echocardiography	This will demonstrate the cardinal features, but cardiac catheterisation may rarely be required to show the detailed anatomy of the coronary arteries

Management

Initial management is medical, with definitive surgery at around 6 months of age. It involves closing the VSD and relieving right ventricular outflow tract obstruction, sometimes with an artificial patch, which extends across the pulmonary valve.

Infants who are very cyanosed in the neonatal period require a surgically placed shunt to increase pulmonary blood flow. However, the trend now is to offer complete surgical repair when indicated without shunt palliation.

Hypercyanotic spells

Hypercyanotic spells are usually self-limiting and followed by a period of sleep. If prolonged (beyond about 15 minutes), they require prompt treatment with:

• Hypercyanotic spells are usually self-limiting and followed by a period of sleep. If prolonged (beyond about 15 minutes), they require prompt treatment with:
• Knee-chest position: May help to reduce venous return and increase systemic vascular resistance, thereby decreasing right-to-left shunting
• Fluid: 20 ml/kg bolus
• Oxygen: high-flow
• Beta-blockers: intravenous esmolol
• Antibiotics: assume infection was the precipitating factor
• Morphine can be used sparingly, with care to avoid respiratory depression, (50 100 mcg/kg sc/im/iv)
• Alpha-agonist: this can be lifesaving if other measures have not worked quickly. Use phenylephrine (0.1 mg in a 10 ml syringe, dilute to 10 ml with saline, and give very small aliquots until pulse and cardiac output return). The patients hands and feet will go white temporarily
• Hypercyanotic spells are an indication for early surgery. Do not send a child home from the emergency department (ED) without obtaining a cardiology consultation.

(2) Transposition of the Great Arteries

Second most common cause of cyanotic CHD diagnosed by 1 year of age

The most common cyanotic CHD that presents in the first day of life.

The aorta lies anteriorly and arises from the right ventricle; the pulmonary artery is relatively posterior and connected to the left ventricle (ventriculoarterial discordance). Deoxygenated blood is therefore returned to the body and oxygenated blood is returned to the lungs. The pulmonary and systemic circuits are arranged in parallel. Unless there is mixing of blood between them, this condition is incompatible with life.

The presentation for infants with TGA depends on the degree of blood mixing. Fortunately, there are a number of naturally occurring associated anomalies, e.g. VSD, ASD and PDA. Initial survival depends on the presence of a shunt, allowing mixing between the systemic and pulmonary circulations.

These infants present with cyanosis at birth because of right-to-left shunting, and the cyanosis becomes more severe when the ductus arteriosus closes.

Fig 2: Transposition of the Great Arteries

Clinical presentation

Symptoms	The lesion is frequently detected antenatally. Cyanosis is the predominant symptom. Presentation is usually on day 2 of life when ductal closure leads to a marked reduction in mixing of the desaturated and saturated blood. Cyanosis may be less severe and presentation is delayed if there is more mixing of blood from associated anomalies, e.g. an ASD. Hypoxia and acidosis
Physical signs	Cyanosis is always present The second heart sound is often loud and single Usually no murmur

Investigations

Chest radiograph	“egg on a string” appearance The “egg” = enlarged and globular shaped heart with an abnormally convex right atrial border and an enlarged left atrium The “string” = narrow mediastinum due to the anteroposterior (AP) position of the great vessels Cardiomegaly with increased vascular markings (increased pulmonary blood flow)
ECG	Right axis deviation (RAD) and right ventricular hypertrophy (RVH)
Echocardiography	Demonstrate the abnormal arterial connections and associated abnormalities

Management

In the sick cyanosed neonate, the key is to improve mixing. The outcome depends on the degree of blood “mixing,” the magnitude of tissue hypoxia, and the ability of the right ventricle to maintain the systemic circulation. Without surgery, most patients die within months.

Maintaining the patency of the ductus arteriosus with a prostaglandin infusion is helpful. However, this systemic-to-pulmonary connection tends to close early and thus intervention is required to create a new shunt such as balloon atrial septostomy within the first few days of life.

3) Total Anomalous Pulmonary Venous Return (TAPVR)

Rare CHD; 2% to 3% of CHD presenting in the neonatal period.

It is characterized by anomalous drainage of all pulmonary veins to the systemic circulation. There is embryologic failure of the pulmonary veins to form a connection to the left atrium, and thepulmonary vein carries blood from the lungs to the right atrium. This results in a left-to-right shunt of oxygenated blood back to the lungs rather than to the body. Though pulmonary venous blood does come to the right side, there is complete mixing in the right atrium, and right-to-left shunting across the ASD making this a cyanotic lesion.

It is classified depending on where the pulmonary vein drains:

• Type I: Superior vena cava (supra-cardiac) 55%
• Type II: Right atrium (via the coronary sinus) 30%
• Type III: Portal vein (infra-cardiac)
• Type IV: Mixed with 2 or more anomalous connections

Anatomically it can be classified as

• Supra-diaphragmatic (supra-cardiac or cardiac)
• Infra-diaphragmatic; depending on the location where the anomalous venous connection occurs

Physiologically, this can be classified as obstructive or nonobstructive (depending on whether free flow through the pulmonary veins is impeded or not)

• The most frequent is the non-obstructive, supradiaphragmatic form
• The most classic is infra-diaphragmatic with obstruction
• Presentation: Presents in early infancy; 50% within the first month and almost 90% by one year of age.
• Obstructive TAPVR present with cyanosis in the first hours to days of life.
• Non-obstructive TAPVR has minimal no cyanosis and presents with CHF between the ages of 4 and 6 weeks
• Congestive heart failure (obstruction in these anomalous connections)
• Cyanosis (subtle in unobstructed forms, severe in obstructed forms)
• Loud single S2 (fixed, widely split)
• EKG: Right axis deviation, right ventricular hypertrophy and right atrial enlargement
• Chest Radiograph: The findings depend on the level of venous drainage and the presence or absence of obstruction
• Significant cardiomegaly with increased pulmonary vascular markings (snowman appearance or “figure-of-eight” sign in infants over 4 months in type I TAPVR)
• “snowman” head = Wide mediastinum due to dilated right SVC and a left vertical vein represents the confluence of the pulmonary veins posterior to the left atrium.
• “snowman” body = heart
• Supra-diaphragmatic TAPVR without obstruction = cardiomegaly, increased pulmonary vascularity, and pulmonary arterial dilation
• Infra-diaphragmatic TAPVR with obstruction = small heart with pulmonary venous congestion

Management

Surgical correction in which the common pulmonary venous confluence or the individual pulmonary veins are mobilized and anastomosed with the left atrium.

4 ) Truncus Arteriosus

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

Outflow obstruction in the well child

(1) Aortic Stenosis

The aortic valve leaflets are partly fused together, giving a restrictive exit from the left ventricle. There may be one to three aortic leaflets. Aortic stenosis may not be an isolated lesion.

May occur at valvular, supra-valvular or sub-valvular level.

Bicuspid aortic valve is most common type

Williams syndrome: supra-valvular stenosis

Clinical presentation

Symptoms	Most present with an asymptomatic murmur Congestive heart failure (with severe obstruction) In the neonatal period, those with critical aortic stenosis and a duct-dependent systemic circulation may present with severe heart failure leading to shock
Physical signs	Small volume, slow rising pulses Systolic thrill (right sternal border, suprasternal notch or carotid arteries) Ejection systolic murmur maximal at the upper right sternal edge radiating to the neck Delayed and soft aortic second sound Apical ejection click

Investigations

Chest radiograph	Normal or prominent left ventricle with post-stenotic dilatation of the ascending aorta
ECG	Left ventricular hypertrophy

Management

In children, regular clinical and echocardiographic assessment is required in order to assess when to intervene. Children with symptoms on exercise or who have a high resting pressure gradient (more than 50 mm Hg) across the aortic valve will undergo balloon valvotomy.

Most neonates and children with significant aortic valve stenosis requiring treatment in the first few years of life will eventually require aortic valve replacement. Early treatment is therefore palliative and directed towards delaying this for as long as possible.

(2) Pulmonary Stenosis

The pulmonary valve leaflets are partly fused together, giving a restrictive exit from the right ventricle (see figure).

Clinical presentation

Symptoms	Most are asymptomatic A small number of neonates with critical pulmonary stenosis have a duct-dependent pulmonary circulation and present in the first few days of life with cyanosis
Physical Signs	An ejection systolic murmur best heard at the upper left sternal edge; thrill may be present An ejection click best heard at the upper left sternal edge When severe there is a prominent right ventricular impulse (heave)

Investigations

Chest radiograph	Normal or post-stenotic dilatation of the pulmonary artery
ECG	Shows evidence of right ventricular hypertrophy (upright T wave in V1)

Management

When there is critical or severe valvular pulmonary stenosis, balloon valvuloplasty of the pulmonic valve is performed in the neonatal period. In cases of moderate pulmonary stenosis, the procedure is performed when the gradient across the pulmonary valve exceeds 50 mm Hg. Cases of mild pulmonary stenosis are usually followed conservatively.

(3) Adult type Coarctation of the Aorta

Coarctation of the aorta is a narrowing of the aorta.

Clinical presentation

Symptoms	Asymptomatic
Physical signs	Systemic hypertension Ejection systolic murmur at upper sternal edge Collaterals heard with continuous murmur at the back Radio-femoral delay. This is due to blood bypassing the obstruction via collateral vessels in the chest wall and hence the pulse in the legs is delayed

Investigations

Chest radiograph	Rib-notching due to the development of large collateral intercostal arteries running under the ribs posteriorly to bypass the obstruction
ECG	Left ventricular hypertrophy

Management

The approach to native coarctation varies across centers. Most centers recommend surgical correction of a native coarctation. Others perform balloon angioplasty with or without placement of a stent to relieve coarctation in the adult.

Summary of Outflow obstruction in the well child

Outflow obstruction in the sick infant

Coarctation of the aorta presenting in infancy

CoA is due to arterial duct tissue encircling the aorta just at the point of insertion of the duct. When the duct closes, the aorta also constricts causing severe obstruction to the left ventricular outflow. These children usually present as ill with heart failure and shock in the neonatal period.

Clinical presentation

Symptoms	Examination on the first day of life is usually normal. These neonates usually present with acute circulatory collapse at 2 days of age when the duct closes
Physical signs	A sick baby, with severe heart failure and absent femoral pulses Severe metabolic acidosis

Investigations

Chest radiograph	Cardiomegaly from heart failure and shock
ECG	Normal

Management

• Management is to stabilize first (ABC).
• Maintain adequate tissue perfusion and oxygenation
• Prostaglandin E1 should be administered if there is clinical suspicion for a ductal-dependent lesion (dose 0.05- 0.1 mcg/kgper minute; maximum 0.1 mcg/kgper minute). Beware of complications of prostaglandin E1 infusion such as hypotension, tachycardia, and apnea. Protect the airway by intubation and mechanical ventilation before transporting the patient to another medical facility.
• Referral is made to a cardiac Centre for early surgical intervention

Eisenmenger Syndrome

• Severe pulmonary hypertension (leading to shunt reversal) due to a left-to-right intracardiac shunt
• As a consequence of a large left-to-right shunt for many years, the pulmonary vascular resistance will slowly rise. Eventually, the shunt will reverse and the patient will become cyanosed, typically at about 15-20 years of age (Eisenmenger Syndrome).
• Common cause: unrestricted and unrepaired VSD
• Patients are usually stable for many years, with typical survival into the 4th or 5th decade of life. However, they may then present with some of the complications of a right-to-left shunt and of pulmonary hypertension.
• Patients with Eisenmenger Syndrome can present with:

(i) Syncope

• This may be the first presenting feature in a child or young adult with pulmonary hypertension. It should be differentiated from teenagers who present with neurocardiogenic syncope or vasovagal syncope.
• Clinical examination may reveal cyanosis, a loud P2 and a right ventricular heave.
• When Eisenmenger syndrome develops, the associated cardiac murmur may disappear
• ECG: Right ventricular hypertrophy
• Chest Radiograph: Prominent pulmonary vessels

(ii) Exercise intolerance and asthma or COPD or breathlessness on exertion

This is often the next insidious symptom of pulmonary hypertension, due to Eisenmenger syndrome. Non-wheezing asthma is the cardinal feature. Again, full history, clinical examination and ECG assist in the detection of such patients. Generally, the first presentation of severe asthma should prompt the physician to obtain an ECG after initial stabilization.

(iii) Haemoptysis

This is often a preterminal event in pulmonary hypertension or Eisenmenger Syndrome. It may occur with a chest infection or when there is severe right heart failure.

(iv) During Pregnancy

Those with pulmonary hypertension due to any cause are usually advised not to become pregnant. If this does occur, it is lethal in 50% of cases and termination is generally advised.

General approach to management in the ED

As discussed earlier, there are three main ways CHD may present to the ED:

• Cyanosis
• Heart failure
• Collapse and shock

Infants may present to the ED with features of cardiovascular collapse due to non-cardiac causes as well. It is important to remember other causes of cardiorespiratory compromise. In particular, it is often difficult to differentiate CHD from pulmonary disease or sepsis in the newborn.

Learning Bite

Always include CHD in the differential diagnosis of any critically ill newborn or infant.

(1) Collapse and shock

A patient with CHD may present with collapse and shock, which is defined as an acute state where the circulation is inadequate to meet the metabolic demands of tissues.

However, other cardiac conditions (e.g. cardiomyopathies, arrhythmias, pericardial effusion, etc.) may also present in a shocked state. There are also many non-cardiac causes of shock (e.g. sepsis, anaphylaxis, inborn errors of metabolism) which must be considered in the differential diagnosis of shock and metabolic acidosis.

Collapse and/or shock due to structural heart disease is usually associated with left-sided obstructive lesions that result in inadequate systemic blood flow (e.g. aortic stenosis, coarctation of aorta).

Specific features of shock include:

• Reduced spontaneous movements
• Mottled skin
• Prolonged capillary refill time
• Decreased pulses or narrow pulse pressure
• Hypothermia and widening of toe-core temperature difference
• Tachycardia
• Tachypnoea and respiratory distress
• Hypotension
• Oliguria/ anuria
• Lactic acidosis

Management

General principles

General principles of resuscitation are essential; airway, breathing then circulation. Maintain adequate inspired oxygenation, regardless of the cause.

There is often a concern that oxygen administration may be dangerous, (e.g. might close a life-sustaining ductus). In general resuscitation, this is highly unlikely and standard resuscitation interventions should be used first. Once the cause of collapse is known, this may then be modified.

Management of the neonate

• Strongly consider commencing a prostaglandin infusion even before a diagnosis has been made.
• Starting dose of PGE2 is typically 0.05 0.1 mcg/kg/minute
• Monitor for apnoea
• Consider volume expansion, but only repeat if there is an improvement
• Volume expansion
• Judicious fluid administration: Only administer fluid if there is good evidence of hypovolemia
• Follow local policy on whether to use colloid or crystalloid but consider:
• Plasma expander (e.g. 4.5% Human Albumin Solution) 5 ml/kg
• Normal Saline 10 ml/kg
• Packed red cells 5 ml/kg if there is evidence of recent blood loss or PCV <0.35
• Give fluid volume cautiously in increments over 30 minutes
• Larger boluses may be required for rapid intravascular expansion in hypovolemic patients
• Discuss with a pediatric cardiologist early
• Consider Invasive BP monitoring (always be aware of possibility of coarctation)
• Consider CVP monitoring
• Correct metabolic acidosis
• Consider inotropes if there is:
• Large heart on chest radiograph
• No improvement with fluid bolus
• Catecholamines (adrenaline, noradrenaline, dopamine, dobutamine)
• Phosphodiesterase inhibitors (milrinone, enoximone) rarely used in the emergency situation
• Use markers of tissue perfusion to decide threshold for intervention
• Assess effects of intervention using HR, BP, acid base status and perfusion

Non-cardiac causes of collapse and shock in the infant:

The table below outlines the management you should always consider when a sick collapsed baby presents to the ED.

Learning Bite

Do not forget non-cardiac causes of shock in a patient with CHD, especially sepsis.

(2) Heart failure

Tachypnoea is an early feature of heart failure in children.

The diseases implicated are very different in the first week of life relative to those presenting after this time:

Up to 7 days, most infants with heart failure have an obstructed left heart, especially with duct dependent lesions (most likely to be coarctation of the aorta)

After 7 days, this is most likely to be due to left to right shunt (most likely to be VSD)

Specific features of heart failure

• Poor feeding
• Excessive weight gain
• Tachypnoea, breathlessness
• Respiratory distress
• Fine crepitations on auscultation
• Poor peripheral perfusion
• Sweating
• Mottled, clammy, cool skin
• Tachycardia
• Hyperdynamic precordium
• Gallop rhythm
• Hepatomegaly
• Cardiomegaly and increased pulmonary vascularity on chest radiograph
• Specific signs due to underlying cause

Children do not present in heart failure with left to right shunt due to CHD after 1 year, since they have developed pulmonary vascular disease by this time. The thickening of the pulmonary artery walls in response to the left-to-right shunt will limit the pulmonary blood flow and the signs of heart failure.

Management

The principles of managing heart failure in the first week of life are to administer prostaglandin with or without inotropes

The principles of managing heart failure after the first week of life are to reduce preload with diuretics and reduce afterload with ACE inhibitors (use of ACEi somewhat controversial) whilst maintaining optimal nutritional intake.

During the first year of life, the pulmonary vascular resistance continues to rise, such that the features of cardiac failure gradually resolve. Patients will be developing pulmonary hypertension and pulmonary vascular disease.

Specific features of managing heart failure include the following:

• Resuscitate as appropriate, but be careful: do not administer too much fluid
• Evaluate whether the infant is improving with each bolus of fluid
• If not, then consider that an inotrope or other infusion may be needed
• Consider commencing a prostaglandin infusion even before an exact diagnosis has been made if there is suspicion of a duct-dependent lesion
• Discuss with a cardiologist early if cause unknown
• Correct anaemia if present
• Consider inotropes if there is evidence of myocardial dysfunction
• Give furosemide IV 1 mg/kg 6 to 12 hourly, if there are good femoral pulses

Learning Bite

Prostaglandin is likely to be beneficial for infants with heart failure in the first week of life; pre-load and after-load reduction with diuretics and ACE Inhibitors are used for heart failure presenting beyond 1 week, once outflow tract obstruction is excluded.

(3) Cyanosis

Cyanosis is the clinical description of the bluish discolouration of the skin and mucous membranes that corresponds to greater than 5 g/dl of deoxygenated haemoglobin in the blood. Mild degrees may not be observed and a saturation monitor should be used to confirm normality. Look for central cyanosis in the tongue and mucous membranes.

Cyanosis (oxygen saturation less than 94%) may be due to cardiac disease, respiratory disease, metabolic disease or sepsis.

Pitfall

Be mindful of where the saturation probe is positioned. It should be in the right hand to pick up cyanotic heart disease (pre-ductal saturation). If only the feet are blue (post-ductal saturation), then it could be due to right to left shunt at the duct in coarctation of the aorta.

Assessing cyanosis

When assessing whether cyanosis may be present, remember the following points:

• Peripheral cyanosis is normal in the first few days of life and cyanosis only whilst crying is rarely significant
• Polycythaemia or methaemoglobinaemia may cause a baby to appear blue, but these are not associated with structural cardiac defects
• Anaemia and dark skin tones make it more difficult to detect cyanosis
• Some babies with cyanotic heart disease may appear fairly pink due to the high affinity for oxygen of fetal haemoglobin

Learning Bite

Cyanosis with little or no respiratory distress and lack of radiographic evidence of lung disease suggests underlying congenital heart disease.

Management

A hyperoxia test is useful in distinguishing between cardiac and pulmonary causes of desaturation. With the infant inhaling 100% FiO2, the arterial PaO₂does not increase significantly if the cause is cardiac. In a neonate (under 4 weeks), it is always worth considering the use of a prostaglandin infusion. Oxygen is not helpful in the treatment of cyanotic CHD: indeed, one of the ways to make the diagnosis is to show that there is little improvement in saturations when oxygen is administered. Then an echocardiogram should be performed. Surgical procedure performed based on the lesion.

MedicoLegal and other considerations

Key Learning Points

• It is important to perform a complete evaluation in a patient with CHD; beware that CHD is often part of a syndrome with physiological disturbances beyond the heart
• Consider ductal dependent lesion in the first week of life; these are potentially life threatening and may require a prostaglandin infusion
• A pulse oximeter should not be used for the hyperoxia test because it may not detect an inadequate increase in oxygen tension
• Heart failure in the infant beyond the first week of life is due to a left to right shunt, usually a VSD
• A sick collapsed neonate should be treated for respiratory disease, sepsis and cardiac disease together until a definitive diagnosis is established
• Many patients with CHD present with non-specific symptoms and signs, such as breathlessness and failure to thrive. In such situations, the diagnosis may be delayed.
• Left to right shunts usually do not present with heart failure after the first year of life
• Cyanotic congenital heart disease may not show improvement with oxygen therapy
• Adults with CHD may present to the ED as a complication of known CHD, or as a new presentation with complications
• Pulmonary hypertension has many causes, any of which may improve with oxygen therapy

References:

1. Paediatric Heart Disease: a Clinical Guide. Piers Daubeney, Michael Rigby, Michael Gatzoulis, Koichiro Niwa. BMJ Books 2012.
2. Congenital Diseases of the Heart: Clinical-Physiological Considerations. Abraham Rudoplh. Wiley-Blackwell Publications. 2009.
3. Strobel AM, Lu le N. The Critically Ill Infant with Congenital Heart Disease. Emerg Med Clin North Am. 2015 Aug;33(3):501-18
4. Zucker EJ, Koning JL, Lee EY.Cyanotic Congenital Heart Disease: Essential Primer for the Practicing Radiologist. Radiol Clin North Am. 2017 Jul;55(4):693-716
5. Yee L. Cardiac emergencies in the first year of life. Emerg Med Clin North Am. 2007 Nov;25(4):981-1008

Web resources

• Childrens Heart Federation website
• Congenital Heart Defects website