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Overview of Congenital Cardiovascular Anomalies

by Jeanne Marie Baffa, MD

(See also Valvular Disorders.)

Congenital heart disease (CHD) is the most common congenital anomaly, occurring in almost 1% of live births. Among birth defects, CHD is the leading cause of infant mortality.

Etiology

Environmental and genetic factors contribute to the development of CHD.

Common environmental factors include maternal illness (eg, diabetes, rubella, systemic lupus erythematosus) or maternal intake of teratogenic agents (eg, lithium, isotretinoin, anticonvulsants). Paternal age may also be a risk factor.

Certain numerical chromosomal abnormalities, such as trisomy 21, trisomy 18, trisomy 13, and monosomy X (Turner syndrome), are strongly associated with CHD. However, these abnormalities account for only about 5% of patients with CHD. Many other cases involve microscopic deletions on chromosomes (see Contiguous Gene Syndromes) or single-gene mutations. Often, the microscopic deletions and mutations cause congenital syndromes affecting multiple organs in addition to the heart. Examples include DiGeorge syndrome (microdeletion in 22q11.2) and Williams-Beuren syndrome (microdeletion in 7p11.23). Single-gene defects that cause syndromes associated with CHD include mutations in fibrillin-1 (Marfan syndrome), TXB5 (Holt-Oram syndrome), and possibly PTPN11 (Noonan syndrome). Single-gene defects can also cause isolated (ie, nonsyndromic) congenital heart defects.

The recurrence risk of CHD in a family varies depending on the cause. Risk is negligible in de novo mutations, 2 to 5% in nonsyndromic multifactorial CHD, and 50% when an autosomal dominant mutation is the cause. It is important to identify genetic factors because more patients with CHD are surviving into adulthood and potentially starting families.

Pathophysiology

Congenital heart anomalies are classified (see Table: Classification of Congenital Heart Anomalies*) as

  • Cyanotic

  • Acyanotic (left-to-right shunts or obstructive lesions)

The physiologic consequences of congenital heart anomalies vary greatly, ranging from an asymptomatic heart murmur or abnormal pulses to severe cyanosis, congestive heart failure (HF), or circulatory collapse.

Classification of Congenital Heart Anomalies*

Classification

Examples

Cyanotic

Tetralogy of Fallot

Transposition of the great arteries

Tricuspid atresia

Pulmonary atresia

Persistent truncus arteriosus

Total anomalous pulmonary venous return

Acyanotic

Left-to-right shunt

Ventricular septal defect

Atrial septal defect

Patent ductus arteriosus

Atrioventricular septal defect

Obstructive

Pulmonic stenosis

Aortic stenosis

Aortic coarctation

Hypoplastic left heart syndrome (often also manifests with cyanosis, which may be mild)

*In decreasing order of frequency.

Left-to-right shunts

Oxygenated blood from the left heart (left atrium or left ventricle) or the aorta shunts to the right heart (right atrium or right ventricle) or the pulmonary artery through an opening or communication between the 2 sides. Immediately after birth, pulmonary vascular resistance is high and flow through this communication may be minimal or bidirectional. Within the first 24 to 48 h of life, however, the pulmonary vascular resistance progressively falls, at which point blood will increasingly flow from left to right. The additional blood flow to the right side increases pulmonary blood flow and pulmonary artery pressure to a varying degree. The greater the increase, the more severe the symptoms; a small left-to-right shunt typically does not cause symptoms or signs.

High-pressure shunts (those at the ventricular or great artery level) become apparent several days to a few weeks after birth; low-pressure shunts (atrial septal defects) become apparent considerably later. If untreated, elevated pulmonary blood flow and pulmonary artery pressure may lead to pulmonary vascular disease and eventually Eisenmenger syndrome (see Eisenmenger Syndrome). Large left-to-right shunts (eg, large ventricular septal defect [VSD], patent ductus arteriosus [PDA]) cause excess pulmonary blood flow and volume overload, which may lead to signs of HF and during infancy often result in failure to thrive. A large left-to-right shunt also decreases lung compliance, leading to frequent lower respiratory tract infections.


Obstructive lesions

Blood flow is obstructed, causing a pressure gradient across the obstruction. The resulting pressure overload proximal to the obstruction may cause ventricular hypertrophy and HF. The most obvious manifestation is a heart murmur, which results from turbulent flow through the obstructed (stenotic) point. Examples are congenital aortic stenosis, which accounts for 3 to 6% of congenital heart anomalies, and congenital pulmonary stenosis, which accounts for 8 to 12% (for both, see Valvular Disorders).


Cyanotic heart anomalies

Varying amounts of deoxygenated venous blood are shunted to the left heart (right-to-left shunt), reducing systemic arterial O 2 saturation. If there is > 5 g/dL of deoxygenated Hb, cyanosis results. Detection of cyanosis may be delayed in infants with dark pigmentation. Complications of persistent cyanosis include polycythemia, clubbing, thromboembolism (including stroke), bleeding disorders, brain abscess, and hyperuricemia. Hypercyanotic spells can occur in infants with unrepaired tetralogy of Fallot (see Tetralogy of Fallot).

Depending on the anomaly, pulmonary blood flow may be increased (often resulting in HF in addition to cyanosis), normal, or reduced, resulting in cyanosis of variable severity. Heart murmurs are variably audible and are not specific.


Heart failure

Some congenital heart anomalies (eg, bicuspid aortic valve, mild aortic stenosis) do not significantly alter hemodynamics. Other anomalies cause pressure or volume overload, sometimes causing HF. HF occurs when cardiac output is insufficient to meet the body’s metabolic needs or when the heart cannot adequately handle venous return, causing pulmonary congestion (in left ventricular failure), edema primarily in dependent tissues and abdominal viscera (in right ventricular failure), or both (see Heart Failure (HF)). HF in infants and children has many causes other than congenital heart anomalies (see Table: Common Causes of Heart Failure in Children).

Common Causes of Heart Failure in Children

Age at Onset

Causes

In utero

Chronic anemia with subsequent high-output heart failure

Large systemic arteriovenous fistulas (eg, cerebral vein of Galen shunt)

Myocardial dysfunction secondary to myocarditis

Sustained intrauterine tachycardia

Birth through first few days

Any of the above

Critical aortic stenosis or critical coarctation

Ebstein anomaly with severe tricuspid and/or pulmonary insufficiency

Hypoplastic left heart syndrome

Intrauterine or neonatal paroxysmal supraventricular tachycardia

Metabolic disorders (eg, hypoglycemia, hypothermia, severe metabolic acidosis)

Perinatal asphyxia with myocardial damage

Severe intrauterine anemia (hydrops fetalis)

Total anomalous pulmonary venous drainage with severe obstruction (usually infracardiac type)

Up to 1 mo

Any of the above

Anomalous pulmonary venous drainage (with less severe obstruction)

Coarctation of aorta, with or without associated abnormalities

Complete heart block associated with structural heart anomalies

Large left-to-right shunts in premature infants (eg, patent ductus arteriosus)

Transposition of great arteries with a large ventricular septal defect

Infancy (especially 6 to 8 wk)

Anomalous pulmonary venous return (unobstructed)

Bronchopulmonary dysplasia (right ventricular failure)

Complete atrioventricular septal defects

Patent ductus arteriosus

Persistent truncus arteriosus

Rare metabolic disorders (eg, glycogen storage disease)

Single ventricle

Supraventricular tachycardia

Ventricular septal defect

Childhood

Acute cor pulmonale (caused by upper airway obstructions such as large tonsils)

Acute rheumatic fever with carditis

Acute severe hypertension (with acute glomerulonephritis)

Bacterial endocarditis

Chronic anemia (severe)

Dilated congestive cardiomyopathy

Iron overload due to altered iron metabolism (juvenile hemachromatosis) or due to frequent transfusions (eg, for thalassemia major)

Nutritional deficiencies

Valvular heart disorders due to congenital or acquired cardiac disease (eg, rheumatic fever)

Viral myocarditis

Volume overload in a noncardiac disorder


Symptoms and Signs

Manifestations of CHDs are varied but commonly include

  • Murmurs

  • Cyanosis

  • HF

Other physical examination abnormalities may include circulatory shock, poor perfusion, abnormal 2nd heart sound (S 2 —single or widely split), systolic click, gallop, or irregular rhythm.

Murmurs

Most left-to-right shunts and obstructive lesions cause systolic murmurs. Systolic murmurs and thrills are most prominent at the surface closest to their point of origin, making location diagnostically helpful. Increased flow across the pulmonary or aortic valve causes a midsystolic crescendo-decrescendo (ejection systolic) murmur. Regurgitant flow through an atrioventricular valve or flow across a VSD causes a holosystolic (pansystolic) murmur, often obscuring heart sounds as its intensity increases.

PDA causes a continuous murmur that is uninterrupted by the S 2 because blood flows through the ductus during systole and diastole. This murmur is 2-toned, having a different sound during systole (when driven by higher pressure) than during diastole.


Cyanosis

Central cyanosis is characterized by bluish discoloration of the lips and tongue and/or nail beds; it implies a low O 2 level (usually O 2 saturation < 90%). Perioral cyanosis and acrocyanosis (cyanosis of the hands and feet) without lip or nail bed cyanosis is caused by peripheral vasoconstriction rather than hypoxemia and is a common, normal finding in neonates. Older children with longstanding cyanosis often develop clubbing of the nail beds.


Heart failure

In infants, symptoms or signs of HF include

  • Tachycardia

  • Tachypnea

  • Dyspnea with feeding

  • Diaphoresis, especially with feeding

  • Restlessness, irritability

  • Hepatomegaly

Dyspnea with feeding causes inadequate intake and poor growth, which may be worsened by increased metabolic demands in HF and frequent respiratory tract infections. In contrast to adults and older children, most infants do not have distended neck veins and dependent edema; however, they occasionally have edema in the periorbital area. Findings in older children with HF are similar to those in adults (see Heart Failure (HF) : Symptoms and Signs).


Other manifestations

In neonates, circulatory shock may be the first manifestation of certain anomalies (eg, hypoplastic left heart syndrome, critical aortic stenosis, interrupted aortic arch, coarctation of the aorta). Neonates appear extremely ill and have cold extremities, diminished pulses, low BP, and reduced response to stimuli.

Chest pain in children is usually noncardiac. In infants, chest pain may be manifested by unexplained marked irritability, particularly during or after feeding, and can be caused by anomalous origin of the left coronary artery from the pulmonary artery. In older children and adolescents, chest pain due to a cardiac etiology is usually associated with exertion and may be caused by a coronary anomaly, myocarditis, or severe aortic stenosis.

Syncope, typically without warning symptoms and often in association with exertion, may occur with certain anomalies including cardiomyopathy, anomalous origin of a coronary artery, or inherited arrhythmia syndromes (eg, long QT syndrome, Brugada syndrome). High school–age athletes are most commonly affected.


Diagnosis

  • Screening by pulse oximetry

  • ECG and chest x-ray

  • Echocardiography

  • Sometimes cardiac MRI or CT angiography, cardiac catheterization with angiocardiography

When present, heart murmurs, cyanosis, abnormal pulses, or manifestations of HF suggest CHD. In such neonates, echocardiography is done to confirm the diagnosis of CHD. If the only abnormality is cyanosis, methemoglobinemia also should be ruled out.

However, manifestations of CHD may be subtle or absent in neonates, and failure or delay in detecting CHD, particularly in the 10 to 15% of neonates who require surgical or inpatient medical treatment in the first month of life (termed critical congenital heart disease [CCHD]), may lead to neonatal mortality or significant morbidity. Thus, all asymptomatic neonates are screened for CCHD before hospital discharge using pulse oximetry. The screening is done when infants are ≥ 24 h old and is considered positive if ≥ 1 of the following is present:

  • Any O 2 saturation measurement is < 90%.

  • The O 2 saturation measurements in both the right hand and foot are < 95% on 3 separate measurements taken 1 h apart.

  • There is > 3% absolute difference between the O 2 saturation in the right hand (preductal) and foot (postductal) on 3 separate measurements taken 1 h apart.

All neonates with a positive screen should undergo a comprehensive evaluation for CHD and other causes of hypoxemia (eg, various respiratory disorders, CNS depression, sepsis) typically including a chest x-ray, ECG, echocardiography, and often blood testing. Sensitivity of pulse oximetry screening is slightly > 75%; the CHD lesions most often missed are left heart obstructive lesions (eg, coarctation of the aorta).

Cardiac MRI or CT angiography may clarify important anatomic details. Cardiac catheterization with angiocardiography is occasionally needed to confirm the diagnosis or to assess severity of the anomaly; it is done more often for therapeutic purposes.

Treatment

  • Medical stabilization of HF (eg, with O 2 , diuretics, ACE inhibitors, digoxin, and salt restriction)

  • Surgical repair or transcatheter intervention

After medical stabilization of acute HF symptoms or cyanosis, most children require surgical or transcatheter repair; the exceptions are certain VSDs that are likely to become smaller or close with time or mild valve dysfunction. Transcatheter procedures include balloon atrial septostomy for palliation of severely cyanotic neonates with transposition of the great arteries, balloon dilation of severe aortic or pulmonary valve stenosis, and transcatheter closure of cardiac shunts (most often atrial septal defect and PDA).

Heart failure in neonates

Acute, severe HF or cyanosis in the first week of life is a medical emergency. Secure vascular access should be established, preferably via an umbilical venous catheter.

When critical CHD is suspected or confirmed, an IV infusion of prostaglandin E 1 should be started at an initial dose of 0.01 mcg/kg/min. Occasional infants will require higher doses, such as 0.05 to 0.1 mcg/kg/min, to reopen or maintain patency of the ductus arteriosus. Keeping the ductus open is important because most cardiac lesions manifesting at this age are ductal-dependent for either systemic blood flow (eg, hypoplastic left heart syndrome, critical aortic stenosis, coarctation of the aorta) or pulmonary blood flow (cyanotic lesions such as pulmonary atresia or severe tetralogy of Fallot).

Mechanical ventilation is often necessary in critically ill neonates. Supplemental O 2 should be given judiciously or even withheld because O 2 can decrease pulmonary vascular resistance, which is harmful to infants with certain defects (eg, hypoplastic left heart syndrome).

Other therapies for neonatal HF include diuretics, inotropic drugs, and drugs to reduce afterload. The diuretic furosemide is given as an initial bolus of 1 mg/kg IV and titrated based on urine output. Infusions of the inotropes dopamine or dobutamine can support BP but have the disadvantage of increasing heart rate and afterload, thus increasing myocardial O 2 consumption. Milrinone, frequently used in postoperative patients with CHD, is both a positive inotrope and a vasodilator. Dopamine, dobutamine, and milrinone all have the potential to increase the risk of arrhythmias. Nitroprusside, a pure vasodilator, is often used for postoperative hypertension. It is started at 0.3 to 0.5 mcg/kg/min and titrated to desired effect (usual maintenance dose is about 3 mcg/kg/min).


Heart failure in older infants and children

Therapies often include a diuretic (eg, furosemide 0.5 to 1.0 mg/kg IV or 1 to 3 mg/kg po q 8 to 24 h, titrated upward as needed) and an ACE inhibitor (eg, captopril 0.1 to 0.3 mg/kg po tid). A potassium-sparing diuretic (eg, spironolactone 1 mg/kg po once/day or bid, titrated up to 2 mg/kg/dose if needed) may be useful, particularly if high-dose furosemide is required. β-Blockers (eg, carvedilol, metoprolol) are often added for children with chronic congestive HF. Digoxin is used less often than in the past but may still have a role in children with HF who have large left-to-right shunts, in certain postoperative patients with CHD, and in some infants with supraventricular tachycardia (dose varies by age; see Table: Oral Digoxin Dosage in Children*).

Oral Digoxin Dosage in Children*

Age

Total Digitalizing Dose (mcg/kg)

Maintenance Dose (mcg/kg bid)

Preterm neonates

20

2.5

Term neonates

30

5

1 mo–2 yr

30–50

5–6

2–5 yr

30–40

4–5

6–10 yr

20–35

2.5–4

> 10 yr §

10–15

1.25–2.5

*All doses are based on ideal body weight for children with normal renal function. The IV dose is 75% of the oral dose.

The digitalizing dose is usually only necessary when treating arrhythmias or acute congestive heart failure. The total digitalizing dose is usually given over 24 h with half of the dose given initially, followed by 1 / 4 of the dose given twice, separated by 8- to 12-h intervals; ECG monitoring is necessary.

The maintenance dose is 25% of the digitalizing dose, given in 2 divided doses.

§ Not to exceed adult digitalizing/maintenance doses of 1–1.5 mg/0.125–0.250 mg/day (once/day dosing acceptable after age 10 yr).

Supplemental O 2 may lessen hypoxemia and alleviate respiratory distress; when possible, fractional inspired O 2 (F io 2 ) should be kept < 40% to minimize the risk of pulmonary epithelial damage.

In general, a healthy diet, including salt restriction, is recommended, although dietary modifications may be needed depending on the specific disorder and manifestations. HF increases metabolic demands and the associated dyspnea makes feeding more difficult. In infants with CCHD, particularly those with left heart obstructive lesions, feedings may be withheld to minimize the risk of necrotizing enterocolitis. In infants with HF due to left-to-right-shunt lesions, enhanced caloric content feedings are recommended; these feedings increase calories supplied and do so with less risk of volume overload. Some children require tube feedings to maintain growth. If these measures do not result in weight gain, surgical repair of the anomaly is indicated.


Endocarditis prophylaxis

Current guidelines of the American Heart Association for prevention of endocarditis (see Infective Endocarditis : Prevention) state that antibiotic prophylaxis is required for children with CHD who have the following:

  • Unrepaired cyanotic CHD (including children with palliative shunts and conduits)

  • Completely repaired CHD during the first 6 mo after surgery if prosthetic material or a device was used

  • Repaired CHD with residual defects at or adjacent to the site of a prosthetic patch or prosthetic device


Resources In This Article

Drugs Mentioned In This Article

  • Drug Name
    Select Trade
  • SOTRET
  • LITHOBID
  • LANOXIN
  • LASIX
  • No US brand name
  • NITROPRESS
  • LOPRESSOR, TOPROL-XL
  • CAPOTEN
  • COREG
  • ALDACTONE

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