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(See also Valvular Disorders.)
Congenital anomalies of the heart and blood vessels arise during the first 10 wk of embryonic development and are present at birth. The incidence is 1/120 live births; estimated risk is 2 to 3% in children with an affected 1st-degree relative.
Etiology
About 5% of patients have a chromosomal abnormality (eg, trisomy 13, 18, or 21; Turner's syndrome); other anomalies may be part of a genetic syndrome (eg, Holt-Oram, Noonan's, Williams, 22q11 deletion). Other possible causes are maternal illnesses (eg, diabetes mellitus, SLE, rubella), environmental exposure (eg, to thalidomide, isotretinoin, lithium [Ebstein's anomaly], or alcohol [fetal alcohol syndrome]), or a combination. Usually, no specific cause is identified.
Pathophysiology
Congenital heart anomalies are classified (see Table 1: Congenital Cardiovascular Anomalies: Classification of Congenital Heart Anomalies* ) as
The physiologic consequences of congenital heart anomalies vary greatly, ranging from an asymptomatic heart murmur or abnormal pulses to severe cyanosis and heart failure (HF).
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Table 1
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| Classification of Congenital Heart Anomalies* |
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Classification
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Examples
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Cyanotic
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—
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Tetralogy of Fallot
Transposition of the great arteries
Tricuspid atresia
Pulmonary atresia
Hypoplastic left heart syndrome
Persistent truncus arteriosus
Total anomalous pulmonary venous return
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Acyanotic
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Left-to-right shunt
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Ventricular septal defect
Atrial septal defect
Patent ductus arteriosus
Atrioventricular septal defect
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Obstructive
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Pulmonic stenosis
Aortic stenosis
Aortic coarctation
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*In decreasing order of frequency.
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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 abnormal opening between the 2 sides. Blood flows from left to right initially because systemic pressure and vascular resistance are higher than pulmonary artery pressure and resistance. 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 is usually asymptomatic.
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 artery pressure may lead to Eisenmenger's syndrome (see Congenital Cardiovascular Anomalies: Eisenmenger's Syndrome). Large left-to-right shunts (eg, large ventricular septal defect [VSD], patent ductus arteriosus [PDA]) cause volume overload, which may lead to HF and during infancy often results 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 without shunting, causing a pressure gradient across the obstruction. The resulting pressure overload proximal to the obstruction may cause ventricular hypertrophy and HF. The principal 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 O2 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 frequently occur in infants with tetralogy of Fallot (see Congenital Cardiovascular Anomalies: 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. Others 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: Heart Failure (HF)). HF in infants and children has many causes other than congenital heart anomalies (see Table 2: Congenital Cardiovascular Anomalies: Common Causes of Heart Failure in Children).
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Table 2
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| Common Causes of Heart Failure in Children |
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Age at Onset
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Causes
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In utero (uncommon)
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Chronic anemia with subsequent high-output heart failure
Myocardial dysfunction secondary to myocarditis
Sustained intrauterine tachycardia
Large systemic arteriovenous fistulas (eg, cerebral vein of Galen shunt)
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Birth through first few days
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Any of the above
Critical aortic or pulmonic stenosis (severe cyanosis usually present)
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)
Severe tricuspid or pulmonary insufficiency related to hypoxia
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Up to 1 mo
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Any of the above
Anomalous pulmonary venous drainage (disproportionate degree of pulmonary edema if pulmonary vein obstruction is present)
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
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Infancy (especially 6 to 8 wk)
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Anomalous pulmonary venous return
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
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Childhood
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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
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Symptoms and Signs
Manifestations of the various heart anomalies are limited to several common ones:
Less commonly, chest pain, diminished or nonpalpable pulses, circulatory shock, and arrhythmias are present.
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 (ejection systolic) murmur. Regurgitant flow through an atrioventricular valve or flow across a VSD causes a holosystolic (pansystolic) murmur, possibly obscuring heart sounds as its intensity increases.
PDA causes a continuous murmur that is uninterrupted by the 2nd heart sound (S2) 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:
This manifestation is characterized by bluish discoloration of mucous membranes or nail beds, clubbing of nail beds, or pulse oximetry < 93 to 95%.
Heart failure:
In infants, symptoms or signs of HF include
Dyspnea with feeding causes inadequate intake and poor growth, which may be worsened by increased metabolic demands in HF and frequent respiratory tract infections. Hepatomegaly is common. However, in contrast to adults and older children, most infants do not have distended neck veins and dependent edema, although they occasionally have edema in the periorbital area. Findings in older children with HF are similar to those in adults (see Heart Failure: 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 may be manifested by unexplained irritability in infants with a coronary artery anomaly. In older children and adolescents, chest pain due to a cardiac etiology is usually associated with exertion and may be caused by severe aortic stenosis, pulmonic stenosis, or Eisenmenger's syndrome.
Diagnosis
Diagnosis is suggested by the presence of heart murmurs, abnormal pulses, cyanosis, or HF. Cyanosis is usually noticed during the first few months of life. Cyanosis due to heart defects should be distinguished from that due to other disorders (eg, various respiratory disorders, CNS depression, hypothermia, hypoglycemia, hypocalcemia, sepsis, methemoglobinemia). Pulse oximetry, ECG, and chest x-ray are required. Echocardiography usually confirms the diagnosis.
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
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. 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. For HF, diuretics, inotropic drugs, and drugs to reduce afterload are given. The diuretic furosemide or ethacrynic acid is given as an initial bolus of 1 mg/kg IV and titrated based on urine output. The inotropic drug dopamine or dobutamine is given as an IV infusion of 5 to 15 μg/kg/min. Milrinone or, less frequently, nitroprusside is given to reduce afterload. Milrinone is given as a loading dose of 50 to 75 μg/kg IV over 10 to 60 min followed by an infusion of 0.5 μg/kg/min. Nitroprusside is started at 0.3 to 0.5 μg/kg/min and titrated to desired effect (usual maintenance dose is about 3 μg/kg/min).
Once a congenital cardiac lesion is suspected as the cause of the HF or cyanosis, an IV infusion of prostaglandins should be started (eg, prostaglandin E1 0.05 to 0.1 μg/kg/min) and titrated to the lowest dose that maintains patency of the ductus arteriosus. Keeping the ductus open is important because most cardiac lesions manifesting at this age are ductal-dependent either for systemic blood flow (eg, hypoplastic left heart syndrome, critical aortic stenosis, coarctation of the aorta) or for pulmonary blood flow (cyanotic lesions such as pulmonary atresia or severe tetralogy of Fallot).
Mechanical ventilation is often necessary; O2 should be given judiciously or even withheld because O2 can decrease pulmonary vascular resistance, which is harmful to infants with certain defects (eg, hypoplastic left heart syndrome).
Heart failure in older infants and children:
Standard approaches to acute and chronic heart failure, similar to those in adults, are used. These approaches may 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), an ACE inhibitor (eg, captopril 0.1 to 0.3 mg/kg po tid), digoxin (dose varies by age; see Table 3: Congenital Cardiovascular Anomalies: Oral Digoxin Dosage in Children*), and salt restriction. A potassium-sparing diuretic (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.
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Table 3
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| Oral Digoxin Dosage in Children* |
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Age
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Total Digitalizing Dose† (μg/kg)
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Maintenance Dose‡ (μg/kg bid)
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Preterm neonates
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20
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2.5
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Term neonates
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30
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5
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1 mo–2 yr
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30–50
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5–6
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2–5 yr
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30–40
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4–5
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6–10 yr
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20–35
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2.5–4
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> 10 yr§
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10–15
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1.25–2.5
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*All doses are based on ideal body weight for children with normal renal function. The IV dose is 75% of the oral dose.
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†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.
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‡The maintenance dose is 25% of the digitalizing dose, given in 2 divided doses.
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§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).
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A croupette, mask, or nasal prongs with adequate fractional inspired O2 (Fio2) should be given to prevent cyanosis and alleviate respiratory distress; when possible, Fio2 should be kept < 40% to prevent pulmonary epithelial damage. A cardiac chair position may benefit small infants and children; this position reduces upward pressure into the thorax exerted by abdominal organs and thus reduces work required for breathing.
Because HF increases metabolic demands and makes feeding more difficult, enhanced caloric content feedings are recommended; these feedings increase calories supplied and do so with less risk of volume overload. Some children require nasogastric or gastrostomy 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 Endocarditis: Prevention) state that antibiotic prophylaxis is required for children with congenital heart disease (CHD) who have the following:
Last full review/revision March 2010 by Lee B. Beerman, MD
Content last modified February 2012
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