Cardiovascular Congenital Anomalies Introduction

Congenital anomalies of the heart and blood vessels arise during the 1st 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.

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 syndrome). Other possible causes are maternal illnesses (eg, diabetes mellitus, SLE, rubella), environmental exposure (eg, to thalidomide, isotretinoin, or alcohol [fetal alcohol syndrome]), or a combination. Usually, no specific cause is identified.

Pathophysiology

Congenital heart anomalies are classified as acyanotic or cyanotic, and acyanotic anomalies are classified as left-to-right shunts or obstructive lesions.

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 BPs are normally higher on the left side. The additional blood on 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. A large left-to-right shunt (eg, large ventricular septal defect [VSD], patent ductus arteriosus) 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%.
Cyanotic heart anomalies: Varying amounts of deoxygenated venous blood are shunted to the left heart, reducing systemic arterial O2 saturation. If there is > 5 g/dL of deoxygenated Hb, cyanosis (bluish discoloration of the skin, mucous membranes, and nails) results. Detection of cyanosis may be delayed in infants with dark pigmentation. Complications of persistent cyanosis include polycythemia, clubbing, thromboembolism, bleeding disorders, and hyperuricemia. Hypercyanotic spells frequently occur in infants with tetralogy of Fallot.

Depending on the anomaly, pulmonary blood flow may be increased (often resulting in HF), normal, or reduced (manifesting with severe cyanosis). 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 producing HF. HF occurs when cardiac output is insufficient to meet the body's metabolic needs or when the heart cannot adequately dispose of venous return, causing pulmonary congestion (in left ventricular failure), edema primarily in dependent tissues and abdominal viscera (in right ventricular failure), or both. HF in infants and children has many causes other than heart anomalies.

Common Causes of Heart Failure in Children

Age at Onset

Causes


In utero (uncommon)

Chronic anemia with subsequent volume overload

Myocardial dysfunction secondary to myocarditis

Sustained intrauterine tachycardia


Birth through 1st few days

Any of the above

Critical aortic or pulmonic stenosis

Hypoplastic left heart syndrome

Intrauterine or neonatal paroxysmal supraventricular tachycardia

Large systemic arteriovenous fistulas

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


Up to 1 mo

Any of the above

Anomalous pulmonary venous drainage, particularly with pulmonary vein obstruction

Coarctation of aorta, with or without associated abnormalities

Complete heart block associated with structural heart anomalies

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

Systemic arteriovenous fistulas

Transposition of great arteries


Infancy

(especially 6 to 8 wk)

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


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

Nutritional deficiencies

Valvular heart disorders due to rheumatic fever

Viral myocarditis

Volume overload in a noncardiac disorder


Symptoms and Signs

Manifestations of the various heart anomalies are limited to several common ones (eg, murmurs, cyanosis, HF). Less commonly, chest pain, diminished or impalpable pulses, circulatory shock, and arrhythmias are present.

Most left-to-right shunts and obstructive lesions produce 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 produces a midsystolic (ejection systolic) murmur. Regurgitant flow through an atrioventricular valve or flow across a VSD produces a holosystolic (pansystolic) murmur, possibly obscuring heart sounds as its intensity increases. Patent ductus arteriosus produces a continuous murmur that is uninterrupted by the 2nd heart sound (S2) because blood flows through the ductus during systole and diastole.

In infants, signs of HF include tachycardia, tachypnea, dyspnea with feeding, diaphoresis, restlessness, and irritability. 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 except with some left-to-right shunts. 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.
n neonates, circulatory shock may be the 1st manifestation of certain anomalies (eg, hypoplastic left heart syndrome, critical aortic or pulmonic stenosis, coarctation of the aorta). Patients appear extremely ill and have cold extremities, diminished pulses, low BP, and reduced response to stimuli.

Chest pain may be the 1st symptom in infants with a coronary artery anomaly or in older children with severe aortic or pulmonic stenosis. Eisenmenger's syndrome may also cause chest pain.

Diagnosis

Diagnosis is suggested by the presence of heart murmurs, HF, or cyanosis, usually during the 1st 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). Pulse oximetry, ECG, and chest x-ray are required. Echocardiography usually confirms the diagnosis. Cardiac catheterization and angiocardiography may be needed to confirm the diagnosis or to assess severity of the anomaly before surgery.

Treatment

Specific anomalies are treated, sometimes with surgery. Medical treatment of HF is similar to that in adults; it may include a diuretic, an ACE inhibitor, digoxin, and salt restriction.

Because HF increases metabolic demands but makes feeding more difficult, enhanced caloric content feedings are recommended. Some patients require nasogastric or gastrostomy feedings to maintain growth. If these measures do not result in weight gain, surgical repair of the anomaly is indicated.

Acute severe HF in neonates or infants is a medical emergency. Vascular access should be established via an umbilical venous catheter to administer a diuretic and to infuse inotropic drugs. Humidified O2 should be given by croupette, mask, or nasal prongs with adequate Fio 2 to prevent cyanosis and alleviate respiratory distress; when possible, Fio 2 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.

Need for prophylaxis against infective endocarditis depends on the specific anomaly.

I received this email with some very helpful information and a super informative link that I've added to the helpful links to families and professionals section!

Your blog came up under my google alert for trisomy 13 with your latest article. I wanted to share an amazing support community with you. Often families given a prenatal or post-natal diagnosis of trisomy 13 are flooded with the negative information that comes with this syndrome. There is an online support community which brings together many of these families through stories, photos and message boards. There is an extensive list of support resources which help these families move forward with the many decisions and choices they will need make regarding their child. It would be wonderful if you could add the Living with Trisomy 13 - Patau Syndrome website to your list of family and professional resources. Doctor's need to know they can survive too. So often they give these families no hope. Thank you.


Blessings,

Thereses Ann,

mom to Natalia (full trisomy 13) almost 8 yrs.


Living with Trisomy 13 - Patau Syndromehttp://www.livingwithtrisomy13.org

 
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