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Chapter VII.2. Acyanotic Congenital Heart DiseaseAlyson A. Tamamoto, MD

July 2013

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The editors and current author would like to thank and acknowledge the significant contributionof the previous author of this chapter from the 2004 first edition, Dr. Edgar C.K. Ho. This current

second edition chapter is a revision and update of the original authors work.

A 7-year old male presents in the office for a school physical examination. In the course of the

interview, his mother mentions that he seems to get short of breath with exercise recently. It isespecially noticeable during his swimming lessons when he tires before the other children do in

his class. He has otherwise been in good health since his last physical exam one year ago. Hisrecords for the past year show 3 office visits for minor upper respiratory illnesses and no

emergency room visits. He has never had wheezing during his colds.

Exam: T 37 degrees C, HR 92, RR 25, BP (right arm) 97/70, oxygen saturation 98% in room air.

Height and weight are at the 25th percentile. He is cooperative, well nourished, and in no

distress. HEENT and neck exams are normal. His chest is symmetrical. Heart exam reveals no

palpable thrill, normal 1st and 2nd heart sounds, no clicks or rubs, grade 1/6 systolic ejectionmurmur heard along the left sternal border with radiation to the back between the scapulae, and

no diastolic murmur. Lungs are clear to auscultation. Abdomen negative for organomegaly orpalpable masses. Extremities noted to have slightly diminished femoral pulses, no peripheraledema, clubbing or cyanosis of the nail beds. His neurologic exam is normal.

He receives his immunizations, tuberculin skin test, and, because of the new onset heart murmur,a CXR and EKG are ordered. He returns in 3 days to have his skin test read and to review his

cardiac tests. Before entering the exam room the nurse re-measures his vital signs and records in

his chart: BP (left arm) 127/86, HR 88, RR 24. His CXR shows a cardiac/thoracic ratio of 0.55,
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normal cardiac configuration, and normal pulmonary vasculature. His EKG has tall R waves of

40mm in lead V5 and 35mm in lead V6. An echocardiogram is performed the following day and

demonstrates a coarctation of the aorta and bicuspid aortic valve. A MRI shows a discrete

narrowing of the distal aortic arch just beyond the origin of the left subclavian artery and alsoreveals an aberrant right subclavian artery originating from the proximal descending aorta

below the coarctation.

Congenital heart disease (CHD) in a moderate or severe form has an incidence of 6 in every1,000 live births. Acyanotic congenital heart disease accounts for 70% of all congenital heart

disease. These defects include atrial septal defect (ASD), tricuspid stenosis and regurgitation (TSand TR), milder forms of Ebstein's anomaly of the tricuspid valve, pulmonic stenosis and

regurgitation (PS and PR), partial anomalous pulmonary venous drainage to right side of heart,

ventricular septal defect (VSD), mitral stenosis and regurgitation (MS and MR), aortic stenosis

and regurgitation (AS and AR), atrioventricular (AV) canal defect, patent ductus arteriosus

(PDA), and coarctation of the aorta. As opposed to cyanotic CHD in which hypoxia is the mainconcern, development of congestive heart failure (CHF) is the main concern in acyanotic CHD.

CHF presents as sweating, feeding difficulties, poor growth or failure to thrive (FTT), S3 gallop,and if left-sided, also tachypnea, subcostal retractions, and/or pulmonary rales. Chest radiographs

in CHF may demonstrate cardiomegaly and increased pulmonary vascular congestion and

edema. Echocardiograms are the primary diagnostic modality, but magnetic resonance imaging

provides excellent anatomic evaluation and often yields even more information thanangiography.

VSD, ASD and PDAs account for a large percentage of all congenital heart defects. They sharecommon physiologic hemodynamics and will be discussed together. These defects represent

abnormal communication between the high-pressure left side of the heart and the low-pressureright side of the heart. The pressure differential results in left-to-right shunting of blood throughthe defect consequently leading to turbulence of abnormal blood flow producing a heart murmur

in systole and sometimes in diastole, excessive blood flow into the lungs causing pulmonary

vascular congestion leading to shortness of breath, increased volume overload of themyocardium resulting in hypertrophy and chamber dilation, and eventual CHF. Untreated defects

with large shunts will eventually result in injury to the pulmonary arterioles, vascular

obstruction, and pulmonary hypertension. The development of permanent injury to the

pulmonary vessels is a function of the duration of exposure to this excessive blood flow, andoccurs more rapidly in VSD and PDA than in ASD. If this process is not reversed, eventually the

Eisenmenger's complex of right to left shunting may occur as the elevated right-sided pressures

(pulmonary hypertension) exceed left-sided pressures.

Ventricular Septal DefectVSD is the most common form of CHD at 15-20% of all cases of isolated CHD. It may occur in

any of the following septal locations: 1) perimembranous; 2) infundibular; 3) muscular; 4) inlet.The VSD's hemodynamic impact is related to the size of the defect and can range from

insignificant to severe. Cardiac auscultation findings may include a II-III/VI harsh holosystolic

murmur along the lower left sternal border (harsher in small VSDs due to more turbulence) and a


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prominent P2 as the pulmonic valve closes later than the aortic valve. Frequently, a VSD

murmur is not heard on the day of birth since pulmonary vascular resistance and pulmonary

pressure may still be high. After birth, as the pulmonary vascular resistance decreases, the left-to-right shunt increases resulting in a new emergence or increased severity of murmur on day 2

or day 3 of life.

Smaller defects (2-4 mm) are usually asymptomatic and more likely to spontaneously close (50%

by 2 years). About 30-40% of small perimembranous and muscular defects spontaneously close

within the first six months of life. Small defects usually do not require surgery or activityrestrictions and patients are monitored with periodic follow-up. Larger defects are more likely to

be symptomatic and less likely to spontaneously close. The defect may lead to CHF, which can

manifest around six to eight weeks of age. Surgical repair may be indicated. Postoperative

complications include conduction defects, such as AV conduction abnormalities and transientright bundle branch block.

Atrial Septal Defect

ASD is a defect in the septum dividing the right and left atria. These account for 10% of all CHDand are more common in females. There are three different types based on location: 1) sinus

venosus; 2) secundum; 3) primum. Secundum defects are the most common and occur throughthe fossa ovalis. Sinus venosus defects are located near the opening of the SVC. Endocardial

cushions separate the atrioventricular valves and form the lower portion of the atrial septum and

the upper portion of the interventricular septum. Primum defects are a form of endocardial

cushion defects involving the lowest part of the atrial septum between the atrioventricular valves.These are almost always associated with abnormal development of atrioventricular valves, most

commonly a cleft mitral valve. Primum defects can be associated with Down syndrome, Ellis-

Van Creveld syndrome, and Holt-Oram syndrome. Most patients remain asymptomatic, but someindividuals can develop right atrial and ventricle dilation, leading to atrial arrhythmias and

ventricular dysfunction. Patients may have a hyperactive precordium, right ventricular heave,

fixed wide split S2, systolic ejection murmur at the second left intercostal space (increased flow

across the pulmonic valve), or a mid-diastolic murmur at the lower right sternal border(increased flow across the tricuspid valve). Flow across the ASD is low velocity and not

turbulent, so there is no audible murmur from the ASD itself.

Similar to VSDs, smaller defects are expected to spontaneously close while larger ones usually

require surgical intervention with patch closure. Cardiac dysrythmias and mitral valve prolapse

may be late sequelae of a treated or untreated ASD. Atrial flutter or fibrillation may also occur inadults with a history of atrial septal defect, regardless of the treatment.

Patent Ductus ArteriosusPDA results from retention of the fetal ductus arteriosus, which normally closes at about one to

two weeks of age. This defect accounts for 5-10% of CHD and is more common in females.

PDA is associated with coarctation of the aorta, VSD, prematurity, prenatal indomethacin

exposure, and rubella exposure during the first trimester. As pulmonary vascular resistancedecreases, blood shunts from the aorta into the pulmonary artery, resulting in increased

pulmonary artery blood flow and left atrial and ventricular overload. There is minimal blood

flow across small lesions and pressures in the right atrium and ventricle are usually normal. A


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large PDA results in pulmonary overcirculation and low aortic diastolic pressure, leading to

extensive aortic runoff and systemic end-organ hypoperfusion. Pulmonary vascular obstructive

disease may occur as early as one year of age. Clinical presentation includes bounding arterialpulses, a widened pulse pressure, an enlarged heart, a prominent apical impulse, a classic

continuous machine-like murmur at the base, and a mid-diastolic murmur at the apex. Small

defects are usually asymptomatic, while large PDAs present with recurrent pulmonary infections,CHF, and failure to thrive. Closure may occur spontaneously. Indomethacin can be used formedical closure. Some require surgical closure with placement of an embolic device, such as an

intravascular coil or PDA occluder, ligation, or division. PDA is the only CHD that is considered

surgically "cured" without long-term sequelae.

Pulmonic StenosisPS is a right ventricular outflow tract obstruction presenting as 1) valvular; 2) subvalvular; or 3)supravalvular. This defect accounts for 7-10% of all CHD. These usually are isolated lesions, but

may have bicuspid or fusion of two or more leaflets of the pulmonic valve. Obstruction leads to

right ventricular hypertrophy and eventual right ventricular dysfunction. Symptoms depend on

the pressure gradient and range from asymptomatic to right-sided congestive heart failure.Patients with mild PS are usually asymptomatic. Patients with moderate to severe PS may

present with right ventricular lift, split S2 with delay, ejection click followed by systolic murmur,heart failure, and even cyanosis in critical PS due to right-to-left shunt through a patent foramenovale.

Mild PS may be monitored while moderate to severe PS requires intervention. Newborns withsevere PS may require prostaglandin E1 infusion to keep the ductus arteriosus patent for

adequate pulmonary blood flow. Percutaneous balloon valvuloplasty to dilate the stenosis,

surgical resection of the obstructive tissue, or addition of a patch may be used. Post-operativepleural effusion can occur after alleviating right ventricle outflow obstruction.

Aortic StenosisAS is the obstruction of the left ventricle outflow tract. AS accounts for 7% of CHD and is

described by location: 1) valvular (most common); 2) subvalvular or subaortic; or 3)

supravalvular (least common, associated with Williams Syndrome). As the child grows, thecardiac output increases resulting in an increased pressure gradient across the stenosis.

Obstructed flow from the left ventricle results in increased pressure and hypertrophy. Mild AS is

usually asymptomatic with some exercise intolerance and easy fatigability. Moderate AS may

present with chest pain, dyspnea on exertion, dizziness, and syncope. Severe AS presents withweak pulses, left-sided heart failure, and chest pain and could lead to sudden death. Clinical

exam may reveal a left ventricular thrust at the apex, systolic thrill at the right base or

suprasternal notch, ejection click, or III-IV/VI systolic murmur at sternal border with radiation to

carotids.

AS can be alleviated or even appropriately treated by percutaneous balloon valvuloplasty similar

to that in PS. Surgical intervention with valvulotomy or valve replacement is indicated forsymptomatic patients with high pressure gradients across the narrowed valve. There is no activity

restriction in mild AS, but no competitive sports are allowed for moderate to severe AS. Lifelong

anticoagulation therapy is required if a prosthetic valve replacement is performed.


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Coarctation of the AortaCoarctation of the aorta accounts for 6-8% of CHD. It is a narrowing of the aorta that may occur

anywhere along its length, but 98% of cases occur distal to the left subclavian artery, where thePDA inserts into the descending aorta. Various theories have been proposed to explain this

abnormal development. One theory associates the presence of ductal tissue encircling the aorta at

the site of the coarctation suggesting a constrictive effect of the ductal tissue. Varying degrees ofaortic arch hypoplasia may coexist. In contrast to the previous lesions discussed, males are morecommonly affected than females. Children with Turner syndrome are at increased risk compared

to the general population. Other associated anomalies include a bicuspid aortic valve (85%) that

may obstruct left ventricular outflow, or an aberrant origin of the right subclavian artery distal tothe coarctation (1%).

Although present at birth, patients may be asymptomatic until childhood depending on theseverity of constriction and associated cardiac lesions. Symptoms may include shortness of

breath with exertion, leg pain with exercise, and chest pain with exercise. The classic clinical

sign is a higher blood pressure and bounding pulses in the arms, especially the right as most

defects are distal to the right subclavian artery, compared to decreased blood pressure anddiminished pulses in the legs. In the few defects occurring proximal to the right subclavian

artery, the BP and pulses of the right arm may be equal to the legs. It is useful to measure bloodpressure in both arms and at least one leg to detect blood pressure differential. Obstruction ofoutflow from the left ventricle leads to left ventricular hypertrophy. In newborns, the ductus

arteriosus usually allows for adequate lower body perfusion until it closes at its normal time.

Severe obstruction leads to hypoperfusion, acidosis, heart failure, and shock. In severe cases, aductus arteriosus patency should be maintained with a prostaglandin E1 infusion. A severe

coarctation in association with a VSD causes increased left-to-right shunting across the VSD,

leading to CHF within the first few months of life. Cardiac auscultation reveals a systolic

murmur at the left sternal border, and especially on the back between the scapulae. Chestradiography may demonstrate cardiomegaly due to left ventricular hypertrophy, inferior rib

notching due to erosion by collateral arterial circulation to bypass the obstruction, and a "reverse

3 sign" indicating the indentation of the aorta. The echocardiogram demonstrates narrowing of

the distal aortic arch. The MRI produces a clearer picture than the echocardiogram of theanatomy of the coarctation. An angiogram is sometimes necessary to clarify the presence of

associated cardiac lesions. Surgical repair is usually performed between the ages of one to two

years. Urgent surgical repair is performed in infants with circulatory shock, cardiomegaly, bloodpressure extremes or severe CHF. Rebound systemic hypertension may occur post-operatively

and should be adequately managed. One postoperative complication is the syndrome of

mesenteric arteritis, caused by reflex spasm of mesenteric arteries that are suddenly exposed to

higher pressures after the coarctation is removed. The spasm can be severe enough to result inbowel ischemia. This complication is less common now as patients are being operated on at a

younger age preventing the mesenteric arteries from prolonged exposure to low pressures.

Health MaintenanceSpecial health maintenance is indicated in patients with acyanotic CHD. Growth impairment is

directly proportional to the severity of hemodynamic disturbance. Patient with acyanotic CHDtend have more weight than height growth delay (versus both weight and height in cyanotic

CHD). Contributing factors are caloric deprivation and reduced adipose stores, lower birth


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weight, increased caloric requirements, coexisting musculoskeletal, neurologic, renal, or

gastrointestinal malformations, mild steatorrhea, and excess protein loss. Up 10% of individuals

may have genetic syndromes. Poor nutrition results from anorexia, fatigability, vomiting, fluidrestriction, and frequent respiratory infections. Cardiac drugs (i.e., diuretics) may exacerbate

anorexia and cause early satiety. Systemic and respiratory illnesses can increase the body

temperature and raise the metabolic rate by up to 13% for each degree centigrade above normal.Hypertrophic cardiac muscle can account for up to 30% of total oxygen consumption comparedto the usual 10%. The caloric intake for catch-up growth is estimated at 140 to 200 calories per

kg per day. In infants unable to gain sufficient weight with breastfeeding, supplementation can

be achieved with a higher caloric density formula or tube feedings. In most patients, catch-upgrowth is largely complete within six to 12 months of surgery. The CDC (Centers for Disease

Control) recommends that the routine immunization schedule should be followed with some

exceptions: 1) Varicella and MMR (measles, mumps, and rubella) vaccines are indicated at 12

months of age rather than at 15 months; 2) Polyvalent pneumococcal vaccine (the pneumococcalvaccine usually used in adults) is recommended at two years of age (this is in addition to

pneumococcal conjugate vaccine give at 2, 4, 6, and 12 to 15 months); and 3) Influenza vaccine

should be given yearly beginning at age six months in this higher-risk population. Prophylaxisagainst bacterial endocarditis should be instituted in patients undergoing certain procedures. In

2007, the American Heart Association (AHA) released the most recent revision of the 1997

guideline on infective endocarditis prophylaxis. The new guidelines advise prophylaxis for

conditions that are associated with the highest risk for adverse outcomes secondary to infectiveendocarditis. These conditions include: 1) prosthetic cardiac valve or prosthetic material used for

valve repair, 2) previous infective endocarditis, 3) unrepaired cyanotic CHD (including palliative

shunts and conduits), 4) completely repaired CHD with prosthetic material or device, whetherplaced by surgery or by catheter intervention, during the first six months after the procedure as

endothelization of prosthetic material usually occurs during that time period, 5) repaired CHD

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

(which inhibit endotheliazation) and 6) cardiac transplant recipients who develop cardiacvalvulopathy. Antibiotic prophylaxis is no longer recommended for any other form of CHD other

than those listed above.

Questions

1. True/False: Congenital heart disease is always detectable at birth.

2. True/False: Equal blood pressures in the right arm and left leg rule out the diagnosis of

coarctation of the aorta.

3. Name the three most common acyanotic congenital heart lesions?

4. True/False: The presence of palpable femoral pulses rules out the diagnosis of aortic

coarctation.


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5. Explain how a child with an isolated VSD (classified as an acyanotic lesion) could become

cyanotic?

6. True/False: Medical students and residents will typically not hear the murmur of a VSD during

the initial newborn assessment in the nursery because the murmur of a VSD is subtle and low

pitched.

References

1. Hoffmann JI, Kaplan S. The incidence of congenital heart disease. J Am Coll Cardiol

2002;39:1890-1900.

2. Kliegman RM, Behrman RE, Jenson HB, Stanton BF. Nelson Textbook of Pediatrics, 18th ed.

2007, Saunders.

3. Miyague NI, Cardoso SM, Meyer F, et al. Epidemiological study of congenital heart defects in

children and adolescents. Analysis of 4,538 cases. Arq Bras Cardiol 2003;80:274-278.

4. Norton ME. Teratogen Update: Fetal Effects of Indomethacin Administration During

Pregnancy. Teratology 1997;56:282-292.

5. Silberbach M, Hannon D. Presentation of Congenital Heart Disease in the Neonate and Young

Infant. Pediatr Rev 2007;28:123-131.

6. Suarez VR, Thompson LL, Jain V, et al. The effect of in utero exposure to Indomethacin on

the need for surgical closure of a patent ductus arteriosus in the neonate. Am J Obstet Gynecol2002;187:886-888.

7. Wilson W, Taubert KA, Gewitz M, et al. Prevention of Infective Endocarditis: GuidelinesFrom the American Heart Association: A Guideline From the AHA Rheumatic Fever,

Endocarditis, and Kawasaki Disease Committee. Circulation 2007;116:1736-1754.

8. Centers for Disease Control and Prevention. Birth-18 Years and Catch-up Immunization

Schedules. http://www.cdc.gov/vaccines/schedules/hcp/child-adolescent.html. US 2013.

Answers to questions

1. False. The physiologic pulmonary hypertension present in a newborn can prevent blood flow

across a septal defect or PDA. These can be detected several hours after birth or several daysafter birth. Other congenital heart disease lesions may remain occult for a longer period of time.


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2. False. An aberrant right subclavian artery originating below a coarctation will produce equal

pressures in the right arm and leg.

3. VSD, ASD, PDA. Of these, VSD is the most common.

4. False. Development of collateral vessels to the lower body can produce palpable femoralpulses.

5. Congestive heart failure and pulmonary edema may cause hypoxia. If the hypoxia is severe

enough, visible cyanosis will result, although this can be overcome with oxygen and other

treatments for pulmonary edema and congestive heart failure. A second mechanism is that longstanding excessive pulmonary blood flow leads to pulmonary hypertension and Eisenmenger's

complex, right to left shunting and cyanosis.

6. False. They cannot hear the murmur of a VSD on day 1 because on day 1, pulmonary vascularresistance is still high, which restricts left to right flow through the VSD. On day 2, pulmonary

vascular resistance is lower, so left to right shunting through the VSD increases making themurmur louder.

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