Approach To Acyanotic Congenital Heart Lesions

Sushila Dhaon

Acyanotic congenital heart lesions can be classified depending on the physiologic load they place on the heart as shown in box below:

L -R shunts and obstruction to ventricular outflow are more common and their clinical manifestations and management is given in brief.

Atrial Septal Defect (ASD)

5-10% of all CHD; three types of ASD exist.

1. Ostium secondum defect: Commonest defect 50-70% of all ASDs ;defect is present at the site of fossa-ovalis, allowing shunting of blood from LA to RA.
2. Ostium primum ;30% of all ASDs due to endocardial cushion defect.
3. Sinus venosus defect - 10% of all ASD mostly located at the entry of SVC in to RA.

Clinical Manifestations

Infants and children with ASD are usually asymptomatic and murmur may have been detected during school health examination. Mild symptoms like palpitation on exertion, dyspnoea, fatigue may be present in older children. Rarely an infant with isolated ASDmay have growth failure, recurrent chest infections congestive heart failure and pulmonary hypertension.

Physical Examination
Hyperactive impulse, mild para sternal lift and a wide- fixed second heart sound. There is grade 2-3/6 ejection systolic murmur. With a large L-R shunt a mid-diastolic rumble at lower left sternal border resulting from relative tricuspid stenosis may be heard.

ECG shows right axis deviation of + 90 to + 180 degrees. Right ventricular hypertrophy (RVH) and Right Bundle Branch block (RBBB) pattern in VI are typical. In cases with primum ASD; left axis deviation may be seen.

X-ray Studies

1. Cardiomegaly with right atrial and right ventricular enlargement.
2. Prominent pulmonary artery may be seen due to increased pulmonary blood flow with plethora.

Echo Cardiography
2-D Echo-cardiograph is diagnostic. It shows dilated right atrium and ventricle. The position of the defect can be seen in subcostal and four chamber view. Colour flow mapping shows the flow across the defect.

Sinus venosus type of ASD may be difficult to profile and may require trans-oesophageal echocardiography. Cardiac catheterization is generally not needed.

Management
In ASD less than 3 mm, spontaneous closure occurs in 100% before one and a half years of age. Most of the children remain active and asymptomatic. No exercise restriction is indicated.

CHF - may rarely develop during infancy, and should be treated urgently because of possibility of spontaneous closure. Non surgical closure is indicated in uncomplicated and smaller defects by clampshell or buttoned devices.

Ventricular Septal Defects (VSD)

VSD is the commonest (20%) of congenital cardiac defects. It may be single or multiple. The site of VSD is used to classify tube defects.

1. Perimembranous (most common)
2. Muscular : Inlet (Beneath the pulmonary valve inlet) Trabecular septum: Central, Marginal, apical Outlet - infundibular.

Clinical Manifestations vary according to the size of VSD

1. Small VSD asymptomatic and growth is normal. Child is acyanotic.
2. Moderate to large VSD
   1. Repeated pulmonary infection - tachypnea, poor weight gain and CHF.
   2. Decreased exercise tolerance.
   3. failure to thrive
   4. Reversal of shunt may cause

Pulm hypertension, cyanosis and level of activity decrease, clubbing, respiratory distress. S1 and S2 well heard - P2 may be single and loud in presence of PAH. Pansystolic murmur 3-5/6 is heard at left sternal border. Apical diastolic murmur is also present in large shunt.

ECG
Moderate size VSD: LVH with or without LAH
Large VSD : combined ventricular hypertrophy. Eisenmenger's complex : RVH.

X-ray studies

1. Cardiomegaly of varying degrees depending on the size of VSD and magnitude of L-R shunt.
2. When reversal of shunt takes place - PA enlarges and lung fields become oligemic.

Echo Cardiography
Can identify the number, size, exact location of defect estimate PA pressure by using modified Bernuoulli-equation and magnitude of the shunt.

Management

1. Spontaneous closure in 30-40% of cases with membranous and muscular small VSDs.
   1. No exercise restriction in the absence of pulmonary hypertension.
   2. Good dental hygiene and antibiotic prophylaxis against infective endocarditis is very important.
   3. Treatment of CHF -It usually develops after 8 weeks of age. Poor feeding, sweating, easy fatiguability tachypnoea, leading on to failure to thrive. To be treated with decongestive therapy - Digoxin and Diuretics, and ACE inhibitors if necessary.
   4. High caloric diet with correction of anemia by iron therapy or blood transfusion.
   5. Umbrella closure of selected muscular defects is possible - but still not established.

Patent Ductus Arteriosus (PDA)

5-10% of all CHDs, excluding infants ;more common in females than males 1:3. There is persistance of normal fetal structure between LPA (left pulmonary artery) and Descending aorta 5-10 mm distal to the origin of the left sub clavian artery.

Clinical Manifestations
When ductus is small - Asymptomatic.
Large shunt PDA: tachypnoea, hyperdynamic circulation and poor weight gain may be associated with repeated chest infection and CHF.

Physical Examination
Hyperactive precordium with a systolic thrill at the upper left sternal border. Bounding peripheral pulses with wide pulse pressure and other features of hyperdynamic circulation.

P2 loud in presence of pulmonary hypertension : Loud and harsh 4/6 continuous machinery murmur best heard at left -infraclavicular area.

ECG

• Small to moderate PDA - normal or LVH
• Large PDA - combined ventricular hypertrophy.
• Reversal of shunt - RVH

X-ray

• Small PDA: normal x-ray
• Large PDA: Cardiomegaly with enlargement of left atrium (LA) Left ventricle (LV) and ascending aorta.

Echo

2D Echo in high parasternal or susprasternal view to image PDA.

Management

• PDA in premature infants: small flow across duct may produce no problems. spontaneous closure ocurres usually.
• Large flow; may present with tachypnoea.
• Tachycardia and carbon dioxide retention. Typical continuous murmur is often missing.
• Echo Doppler is diagnostic.
• Decongestion with digoxin and diuretic is needed in cases with CHF.
• Oral or IV Indomethacin 0.1 -0.2 mg/kg/dose 12 hrly for a total of 3 doses is used to close the duct.

Success rate is high. Urine output to be watched as the drug is nephrotoxic. Surgery indicated if drug has failed. Recently small duct is being closed nonsurgically using coils or devices delivered through catheter.

Large PDA

It is important to look for evidence of associated coarctation of aorta in all these cases. In cases of isolated PDA - surgical closure is performed anytime between 6 mth- 2 yr. Ligation and division through left posterolateral thoracotomy without cardiopulmonary bypass is a safe procedure with less than 1% mortality. Indomethacin is not useful to close ductus in term babies.

Atrioventricular Septal Defects

This defect also called endocardial cushion defect is uncommon. Association with Down's Syndrome is well established. Clinical manifestation - usually in early infancy with congestive heart failure; growth failure and feeding difficulties.

Pulmonary Stenosis 8-12% of all CHDs
It may be: Pulmonary valve is thickened.
Valvular

• Subvalvular Infundibular) Rare
• Supravalvular - stenosis of the main PA seen with Rubella. Syndrome and William's syndrome

Clinical Manifestations

1. Children with mild PS are asymptomatic.
2. Exertional dyspnoea and fatiquability may be present in patients with moderately severe cases.
3. Heart failure and exertional chest pain may develop in severe cases.

Physical Examination
Most patients are acyanotic and well-developed. Right ventricular tap and a systolic thrill may be present at the ULSB and occasionally SSN.

A systolic ejection click is present with valvular stenosis at ULSB. S2 may be split widely and P2 may diminish in intensity; systolic ejection murmur (Grade 2-5/6) is best audible at the ULSB .The louder and longer the murmur, the more severe the stenosis.

ECG
Normal in mild cases. RAD and RVH is present in moderate PS. The degree of RVH correlates with the severity of PS ( R wave in V1) 20 mm is usually associated with systemic presssure in RV).
Neonates with critical PS are cyanosed and tachypneic due to R-L flow through P.F.O.

X-Ray Studies

Heart size is usually normal, Main pulmonary artery segment (MPA) is prominent , cardiomegaly is present if CHF is present. PVM are usually normal but may decrease with severe PS.

Echocardiography

2D echo in parasternal short axis view shows thick pulmonary valve cusps with domming; size of pulmonary valve annulus can be estimated. MPA is often dilated. Doppler study can estimate, pressure gradient.

Management: Medical

• Restriction of activity is not necessary except in patients with severe PS.
• Antibiotic prophylaxis against SBE should be observed when indicated.
• Balloon valvuloplasty is performed with success and preferred than surgical repair.

Aortic Stenosis

3-6% of all CHDs; M:F - 4:1
Stenosis may be: valvular, subvalvular, supravalvular.

Clinical Manifestations
Most children with mild to moderate AS are asymptomatic. Exertional exercise intolerance and chest pain, fatiguability or syncope may be present in severe degree of obstruction.

Physical Examination

Patients are acyanotic and develop normally.
Blood pressure in normal is most patients but narrow pulse pressure is present in severe AS. Patients with supravalvular AS may show higher systolic pressure in the right arm than in the left.

• A systolic thrill may be palpable at the UPSB, in SSN or over carotid arteries.
• Ejection click may be heard with valvular AS. S2 may be split normally or a bit narrowly
• Harsh SEM 2-4/6 best heard at the neck, and apex.
• High pitched early diastolic decrescendo murmur may be heard due to AR

Peculiar elfin facies and mental retardation may be associated with supravalvular AS.

EEG

Mild cases - ECG normal
Severe cases - LVH with strain pattern.

X-ray
Heart size is usually normal. Dilated ascending aorta or prominent aortic knob may be seen in valvular AS.

Echocardiography
Echocardiography identifies the site and severity of obstruction. Doppler studies determine the peak and mean systolic left ventricular outflow track gradients .2D echo shows LVH, the thickened and domed aortic valve, the number of valve leaflets and subaortic or supraortic membrane.

Management - Medical
Maintenance of good oral hygiene and antibiotic prophylaxis against bacterial endocarditis is important for patients.
Children with moderate to severe AS should not perform strenous exercise.
Per cutaneous balloon valvuloplasty may be tried with some success.

Serial Echo doppler ultrasound evaluation is needed every 2 years in asymptomatic children with mild to moderate stenosis, and more often in children with severe stenosis.

Coarctation Of Aorta (COA)

8-10% of all CHDs M:F 2:1

Clinical Manifestations
Poor feeding, dyspnoea, and poor weight gain or signs of acute circulation shock develop in first 6 weeks of life. Infants with COA are pale, acidemic. Differential cyanosis may be present because of Rt to Lt ductal shunt. Peripheral pulses may be weak and thready.

S₂ is single and loud, a loud S3 gallop is usually present. No heart murmur is present in 50% of sick infants. A non specific ESM may be audible over precordium.

ECG
Normal or rightward QRS axis and RVH or BBB are present in most infants.

X-ray Studies
Marked cardiomegaly and pulmonary oedema or pulmonary venous congestion are present.

Echocardiography
Shows the site and extent of the coarctation.

Management - Medical

1. During the 1st week of life, prostaglandin E1 infusion to be started to reopen the ductus arteriosus
2. Intensive decongestive measure with short acting inotropic agents, diuretics and oxygen to be started.
3. Balloon angioplasty is a useful procedure in sick infants in whom standard procedure carries high risk.

References

1. IAP Text Book of Pediatrics, 1999, Jaypee Brothers Medical Publishers (P) Ltd., New Delhi.
2. Pediatric Cardiology for Practitioners, Third Edition, 1996. Myung Park. Mosby A Time Mirror company USA.
3. Nelson Text Book of Pediatrics, 16th Edition, 2000.
4. Saxena Anita - Common Left to Right Shunts in Children : Evaluation, Management and Timing of Surgery, IAP Journal Pediatrics Vol.5, No.2, 1997.