Ghai Essential Pediatrics8th

reduction in pulmonary blood flow. Pink TOF is typically associated with a loud ejection systolic murmur because of a reasonable volume of blood flowing across the RVOT. As the severity of PS increases, pulmonary blood flow declines and the intensity of murmur declines progressively. Identical symptoms and physical findings are present in (i) complete transposition of great arteries with VSD and pulmonic stenosis, (ii) double outlet right ventricle with pulmonic stenosis and a large subaortic VSD, (iii) tricuspid atresia with diminished pulmonary blood flow, (iv) single ventricle with pulmonic stenosis, and (v) corrected transposition of great arteries with VSD and pulmonic stenosis.

Single ventricle physiology This refers to a group of conditions where there is complete mixing of pulmonary andsystemicvenousreturns. Inadditiontosingleventricle (doubleinletventricle),a varietyofconditionscomeunder thecategoryofsingleventricularphysiology.Atresiaofone oftheAV valves, severe hypoplasiaof oneoftheventricles, severe straddling of one of the AV valves over a large VSD are all examples of situations where there is mixing of pulmonary and systemic venous returns. The clinical manifestations are dictated by the whether or not there is PS. In absence of PS, there is excessive pulmonary flow especially in infants because of the relatively lower pulmonary vascular resistance. The proportion of oxygenated blood frompulmonary veins that mixes with thesystemicvenousreturn ishigh.Cyanosisisminimaland measured oxygen saturation may be in the 90s. However, the price for preserved oxygenation is heart failure and permanent elevation of pulmonary vascular resistance (pulmonary vascular obstructive disease or PVOD). If the child survives infancy, pulmonary vascular resistance progressively increases with increasing cyanosis.

Single ventricle and its physiologic variants can be associated with varying degrees of PS. The features are similar to VSD-PS physiology except for relatively severe hypoxiabecause of free mixingof systemic and pulmonary venous return.

Palliative operations are the only option for the large number of conditions that come under the category of single ventricle physiology. Single ventricle palliation is done instages. The final procedure is the Fontan operation that allows separation of systemic venous return from pulmonary venous return thereby, eliminating cyanosis.

Duct dependent lesions An infant or a newborn with CHD that is dependent on the patency of the ductus­ arteriosus for survival can be termed as having a duct dependentlesion. These are newbornswhere the systemic blood supply is critically dependent on an openPDA (duct dependent systemic circulation, DDSC) or pulmonary bloodflow is duct dependent (ductdependent pulmonary circulation, DDPC). Closure of the PDA in DDSC results in systemic hypoperfusion (often mistaken as neonatal sepsis), as in hypoplastic left heart syndrome where the

Disorders of Cardiovascular System

entire systemic circulation is supported by the right ventricle through the PDA and interrupted aortic arch where the descending aortic flow is entirely through the PDA. Severecoarctation andcriticalaorticstenosis arealso examples of DDSC. Closure of PDA in DDPC results in severe hypoxia and cyanosis in neonates; examples include all forms of pulmonary atresia (irrespective of underlying heart defect) where the PDA is the predominant source of pulmonary blood flow. Patients with pulmonary atresia, where pulmonary blood supply is from major aorto-pulmonary collaterals, may survive even after the PDA closes. Critical PS can present as duct dependent pulmonary blood flow. Newborns with severe Ebstein anomaly can also present as DDPC (physiologic pulmonary atresia) even though the pulmonary valve is anatomically normal because of inability of the right ventricle to function effectively.

Neonates with duct dependent physiology require prostaglandin El (PGEl) for survival. Early recognition of a duct dependent situation allows early initiation of PGEl and stabilization until definitive procedure is accomplished.

Unfavorable streaming and parallel circulation

Unfavorable streaming refers to a situationwhereoxygen rich pulmonary blood flow is directed towards the pul­ monary valve and poorly oxygenated blood towards the aortic valve. The best example of unfavorable streaming is the parallel circulation in transposition of great arteries (TGA) with intact ventricular septum. Here survival is dependent of the presence of a communication (ideally at atrial level)thatallows mixing of pulmonary and systemic venous return. The presence of a VSD may improve the situation in TGA but significantcyanosisisusuallypresent unless the pulmonary blood flow is torrential.

Recognition and Diagnostic Approach

While it is often easy to recognize the presence of CHD in older children, manifestations of heart disease can often be subtle in newborns and young infants. Conditions that do not primarily involve the cardiovascular system can result in clinical manifestations that overlap with those resulting from CHD in the newborn. Nonetheless, careful clinical evaluation is often rewarding and allows identificationofCHDinmost infants and many newborns. The following clinical features should alert the paediatrician regarding the presence of CHD.

Cyanosis. Parentsseldomreportcyanosisunlessitisrelatively severe (saturation <80%). Itis often easier forthemto notice episodic cyanosis (when the child cries or exerts).

Difficult feeding and poor growth. The parent of an infant with CHD may complain that the child has difficulty with feeds. This isusually afeature ofan infant with congestive heart failure resulting from CHD. The history may be of slow feeding, small volumes consumed during each feed,

tiring easily following feeds and requirement of periods of rest during feeds. Excessive sweating involving forehead or occiput is commonly associated. Not infrequently, no history of feeding difficulty may be obtained, butexamination of the growth chartswillreveal that the child's growth rate is not appropriate for age. A recent decline in growth rate (falling off the growth curve) or weight that is inappropriate for age (<5th centile) may result from a large left to right shunt. Characteristically, growth retardation affects weight more that height.

Difficult breathing. Tachypnea (respiratory rates more than 60/min in infants <2 months; >50/min in older infants; >40/min after 1 yr) is a characteristic manifestation of heart failure in newborns. For infants, subcostal or intercostal retractions together with flaring of nostrils are frequently associated with tachypnea.

Frequent respiratory infections. The association of respiratory infections that are frequent, severe and difficult to treat with large left to right shunts is not a specific feature.

Specific syndromes. Thepresenceof chromosomal anomalies or other syndromes that are associated with CHD should alertthe clinician to thepresenceofspecificcardiac defects. Trisomy 21 is the commonest anomaly associated with heart disease; others include trisomy 13 and 18, Turner and Noonan syndromes, and velocardiofacial and Di George syndromes (Table 15.7).

Nadas' Criteria

The assessment for presence of heart disease can be done using the Nadas' criteria. Presence of one major or two minor criteria are essential for indicating the presence of heart disease (Table 15.11). It is important to recognize that these criteria are of limited use in newborns, where clinical signs are subtle.

Major criteria

(i) Systolicmurmur grade III or more in intensity. A pansystolic murmur is always abnormal no matter what is its intensity. There are only three lesions that produce a pansystolic murmur, and these are (a) VSD, (b) mitral regurgitation and (c) tricuspid regurgitation. An ejection systolic murmur may be due to an organic cause or it may be functional. An ejection systolic murmur associated with a thrill is an organic murmur. Grade III ejection systolic murmur of a

Table 15.11: Nadas' criteria for clinical diagnosis of congenital heart disease

Major Minor

Systolic murmur grade III Systolic murmur grade I or II

functional type may be heard in anemia or high fever especially in small children.

A number of children around the age of 5 yr may have a soft ejection systolic murmur. If it is accompaniedwith a normal second sound then it is unlikely to be significant. Before discarding a murmur as of no significance, it is necessary to obtain an electrocardiogram, and a thoracic roentgenogram. If they are also normal, one can exclude heart disease, but at least one more evaluation after six months is essential.

(ii)Diastolic murmur. The presence of a diastolic murmur almost always indicates the presence of organic heart disease.

(iii)Central cyanosis. Central cyanosis suggests that either unoxygenated blood is entering the systemic circulation through a right to left shunt or the blood passing through the lungs is not getting fully oxygenated. The oxygen saturation of the arterial blood is less than normal, the normal being around 98%. If the blood is not getting fully oxygenated in the lungs, it is called pulmonary venous desaturation and indicates severe lung disease. Cyanosis due to a right to left cardiac shunt indicates presence of heart disease. Central cyanosis is present in fingers and toes as well as in the mucous membranes of mouth and tongue. It results in polycythemia and clubbing.

Peripheralcyanosisdoesnotimply the presence ofheart disease. Peripheral cyanosis is the result of increased oxygen extractionfrom the blood by the tissues. It is seen in fingers and toes but not in mucous membrane of mouth and tongue. Thearterialoxygensaturationis normal. Presence of central cyanosis always indicates presence of CHD if lung disease has been excluded. However, cyanosis that is obvious clinically usually results from significant desaturation (typically <85%). Poorlighting, anemia, dark skin complexion may further mask hypoxia. Routine use of the pulse oximeter allows detection of milder forms of hypoxia. Saturations of 95% or lower while breathing room air are abnormal.

(iv) Congestive cardiac failure. Presence of congestive cardiac failure indicates heart disease except in neonates and infants, who might show cardiac failure due to extra­ cardiac causes, including anemia and hypoglycemia.

Minor criteria

(i)Systolic murmur less tlzan grade III. It is emphasized that soft, less than grade three murmurs by themselves do not exclude heart disease.

(ii)Abnormal second sound. Abnormalities of the second sound always indicate presence of heart disease. It has been included as a minor criterion only because auscultation is an individual and subjective finding.

(iii)Abnonnal electrocardiogram. Electrocardiogram is used to determine the mean QRS axis, right or left atrial hypertrophy and right or left ventricular hypertrophy.

Criteriaforventricularhypertrophy, based only on voltage criteria are not diagnostic for the presence of heart disease. The voltage of the QRS complexes can be affected by changes in blood viscosity, electrolyte imbalance, position of the electrode on the chest wall and thickness of the chest wall.

(iv) Abnormal X-ray. The reason for considering abnormal X-ray as a minorcriterionis twofold. In infants andsmaller children, the heart size varies considerably in expiration and inspiration. If there is cardiomegaly on a good inspiratory film, it suggests presence of heart disease. The second reason is the presence of thymus in children up to the age of two years, which might mimic cardiomegaly. Fluoroscopy is helpful in separating the shadow of the thymus from the heart.

(v) Abnormal blood pressure. It is difficult to obtain accurate blood pressure in smaller children. It is important to use appropriate sized cuffs while measuring blood pressure.

Diagnostic Implications of

the Second Heart Sound

Auscultation of the heart provides important diagnostic information. Of the various heart sounds and murmurs the most important is the assessment of the second heart sound (Fig. 15.5). The normal second heart sound can be described in three parts:

1.Has two components: aortic closure sound (A2) and pulmonary closure sound (P2).

ii. During quiet breathing both the components are

Second Heart Sound

Fig. 15.5: Second sound (S2): The relationship of aortic (A2) and pulmonic component (P2) in inspiration and expiration. Single S2 means that it may be either A2 or P2 or a combination of both

Disorders of Cardiovascular System

superimposed on each other during expiration, thus only a single second sound is heard. During inspiration, the aortic component comes early whereas the pulmonary component is delayed, resulting in a splitting of the second sound in which the A2 precedes the P2.

iii.The aortic component is louder than the pulmonary component, except in infants below 3-6 months old.

When we say that the second sound is normal, it is in context of the above three aspects. Abnormalities of the second sound might occur in each of these aspects.

Abnormalities of Aortic Component of the Second Sound

The A2 may be accentuated or diminished in intensity. It can also occur early or late in timing. The A2 is accentuated in systemic hypertension from any cause and in AR, and diminished or may be absent when the aortic valve is immobile because of fibrosis or calcification or if absent, as in aortic valve atresia.

The A2 is delayed when the left ventricular ejection is prolonged as in aortic valvar or subvalvar stenosis, patent ductus arteriosus with a large left to right shunt, AR, left bundle branch block and left ventricular failure. The A2 occurs early in VSD, mitral regurgitation and constrictive pericarditis.

Abnormalities of Pu/manic Component of the Second Sound

The P2 may be accentuated or diminished in intensity or delayed in timing. Although it may be occurring early in tricuspid regurgitation, it is not recognized as such on the bedside since tricuspid regurgitation as an isolated lesion (without pulmonary arterial hypertension) is rare. Accentuated P2 is present in pulmonary arterial hyper­ tension from any cause. The P2 is diminished in intensity in pulmonic stenosis. It is absent when the pulmonary valve is absent as in pulmonary valvar atresia. The P2 is delayed in pulmonic stenosis, atrial septal defect, right bundle branch block, total anomalouspulmonary venous connection and type A WPW syndrome.

Abnormalities in Splitting of the Second Sound (S2)

As indicatedabove the normalS2 is single (or closely split, <0.03 sec) in expiration and split in inspiration with the louder A2 preceding P2. Wide splitting of the second sound is defined as splitting during expiration due to an early A2 or late P2 or the A2-P2 interval 0.03 sec or more during expiration. If the interval increases during inspiration, it is called wide variable splitting, but if it is the same in expiration andinspiration it is defined as widely split and fixed second sound. Wide and variablesplitting of52 is seen in pulmonic stenosis, mitral regurgitation and VSD. In pulmonic stenosis it is due to a delay in P2 whereas in mitral regurgitation and VSD it is due to an early A2. Wide and fixed splitting of the S2 occurs in atrial septal defect,

right bundle branch block and total anomalouspulmonary venous connection and is due to a delay in P2.

The delay in A2 results in closely split, single or paradoxically split S2. In paradoxically split S2, the split is wide in expiration but narrows during inspiration (Fig. 15.5). A single second sound means that it is either A2 or P2 or a combination. The decision whether it is aortic or pulmonic or a combination, depends not on thelocation or intensity of the single second sound, but on the clinical profile. In tetralogy of Fallot only a single S2 is heard and it is the A2 since the pulmonic component is delayed and so soft that it is inaudible. In VSO with pulmonary arterial hypertension and right to left shunt (Eisenmenger complex) again a single S2 is heard and represents a combination of A2 and P2. While based on auscultation alone, it might be difficult to differentiate between tetralogy of Fallot andEisenmenger complex, the history and thoracic roentgenogram can easily distinguish

between theseconditions. Thus, the interpretationof single second sound is not dependent on auscultation alone.

Imaging Studies

Echocardiography (Fig. 15.6) Echocardiography has revolutionised the diagnosis of CHO and its high diagnostic yield makes this investigation cost effective. This isparticularly truefor infantsand newborns in whom excellent images are readily obtained. Transesophageal echocardiography can supplement transthoracic studies.

Cardiac magnetic resonance imaging Cardiac magnetic resonance imaging is an important modality for evaluation of CHO, especially in older patients and for postoperative evaluation. Magnetic resonance imaging can also define extracardiac structures such as branch pulmonaryarteries, pulmonary veinsandaortopulmonary collaterals. Very useful physiologic data (especially blood

substantial, especially after 10-20 yr followup. These include the Senning operations (atrial switch) for trans­ position where the right ventricle continues to support thesystemic circulation, TOFrepairwherethepulmonary valve is rendered incompetent through a transannular patch and operations that require theplacement of a right ventricle to pulmonary artery conduit. Corrective surgeries associated with excellent longterm survival include the arterial switch operations, repair of total anomalous pulmonary venous connectionandcoarctation.

Surgery for single ventricle physiology This category

includes all anatomic examples of single ventricle. In addition, this includes situations when oneatrioventricular valve is atretic or one of the ventricles is hypoplastic. The surgical management of single ventricle physiology is performed in stages. The first stage involves early pulmonary arterial band (usually under the age of 3 months)forpatientswho have increasedpulmonary blood flow and themodified Blalock-Taussig shunt for those who have reduced pulmonary blood flow with cyanosis. The second operation is the bidirectional Glen shunt. The superior vena cava is anastomosed to the right pulmonary artery. This operation allows effective palliation until the age of 4-6 yr. The Fontan operation is finally required for elimination of cyanosis. All the systemic venous return is routed to the pulmonary artery. Several requirements

shouldbe fulfilled beforethisoperation can be successfull; undertaken. This is a palliative procedure and there an important longterm issues in a substantial proportion 01 the survivors.

Catheter Interventions

Catheter interventions are possible in many patients with CHD. Many simple defects such as secundum ASD, PDA and selected muscular VSD can now be closed in the catherization laboratory. Additionally, balloon valvo­ tomy is now the first line of treatment for congenital stenosis of the pulmonary and aortic valves. Additional details of catheter intervention procedures are shown in Table 15.12. Catheter-based interventions are far less traumatic than surgery, accomplished with ease and allow rapid recovery.

Complications of Congenital Heart Disease

A number of complications occur in patients with CHD.

Pulmonary arterial hypertension (PAH) Lesions that

have the greatest likelihood of developing PAH include cyanotic heart disease with increased pulmonary blood flow. Here irreversible changes in pulmonary vasculature develops rapidly often during infancy. It is particularly important to correct or appropriately palliate these lesions early (ideally within the first few months of life). Large

acyanotic post-tricuspid shunts are also prone to early development of PAH and should be ideally corrected early, preferably within the first year. In pre-tricuspid shunts, PAH develops slowly and unpredictably. While most patients with ASD will have mild or no PAH throughout their lives, a small proportion develop acce­ lerated changes in the pulmonary vasculature. Some of the key features associated with the development of PAH include: large size of the defect; presence of pulmonary venous hypertension; airway obstruction or syndromic association, (e.g. trisomy 21); prolonged duration of expo­ sure to increased pulmonary blood flow; and residence at high altitude.

Infective endocarditis or endarteritis (IE) Endocarditis can complicate CHD, especially in patients with significant turbulence created by high-pressure gradients, e.g. restric­ tive VSD and PDA, tetralogy of Fallot, and left ventricular outflow tract obstruction. Some surgical operations (such as the Blalock-Taussig shunt) are also associated with increased risk of IE or endarteritis. Lesions with little or no turbulent flows, such as ASD are not associated with increased risk. The risk of endocarditis increases after dentition, hence the importance of good dental hygiene in patients with CHD cannot be over emphasized.

Growth andnutrition This is affected in all forms of CHD and is particularly striking in large left to right shunts. Children with CHD show high prevalence of malnutrition, which improves after correction of the underlying condition. Catch up growth is slow if CHDis corrected late.

Myocardial dysfunction Chronic volume overload results in ventricular enlargement and ventricular dysfunction that is typically reversed after correction. A small proportion of patients with severe hypoxia also develop severe dysfunction involving both ventricles. Heart failure is mostly the result of hemodynamic consequences of increased pulmonary blood flow, mitral or tricuspid valve regurgitation and severe myocardial hypertrophy. Systolic dysfunction is a relatively less common cause.

Neurologic and neurodevelopmental conse­ quences Chronic hypoxia, in utero hypoxia and hypo­

perfusion and open-heart surgery contribute substantially to morbidity. Brain abscess is uniquely associated with cyanotic heart disease (typically beyond the age of 2 yr) where the right to left shunt bypasses the pulmonary filter. Polycythemia Older children with cyanotic CHD are prone to complications from a chronically elevated red cell turnover. These include symptoms of hyperviscosity, gout, renal failure and gall stones.

Rhythm disorders and sudden death Chronic enlarge­ ment of heart chambers predispose to tachyarrhythmia. Chronic right atrial enlargement (such as atrial septal defect, Ebstein syndrome, severe tricuspid regurgitation)

Disorders of Cardiovascular System -

predisposes to atrial flutter, which might be persistent and refractory. Chronic right ventricular enlargement pre­ disposes to ventricular tachycardia and may precipitate suddencardiacarrest. This is a significant longterm concern after TOP repair where the pulmonary valve is rendered incompetent. Similarly left ventricular hypertrophy and dysfunction are associated with high risk of ventricular tachycardia.

Cyanotic spells Patients with the VSD-PS physiology are prone to cyanotic spells. Cyanotic spells are due to an acute decrease in pulmonary blood flow, increased right to left shunt and systemic desaturation due to (i) Infundibular spasm due to increase in circulating catecholamines, during feeding or crying; (ii) Activation of mechano­ receptors in right ventricle (due to decrease in systemic venous return) or in left ventricle (due to decrease in pulmonary blood flow), leads to peripheral vasodilatation and fall in systemic vascular resistance producing increased right to left shunt and systemic desaturation.

A cyanotic spell is an emergency, which requires prompt recognition and intervention to prevent disabling cerebrovascular insults or death. The spell needs to be taken seriously not just because of the immediate threat but also because it indicates the need for early operation. It is commonly seen below 2 yr (peaks between 2 and 6 months). The onset is spontaneous and unpredictable and occurs more often in early morning, although it can occur at anytime in the day. The infant cries incessantly, is irritable and inconsolable. Tachypnea is prominent feature; there is deep and rapid breathing without significant subcostal recession. Cyanosis deepens as the spell progresses. Later gasping respiration and apnea ensues, which leads to limpness andultimatelyanoxic seizures. Spells can last from minutes to hours. Auscultation reveals softening or dis­ appearance of pulmonary ejection murmur. The manage­ ment is summarized in Table 15.13.

Natural History

Some defects have a tendency towards spontaneous closure and this can influence the timing of intervention. The defects known to close spontaneously are atrial and ventricular septal defects, and patent ductus arteriosus. The variables influencing the likelihood of spontaneous closure include: age at evaluation (lower likelihood of closure with increasing age), size of the defect (smaller defects more likely to close) and location of the defects (fossa ovalis ASD and perimembranous and muscular VSDs can close on their own) (Table 15.14).

A review of natural history of common forms of CHD shows that without correction, many children with CHD (especially those with cyanotic CHD) will not survive beyond early childhood. The outcomes are improved by correction through surgery and, in some situations, through catheter interventions. Despite curative surgery, some patients have important longterm sequelae. For example, patients with tetralogy of Fallot who have

Table 15.13: Management of hypercyanotic spells

Immediate steps

Check airway; deliver oxygen by face mask or nasal cannula Knee chest position

Sedate with morphine (0.2 mg/kg subcutaneously or ketamine 3-5 mg/kg/dose intramuscular)

Administer sodium bicarbonate at 1-2 ml/kg (diluted 1:1 or in 10 ml/kg N/5 in 5% dextrose)

Correct hypovolemia (10 ml/kg of dextrose normal saline) Keep child warm

Transfuse packed red cell if anemic (hemoglobin <12 g/dl) Use beta blockers unless contraindicated by bronchial asthma or ventricular dysfunction; metoprolol is given at 0.1 mg/kg IV slowly over 5 min and repeated every 5 min for maximum 3 doses; may be followed by infusion at 1 -2 µg/kg/min Monitor saturation, heart rates and blood pressure; keep heart rate below 100/minute

Persistent desaturation and no significant improvement

Considervasopressorinfusion: methoxamine 0.1-0.2 mg/kg/ dose IV or 0.1- 0.4 mg/kg/dose IM, or phenylephrine 5 µg/ kg as IV bolus and 1-4 µg/kg/min as infusion

If spells persist: Paralyze the patient, electively intubate and ventilate; plan for palliative or corrective surgery

Seizures are managed with diazepam at 0.2 mg/kg IV or midazolam at 0.1-0.2 mg/kg/dose IV

Following a spell

Conduct a careful neurological examination; perform CNS imaging if focal deficits are present

Initiate therapy with beta-blocker at the maximally tolerated dose (propranolol 0.5-1.5 mg/kg q 6-8 hr); helps improve resting saturation and decreases frequency of spells Ensure detailed echocardiography for disease morphology Plan early corrective or palliative surgery

Administer ironin therapeutic (ifanemic)orprophylactic dose

Prevention

Counsel parents regarding the possibility of recurrence of spells and precipitating factors (dehydration, fever, pain) and measures to avoid them (e.g. use of local anesthetic patches and/or sedation with IM ketamine to avoid pain during venesection)

Encourage early surgical repair

undergone curative repair might show progressive right ventriculardilation withincreased risk of late heart failure and sudden cardiac death. There are longterm concerns after the arterial switch operation (aortic root dilation, silent coronary occlusion), AV canal repair (AV valve regurgitation) and coarctation (residual hypertension, aortic aneurysm). Operations that involve placement of conduits (pulmonary atresia, Rastelli operations) require replacement upon growth of the child. Conditions associated with satisfactory longterm survival include small left to right shunts and bicuspid aortic valves. survival is also satisfactory for many patients with atrial septal defect, coarctation of aorta, pink TOF, mild Ebstein anomaly and some forms of corrected transposition of great arteries.

Prevention of CHO

Education of lay public on the risks associated with consanguinity, drugs and teratogens in the first trimester of pregnancy and widespread immunization against rubellahaslimited role in preventing CHD. However, most CHD do not have an identifiable etiology and there is no effective strategy for their prevention in the periconcep­ tional period.

Fetal echocardiography is emerging as a modality for early diagnosis of CHD. Conditions that involve major chamber discrepancy (such as hypoplastic left heart syndrome), single ventricles and commonAV canalcan be identified by routine screening as early as 14-16 weeks gestation.Withsomerefinement, additional conditionssuch as tetralogy of Fallot, large VSD, transposition of great vessels and persistent truncus arteriosus can be detected. Once a serious CHD is identified, it is vital to counsel the families about postnatal manifestations, natural history, surgical options and their longterm outlook. Before 20 weeks of gestation, medicaltermination of pregnancy is an option. Results of fetal echocardiography enable delivery at a center with comprehensive pediatric heart program. While echocardiography is recommended for future pregnancies after diagnosis of serious CHD in a child, this practice has low yield because only 2-8% CHD recur. The

highest chance of recurrence is with obstructive lesions of the left heart.

ACYANOTIC CONGENITAL HEART DEFECTS

Atrial Septal Defect

Atrial septal defect (ASD) account for as an isolated anomaly 5-10% of all CHD. Based on anatomy, ASD is classified as follows:

Fossa ova/is ASD. They are located in the central portion of atrial septum, in the position of foramen ovale. These defects are amenable to closure in the catheterization laboratory.

Sinus venosusASD. Thesearelocatedatjunction of superior vena cava and right atrium. These defects do not have a superior margin because the superior vena cava straddles the defect. These defects are associated with anomalous drainage of one or more right pulmonary veins.

Ostium primum ASD. These defects are created by failure of septum primum, and are in lower part of the atrial septum; inferior margin of ASD is formed by the atrioventricular valve.

Coronary sinus ASD. An unroofed coronary sinus is a rare communication between the coronary sinus and the left atrium, which produces features similar to other types of ASD.

Physiology and Findings

The physiology of ASD is that of a pre-tricuspid shunt. The enlarged right ventricle results in a parasternal impulse.Theejection systolic murmur originates from the pulmonary valve because of the increased blood flow. An increased flow through the tricuspid valve may result in a soft delayed diastolic rumble at the lower left sternal border. The overload of the right ventricle due to an increase in venous return prolongs the time required for its emptying resulting in delayed P2. This delay also results fromthe prolonged 'hang-out' intervalbecause of the very low resistance in the pulmonary circulation. Additionally,sincethe twoatriabeinglinked via thelarge ASD, inspiration does not produce any net pressure change between themand respirationrelatedfluctuations in systemic venous return to the right side of the heart are abolished; thereby the fixed S2 (Fig. 15.9).

The electrocardiogram of ostium secundum ASD is characterized byrightaxis deviation and right ventricular hypertrophy. The characteristic configuration of the lead Vl is rsR' seen in almost90% patients (Fig. 15.10).Presence ofleft axisdeviationbeyond -30° suggests ostiurn primum ASD (Fig. 15.11). The chest X-ray shows mild to moderate cardiomegaly, right atrial and right ventricular enlargement, prominent main pulmonary artery segment, a relatively small aortic shadow and plethoric lung fields. The left atrium does not enlarge in size in atrial septal defect, unless associated with other anomalies like mitral

Disorders of Cardiovascular System -

Atrial Septal Defect

Sounds

Fig. 15.9: Summary of auscultatory findings in the atrial septal defect, Ao aorta; A2 aortic component of the second sound; ESM ejection systolic murmur; LA left atrium; LV left ventricle; PA pulmonary artery;

P2 pulmonic component of the second sound; RA right atrium; RV right ventricle; S1 first sound; S2 second sound; X click

j

!L

I

Fig. 15.10: Electrocardiogram of atrial septaI defect of the secundum type showing rSR' pattern in lead V1

regurgitation. Echocardiogramshowsincreasedsize of the rightventriclewith paradoxical ventricularseptalmotion. 2D echo in subcostal view often best identifies the defect. The echocardiogram allows decisionregarding suitability of catheter closure, based on measurements of the defect and the adequacy of margins (Fig. 15.12).

- Essential Pediatrics

, ,r1 ! . ='-:=.;·=·=-

Fig. 15.11: Electrocardiogram of atrial septaI defect of the primum type associated with endocardial cushion defect. The mean ORS axis is-60°

f'ig. 15.12: Echocardiogram of atrial septa! defect Subxiphoid short axis view of the atrial septum shows deficient posterior-inferior rim (arrow). IVC inferior vena cava; LA left atrium; RA right atrium; SVC superior vena cava

Assessment of the Severity

The size of the left to right shunt is directlyproportional to the intensity of the murmurs and heart size. The larger the shunt, the more the cardiomegaly and the louder the pulmonary and tricuspid murmurs.

Natural History and Complications

Heart failure is exceptional in infancy. A small proportion of patients might develop pulmonary hypertension, by the second or third decade. ASD closure is recommended to prevent complications of atrial arrhythmias and heart failure in late adulthood.

Treatment

Most fossa ovalis defects with good margins can be closed percutaneously in the catheterization laboratory with occlusive devices. Others require surgical closure. Closure is recommended before school entry to prevent late complications. Small defects (<8 mm) can be observed.

Spontaneous closure is well recognized in small defects that are diagnosed in infancy or early childhood.

Ventricular Septal Defect (VSD)

This is the most common congenital cardiac lesion identified at birth accounting for one-quarter of all CHD.

VSD is a communication between the two ventricles; 90% are located in the membranous part of the ventricular septumwith variable extension into themuscular septum. Others are located in the muscular septum and can be multiple (Fig. 15.13).

Hemodynamics

VSD results in shunting of oxygenated blood from the left to the right ventricle. The left ventricle starts contracting

Moderator

band

f'ig.15.13: Diagrammatic representation of the common locations of ventricular septa! defects (VSD). Membranous septum is the commonest location. Subpulmonic VSD, located inthe outlet septum, have a high risk of aortic valve prolapse. Muscular VSDs can occur anyvvhere in the muscular part of septum