Medical School · Year 3 · Pediatrics · includes a quiz and discussion video

Seminar 07: Pediatric Cardiac Disorders

Year 3: Pediatrics Clerkship

Learning Objectives

By the end of this seminar, students will be able to:

1. Identify innocent vs pathologic heart murmurs
2. Classify congenital heart defects
3. Recognize cyanotic and acyanotic lesions
4. Describe acquired heart disease in children
5. Identify heart failure in pediatric patients
6. Apply principles of pediatric cardiovascular assessment

Lecture Outline

I. Cardiovascular Assessment

The cardiovascular assessment in children begins with age-appropriate vital signs, which vary significantly throughout childhood and must be interpreted using age-specific normal ranges. Newborns demonstrate heart rates of 100-180 beats per minute with blood pressures around 60-90/20-60 mmHg, reflecting their high cardiac output and low systemic vascular resistance. Infants maintain heart rates of 100-160 with blood pressures of 80-100/50-70, while toddlers and preschoolers show gradual decreases in heart rate to 80-140 and increases in blood pressure to 90-110/55-75. School-age children and adolescents approach adult values with heart rates of 60-100 and blood pressures of 100-120/60-85, and any values outside these ranges warrant further investigation for underlying cardiac or systemic disease.

Physical examination of the cardiovascular system requires systematic assessment of inspection, palpation, and auscultation. Inspection evaluates for cyanosis (central versus peripheral), respiratory distress, chest wall deformity, and visible precordial activity suggesting cardiac enlargement or hyperactivity. Palpation assesses the point of maximal impulse, which is normally at the left midclavicular line in the fourth or fifth intercostal space, with displacement suggesting cardiac enlargement, and the presence of a thrill indicates a loud murmur grade IV or higher. Palpation of peripheral pulses in all extremities is essential, as diminished or absent femoral pulses compared to upper extremity pulses strongly suggests coarctation of the aorta and requires urgent evaluation.

Auscultation of heart sounds requires identification of S1 and S2, evaluation of splitting, and detection of additional sounds or murmurs. S1 represents mitral and tricuspid valve closure and is best heard at the apex, while S2 represents aortic and pulmonic valve closure and normally splits with inspiration due to increased venous return prolonging right ventricular ejection. Fixed splitting of S2, where the split does not vary with respiration, suggests atrial septal defect with right ventricular volume overload. S3 may be physiologic in children, representing rapid ventricular filling, while S4 (atrial gallop) is always pathologic and indicates decreased ventricular compliance. Murmur evaluation characterizes timing (systolic versus diastolic versus continuous), location, radiation, grade (I-VI), and quality (harsh, blowing, musical).

Determining when to refer for cardiology evaluation requires recognition of features distinguishing pathologic from innocent murmurs. Diastolic murmurs are always pathologic and require evaluation, as they suggest valvular regurgitation or stenosis. Harsh, loud murmurs grade III or higher warrant referral, as do murmurs associated with symptoms including poor feeding, failure to thrive, exercise intolerance, syncope, or chest pain. Abnormal electrocardiogram or chest radiograph findings, including cardiomegaly, abnormal cardiac silhouette, or pulmonary vascular changes, require cardiology consultation. Any murmur in a neonate or young infant should prompt echocardiography given the higher prevalence of structural heart disease in this population.

<image>Panel A: Age-specific normal ranges for heart rate and blood pressure displayed as reference chart from newborn through adolescence with color-coded zones for normal, borderline, and abnormal values. Panel B: Anatomical illustration showing proper stethoscope placement for cardiac auscultation including aortic, pulmonic, tricuspid, and mitral areas with corresponding heart sounds heard at each location. Panel C: Physical examination techniques demonstrating palpation of precordium for point of maximal impulse and comparison of upper and lower extremity pulses for coarctation screening. Panel D: S2 splitting patterns showing normal physiologic splitting, fixed splitting of ASD, and paradoxical splitting with corresponding hemodynamic explanations.</image>

II. Innocent (Functional) Murmurs

Innocent murmurs occur in up to 50% of children at some point during childhood and represent normal blood flow turbulence without structural heart disease. These murmurs share characteristic features that distinguish them from pathologic murmurs, including intensity grade I-II/VI, purely systolic timing, musical or vibratory quality, and variation with position changes typically softening when the child moves from supine to standing. Innocent murmurs occur in otherwise healthy children with normal growth and development, normal physical examination findings, and absence of any symptoms suggestive of cardiac disease. Recognition of innocent murmur characteristics allows confident reassurance without unnecessary testing.

Still's murmur represents the most common innocent murmur, typically heard in children aged 2-7 years. This murmur has a characteristic vibratory or musical quality often described as "twanging string" and is best heard at the left lower sternal border or between the left lower sternal border and apex. The murmur is grade I-II/VI, purely systolic, and decreases significantly or disappears when the child stands or during Valsalva maneuver. The mechanism involves normal blood flow through the left ventricular outflow tract, and the murmur often becomes more prominent during states of increased cardiac output including fever, anemia, or anxiety. The murmur typically resolves by adolescence.

Other common innocent murmurs include pulmonary flow murmur, venous hum, and peripheral pulmonic stenosis of the newborn. Pulmonary flow murmur is a soft, blowing, systolic murmur heard at the left upper sternal border caused by normal flow across the pulmonic valve, commonly heard in children, adolescents, and young adults, particularly during high-output states. Venous hum is a continuous murmur heard in the neck and supraclavicular area caused by blood flow in the jugular veins; it disappears when the child lies supine or with gentle compression of the jugular vein. Peripheral pulmonic stenosis produces a soft systolic murmur heard in the back and axillae in newborns due to relative narrowing of branch pulmonary arteries, resolving by age 6 months as the pulmonary arteries grow.

When an innocent murmur is suspected based on classic features, evaluation and documentation guide appropriate management. If all features are classic for an innocent murmur in an otherwise healthy child with normal growth and no symptoms, echocardiography is not necessary. Documentation should include murmur characteristics (grade, location, timing, quality), position changes, and clinical assessment as innocent or functional. Parents require clear reassurance that the murmur represents normal blood flow, does not indicate heart disease, requires no activity restrictions, and needs no further testing or follow-up specifically for the murmur. If uncertainty exists regarding the diagnosis, particularly in young infants or if any atypical features are present, echocardiography provides definitive evaluation.

<image>Panel A: Comparison chart contrasting features of innocent and pathologic murmurs including intensity, timing, quality, position changes, associated findings, and recommended management. Panel B: Anatomical location diagram showing where each type of innocent murmur is best heard including Still's murmur at LLSB, pulmonary flow murmur at LUSB, and venous hum in neck. Panel C: Clinical demonstration of maneuvers that affect innocent murmurs including standing, Valsalva, and lying supine with expected changes in murmur intensity. Panel D: Documentation template for innocent murmur showing required elements and sample reassurance language for parent education.</image>

III. Classification of CHD

Congenital heart defects affect approximately 1% of live births and range from simple lesions requiring no intervention to complex defects requiring multiple surgeries. The primary classification divides defects into acyanotic and cyanotic lesions based on whether deoxygenated blood reaches the systemic circulation. Acyanotic defects typically involve left-to-right shunts where oxygenated blood is shunted to the pulmonary circulation, increasing pulmonary blood flow but maintaining normal systemic oxygen saturation. Cyanotic defects involve right-to-left shunts allowing deoxygenated blood to bypass the lungs and enter systemic circulation, causing visible cyanosis when oxygen saturation falls below 85%.

Acyanotic defects include shunt lesions and obstructive lesions that do not cause cyanosis under normal conditions. Ventricular septal defect is the most common congenital heart defect, comprising 25-30% of all CHD, followed by atrial septal defect at approximately 10% and patent ductus arteriosus at 5-10%. Coarctation of the aorta represents the most common obstructive lesion, affecting 5-8% of patients with CHD, while aortic stenosis and pulmonary stenosis occur less frequently. These lesions cause volume overload (shunts) or pressure overload (obstructive lesions) of cardiac chambers but maintain normal systemic oxygenation unless severe heart failure develops or pulmonary vascular disease reverses shunt direction.

Cyanotic defects involve structural abnormalities that allow deoxygenated blood to enter the systemic circulation. Tetralogy of Fallot is the most common cyanotic heart defect, comprising 5-8% of all CHD, characterized by four features: ventricular septal defect, overriding aorta, right ventricular outflow tract obstruction, and right ventricular hypertrophy. Transposition of the great arteries accounts for approximately 5% of CHD and presents with severe cyanosis at birth due to parallel rather than series circulations. Other cyanotic lesions include tricuspid atresia, total anomalous pulmonary venous return, truncus arteriosus, and hypoplastic left heart syndrome, each with distinct anatomy and management requirements.

Certain genetic syndromes strongly associate with specific cardiac defects, and cardiac evaluation should be performed in all affected patients. Down syndrome (trisomy 21) associates with atrioventricular septal defects and ventricular septal defects in 40-50% of patients, requiring echocardiography at birth. Turner syndrome (45,X) associates with bicuspid aortic valve and coarctation of the aorta. DiGeorge syndrome (22q11.2 deletion) causes interrupted aortic arch, truncus arteriosus, and tetralogy of Fallot as part of the CATCH-22 spectrum. Williams syndrome associates with supravalvular aortic stenosis and peripheral pulmonary stenosis, while Noonan syndrome classically presents with pulmonary valve stenosis. Marfan syndrome causes aortic root dilation requiring surveillance echocardiography.

<image>Panel A: Schematic diagram showing blood flow patterns in acyanotic (left-to-right shunt) versus cyanotic (right-to-left shunt) congenital heart defects with oxygen saturation values in each chamber. Panel B: Pie chart showing relative frequency of different congenital heart defects with VSD, ASD, PDA, and TOF highlighted with their percentage contributions. Panel C: Summary chart of genetic syndromes associated with specific cardiac defects including Down syndrome, Turner syndrome, DiGeorge syndrome, Williams syndrome, and Noonan syndrome. Panel D: Classification tree organizing congenital heart defects by presence of cyanosis and whether pulmonary blood flow is increased or decreased.</image>

IV. Acyanotic Heart Defects

Ventricular septal defect represents the most common congenital heart defect and exemplifies the pathophysiology of left-to-right shunting. The defect allows blood to flow from the high-pressure left ventricle to the lower-pressure right ventricle, increasing pulmonary blood flow and potentially causing volume overload of the left atrium and left ventricle. Small VSDs produce loud holosystolic murmurs at the left lower sternal border (smaller defects create more turbulence) but are hemodynamically insignificant, while large VSDs may produce softer murmurs but cause significant symptoms. Many small VSDs close spontaneously, particularly muscular defects, with closure rates highest in the first two years of life. Large VSDs causing heart failure, failure to thrive, or pulmonary hypertension require surgical repair.

Atrial septal defect creates left-to-right shunting at the atrial level, causing right ventricular volume overload and increased pulmonary blood flow. Secundum ASD is the most common type, located in the central portion of the atrial septum at the fossa ovalis, while primum ASDs occur lower and associate with atrioventricular septal defects and Down syndrome. The classic auscultatory finding is fixed splitting of S2, reflecting the consistently increased right ventricular volume regardless of respiratory phase, along with a systolic flow murmur at the left upper sternal border. Most ASDs are asymptomatic in childhood, with symptoms of exercise intolerance and arrhythmias developing in adulthood if uncorrected. Device closure is indicated for significant shunts and can often be accomplished in the catheterization laboratory.

Patent ductus arteriosus represents persistence of the fetal connection between the aorta and pulmonary artery that normally closes within the first 24-48 hours of life. Risk factors for persistent PDA include prematurity and hypoxia, with the incidence inversely proportional to gestational age. The classic murmur is a continuous "machinery" murmur best heard at the left upper sternal border and infraclavicular area, resulting from continuous flow from the aorta to the pulmonary artery throughout systole and diastole. Large PDAs cause left heart volume overload and may present with heart failure, pulmonary edema, and failure to thrive. Medical closure with indomethacin or ibuprofen is effective in premature infants, while surgical ligation or catheter-based device closure is used for larger or persistent PDAs.

Atrioventricular septal defect, also called endocardial cushion defect or atrioventricular canal defect, involves abnormal development of the atrioventricular septum creating a combined ASD and VSD with abnormal atrioventricular valve morphology. This defect strongly associates with Down syndrome, occurring in approximately 40% of children with Down syndrome who have congenital heart disease. Complete AVSD presents with large shunts causing significant heart failure and pulmonary hypertension early in life, typically requiring surgical repair in the first 6 months. Partial AVSD (primum ASD with cleft mitral valve) may present later with milder symptoms. Repair involves patch closure of the septal defects and reconstruction of the atrioventricular valves.

<image>Panel A: Anatomical diagram of ventricular septal defect showing left-to-right shunt with blood flow arrows, chamber enlargement, and location of holosystolic murmur with phonocardiogram tracing. Panel B: Atrial septal defect illustration demonstrating fixed S2 splitting mechanism with comparison of normal and fixed splitting patterns across respiratory cycle. Panel C: Patent ductus arteriosus anatomy showing continuous flow from aorta to pulmonary artery with machinery murmur waveform and hemodynamic consequences. Panel D: Atrioventricular septal defect anatomy showing common AV valve, atrial and ventricular components, and association with Down syndrome with surgical repair approach.</image>

V. Obstructive Lesions

Coarctation of the aorta is a narrowing of the aorta typically occurring just distal to the left subclavian artery at the site of ductal tissue insertion. This location means blood pressure is elevated proximal to the obstruction (upper extremities) and reduced distal to it (lower extremities), producing the characteristic blood pressure differential and diminished or delayed femoral pulses. Critical coarctation presents in neonates when the ductus arteriosus closes, causing acute left ventricular failure and shock, and requires prostaglandin E1 infusion to reopen the ductus and maintain lower body perfusion. Older children with less severe coarctation present with upper extremity hypertension, headaches, and claudication with exercise. Examination reveals discrepant arm and leg blood pressures (>20 mmHg higher in arms), delayed or weak femoral pulses, and a systolic murmur heard best in the left infraclavicular area and back.

Aortic stenosis in children most commonly involves the valve itself (valvular stenosis) but may also occur above the valve (supravalvular, associated with Williams syndrome) or below the valve (subvalvular). Valvular aortic stenosis often involves a bicuspid aortic valve, the most common congenital cardiac anomaly, occurring in 1-2% of the population. The characteristic murmur is a harsh systolic ejection murmur at the right upper sternal border radiating to the carotids, often with an ejection click from the abnormal valve. Severe aortic stenosis causes symptoms of syncope, chest pain, and heart failure, with sudden death risk during exertion making activity restriction necessary for severe stenosis. Treatment includes balloon valvuloplasty for children when intervention is needed, though valve replacement is eventually required in most patients.

Pulmonary stenosis may be valvular, subvalvular (infundibular), or supravalvular (peripheral pulmonary stenosis). Valvular pulmonary stenosis is most common and presents with a systolic ejection murmur at the left upper sternal border radiating to the back, often preceded by an ejection click. Mild to moderate pulmonary stenosis is typically well-tolerated and may not require intervention, while severe stenosis causes right ventricular failure and cyanosis from right-to-left shunting through a patent foramen ovale. Balloon valvuloplasty is highly effective for valvular pulmonary stenosis and is the treatment of choice. Peripheral pulmonary stenosis may be benign and transient in newborns or associated with syndromes including Williams, Alagille, and congenital rubella.

Critical obstructive lesions in the newborn present with cardiovascular collapse when the ductus arteriosus closes, as ductal flow is necessary to maintain either pulmonary or systemic blood flow. Ductal-dependent pulmonary blood flow occurs in critical pulmonary stenosis, pulmonary atresia, and tricuspid atresia, where the PDA provides the only source of pulmonary blood flow. Ductal-dependent systemic blood flow occurs in critical coarctation, interrupted aortic arch, and hypoplastic left heart syndrome, where the PDA provides flow to the lower body or entire systemic circulation. Presentation occurs at 1-3 days of life as the ductus closes, with poor feeding, lethargy, respiratory distress, and shock. Immediate management requires prostaglandin E1 infusion to reopen the ductus, with monitoring for apnea (a common side effect requiring intubation readiness).

<image>Panel A: Coarctation of the aorta anatomy showing juxtaductal narrowing, upper and lower extremity blood pressure discrepancy, and collateral circulation development with rib notching on chest radiograph. Panel B: Aortic stenosis at valvular, subvalvular, and supravalvular levels with murmur characteristics, physical findings, and associated syndromes for each type. Panel C: Pulmonary stenosis demonstrating systolic ejection murmur, ejection click timing, and grading of severity by Doppler gradient with corresponding management approach. Panel D: Critical ductal-dependent lesions flowchart showing lesions requiring ductal patency for pulmonary versus systemic blood flow with prostaglandin E1 mechanism and monitoring requirements.</image>

VI. Cyanotic Heart Defects

Tetralogy of Fallot is the most common cyanotic heart defect and consists of four anatomical abnormalities that share a common embryologic origin: malalignment ventricular septal defect, overriding aorta positioned over the VSD, right ventricular outflow tract obstruction, and right ventricular hypertrophy secondary to the obstruction. The degree of cyanosis depends primarily on the severity of right ventricular outflow tract obstruction, with mild obstruction producing minimal cyanosis (pink tetralogy) and severe obstruction causing profound cyanosis. Characteristic chest radiograph shows a boot-shaped heart due to right ventricular hypertrophy and absence of the normal pulmonary artery segment. Electrocardiogram demonstrates right ventricular hypertrophy with right axis deviation.

Hypercyanotic episodes, or "tet spells," represent acute increases in right-to-left shunting causing profound cyanosis and may progress to syncope, seizure, stroke, or death. These episodes occur most commonly in the morning or after crying, feeding, or defecation, triggered by decreased systemic vascular resistance or increased right ventricular outflow tract obstruction from infundibular spasm. Children instinctively squat during spells, which increases systemic vascular resistance and decreases venous return, reducing right-to-left shunting. Medical management includes positioning with knees to chest, supplemental oxygen, intravenous fluids for preload augmentation, morphine for sedation and decreased catecholamine response, and beta-blockers to relax the infundibulum. Definitive treatment is surgical repair, typically performed in infancy.

Transposition of the great arteries presents the most urgent cyanosis in the newborn period because the parallel circulation cannot sustain life without mixing. In TGA, the aorta arises from the right ventricle and the pulmonary artery from the left ventricle, creating two separate circuits where deoxygenated blood recirculates through the body and oxygenated blood recirculates through the lungs. Survival depends on mixing between the circuits through the foramen ovale, ductus arteriosus, or associated defects. Newborns present with profound cyanosis within hours of birth that does not improve with supplemental oxygen. Initial management requires prostaglandin E1 to maintain ductal patency and balloon atrial septostomy (Rashkind procedure) to enlarge atrial communication. Definitive treatment is the arterial switch operation, ideally performed within the first two weeks of life.

Other cyanotic lesions include hypoplastic left heart syndrome, total anomalous pulmonary venous return, truncus arteriosus, and tricuspid atresia, each with distinct presentations and management. Hypoplastic left heart syndrome involves underdevelopment of left heart structures and presents with shock as the ductus closes, requiring prostaglandin and staged surgical palliation (Norwood, Glenn, Fontan) or heart transplantation. Total anomalous pulmonary venous return involves drainage of pulmonary veins to systemic venous structures rather than the left atrium, presenting with cyanosis and respiratory distress, with obstructed forms constituting surgical emergencies. Truncus arteriosus features a single arterial trunk giving rise to the aorta, pulmonary arteries, and coronary arteries, requiring early surgical repair. Tricuspid atresia involves absence of the tricuspid valve with obligate right-to-left shunt at the atrial level.

<image>Panel A: Tetralogy of Fallot anatomy showing all four components with blood flow patterns, boot-shaped heart on chest radiograph, and ECG demonstrating right ventricular hypertrophy. Panel B: Hypercyanotic (tet) spell physiology showing triggers, pathophysiology of increased right-to-left shunting, squatting position benefit, and stepwise medical management algorithm. Panel C: Transposition of the great arteries showing parallel circulations, sites of mixing (ASD, VSD, PDA), balloon atrial septostomy procedure, and arterial switch operation. Panel D: Comparison of other cyanotic lesions including HLHS, TAPVR, truncus arteriosus, and tricuspid atresia with key features and initial management for each.</image>

VII. Heart Failure in Children

Heart failure etiology varies dramatically by age group, making age-based differential diagnosis essential for evaluation. Fetal heart failure (hydrops fetalis) results from arrhythmias, severe anemia, twin-twin transfusion, or structural heart disease. Newborn heart failure typically indicates critical congenital heart disease including hypoplastic left heart syndrome, severe coarctation, or critical aortic stenosis, presenting when the ductus closes. Infant heart failure most commonly results from large left-to-right shunts (VSD, AVSD, PDA) becoming symptomatic as pulmonary vascular resistance falls in the first weeks of life. Older children develop heart failure from cardiomyopathy, myocarditis, or acquired heart disease rather than undiagnosed congenital defects.

Clinical recognition of heart failure differs in infants compared to older children due to developmental differences in symptom expression. Infants with heart failure demonstrate poor feeding, taking small volumes with fatigue and diaphoresis, prolonged feeding times, and failure to gain weight despite adequate caloric intake. Tachypnea and increased work of breathing during feeding reflect pulmonary edema and decreased lung compliance. Older children present more similarly to adults with fatigue, exercise intolerance, dyspnea on exertion, and orthopnea. Physical examination findings common to all ages include tachycardia, hepatomegaly (the most reliable sign in infants), gallop rhythm (S3), and peripheral edema (less common in infants than older children).

Evaluation of suspected heart failure combines clinical assessment with diagnostic testing to identify the underlying cause. Chest radiograph demonstrates cardiomegaly and pulmonary vascular congestion including Kerley B lines, pulmonary edema, and pleural effusions. Electrocardiogram may reveal chamber enlargement, hypertrophy patterns, or arrhythmias contributing to heart failure. Echocardiography is essential for evaluating cardiac structure and function, identifying congenital defects, and assessing ventricular systolic and diastolic function. Brain natriuretic peptide (BNP) or N-terminal pro-BNP levels are elevated in heart failure and may help distinguish cardiac from pulmonary causes of respiratory symptoms. Additional testing including cardiac catheterization and MRI provides detailed hemodynamic and anatomic information when needed.

Management of pediatric heart failure addresses both symptom relief and treatment of the underlying cause. Diuretics, primarily furosemide, reduce preload and relieve congestion, with careful attention to electrolyte abnormalities particularly hypokalemia. Afterload reduction with ACE inhibitors (enalapril, captopril) improves cardiac output and reduces myocardial oxygen demand, with starting doses lower than adult doses and careful blood pressure monitoring. Digoxin provides mild positive inotropic effect and may improve symptoms, though its role has diminished with the advent of newer therapies. Beta-blockers (carvedilol, metoprolol) improve outcomes in chronic heart failure but should be initiated at very low doses and uptitrated slowly. Treatment of the underlying cause, such as surgical repair of congenital defects, treatment of myocarditis, or antiarrhythmic therapy, remains paramount.

<image>Panel A: Age-based etiology chart for pediatric heart failure showing fetal causes (arrhythmia, anemia), neonatal causes (critical CHD), infant causes (large shunts), and childhood causes (cardiomyopathy, myocarditis). Panel B: Clinical features of infant heart failure including feeding difficulty, diaphoresis, tachypnea, hepatomegaly, and failure to thrive with photographs demonstrating key examination findings. Panel C: Diagnostic evaluation pathway showing chest radiograph findings, echocardiography assessment, BNP levels, and additional testing indications. Panel D: Heart failure treatment algorithm showing diuretics, ACE inhibitors, digoxin, and beta-blockers with dosing considerations and monitoring parameters for pediatric patients.</image>

VIII. Acquired Heart Disease

Kawasaki disease is an acute febrile vasculitis of unknown etiology that primarily affects children under 5 years and represents the leading cause of acquired heart disease in developed countries. Diagnosis requires fever for at least 5 days plus at least 4 of 5 clinical criteria: bilateral non-exudative conjunctivitis, oral mucosal changes (cracked lips, strawberry tongue), polymorphous rash, extremity changes (erythema, edema, and later desquamation), and cervical lymphadenopathy (typically unilateral, >1.5 cm). Incomplete Kawasaki disease occurs when fever and fewer than 4 criteria are present, requiring high clinical suspicion and supplementary laboratory and echocardiographic criteria for diagnosis. The primary concern is coronary artery aneurysm development, which occurs in 25% of untreated patients but decreases to 4% with appropriate treatment.

Treatment of Kawasaki disease aims to reduce inflammation and prevent coronary artery complications. High-dose intravenous immunoglobulin (2 g/kg as single infusion) given within 10 days of fever onset reduces coronary aneurysm risk from 25% to approximately 4%. High-dose aspirin (80-100 mg/kg/day in 4 divided doses) provides anti-inflammatory effect during the acute phase, then transitions to low-dose aspirin (3-5 mg/kg/day) for antiplatelet effect continued for 6-8 weeks in patients without coronary involvement or indefinitely in those with coronary abnormalities. Echocardiography should be performed at diagnosis, at 2 weeks, and at 6-8 weeks to assess for coronary involvement. IVIG-resistant patients (persistent fever 36 hours after completing IVIG) may require a second IVIG dose, corticosteroids, or infliximab.

Acute rheumatic fever results from an autoimmune response to Group A streptococcal pharyngitis and remains common in developing countries and indigenous populations. The Jones criteria require evidence of preceding streptococcal infection (positive throat culture, rapid strep test, or elevated streptococcal antibodies) plus 2 major criteria or 1 major and 2 minor criteria. Major criteria include migratory polyarthritis (most common, affecting large joints), carditis (ranging from asymptomatic valve involvement to heart failure), Sydenham chorea (delayed manifestation with involuntary movements), erythema marginatum (evanescent pink rings on trunk), and subcutaneous nodules (rare). Minor criteria include arthralgia, fever, elevated ESR or CRP, and prolonged PR interval. Rheumatic heart disease from recurrent episodes causes progressive valvular damage, particularly mitral regurgitation and stenosis.

Myocarditis presents a spectrum from asymptomatic to fulminant heart failure and arrhythmias. Viral etiologies predominate, particularly enteroviruses (coxsackievirus, echovirus) and adenovirus, though parvovirus B19 and human herpesvirus 6 are increasingly recognized. Presentation ranges from nonspecific viral prodrome with subtle cardiac symptoms to acute heart failure, cardiogenic shock, or sudden death from arrhythmia. Diagnosis involves elevated troponin, electrocardiographic changes (ST-T abnormalities, arrhythmias), echocardiographic evidence of ventricular dysfunction, and characteristic findings on cardiac MRI (edema, late gadolinium enhancement). Treatment is primarily supportive, including heart failure management, antiarrhythmic therapy, and mechanical circulatory support for refractory cases. The role of immunosuppression and IVIG remains controversial without clear evidence of benefit.

<image>Panel A: Kawasaki disease diagnostic criteria illustrated with photographs showing conjunctivitis, oral changes, rash, extremity changes, and cervical lymphadenopathy with fever duration requirement. Panel B: Kawasaki disease treatment protocol showing IVIG timing and dosing, aspirin regimen, echocardiography schedule, and management of IVIG-resistant disease. Panel C: Jones criteria for acute rheumatic fever displayed with major and minor criteria, evidence of streptococcal infection requirements, and long-term prophylaxis recommendations. Panel D: Myocarditis presentation spectrum from mild viral syndrome to cardiogenic shock with diagnostic modalities (troponin, ECG, echo, cardiac MRI) and supportive management approach.</image>

IX. Arrhythmias

Supraventricular tachycardia is the most common symptomatic arrhythmia in pediatric patients, characterized by regular, rapid heart rates typically exceeding 220 beats per minute in infants and 180 in older children. The mechanism most commonly involves reentry through an accessory pathway (Wolff-Parkinson-White syndrome and concealed pathways) or within the AV node (AVNRT), though automatic atrial tachycardia and atrial flutter also occur. Infants present with irritability, poor feeding, pallor, or heart failure if SVT is prolonged, while older children report palpitations, chest discomfort, and dizziness. ECG during tachycardia shows narrow QRS complexes (unless aberrant conduction or pre-existing bundle branch block), absent or abnormal P waves, and a regular rhythm.

Acute management of SVT begins with vagal maneuvers if the patient is hemodynamically stable. Ice to the face (diving reflex) is highly effective in infants, while older children can perform Valsalva maneuver or carotid massage. If vagal maneuvers fail, adenosine is first-line pharmacotherapy, given as a rapid intravenous push followed immediately by saline flush due to its ultrashort half-life. Initial dose is 0.1 mg/kg (maximum 6 mg), increased to 0.2 mg/kg (maximum 12 mg) if the first dose is ineffective. Patients should be warned about transient flushing, chest discomfort, and brief asystole. Synchronized cardioversion at 0.5-1 J/kg is indicated for hemodynamically unstable patients. Long-term management options include daily prophylactic medications (beta-blockers, flecainide, sotalol) or catheter ablation, which is increasingly preferred for older children due to high success rates.

Long QT syndrome represents a potentially life-threatening disorder of cardiac repolarization that predisposes to torsades de pointes and sudden death. Causes include congenital ion channel mutations (Romano-Ward syndrome, Jervell and Lange-Nielsen syndrome with associated deafness) and acquired conditions including electrolyte abnormalities and QT-prolonging medications. Diagnosis requires QTc prolongation (>460 ms in prepubertal children, >470 ms in postpubertal males, >480 ms in postpubertal females) along with clinical features or genetic confirmation. Symptoms include syncope or seizures precipitated by specific triggers (swimming in LQT1, emotional stress/sudden noise in LQT2, sleep in LQT3) and family history of sudden death. Treatment includes beta-blockers for all patients, avoidance of QT-prolonging drugs, trigger avoidance, and implantable cardioverter-defibrillator for high-risk patients.

Heart block ranges from benign first-degree block to life-threatening complete heart block requiring pacing. First-degree AV block (prolonged PR interval with 1:1 conduction) is often benign and may occur with increased vagal tone, medications, or electrolyte disturbances. Second-degree Mobitz type I (Wenckebach) shows progressive PR prolongation before a dropped beat and is typically benign. Second-degree Mobitz type II (constant PR with intermittent dropped beats) and complete (third-degree) heart block are concerning and may require pacing. Congenital complete heart block associates with maternal lupus (anti-SSA/Ro, anti-SSB/La antibodies) causing fetal myocarditis and fibrosis of the conduction system, and may present with fetal hydrops, neonatal symptoms, or be detected incidentally. Indications for pacing include symptoms, ventricular rate below 50-55, wide QRS escape rhythm, and ventricular dysfunction.

<image>Panel A: SVT ECG characteristics showing narrow complex tachycardia, absent P waves, and regular rhythm compared to sinus tachycardia, with common mechanisms (AVRT, AVNRT) illustrated. Panel B: SVT acute management algorithm starting with vagal maneuvers, proceeding to adenosine administration with dosing, and cardioversion for unstable patients. Panel C: Long QT syndrome ECG showing QT prolongation measurement, torsades de pointes rhythm, and specific trigger-phenotype correlations for LQT1, LQT2, and LQT3. Panel D: Heart block classification showing first-degree, second-degree Mobitz I and II, and third-degree patterns with clinical significance and pacing indications for each.</image>

X. Screening and Prevention

Newborn screening for critical congenital heart disease using pulse oximetry has been adopted universally, with screening performed after 24 hours of life or prior to discharge. The protocol measures oxygen saturation in the right hand (preductal) and either foot (postductal), with a passing result requiring SpO2 of 95% or higher in both extremities with 3% or less difference between them. Failed screens require echocardiography and cardiology consultation. This screening detects ductal-dependent lesions and other critical CHD including HLHS, pulmonary atresia, tetralogy of Fallot, TAPVR, TGA, tricuspid atresia, and truncus arteriosus. Limitations include inability to detect lesions with normal saturation (coarctation, ASD, VSD) and potential false negatives early in the transition period before ductus closure.

Pre-participation sports screening aims to identify athletes at risk for sudden cardiac death during exertion. History should assess for prior syncope or near-syncope especially during exercise, chest pain or discomfort with exertion, unexplained shortness of breath or fatigue with exercise, and family history of sudden death before age 50 or known cardiomyopathy. Physical examination evaluates for pathologic murmurs, blood pressure discrepancy suggesting coarctation, and features of Marfan syndrome. The role of routine ECG screening remains controversial, with higher sensitivity for hypertrophic cardiomyopathy and long QT syndrome but significant false-positive rates and cost implications. Any concerning findings require cardiology evaluation before sports clearance.

Evaluation of syncope in children requires distinguishing benign vasovagal syncope from cardiac causes with sudden death risk. Vasovagal syncope, the most common cause, typically features prodromal symptoms (lightheadedness, nausea, visual changes, diaphoresis), identifiable triggers (prolonged standing, heat, emotional stress, pain), and rapid recovery without confusion. Red flags suggesting cardiac syncope include syncope during exertion rather than after, syncope without prodrome (sudden collapse), syncope while supine, associated chest pain or palpitations, and family history of sudden death or cardiomyopathy. Cardiac evaluation with ECG (and often echocardiography) is indicated for any syncope with red flags or atypical features.

Endocarditis prophylaxis recommendations have narrowed significantly, now focusing on highest-risk patients undergoing highest-risk procedures. Current indications include patients with prosthetic cardiac valves or prosthetic material used for valve repair, previous infective endocarditis, unrepaired cyanotic CHD including palliative shunts, completely repaired CHD with prosthetic material for 6 months after repair, repaired CHD with residual defects adjacent to prosthetic material, and cardiac transplant recipients with valvulopathy. Procedures requiring prophylaxis are dental procedures involving gingival manipulation or perforation of oral mucosa. Standard regimen is amoxicillin 50 mg/kg (max 2 g) orally 30-60 minutes before the procedure, with alternatives for penicillin-allergic patients including cephalexin, clindamycin, or azithromycin.

<image>Panel A: Newborn pulse oximetry screening protocol showing measurement locations (right hand and foot), passing criteria (SpO2 ≥95% with ≤3% difference), and algorithm for failed or inconclusive results. Panel B: Pre-participation sports screening components including history red flags, physical examination elements, and ECG findings suggesting cardiac conditions. Panel C: Syncope evaluation distinguishing vasovagal features from cardiac red flags with decision algorithm for cardiac workup indication. Panel D: Current endocarditis prophylaxis guidelines showing cardiac conditions requiring prophylaxis, procedures requiring prophylaxis, and antibiotic regimens with dosing.</image>

Summary

• Innocent murmurs are grade I-II, systolic, vibratory, vary with position, and occur in asymptomatic children with normal examinations
• Ventricular septal defect is the most common CHD; presents with holosystolic murmur at LLSB; many small VSDs close spontaneously
• Atrial septal defect causes fixed splitting of S2; often asymptomatic until adulthood; device closure is possible for secundum ASDs
• Patent ductus arteriosus produces continuous machinery murmur; medical closure with indomethacin/ibuprofen in premature infants
• Coarctation presents with blood pressure differential and diminished femoral pulses; critical coarctation requires prostaglandin E1
• Tetralogy of Fallot is the most common cyanotic CHD; tet spells treated with knee-to-chest positioning, oxygen, morphine, beta-blockers
• Transposition creates parallel circulations requiring mixing; balloon septostomy bridges to arterial switch operation
• Kawasaki disease requires IVIG within 10 days to prevent coronary aneurysms; echocardiography at diagnosis and follow-up
• Acute rheumatic fever follows streptococcal pharyngitis; Jones criteria for diagnosis; long-term penicillin prophylaxis prevents recurrence
• SVT is the most common pediatric arrhythmia; treated acutely with vagal maneuvers and adenosine

Key Terms

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