Pediatrics (System-Integrated)

Congenital heart disease: cyanotic and acyanotic lesions

Clinical Overview and When to Suspect Congenital Heart Disease

— VSD (most common CHD overall), ASD, PDA, AVSD

— Coarctation of aorta, aortic stenosis, pulmonary stenosis

— The classic "5 T's + 1": Tetralogy of Fallot, Transposition of great arteries, Tricuspid atresia, Truncus arteriosus, Total anomalous pulmonary venous return, plus Hypoplastic left heart syndrome

— Failed pulse oximetry screen (≥24 h of life; >3% difference between pre- and post-ductal or SpO₂ <95% in both)

— Murmur beyond 24 h, especially harsh, pansystolic, or with abnormal S2

— Differential cyanosis or differential BP between arms and legs (coarctation, interrupted aortic arch)

— Feeding intolerance, tachypnea, diaphoresis with feeds, failure to thrive

— Shock at 1–2 weeks of life as the ductus closes (duct-dependent systemic circulation)

— Cyanosis in the first hours to days (duct-dependent pulmonary circulation or TGA)

Congenital heart disease (CHD) affects ~8 per 1,000 live births and is the most common congenital anomaly. On Step 3 you must rapidly triage a neonate or infant into cyanotic vs acyanotic and decide whether ductal patency is life-sustaining.

Acyanotic lesions = left-to-right shunts or obstructive lesions without desaturation

Cyanotic lesions = right-to-left shunting or mixing → SpO₂ <90% unresponsive to O₂

When to suspect CHD:

Step 3 management: Any neonate with cyanosis not corrected by 100% O₂ (failed hyperoxia test, PaO₂ <100 mmHg) or shock in the first 2 weeks of life → start prostaglandin E1 (alprostadil) infusion immediately, obtain echocardiography, and arrange transfer to a center with pediatric cardiac surgery. Do not wait for confirmatory imaging if the infant is decompensating.

Board pearl: A neonate who "pinks up" with crying suggests TGA (improved mixing); one who "blues with crying" suggests Tetralogy of Fallot (tet spell from infundibular spasm).

Presentation Patterns and Key History

— First hours of life: TGA, severe Ebstein anomaly, obstructed TAPVR (pulmonary edema picture)

— First days as ductus closes: HLHS, critical coarctation, critical AS, interrupted aortic arch, pulmonary atresia, tricuspid atresia

— 2–8 weeks: Large VSD, AVSD, PDA — pulmonary vascular resistance falls and left-to-right shunt becomes hemodynamically significant → CHF symptoms

— Months to years: ASD (often asymptomatic until adulthood), small VSD, mild PS, bicuspid aortic valve

— Toddler/older child: Repaired TOF survivors with pulmonary regurgitation; unrepaired TOF with tet spells, squatting, polycythemia

— Pulmonary overcirculation (acyanotic L→R shunt): Tachypnea, poor feeding (the infant equivalent of dyspnea on exertion), diaphoresis at the breast/bottle, recurrent respiratory infections, FTT

— Cyanosis without distress: TGA, TOF (until tet spells)

— Cyanosis with respiratory distress: Obstructed TAPVR, persistent pulmonary hypertension of newborn (mimic)

— Shock: Duct-dependent systemic lesion (HLHS, coarctation, critical AS)

— Prenatal: maternal diabetes (TGA, VSD, HCM), rubella (PDA, PS), lithium (Ebstein), alcohol (VSD, ASD), phenytoin/valproate, SSRIs

— Genetic syndromes: Down → AVSD/VSD; Turner → coarctation, bicuspid AV; DiGeorge (22q11) → conotruncal lesions (TOF, truncus, IAA); Williams → supravalvular AS; Noonan → pulmonary stenosis, HCM; Marfan → aortic root dilation

— Family history of CHD increases recurrence risk ~3-fold

Timing of presentation is the single most useful clue on the boards:

Symptom clusters:

Key history elements:

Key distinction: Cyanosis that worsens with feeding/crying = TOF tet spell (decreased SVR, increased infundibular obstruction). Cyanosis that improves with crying = TGA (better mixing through PFO/PDA).

Physical Exam Findings and Hemodynamic Assessment

— Right arm = pre-ductal; either leg = post-ductal

— >3% SpO₂ difference or >20 mmHg systolic gradient (arm > leg) → coarctation or interrupted aortic arch

— Lower SpO₂ in legs than right arm → right-to-left shunting across PDA (PPHN, critical coarctation, HLHS)

— Fixed split S2 → ASD (independent of respiration because of equalized RV stroke volume)

— Single loud S2 → pulmonary hypertension, TGA, truncus arteriosus, pulmonary atresia

— S3 gallop → volume overload (large VSD, PDA)

— Ejection click → bicuspid AV, pulmonary stenosis

— VSD: harsh holosystolic, left lower sternal border, louder with smaller defects

— ASD: systolic ejection murmur at LUSB (from increased flow across pulmonic valve) + fixed split S2; the ASD itself is silent

— PDA: continuous "machinery" murmur at left infraclavicular area

— TOF: harsh systolic ejection at LUSB (from RVOT obstruction, not the VSD); softer during tet spell

— Coarctation: systolic murmur at left interscapular back, delayed/weak femoral pulses, radio-femoral delay

— AS: harsh systolic ejection at RUSB radiating to carotids; AR diastolic murmur if bicuspid

— Pulmonary stenosis: systolic ejection at LUSB radiating to back

Four-extremity blood pressures and pre/post-ductal pulse oximetry are mandatory in any suspected CHD evaluation

Heart sounds:

Murmurs by lesion (high-yield):

Signs of CHF in infants: tachypnea, hepatomegaly (the pediatric equivalent of JVD), gallop, poor perfusion, FTT — peripheral edema is uncommon in infants

Board pearl: Differential cyanosis (pink upper body, blue lower) suggests right-to-left PDA shunting with coarctation or PPHN. Reverse differential cyanosis (blue upper, pink lower) is virtually pathognomonic for TGA with coarctation or interrupted aortic arch.

Diagnostic Workup — Initial Labs, Imaging, ECG

— Pass: SpO₂ ≥95% in right hand AND foot, with ≤3% difference

— Fail: SpO₂ <90% any limb (immediate), or 90–94% / >3% difference on three measurements 1 hour apart → echocardiography

— PaO₂ >250 mmHg → likely pulmonary etiology

— PaO₂ <100 mmHg → cyanotic CHD until proven otherwise

— PaO₂ 100–250 → indeterminate (PPHN, mixing lesion)

— Boot-shaped heart, decreased pulmonary vascularity → Tetralogy of Fallot

— "Egg on a string," narrow mediastinum, increased pulmonary vascularity → TGA

— "Snowman" / figure-of-8 → supracardiac TAPVR

— Cardiomegaly + increased pulmonary markings → large VSD, AVSD, PDA, truncus

— Rib notching (children >5 yr) → coarctation (collateral intercostal vessels)

— Severe cardiomegaly ("wall-to-wall heart") → Ebstein anomaly

— Right axis deviation, RVH → TOF, pulmonary stenosis, TAPVR

— Left axis deviation/superior axis in infant → AVSD, tricuspid atresia (think Down syndrome with cyanosis = tricuspid atresia; Down with CHF = AVSD)

— LVH → AS, coarctation, HLHS (later)

— Biventricular hypertrophy → large VSD, truncus, single ventricle

Pulse oximetry screening (universal in US newborns at ≥24 h):

Hyperoxia test: Place infant in 100% FiO₂ for 10 minutes

Chest x-ray patterns (boards love these):

ECG patterns:

Labs: CBC (polycythemia in chronic cyanosis), BMP (lactic acidosis in shock), BNP (elevated in CHF), pre-op type & screen, genetic testing (FISH 22q11 for conotruncal lesions, karyotype for Down/Turner)

Step 3 management: A failed pulse-ox screen mandates diagnostic echocardiography before discharge — never attribute it to "transitional circulation" without imaging in the well-appearing infant beyond 24 hours.

Diagnostic Workup — Advanced and Confirmatory Studies

— Defines chamber sizes, valve morphology, shunt direction/magnitude (Qp:Qs), gradient across stenotic valves, ventricular function, great-artery relationship

— Color and spectral Doppler quantify shunts and regurgitation

— Bubble study (agitated saline) can detect right-to-left shunts when TTE is equivocal

— Maternal pregestational DM, PKU, lupus/anti-Ro

— Teratogen exposure (lithium, retinoic acid, ACE inhibitors)

— Family history of CHD

— Abnormal obstetric ultrasound (especially abnormal 4-chamber view or outflow tracts)

— Fetal arrhythmia, hydrops, increased nuchal translucency

— Allows planned delivery at a cardiac center for duct-dependent lesions

— Diagnostic: measure pulmonary vascular resistance (critical before Fontan completion or to assess shunt reversibility in Eisenhardt physiology)

— Therapeutic: balloon atrial septostomy (Rashkind for TGA), balloon valvuloplasty (critical PS, AS), PDA/ASD device closure, coarctation stenting

Transthoracic echocardiography (TTE) is the gold standard for anatomic diagnosis of nearly all CHD

Fetal echocardiography (18–22 weeks gestation) indicated for:

Cardiac MRI: Best for post-repair TOF (quantifying pulmonary regurgitation and RV volume to time pulmonary valve replacement), aortic arch anatomy, and complex single-ventricle physiology

Cardiac CT angiography: Coronary anomalies, vascular rings, post-op conduits — faster but ionizing radiation

Cardiac catheterization:

Pulse oximetry with hyperoxia and pre/post-ductal saturations remain essential bedside adjuncts before advanced imaging

Board pearl: A neonate with severe cyanosis, normal heart size on CXR, and "egg-on-a-string" → TGA. Confirm with TTE showing parallel great arteries, then emergent balloon atrial septostomy if mixing is inadequate despite PGE1, followed by arterial switch operation (Jatene) within first 2 weeks of life before LV deconditions.

Risk Stratification and First-Line Management Logic

— Cyanotic + shock OR cyanotic unresponsive to O₂ → assume duct-dependent → PGE1 0.05–0.1 mcg/kg/min IV, secure airway (anticipate apnea), establish access, transfer

— CHF without cyanosis (large L→R shunt presenting at 4–8 weeks) → diuretics, optimize feeding/calories, ACE inhibitor as outpatient, surgical referral

— Asymptomatic murmur with normal exam → outpatient pediatric cardiology referral

— Duct-dependent pulmonary blood flow: Pulmonary atresia, critical PS, tricuspid atresia, severe TOF — present with cyanosis

— Duct-dependent systemic blood flow: HLHS, critical coarctation, critical AS, interrupted aortic arch — present with shock as duct closes

— Parallel circulations requiring mixing: TGA — needs PDA + ASD/PFO

— Increased pulmonary blood flow + cyanosis → TGA, truncus, TAPVR, single ventricle without PS

— Decreased pulmonary blood flow + cyanosis → TOF, tricuspid atresia, pulmonary atresia, Ebstein

— Side effects: apnea (10–12%), hypotension, fever, jitteriness — have intubation equipment ready

— Maintains ductal patency by inhibiting closure

— Continue until definitive surgical or catheter-based palliation

The critical Step 3 decision tree for a sick neonate with suspected CHD:

Duct-dependent lesion categories:

Stratification by pulmonary blood flow:

PGE1 considerations (memorize):

Step 3 management: For the shocked neonate of unclear etiology in the first 2 weeks of life, the differential is sepsis vs duct-dependent CHD vs inborn error of metabolism. Empirically start ampicillin + gentamicin AND PGE1, obtain cultures, lactate, ammonia, and urgent echocardiogram. Withholding PGE1 to "rule out sepsis first" is a tested wrong answer.

Pharmacotherapy — First-Line Drug Regimens

— Dose: 0.05–0.1 mcg/kg/min IV continuous; titrate down to lowest effective dose (0.01–0.03) once duct patent to minimize apnea

— Indication: All suspected duct-dependent lesions until definitive repair

— Monitor for apnea — many institutions intubate before transport

— Furosemide 1–2 mg/kg/dose BID-TID; add spironolactone for K-sparing and aldosterone antagonism

— Monitor electrolytes, growth

— ACE inhibitor (captopril or enalapril) reduces systemic afterload, decreases L→R shunting; standard in moderate-large VSD, AVSD, AR, post-repair single ventricle physiology

— Monitor renal function, K+, hypotension; avoid in HLHS pre-Norwood (systemic output depends on PDA + maintained SVR)

1. Knee-to-chest position (↑SVR)

2. 100% O₂

3. Morphine 0.1 mg/kg SC/IV (decreases hyperpnea, infundibular spasm)

4. IV fluid bolus (increases preload, RV filling)

5. Phenylephrine (↑SVR, reverses shunt)

6. Propranolol or esmolol (relaxes infundibular spasm)

7. Avoid β-agonists (worsen infundibular spasm)

Prostaglandin E1 (alprostadil)

Diuretics for CHF from L→R shunt (large VSD, AVSD, PDA, post-Norwood):

Afterload reduction:

Inotropes: Milrinone (inodilator) preferred in single-ventricle and post-op states; dopamine/epinephrine for refractory shock

Tet spell management (memorize the sequence):

Endocarditis prophylaxis (AHA 2007/2021): Only for unrepaired cyanotic CHD, prosthetic material in first 6 months post-repair, residual defect adjacent to prosthetic patch, and prior IE — amoxicillin 50 mg/kg PO 30–60 min pre-procedure (dental with gingival manipulation)

Board pearl: β-blockers (propranolol) are the chronic outpatient prophylaxis for tet spells while awaiting surgical repair of TOF — they reduce infundibular contractility.

Procedures and Invasive Management

— VSD: Small (<3 mm) muscular VSDs often close spontaneously by age 2. Surgical patch closure for symptomatic large VSDs by 6 months or pulmonary HTN. Device closure increasingly used for muscular VSDs.

— ASD: Close if RV volume overload, Qp:Qs >1.5, or paradoxical embolism. Secundum ASDs → percutaneous device closure (Amplatzer). Primum, sinus venosus, coronary sinus → surgical.

— PDA: Indomethacin or ibuprofen in preterm infants (prostaglandin inhibition). Acetaminophen is an alternative. Term infants/older: catheter-based coil/device closure. Avoid indomethacin in HLHS/duct-dependent.

— Coarctation: Surgical end-to-end anastomosis in neonates; balloon angioplasty ± stenting in older children/recurrence.

— AS/PS: Balloon valvuloplasty first-line for critical neonatal valvar stenosis.

— TOF: Complete repair (VSD closure + RVOT reconstruction) at 3–6 months. Blalock–Taussig–Thomas shunt (subclavian-to-PA) as palliation in symptomatic neonates not yet candidates for full repair.

— TGA: Arterial switch (Jatene) within 2 weeks before LV deconditions. Balloon atrial septostomy (Rashkind) emergently if poor mixing.

— HLHS: Three-stage palliation — Norwood (neonatal) → bidirectional Glenn (4–6 months) → Fontan (2–4 years). Alternative: heart transplant.

— Tricuspid atresia, single ventricle: Glenn → Fontan pathway.

— TAPVR: Surgical anastomosis of pulmonary venous confluence to LA; obstructed TAPVR = surgical emergency (ECMO may be needed).

— Truncus arteriosus: Repair in neonatal period (VSD closure, RV-PA conduit).

Acyanotic lesion repair:

Cyanotic lesion repair:

CCS pearl: For a cyanotic neonate with TGA, the ordered sequence is: PGE1 → echocardiogram → balloon atrial septostomy if SpO₂ remains <75% despite PGE1 → arterial switch operation. Failing to order BAS before the switch is a common CCS error.

Special Populations — Renal/Hepatic and Older Adults with CHD

— Avoid: pregnancy (30–50% maternal mortality), high altitude, dehydration, vasodilators that drop SVR, NSAIDs

— Treat: pulmonary vasodilators (bosentan, sildenafil), phlebotomy only for hyperviscosity symptoms (not routine for Hct), iron repletion (paradoxically iron-deficient despite polycythemia)

— Closure is contraindicated once Eisenmenger develops (acute RV failure)

— Protein-losing enteropathy, plastic bronchitis, Fontan-associated liver disease (cirrhosis, HCC), atrial arrhythmias, thromboembolism

— Require lifelong anticoagulation consideration, hepatology surveillance with elastography/imaging, ACHD-specialist follow-up

— Cyanotic CHD → chronic hypoxia → glomerulopathy, hyperuricemia, gout, cholelithiasis (chronic hemolysis)

— Diuretics: reduce dose in renal impairment, monitor for hypokalemia/contraction alkalosis

— ACE inhibitors: hold for AKI, hyperkalemia; use with caution in single-ventricle physiology

Adult congenital heart disease (ACHD) is a growing population — >90% of CHD patients now survive to adulthood. Step 3 increasingly tests longitudinal management.

Eisenmenger syndrome: Long-standing L→R shunt (unrepaired VSD, ASD, PDA, AVSD) → pulmonary vascular remodeling → pulmonary HTN → shunt reversal to R→L → cyanosis, polycythemia, clubbing

Post-Fontan adult complications:

Renal/hepatic considerations:

Repaired TOF in adulthood: Chronic pulmonary regurgitation → RV dilation, arrhythmias, sudden cardiac death. Monitor with serial cardiac MRI; pulmonary valve replacement when RV end-diastolic volume index >150 mL/m² or symptoms develop.

Board pearl: An adult with prior CHD repair presenting with new atrial flutter or syncope needs urgent ACHD referral — arrhythmia is the leading cause of late mortality in repaired CHD, especially TOF, TGA (atrial switch), and Fontan patients.

Special Populations — Pregnancy and Pediatric Subgroups

— WHO I (low risk): Repaired small ASD/VSD/PDA, mild PS — routine OB care

— WHO II: Repaired TOF, most arrhythmias — cardiology consult each trimester

— WHO III (high risk): Mechanical valve, systemic RV (post-atrial switch TGA, ccTGA), Fontan, cyanotic CHD without pulmonary HTN — high-risk OB + ACHD co-management

— WHO IV (pregnancy contraindicated): Pulmonary hypertension (any cause including Eisenmenger), severe symptomatic obstructive lesions, severe systemic ventricular dysfunction (EF <30%), severe coarctation, Marfan with aortic root >45 mm

— Warfarin teratogenic in first trimester (6–12 weeks); switch to LMWH or UFH

— Resume warfarin in 2nd/3rd trimester, switch back to heparin near delivery

— Symptomatic PDA → fluid restriction, indomethacin or ibuprofen (contraindicated in NEC, IVH, renal failure, thrombocytopenia)

— Surgical/transcatheter closure if medical therapy fails

— Down syndrome: AVSD (40%), VSD — screen all newborns with echo

— Turner syndrome: Bicuspid AV, coarctation — echo at diagnosis, lifelong aortic surveillance

— 22q11.2 deletion (DiGeorge): Conotruncal — TOF, truncus, IAA, vascular ring; also hypocalcemia, T-cell deficiency, cleft palate

— Williams syndrome: Supravalvular AS, peripheral PS, hypercalcemia

— Noonan syndrome: Pulmonary valve stenosis (dysplastic), HCM

— Marfan, Loeys-Dietz, Ehlers-Danlos vascular type: Aortic root dilation, dissection

Pregnancy in CHD stratified by modified WHO classification:

Anticoagulation in pregnancy with mechanical valve:

Preterm neonate with PDA:

Genetic syndromes (recurrent Step 3 stems):

Step 3 management: A woman with Eisenmenger syndrome who becomes pregnant should be offered early therapeutic abortion counseling given 30–50% maternal mortality — informed, nondirective counseling with multidisciplinary team is the correct approach.

Complications and Adverse Outcomes

— Tet spells (TOF): hypercyanotic episodes from infundibular spasm — see chunk 7 for management

— Paradoxical embolism / stroke: any R→L shunt (PFO, ASD, cyanotic CHD) — meticulous IV line air filtering

— Cerebral abscess: classic in cyanotic CHD (R→L shunt bypasses pulmonary filter) — workup new neuro symptoms aggressively

— Infective endocarditis: highest risk in unrepaired cyanotic CHD, prosthetic material, prior IE

— Heart failure: in large L→R shunts, post-op residual lesions

— Pulmonary hypertension / Eisenmenger: untreated large L→R shunts

— Polycythemia → hyperviscosity (headache, visual changes, paresthesia) — phlebotomy only when symptomatic with Hct >65% AND euvolemic

— Iron deficiency (microcytosis with elevated Hct) — paradoxically common; treat iron deficiency before phlebotomy

— Hyperuricemia, gout, cholelithiasis (bilirubin stones), glomerulopathy, scoliosis, growth failure

— Coagulopathy: abnormal platelets, von Willebrand abnormalities — risk of bleeding and thrombosis simultaneously

— Arrhythmias: Atrial flutter post-Fontan; ventricular arrhythmias and SCD post-TOF repair (related to RVOT scar, QRS >180 ms)

— Heart block: post-VSD/AVSD closure (near AV node)

— Residual lesions: Recurrent coarctation, pulmonary regurgitation after TOF repair, baffle leaks post-atrial switch

— Protein-losing enteropathy and plastic bronchitis after Fontan

— Fontan-associated liver disease: cirrhosis, HCC — surveillance with elastography, AFP, imaging

Acute complications:

Chronic cyanosis complications:

Post-surgical complications:

Key distinction: A cyanotic CHD patient with headache + focal neuro signs + fever is brain abscess until proven otherwise (R→L shunt bypasses pulmonary capillary bed). Order MRI brain + blood cultures + neurosurgery consult; empiric vancomycin + ceftriaxone + metronidazole. This differs from the febrile cardiac patient where IE/stroke would be the first thought in older adults.

When to Escalate Care — ICU, Consult, and Inpatient Triage

— Failed newborn pulse-ox screen with SpO₂ <90%

— Cyanotic neonate unresponsive to O₂

— Shocked neonate in first 2 weeks of life (suspect duct-dependent systemic)

— Tet spell unresponsive to first-line measures

— New-onset CHF in infant (tachypnea, hepatomegaly, gallop, FTT)

— Severe respiratory distress with suspected obstructed TAPVR

— Start PGE1 before transport, not after

— Anticipate apnea — intubate prophylactically for long transports or PGE1 doses >0.05 mcg/kg/min

— Maintain euvolemia; avoid over-resuscitation in HLHS (Qp:Qs balance)

— In HLHS, avoid 100% O₂ before Norwood — it lowers PVR, increases Qp, and steals from systemic circulation; target SpO₂ 75–85%

— Failure to wean from cardiopulmonary bypass

— Obstructed TAPVR with refractory hypoxemia

— Refractory cardiogenic shock or post-op low cardiac output

— Bridge to transplant in HLHS variants

— Asymptomatic murmur with normal exam and growth → routine referral

— Murmur with feeding difficulty or growth failure → expedited (days)

— Any abnormal pulse-ox screen → before discharge

— ACHD cardiologist, cardiac surgeon, electrophysiologist, hepatologist (Fontan), pulmonary HTN specialist (Eisenmenger), high-risk OB, genetic counselor

Immediate NICU/PICU + pediatric cardiology + cardiac surgery consultation:

Transport considerations:

ECMO indications:

Outpatient cardiology referral (urgency depends on presentation):

Multidisciplinary teams in ACHD:

CCS pearl: In the CCS case of a 1-week-old with poor feeding, cool extremities, and weak femoral pulses, the correct early orders are: IV access, PGE1 infusion, 4-extremity BP, pre/post-ductal SpO₂, echocardiogram, BMP, lactate, blood culture, ampicillin + gentamicin, NICU transfer. Delaying PGE1 to "complete sepsis workup" loses points.

Key Differentials — Same-Category (Other CHD Lesions)

— VSD vs ASD: VSD has harsh holosystolic LLSB murmur, presents at 4–8 weeks as PVR drops; ASD has soft systolic at LUSB + fixed split S2, often asymptomatic until adulthood

— PDA: continuous machinery murmur, wide pulse pressure, bounding pulses — distinguishes from VSD/ASD

— AVSD: common in Down syndrome; AVSD has both ASD + VSD components + common AV valve → superior/left axis deviation on ECG distinguishes from isolated VSD

— Coarctation: weak/delayed femoral pulses + upper-extremity hypertension + interscapular murmur — the obstructive lesion, not a shunt

— Decreased pulmonary blood flow + cyanosis: TOF, tricuspid atresia, pulmonary atresia, severe Ebstein, critical PS

— Increased pulmonary blood flow + cyanosis: TGA, truncus arteriosus, TAPVR (unobstructed), single ventricle without PS

— TOF = boot-shaped heart, decreased vascularity, RVH

— TGA = egg-on-string, narrow mediastinum, increased vascularity, often normal-sized heart

— TAPVR (supracardiac) = snowman/figure-8, increased vascularity

— Truncus = single great vessel on echo, single S2, often with absent thymic shadow (think 22q11)

— Tricuspid atresia = left axis deviation in a cyanotic infant — pathognomonic combination

— Ebstein anomaly = massive cardiomegaly ("wall-to-wall heart"), maternal lithium exposure, atrialized RV

Distinguishing acyanotic L→R shunts:

Distinguishing cyanotic lesions by chest x-ray and pulmonary blood flow:

Key distinction: A cyanotic infant with Down syndrome and left axis deviation → think tricuspid atresia (not the usual AVSD, which causes CHF, not cyanosis). The axis deviation distinguishes.

Board pearl: Single S2 in a cyanotic infant narrows the diagnosis to truncus arteriosus, TGA, pulmonary atresia, or severe TOF (anything with one functional semilunar valve or a posterior aorta).

Key Differentials — Other-Category Causes of Cyanosis/Distress

— Cyanosis with respiratory distress, often post meconium aspiration, sepsis, asphyxia, or idiopathic

— Pre-/post-ductal SpO₂ gradient (R→L PDA shunt) mimics coarctation/HLHS

— Echo: structurally normal heart with elevated PA pressures, R→L shunt at PDA/PFO

— Treat: oxygen, optimize ventilation (avoid acidosis), inhaled nitric oxide, sildenafil, milrinone, ECMO

— Cyanotic with respiratory distress; hyperoxia test improves PaO₂ >250

— CXR shows pulmonary pathology

— Empiric antibiotics; investigate for underlying CHD concurrently

— Cyanosis with normal PaO₂ but low SpO₂; "chocolate brown" blood, SpO₂ doesn't improve with O₂

— Acquired (dapsone, benzocaine, nitrates, well water nitrates in infants) or congenital (cytochrome b5 reductase deficiency)

— Treat with methylene blue 1–2 mg/kg IV (avoid in G6PD deficiency — use ascorbic acid)

Persistent pulmonary hypertension of the newborn (PPHN):

Sepsis / pneumonia / RDS:

Methemoglobinemia:

Polycythemia of newborn: Acrocyanosis (peripheral) — benign in first 48 h with normal central color

Hypoglycemia, inborn errors of metabolism: Can mimic shock/CHF — check glucose, ammonia, lactate in every sick neonate

Choanal atresia, airway anomalies: Cyanosis relieved by crying (opens oral airway) — opposite of TGA pattern

Diaphragmatic hernia: Scaphoid abdomen, bowel sounds in chest, mediastinal shift — distinct from CHD

Vascular ring / sling: Stridor, dysphagia, recurrent respiratory infections — barium swallow and CT angiography

Step 3 management: A cyanotic neonate with respiratory distress, normal CXR, pre/post-ductal SpO₂ gradient, and echo showing normal anatomy with high PA pressure → PPHN. Treatment is inhaled nitric oxide, not PGE1. Misdiagnosing PPHN as CHD wastes critical time and exposes the infant to unnecessary PGE1 side effects.

Secondary Prevention, Discharge Medications, Long-Term Plan

— Aspirin 81 mg or 3–5 mg/kg after shunts (BT shunt, Glenn, Fontan), device closures (3–6 months), for thromboembolism prevention

— Warfarin for mechanical valves, Fontan with thrombus history, persistent atrial arrhythmias

— Furosemide ± spironolactone for residual CHF

— ACE inhibitor (enalapril, captopril) for residual L→R shunt or ventricular dysfunction

— β-blocker for arrhythmia prophylaxis, awaiting TOF repair (tet spell prevention)

— Sildenafil / bosentan for pulmonary HTN, Eisenmenger

— Unrepaired cyanotic CHD (including palliative shunts)

— Completely repaired CHD with prosthetic material — first 6 months only

— Repaired CHD with residual defect adjacent to prosthetic patch (lifelong)

— Prior infective endocarditis

— Regimen: Amoxicillin 50 mg/kg (max 2 g) PO 30–60 min before dental procedures with gingival/periapical manipulation; clindamycin or azithromycin if penicillin-allergic (no longer recommends clindamycin in 2021 update — use cephalexin or azithromycin)

— Routine schedule including influenza annually, RSV prophylaxis (palivizumab/nirsevimab) for hemodynamically significant CHD in first year

— Live vaccines avoided if on immunosuppression post-transplant

— Most repaired CHD patients can participate in physical activity — restrictions based on residual lesions (Bethesda guidelines)

— Avoid competitive sports with Marfan + aortic root >40 mm, severe AS, LQTS, HCM, Eisenmenger

— Contraception counseling for adolescents — avoid estrogen in Fontan, Eisenmenger, mechanical valve (thromboembolic risk) — IUD or progestin-only preferred

Discharge medications after CHD repair vary by lesion but commonly include:

Endocarditis prophylaxis (AHA 2007/2021 — narrow list):

Immunizations:

Lifestyle counseling:

Board pearl: Bicuspid aortic valve carries lifelong risk of AS, AR, aortic root dilation/dissection — recommend serial echo (q1–2 years) and screen first-degree relatives with echocardiography (autosomal dominant with variable penetrance).

Follow-Up, Monitoring, and Counseling

— Small VSD/ASD spontaneously closing: Annual pediatric cardiology until closure documented; discharge after 2 normal follow-ups

— Repaired VSD/ASD without residual: Every 3–5 years lifelong

— Repaired TOF: Annually with TTE; cardiac MRI every 2–3 years to track pulmonary regurgitation and RV volumes — PVR when RVEDVi >150 mL/m² or symptoms

— Post-arterial switch TGA: Annual cardiology with attention to coronary patency, neoaortic root, RVOT

— Single ventricle / Fontan: Every 6–12 months with ACHD specialist; surveillance for arrhythmia, PLE, plastic bronchitis, FALD (liver elastography, AFP)

— Coarctation repair: Lifelong follow-up for re-coarctation, aneurysm, hypertension, bicuspid AV

— Bicuspid AV: Annual to biennial echo for valve function + aortic dimensions

— Growth charts (FTT signals hemodynamic compromise)

— Pulse oximetry at each visit

— 4-extremity BPs in coarctation patients

— ECG for QRS prolongation in TOF (>180 ms = SCD risk)

— Holter monitor for arrhythmia surveillance in TOF, Fontan, post-atrial switch

— Exercise stress testing for functional capacity, arrhythmia

— BNP, liver enzymes, albumin, protein (PLE in Fontan)

— Formal transition from pediatric to adult congenital cardiology between ages 18–21 — handoff to ACHD-accredited program

— Provide patient with written summary of anatomy, prior surgeries, medications, residual lesions, prophylaxis needs

— Address contraception, pregnancy planning, vocational issues, insurance continuity

— Offer to families with syndromic CHD or strong family history

— Recurrence risk in siblings ~3% (vs 0.8% baseline); higher for left-sided lesions

Follow-up cadence by lesion:

Monitoring parameters:

Transitions of care:

Genetic counseling:

Step 3 management: A 20-year-old with repaired TOF presenting for "establishing care" needs: ACHD cardiologist referral, baseline TTE, cardiac MRI, Holter, ECG (assess QRS duration), and counseling on contraception, pregnancy risk stratification, and exercise. Failure to refer to ACHD is a tested patient safety lapse.

Ethical, Legal, and Patient Safety Considerations

— When fetal echo identifies severe CHD (HLHS, complex single ventricle), parents must be counseled nondirectively about options: comprehensive surgical palliation (Norwood pathway), heart transplant listing, or comfort care/palliation only

— All options are ethically valid; physician's role is informed, balanced disclosure

— Multidisciplinary fetal cardiology team, palliative care consult, ethics committee available

— Discuss mortality, expected long-term outcomes, neurodevelopmental risk (single-ventricle survivors have ~50% rate of developmental delay), need for reoperations

— Document shared decision-making

— Loss to follow-up in adolescent CHD patients leads to preventable morbidity (unrecognized PR after TOF, atrial arrhythmias in Fontan)

— Active transition programs reduce gaps; never simply "graduate" patients out

— Written care summary, encrypted PHR, warm handoff to ACHD provider

— Pulse oximetry screening is mandated by law in all US states for newborns at ≥24 h of age

— Genetic testing requires consent including discussion of implications for family members

— Over-prescribing prophylaxis is a documented safety problem — narrowed indications since 2007 AHA guidelines minimize unnecessary antibiotic exposure and resistance

— Pre-participation screening must include personal/family history of sudden death, syncope, murmur — bicuspid AV, HCM, anomalous coronary artery are leading causes of athletic SCD

— Sign-off requires careful documentation; medico-legal liability significant

— Single-ventricle palliation requires extensive multidisciplinary support — equitable access remains a health-systems concern

Prenatal diagnosis and parental decision-making:

Informed consent for high-risk surgery:

Transition-of-care patient safety:

Mandatory reporting and screening:

Endocarditis prophylaxis stewardship:

Athletic clearance:

Resource allocation:

Step 3 management: Parents of a fetus with HLHS ask the physician what they "should" do. The correct response is to explore their values and present all options without recommending one — surgical palliation, transplant listing, and comfort care are all ethically permissible. Directive counseling toward any single option, even surgery, is a tested wrong answer.

High-Yield Associations and Rapid-Fire Clinical Facts

— Diabetes → TGA, VSD, HCM (asymmetric septal hypertrophy)

— Lithium → Ebstein anomaly

— Rubella → PDA, peripheral PS

— Alcohol → VSD, ASD (FAS)

— Phenytoin → PS, AS, coarctation, PDA

— SSRIs (paroxetine) → mild increase in septal defects

— Retinoic acid → conotruncal

— Maternal SLE/anti-Ro → congenital heart block

— Down → AVSD, VSD

— Turner → coarctation, bicuspid AV

— DiGeorge (22q11) → TOF, truncus, IAA type B

— Williams → supravalvular AS, peripheral PS

— Noonan → dysplastic PS, HCM

— Marfan → aortic root dilation, MVP, AR

— Holt-Oram → ASD + upper limb anomalies

— Alagille → peripheral pulmonary artery stenosis

— CHARGE → TOF, double-outlet RV, AVSD

— Fixed split S2 = ASD

— Continuous "machinery" = PDA

— Boot-shaped heart = TOF

— Egg on a string = TGA

— Snowman = supracardiac TAPVR

— Wall-to-wall heart = Ebstein

— Rib notching = coarctation

— Differential cyanosis = R→L PDA (coarctation, PPHN, HLHS)

— Reverse differential cyanosis = TGA + coarctation

Most common CHD overall: VSD (~30% of all CHD)

Most common cyanotic CHD presenting after newborn period: Tetralogy of Fallot

Most common cyanotic CHD in the newborn (first days): Transposition of the great arteries

Most common CHD requiring surgery in first year: Large VSD, TOF, TGA, AVSD

Maternal disease/exposure associations:

Syndrome associations:

Murmur shortcuts:

Tet spell rescue: knees-to-chest, O₂, morphine, fluids, phenylephrine, β-blocker — never give β-agonists

Board pearl: A neonate with murmur, hypocalcemic seizures, cleft palate, and absent thymus on CXR → 22q11.2 deletion / DiGeorge with TOF, truncus, or interrupted aortic arch type B. Send FISH 22q11 and avoid live vaccines until T-cell function confirmed.

Board Question Stem Patterns

"A 36-hour-old term infant has SpO₂ 88% in the right hand and 82% in the foot." → Next step: echocardiography before discharge. Don't repeat pulse-ox or give O₂ trial alone.

Stem 1 — Failed newborn pulse-ox screen:

Stem 2 — Cyanotic neonate in first hours of life with single S2 and increased pulmonary vascularity: → TGA. Start PGE1, plan balloon atrial septostomy and arterial switch.

Stem 3 — 2-year-old with episodic cyanosis and squatting relieves symptoms: → Tetralogy of Fallot tet spell. Management = knees-to-chest, O₂, morphine, fluids, phenylephrine.

Stem 4 — 1-week-old with poor feeding, weak femoral pulses, mottled extremities, lactic acidosis: → Critical coarctation or HLHS (duct-dependent systemic). Start PGE1 immediately; do not delay for sepsis workup.

Stem 5 — Asymptomatic 6-year-old with fixed split S2 and grade 2 systolic murmur at LUSB: → Secundum ASD. Echo; close if RV dilation, Qp:Qs >1.5, or paradoxical embolism.

Stem 6 — Preterm infant at 3 weeks with bounding pulses, wide pulse pressure, continuous murmur, worsening respiratory status: → Symptomatic PDA. Treat with indomethacin or ibuprofen (or acetaminophen).

Stem 7 — Adolescent with Down syndrome and progressive cyanosis years after unrepaired AVSD: → Eisenmenger syndrome. Pulmonary vasodilators; closure is contraindicated.

Stem 8 — Cyanotic neonate, normal-sized heart, "egg on string" CXR: → TGA.

Stem 9 — Infant with maternal lithium use, massive cardiomegaly, cyanosis: → Ebstein anomaly.

Stem 10 — Child with hypocalcemia, recurrent infections, conotruncal lesion: → 22q11.2 deletion.

Stem 11 — Adult with repaired TOF, new wide QRS (>180 ms), syncope: → Risk of sudden cardiac death; refer for EP study, consider ICD and pulmonary valve replacement.

Stem 12 — Adult Fontan with diarrhea, low albumin, edema: → Protein-losing enteropathy; check stool α1-antitrypsin.

Step 3 management: Recognize the stem's timing + cyanosis + CXR pattern triad to lock in the diagnosis quickly, then default to the PGE1 + echo + transfer algorithm for any duct-dependent presentation.

One-Line Recap

Congenital heart disease management on Step 3 hinges on rapid triage of cyanotic vs acyanotic, recognizing duct-dependent lesions, and initiating PGE1 plus echo while arranging transfer to a pediatric cardiac center.

Acyanotic L→R shunts (VSD, ASD, PDA, AVSD) present at 4–8 weeks with CHF symptoms as PVR drops; treat with diuretics + ACE inhibitor and refer for surgical or device closure when Qp:Qs >1.5 or symptomatic.

Cyanotic lesions present in first hours-days; remember the 5 T's + HLHS, use timing + CXR pattern (boot = TOF, egg-on-string = TGA, snowman = TAPVR, wall-to-wall = Ebstein) to localize, and treat duct-dependent lesions with PGE1 0.05–0.1 mcg/kg/min while anticipating apnea.

Tet spells require knees-to-chest, O₂, morphine, IV fluids, phenylephrine, and β-blocker — never β-agonists; chronic propranolol bridges to definitive TOF repair at 3–6 months.

Long-term ACHD care demands surveillance for arrhythmia (TOF, Fontan), pulmonary regurgitation (post-TOF MRI), Fontan complications (PLE, FALD), Eisenmenger physiology, and bicuspid aortic valve disease; formal pediatric-to-adult transition between 18–21 to ACHD-accredited programs is a patient-safety imperative.

Board pearl: When in doubt on a sick neonate in the first 2 weeks of life with cyanosis or shock — start PGE1, get an echo, transfer. Withholding prostaglandin to "rule out sepsis first" is the most commonly tested wrong answer in pediatric cardiology on Step 3.