Acquired heart disease develops after birth in a structurally normal heart, usually from inflammation, infection, or lifestyle-related risk factors. In high-income countries Kawasaki disease is the leading cause of acquired heart disease in children; worldwide, rheumatic heart disease remains the most common.

Kawasaki disease (KD) — an acute, self-limited vasculitis of medium-sized arteries of unknown cause, occurring mostly in children under 5 years, more often in boys and in children of East Asian ancestry. Its main danger is coronary artery aneurysm, which develops in about a quarter of untreated children and far fewer when IVIG is given early. Aneurysms can thrombose or rupture, causing myocardial infarction or sudden death.

Acute rheumatic fever (ARF) — an autoimmune reaction 2–4 weeks after untreated group A streptococcal (GAS) pharyngitis. Antibodies against streptococcal antigens cross-react with heart, joints, brain, and skin (molecular mimicry). Carditis is the only manifestation that can cause permanent damage — scarring of the mitral (most often) and aortic valves → rheumatic heart disease (RHD). Recurrences with each new strep infection add damage, so secondary prophylaxis is the key to prevention. (Adult RHD: Medical-Surgical topic "Inflammatory Heart Disease.")

Other acquired conditions

• Infective endocarditis — infection of the endocardium or valves; higher risk with CHD (especially cyanotic, prosthetic material), central lines, and poor dental health
• Myocarditis — usually viral; can present with heart failure, arrhythmia, or chest pain
• Multisystem inflammatory syndrome in children (MIS-C) — follows SARS-CoV-2 infection by 2–6 weeks; fever, GI symptoms, rash, shock, and myocardial dysfunction; overlaps with Kawasaki disease
• Cardiomyopathy (dilated, hypertrophic) — inherited or acquired; hypertrophic cardiomyopathy is a cause of sudden death in young athletes
• Hypertension and dyslipidemia — rising with childhood obesity; begin the process of adult cardiovascular disease

Shock — circulatory failure from hypovolemia (most common in children: diarrhea, bleeding), sepsis, or cardiac failure. Children compensate with tachycardia and vasoconstriction, so blood pressure falls only late.

Kawasaki disease — diagnosis: fever for 5 days or more plus at least 4 of 5 principal features

1. Bilateral conjunctival injection without discharge (limbal sparing)
2. Oral changes: red, dry, cracked lips, strawberry tongue, red oral mucosa
3. Polymorphous rash (trunk, perineum); not vesicular
4. Extremity changes: red palms and soles and swelling of hands and feet (acute); peeling of fingers and toes (weeks 2–3)
5. Cervical lymphadenopathy, at least 1.5 cm, usually unilateral and nonsuppurative

Incomplete KD (fewer features, common in infants under 6 months) is diagnosed with lab and echo findings — infants have the highest aneurysm risk. Other findings: extreme irritability, arthritis, abdominal pain, gallbladder hydrops, sterile pyuria, and tachycardia or gallop (myocarditis).

Rheumatic fever — Jones criteria (2015 revision): evidence of recent GAS infection plus 2 major, or 1 major and 2 minor criteria

• Major: carditis (clinical or on echocardiogram — new murmur, tachycardia out of proportion to fever), migratory polyarthritis of large joints, Sydenham chorea (involuntary jerky movements, emotional lability — can appear months later), erythema marginatum (pink rings with clear centers on trunk), subcutaneous nodules (painless, over bony prominences)
• Minor: fever, arthralgia, raised ESR or CRP, prolonged PR interval
• In moderate- and high-risk populations, monoarthritis or polyarthralgia can count as major

Shock and perfusion

• Early (compensated): tachycardia, capillary refill over 2 seconds, weak peripheral pulses, cool extremities with a warm trunk, decreased urine output, irritability
• Late (hypotensive): low BP, lethargy, mottling, bradycardia (pre-arrest)
• Warm septic shock: flash capillary refill, bounding pulses, wide pulse pressure; cold shock: delayed refill, weak pulses, cool mottled skin

Pediatric hypertension — elevated BP (90th to below 95th percentile, or 120/80 or higher in adolescents 13 and older); stage 1 at or above the 95th percentile (or 130/80 in adolescents). Measure with the correct cuff size — a cuff that is too small gives a falsely high reading.

Kawasaki disease (AHA 2024 update)

• IVIG 2 g/kg as a single infusion over 8–12 hours, ideally within the first 10 days of fever (still given after day 10 if fever or inflammation persists)
• Aspirin: moderate dose (30–50 mg/kg/day) or high dose (80–100 mg/kg/day) during the acute febrile phase, then low dose (3–5 mg/kg/day) as an antiplatelet agent until follow-up echo shows no coronary changes (about 4–6 weeks). The benefit of acute-phase aspirin on coronary outcomes is debated, but it remains part of standard therapy
• High-risk children (young infants, early aneurysms): add corticosteroids tapered over 2–3 weeks
• IVIG-resistant KD (fever 36 hours or more after the infusion): second IVIG dose, corticosteroids, or infliximab
• Large aneurysms: anticoagulation (warfarin or low-molecular-weight heparin) with low-dose aspirin; long-term cardiology follow-up

Acute rheumatic fever

• Eradicate GAS: benzathine penicillin G IM once (dose as in secondary prophylaxis below) or oral penicillin for 10 days
• Arthritis: aspirin or naproxen (dramatic response supports the diagnosis)
• Carditis: rest and limited activity until inflammation settles; heart failure treatment; corticosteroids for severe carditis in some protocols
• Chorea: quiet, safe environment; medication for severe cases
• Secondary prophylaxis — benzathine penicillin G IM every 4 weeks (every 3 weeks in high-risk settings): 27 kg (60 lb) or less: 600,000 units; over 27 kg: 1.2 million units (AHA/IDSA, US; WHO 2024 uses under 30 kg / 30 kg or more) to prevent recurrence and valve damage. Duration: no carditis — 5 years or until age 21; carditis without residual valve disease — 10 years or until 21; residual valve disease — 10 years or until age 40, sometimes lifelong (whichever is longer). Oral penicillin or erythromycin if injections are impossible

Infective endocarditis — prolonged IV antibiotics (4–6 weeks) guided by cultures; surgery for valve destruction.

Septic shock — recognize early; antibiotics within 1 hour; isotonic crystalloid boluses of 10–20 mL/kg, reassessing after each for improvement and for fluid overload (crackles, liver enlargement); epinephrine or norepinephrine is preferred over dopamine for fluid-refractory shock.

Hypertension — lifestyle change (DASH-type diet, less sodium, activity, weight management); medication (ACE inhibitor, ARB, calcium channel blocker, thiazide) for stage 2, symptoms, or failed lifestyle change.

Drug safety (doses weight-based and verified against a pediatric reference)

Listed in priority order.

1. Circulation and cardiac function
   • Monitor HR and rhythm, BP, perfusion, SpO₂, and signs of heart failure (tachypnea, hepatomegaly, gallop, edema); report chest pain, arrhythmias, or signs of myocardial ischemia (in infants: irritability, pallor, vomiting)
   • Shock: position flat, oxygen, IV or intraosseous access, fluid boluses and antibiotics as ordered; reassess after each bolus
2. IVIG infusion safety — verify product and dose, use a pump, titrate the rate, monitor vital signs, and stop the infusion and notify the provider for a reaction
3. Fever and comfort (KD)
   • Monitor temperature (every 4 hours or as ordered) and fever pattern — fever lasting 36 hours or more after IVIG suggests resistance
   • Minimize stimulation: the child is very irritable; cluster care, quiet room, parental presence
   • Lip and mouth care: lubricant on cracked lips, soft cool foods and fluids, mouth rinses
   • Skin: keep peeling skin clean; do not pull; lotion as allowed
   • Monitor intake, output, and weight (fluid overload with IVIG, poor intake)
4. Joint and neurologic care (ARF)
   • Support painful joints; avoid pressure from bedclothes; give anti-inflammatory drugs as ordered
   • Chorea: protect from injury (padded rails), assist with feeding and self-care, explain that movements are involuntary and temporary
   • Balance rest with quiet activities during carditis
5. Record and coordinate prophylaxis — dates of each injection, reminders, and follow-up

• Kawasaki: irritability may continue for weeks; peeling of fingers and toes is expected; continue low-dose aspirin as prescribed; do not give ibuprofen; report fever, vomiting, or exposure to chickenpox or influenza; get the yearly inactivated influenza vaccine; delay live vaccines for 11 months after IVIG; keep all echocardiogram appointments
• Rheumatic fever: never miss a prophylaxis injection — each missed dose risks a recurrence and more valve damage; treat any sore throat promptly; keep excellent dental hygiene; tell every provider about the history
• Children with valve damage: ask the cardiologist about endocarditis prophylaxis (only certain high-risk conditions qualify)
• Heart-healthy habits: balanced diet low in salt and saturated fat, 60 minutes of daily activity, no tobacco or vaping, healthy weight; BP checks at every yearly visit from age 3

• Kawasaki: fever 5 days or more + 4 of 5 (bilateral non-purulent conjunctivitis, cracked lips/strawberry tongue, rash, swollen red hands and feet then peeling, unilateral cervical node 1.5 cm or more)
• Main risk: coronary artery aneurysm — echocardiograms at diagnosis, 1–2 weeks, and 4–6 weeks
• IVIG 2 g/kg over 8–12 hours within 10 days + aspirin (moderate or high dose, then low dose 3–5 mg/kg/day)
• IVIG: monitor like a transfusion; delay live vaccines 11 months
• Aspirin in KD: inactivated flu vaccine, report varicella or flu exposure (Reye), no ibuprofen
• Rheumatic fever follows GAS pharyngitis by 2–4 weeks; Jones criteria; carditis causes permanent mitral valve damage
• Secondary prophylaxis: benzathine penicillin G IM every 3–4 weeks for years — adherence is the priority
• Shock in children: tachycardia and delayed capillary refill come first; hypotension is late
• Septic shock: antibiotics within 1 hour, 10–20 mL/kg boluses with reassessment, epinephrine or norepinephrine
• BP measured with the correct cuff size; stage 1 hypertension at or above the 95th percentile