🫀 Chapter 488: Diseases of the Myocardium
Nelson's Textbook of Pediatrics 22e | DCM · HCM · RCM · ARVC · LVNC · Myocarditis · Genetics · Heart failure · Transplantation · Transition
📚 Reference: www.paeds.online — Paediatric Resource Hub
📌 Dilated Cardiomyopathy (DCM)LV dilation + systolic dysfunction (EF <40%). Most common pediatric cardiomyopathy. Causes: idiopathic, genetic (sarcomere, dystrophin), myocarditis, metabolic (carnitine, Barth syndrome), anthracycline toxicity, neuromuscular.
📌 Hypertrophic Cardiomyopathy (HCM)LV hypertrophy (septal > free wall), preserved or hyperdynamic systolic function, diastolic dysfunction. Genetic (sarcomeric proteins: MYH7, MYBPC3). Risk of sudden death, outflow tract obstruction.
📌 Restrictive Cardiomyopathy (RCM)Normal chamber size, preserved EF, severe diastolic dysfunction, massive atria. Poor prognosis. Cardiac transplantation often needed. May be idiopathic or infiltrative (amyloid, hemochromatosis, sarcoid).
📌 MyocarditisInflammatory cardiomyopathy. Viral (enterovirus, adenovirus, parvovirus B19, COVID-19, MIS-C). ECG: low voltage, ST-T changes. Cardiac MRI: late gadolinium enhancement (subepicardial). Endomyocardial biopsy gold standard.
📌 ARVC (Arrhythmogenic Right Ventricular Cardiomyopathy)Fibrofatty replacement RV → VT with LBBB morphology, epsilon wave. Desmosomal gene mutations (PKP2, DSP). Risk of sudden death. ICD for high-risk. Avoid competitive sports.
📌 LVNC (Left Ventricular Noncompaction)Deep trabeculations, thin compacted layer. Associated with DCM, HCM, congenital heart disease. Gene mutations: MYH7, MYBPC3, TAZ (Barth syndrome X-linked).
📌 Diagnosis of cardiomyopathyEchocardiogram (LV size, wall thickness, EF). Cardiac MRI (scar, edema, fat infiltration). Genetic testing (sarcomere, desmosome, metabolic). Endomyocardial biopsy for myocarditis/infiltrative.
📌 Heart failure therapy in DCMDiuretics, ACE inhibitors/ARBs, beta-blockers (carvedilol, metoprolol), aldosterone antagonists (spironolactone). Milrinone for acute decompensation. Digoxin controversial.
📌 Advanced heart failure therapiesVentricular assist devices (Berlin Heart EXCOR, HeartMate 3) as bridge to transplant. ECMO for acute fulminant myocarditis. Cardiac transplantation: 5-year survival ~80% in children.
📌 Transition & cardiomyopathy in adultsLifelong follow-up for HF therapy, arrhythmia surveillance (ICD). Genetic counseling for family. Pregnancy high-risk with DCM or HCM (avoid). Transition to adult heart failure/cardiology.
🔍 Step 1: Recognize prodrome
Viral illness 1-4 weeks prior: fever, myalgia, URI, GI symptoms. Sudden onset of heart failure symptoms: dyspnea, poor feeding, irritability in infants.
📈 Step 2: Clinical presentation
Chest pain, palpitations, fatigue, exercise intolerance, syncope. Signs: tachycardia, gallop rhythm (S3), new murmur (MR), hepatomegaly, pulmonary edema, cardiogenic shock.
🩺 Step 3: Initial diagnostic tests
ECG: sinus tachycardia, low voltage, ST-T changes, conduction delay, ventricular arrhythmias. Troponin I/T elevated. BNP/NT-proBNP elevated. Chest X-ray: cardiomegaly, pulmonary congestion.
🔄 Step 4: Echocardiogram / Cardiac MRI
LV dysfunction, chamber enlargement. MRI: T2 edema, early gadolinium enhancement (hyperemia), late gadolinium enhancement (myocardial necrosis) – Lake Louise criteria.
🚨 Step 5: Endomyocardial biopsy (select cases)
Fulminant myocarditis, suspected giant cell myocarditis, vasculitis, immunosuppression-responsive. PCR for viral genome.
1️⃣ Initial stabilization – Acute myocarditis
▪ Admit to ICU if hemodynamically compromised.
▪ Inotropes: milrinone, dobutamine, dopamine. Avoid epinephrine if possible (arrhythmogenic).
▪ Diuretics (furosemide) for pulmonary edema.
▪ ECMO for refractory cardiogenic shock (fulminant myocarditis).
2️⃣ Chronic heart failure therapy – DCM
▪ ACE inhibitors (captopril, enalapril, lisinopril) – afterload reduction.
▪ Beta-blockers (carvedilol, metoprolol) – start after stabilization.
▪ Aldosterone antagonist (spironolactone) – added in advanced HF.
▪ Anticoagulation if mural thrombus (LVEF <25%).
3️⃣ Hypertrophic Cardiomyopathy (HCM)
▪ Beta-blockers (propranolol, atenolol) for symptoms, reduce gradient.
▪ Verapamil for diastolic dysfunction.
▪ ICD for high-risk: syncope, family history sudden death, massive LVH, non-sustained VT.
▪ Septal myectomy or alcohol septal ablation for obstructive HCM refractory to meds.
4️⃣ Restrictive Cardiomyopathy (RCM)
▪ Diuretics (judiciously).
▪ Avoid digoxin, beta-blockers (may worsen filling).
▪ Anticoagulation for atrial enlargement + atrial fibrillation.
▪ Cardiac transplantation is definitive therapy.
5️⃣ Myocarditis – Immunosuppression
▪ IVIG not proven but used in some centers.
▪ Corticosteroids for giant cell myocarditis, eosinophilic myocarditis.
▪ Avoid routine use in lymphocytic myocarditis.
6️⃣ Genetic counseling & family screening
▪ First-degree relatives screened with ECG, echo, genetic testing.
▪ Cascade testing if pathogenic variant identified.
7️⃣ Transition & adult care
▪ Lifelong follow-up for HF, arrhythmia monitoring, ICD management.
▪ Pregnancy: contraindicated in DCM with severe LV dysfunction, HCM with high-risk features.
▪ Transition to adult cardiologist with expertise in cardiomyopathy/heart failure.
❓ Reflex prompt 1: A 12-year-old presents with acute heart failure, fever, and recent URI. ECG shows low voltage. Troponin elevated. Most likely diagnosis?
✅ Answer: Acute viral myocarditis. Confirm with cardiac MRI (late gadolinium enhancement, T2 edema). Treat with supportive care, inotropes.
❓ Reflex prompt 2: A 14-year-old with HCM and syncope during exercise. Next step?
✅ Answer: ICD implantation for secondary prevention if aborted arrest; primary prevention if high-risk features (massive LVH, NSVT, family history sudden death).
❓ Reflex prompt 3: A 6-year-old with DCM, LVEF 20%, on maximally tolerated medical therapy. Next best option?
✅ Answer: VAD as bridge to transplant. Heart transplant evaluation.
❓ Reflex prompt 4: A 16-year-old with Barth syndrome (X-linked) presents with DCM. Which metabolic abnormality is associated?
✅ Answer: 3-methylglutaconic aciduria, neutropenia, skeletal myopathy. Caused by TAZ gene mutation.
❓ Reflex prompt 5: A 10-year-old with RCM and massive biatrial enlargement develops atrial fibrillation. Anticoagulation?
✅ Answer: Yes – high risk of thromboembolism. Warfarin or DOACs (data limited).
❓ Reflex prompt 6: A newborn with HCM, hypotonia, and macroglossia. Most likely diagnosis?
✅ Answer: Pompe disease (glycogen storage type II). Echocardiogram shows severe concentric LVH, short PR. Enzyme replacement therapy.
📌 Diseases of the Myocardium – Core Concepts (Nelson 22e, Chapter 488)

1. Dilated Cardiomyopathy (DCM):
- Most common pediatric cardiomyopathy. LV dilation + systolic dysfunction (EF <40%).
- Etiology: idiopathic (40-50%), familial (autosomal dominant), myocarditis, metabolic (carnitine, Barth syndrome), neuromuscular (Duchenne), anthracycline toxicity.
- Presentation: heart failure (poor feeding, tachypnea, fatigue, hepatomegaly).
- Treatment: ACE inhibitors, beta-blockers, diuretics, spironolactone. Digoxin adjunct.
- Advanced: VAD, cardiac transplantation.
2. Hypertrophic Cardiomyopathy (HCM):
- LV hypertrophy (septum > free wall), diastolic dysfunction, dynamic outflow obstruction.
- Genetics: sarcomere genes (MYH7, MYBPC3 most common). Noonan syndrome (RASopathy).
- Presentation: chest pain, dyspnea, syncope, sudden death (exercise).
- Treatment: beta-blockers, verapamil. ICD for high-risk. Septal myectomy for severe obstruction.
3. Restrictive Cardiomyopathy (RCM):
- Normal LV size, preserved EF, severe diastolic dysfunction, biatrial enlargement.
- Poor prognosis. Heart transplantation often necessary.
- Differential: constrictive pericarditis.
4. Myocarditis:
- Inflammatory cardiomyopathy. Viral (enterovirus, adenovirus, parvovirus B19, COVID-19).
- Diagnosis: cardiac MRI (Lake Louise criteria), endomyocardial biopsy.
- Treatment: supportive, inotropes, ECMO for fulminant. IVIG (controversial).
5. ARVC & LVNC:
- ARVC: fibrofatty RV, VT (LBBB). ICD. Desmosomal genes.
- LVNC: deep trabeculations. Associated with DCM, HCM, CHD.
6. Genetic screening: First-degree relatives of patients with cardiomyopathy should have clinical screening (ECG, echo) and genetic testing if pathogenic variant identified.
7. Transplantation: Indications: refractory heart failure, life-threatening arrhythmias, failure to thrive. 5-year survival ~80%.
💡 Clinical pearls:
➤ HCM is the most common cause of sudden death in young athletes. Preparticipation screening important.
➤ Myocarditis may mimic acute myocardial infarction (troponin elevation, ST changes). Cardiac MRI critical.
➤ Barth syndrome (X-linked) presents with DCM, neutropenia, and 3-methylglutaconic aciduria.
➤ Transition: DCM patients need lifelong HF management; pregnancy high-risk for those with LV dysfunction.