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Key Features

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  • Hypertrophic cardiomyopathy (HCM) is the leading cause of sudden cardiac death in young persons

  • Usually presents in an older child, adolescent, or adult but may occur in neonates

  • Familial HCM is most common cause; it is found in 1 in 500 individuals

  • Causes of nonfamilial HCM in neonates and young children include

    • Glycogen storage disease (GSD)

      • There at least 10 types

      • Pompe disease (GSD IIa) primarily involves the heart

    • Noonan syndrome

    • Friedreich ataxia

    • Maternal gestational diabetes

    • Mitochondrial disorders

    • Other metabolic disorders

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Clinical Findings

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Familial HCM
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  • May be asymptomatic despite presence of significant hypertrophy

  • Symptoms of inadequate coronary perfusion or heart failure such as

    • Angina

    • Syncope

    • Palpitations

    • Exercise intolerance

  • Sudden cardiac death, often precipitated by sporting activities, may be initial presentation

  • Cardiac examination may be normal on presentation

  • However, a left precordial bulge with a diffuse point of maximal impulse develops in some patients

  • Left ventricular heave or an S4 gallop may be present

  • If outflow tract obstruction exists, a systolic ejection murmur will be audible

  • A murmur may not be audible at rest but may be provoked with exercise or positional maneuvers that decrease left ventricular volume (standing), thereby increasing the outflow tract obstruction

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Glycogen storage disease
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  • Deposition of glycogen within the myocardium is marked

  • Affected infants are well at birth

  • By age 6 months, however, the following symptoms occur

    • Growth and developmental delay

    • Feeding problems

    • Cardiac failure

  • Physical examination reveals

    • Generalized muscular weakness

    • Large tongue

    • Cardiomegaly without significant heart murmurs

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Diagnosis

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Familial HCM
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  • Electrocardiography

    • May be normal

    • However, more typically demonstrates deep Q waves in the inferolateral leads secondary to the increased mass of the hypertrophied septum

    • ST-segment abnormalities may be seen

    • Age-dependent criteria for LV hypertrophy are often present as are criteria for left atrial enlargement

  • Echocardiography

    • Demonstrates asymmetric septal hypertrophy

    • Systolic anterior motion of the mitral valve leaflet may occur and contribute to LV outflow tract obstruction

    • Mitral valve leaflet may become distorted and result in mitral insufficiency

    • LV outflow tract obstruction may be present at rest or provoked with monitored exercise

    • Systolic function is most often hypercontractile in young children but may deteriorate over time, resulting in poor contractility and LV dilation

    • Diastolic function is almost always abnormal.

  • Cardiac catheterization and angiography

    • May be performed in patients with HCM who have

      • Angina

      • Syncope

      • Resuscitated sudden death

      • Worrisome stress test

    • Hemodynamic findings include elevated left atrial pressure secondary to impaired diastolic filling

    • If midcavitary LV outflow tract obstruction is present, an associated pressure gradient will be evident

    • Angiography demonstrates a "ballerina slipper" configuration of the LV secondary to the midcavitary LV obliteration during systole

  • Cardiopulmonary stress testing is valuable to

    • Evaluate for provocable LV outflow tract obstruction, ischemia, and arrhythmias

    • Determine prognosis

  • Cardiac MRI is useful for defining areas of myocardial fibrosis or scarring

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Glycogen ...

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