Cardiomyopathy, Hypertrophic

Key Features

• 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

Clinical Findings

Familial HCM

• 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

Glycogen storage disease

• 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

Diagnosis

Familial HCM

• 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 ...