Updated: 12/9/2020

Hypertrophic Cardiomyopathy

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Snapshot
  • A 17-year-old boy is rushed to the emergency room after collapsing on the basketball court during a game. He is found to have a ventricular arrhythmia on electrocardiogram and died en route to the hospital. Prior to this event, he had a few episodes of syncope. His family history includes sudden cardiac death in 2 maternal uncles. Autopsy reveals markedly hypertrophic interventricular septum.
Introduction
  • Clinical definition
    • a cardiomyopathy characterized by ventricular hypertrophy and diastolic dysfunction
  • Epidemiology
    • risk factors
      • family history of sudden cardiac death
  • Etiology
    • familial (most common)
  • Pathogenesis
    • ventricular concentric hypertrophy (typically of the septum) from sarcomeres added in parallel
      • ↓ left ventricular compliance results in diastolic dysfunction
      • ventricles are hypercontractile and systole occurs rapidly
    • hypertrophic obstructive cardiomyopathy
      • this disease is obstructive in most patients (70%)
      • left ventricular outflow tract obstruction caused by asymmetric septal hypertrophy and systolic anterior motion of the mitral valve
  • Genetics
    • inheritance pattern
      • autosomal dominant
    • mutations
      • chromosome 14
      • genes encoding sarcomere proteins
        • myosin binding protein C and β-myosin heavy chain
  • Associated conditions
    • Friedreich ataxia
    • Pompe disease (type II glycogen storage disease)
  • Prognosis
    • many have normal life expectancy
    • however, there is a risk of sudden cardiac death in the young athletic population
Presentation
  • Symptoms
    • syncope during exercise 
    • dyspnea on exertion
    • angina
    • palpitations
    • sudden death from ventricular arrhythmia
  • Physical exam
    • cardiac
      • S4 gallop (a sign of left ventricular hypertrophy)
      • systolic murmur without radiation to carotids
        • ↑ with valsalva and standing up (↓ preload)  
        • ↓ with hand grip (↑ afterload) and squatting (↑ afterload and ↑ preload)  
      • mitral regurgitation
Imaging
  • Echocardiography
    • indication
      • for all patients as a diagnostic test
    • findings
      • may have normal ejection fraction
      • hypertrophy of ventricular walls and interventricular septum
      • systolic anterior motion of mitral valve with mitral regurgitation
Studies
  • Electrocardiogram
    • findings
      • left ventricular hypertrophy 
      • may have ventricular arrhythmias
  • Histology
    • tangled and disoriented myofibrils
  • Making the diagnosis
    • based on clinical presentation and echocardiogram
Differential
  • Restrictive cardiomyopathy
    • distinguishing factors
      • Kussmaul sign on physical exam
      • electrocardiogram with low voltages
  • Dilated cardiomyopathy
    • distinguishing factors
      • echocardiogram with reduced ejection fraction
      • progressive heart failure
Treatment
  • Management approach
    • typically managed with β-blockers and calcium channel blockers
    • diuretics may be used cautiously in patients without left ventricular outflow tract obstruction
    • digoxin and spironolactone do not provide any benefit
  • Conservative
    • avoidance of overexertion, especially athletic activities
      • indication
        • for all patients
  • Medical
    • β-blockers
      • indication
        • for all patients
    • non-dihydropyridine calcium channel blockers
      • indication
        • for patients who are are contraindicated or refractory to β-blockers
      • drugs
        • verapamil
  • Operative
    • surgical septal myectomy
      • indication
        • if significant heart failure symptoms persist despite maximal medical therapy, or patients have recurrent syncope judged to be related to hemodynamic compromise from LVOT obstruction
    • implantable cardioverter defibrillator (ICD) 
      • indication      
        • patients with a history of syncope or events seen on a Holter monitor
Complications
  • Sudden cardiac death from ventricular arrhythmias
  • Heart failure

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