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Snapshot
  • A 17-year-old boy suddenly collapsed and died on the soccer field shortly after scoring the winning goal. He had no known past medical history. 
Introduction
  • Cardiomyopathies describes a group of intrinsic cardiac disorders that affects the myocardium
    • often results in symptoms secondary to heart failure
    • cardiomyopathies do not include alterations in the heart muscle that are secondary to hypertension, coronary artery disease, or valvular disorders
  • Three major categories include
    • Dilated cardiomyopathy
      • leads to impaired systolic contraction
    • Restrictive (infiltrative) cardiomyopathy
      • leads to impaired diastolic relaxation
    • Hypertrophic cardiomyopathy
      • leads to impaired diastolic relaxation
Dilated Cardiomyopathy (DCM)
  • Overview
    • Most common cardiomyopathy (~90% of cases)
      • leads to systolic dysfunction
      • due to ↓ contractility and resultant ↓ ejection fraction
  • Etiologies
    • idiopathic
    • genetic
      • mutations in proteins that affects the interaction between the cytoskeleton and sarcomere
      • dystrophin gene mutations
        • x-linked
    • toxins
      • alcohol abuse
        • via direct toxic damage to myocardium
        • associated thiamine deficiencyberiberi
      • doxorubicin toxicity
      • cobalt
    • infectious 
      • coxsackievirus
      • chagas' disease (in South America)
        • caused by protozoa Typanosoma cruzi
    • peripartum cardiomyopathy
  • Symptoms/Physical exam
    • ineffective contraction slowly progressive congestive heart failure
      • see Congestive Heart Failure
    • S3 heart sound & mitral regurgitation murmur
  • Evaluation
    • Echocardiography is definitive
      • shows dilated ventricles 
      • confirms decreased EF
    • CXR shows balloon-like heart
  • Treatment
    • ACEIs/ARBs
    • beta-blockers
    • spironolactone
    • digoxin for symptom improvement
      • does not improve mortality
Hypertrophic Cardiomyopathy (HCM)
  • Overview 
    • characterized by hypertrophy of the myocardium, a defect in diastolic filling, and ventricular outflow obstruction (in 1/3 of cases)
      • systolic function is usually preserved
      • high ejection fraction
    • cause of sudden death in young athletes 
      • thickened septal wall too close to the anterior leaflet of mitral valve (shown in top photo)
      • obstructs the outflow to the aortic valve
        • leaflet is drawn open by fast moving blood being ejected during systole
      • conduction irregularities results in arrhythmias
        • cause of death
    • can be inherited
      • autosomal dominant missense mutations (most cases)
      • mutated gene in cardiac cell sarcomere proteins (commonly heavy chain of β-myosin, or troponin) 
      • associated with Friedreich's ataxia
  • Symptoms/Physical exam
    • harsh systolic ejection crescendo-decrescendo murmur heard best in apex and left sternal border. No radiation to the carotids. 
      • ↑ in intensity with decreased preload
        • results from ↑ contraction (therefore ↑ thickening) of the septal wall, which causes ↑ in outflow obstruction
        • can be observed by having the patient go from a squatting to a standing position
  • Evaluation
    • echocardiography is diagnostic and shows
      • asymetrically thickened LV walls
      • involving the interventricular septum
      • but may show normal EF
      • can show concentric ventricular hypertrophy
    • histological examination shows tangled, disoriented myofibrils 
  • Treatment includes
    • beta-blockers
    • calcium channel blockers
      • non-dihydropyridine type (e.g. verapamil)
    • disopyramide
    • septoplasty - in severe cases
    • certain medications and therapies should be avoided including
      • inotropes (i.e. digoxin)
      • vasodilators
      • overdiuresis because decreased blood volume in ventricle increases probability of septum blocking the outflow tract
Restrictive Cardiomyopathy
  • Overview
    • least common of the cardiomyopathies
    • most caused by chronic, progressive, infiltrative or metabolic diseases including
      • amyloidosis
        • transthyretin
          • senile cardiac amyloidosis
            • can accumulate over a lifetime and lead to asymptomatic diastolic dysfunction in the elderly
          • familial amyloid cardiomyopathy
            • mutated transthyretin can deposit in the heart and lead to a symptomatic restrictive cardiomyopathy
      • sarcoidosis
      • hemochromatosis  
      • cancer
      • endocardial fibroelastosis
        • non-compliant endocardium of children
      • Loffler's endocardial fibrosis
        • eosinophilic infiltrate with endomyocardial fibrosis with or without presence of parasitic infection
      • glycogen storage diseases
        • Pompe's disease
    • regardless of cause the functional deficit is a ↓ in ventricular compliance
  • Symptoms/Physical exam
    • patients often present with chronic, progressively worsening diastolic dysfunction
  • Evaluation
    • echocardiography is diagnostic
      • shows LVH
    • tissue biopsy is required
      • to determine underlying cause
    • EKG demonstrates arrhythmias
      • low voltage
 

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