Myocardium

Hypertrophic Cardiomyopathy

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Hypertrophic Cardiomyopathy, Hypertrophic Obstructive Cardiomyopathy, Idiopathic Hypertrophic Subaortic Stenosis, IHSS, HOCM

  • Definition
  1. Left Ventricular Hypertrophy without chamber dilation
  • Epidemiology
  1. Age of onset
    1. Under age 5 years old: 2%
    2. Under age 10 years old: 7%
  2. Prevalence: 1 in 500 patients
    1. Most common Primary Cardiomyopathy in United States
  3. More common in males
  • Pathophysiology
  1. Previously known as Idiopathic Hypertrophic Subaortic Stenosis (IHSS)
  2. Pathogenesis
    1. Idiopathic in 50% of patients (no known risk factors)
    2. Familial
      1. Autosomal Dominant with variable penetrance (not everyone is affected)
      2. Conferred by 11 mutant genes and over 500 transmutations related to sarcomere proteins
  3. Primary Left Ventricular Hypertrophy without ventricular dilation
    1. Contrast with secondary Left Ventricular Hypertrophy
  4. Asymmetric thickening of ventricular septum (variable pattern)
    1. Outflow obstruction (25%)
    2. Mitral leaflet paradoxical movement
    3. Secondary Systolic Dysfunction
    4. Abnormal relaxation and diastolic filling with Diastolic Dysfunction
  • Risk Factors
  1. Cardiac Arrest history
  2. Syncope (esp. Exertional Syncope)
  3. Family History of sudden death
  4. Arrhythmia history
  5. Nonsustained Ventricular Tachycardia (esp. if prolonged)
  6. Exercise-induced Hypotension
  7. Age under 50 years old
  8. Myocardial wall thickness >30 mm
  9. Maron (2002) JAMA 287(10): 1308-20 [PubMed]
  • Symptoms (Often asymptomatic at presentation)
  1. Dyspnea on exertion (most common presenting symptom)
    1. Pulmonary Hypertension due to a non-compliant left ventricle, and secondary decreased end-diastolic volume
  2. Angina (second most common presenting symptom)
    1. Coronary Vessels are unable to adequately perfuse the thick ventricle during increased cardiac demand
  3. Dizziness or light headedness
  4. Fatigue
  5. Exertional Syncope (60%) or Presyncope (due to outflow obstruction)
  6. Family History of Sudden death (20%)
  7. Provocative factors: Increased outflow obstruction
    1. Volume depletion or dehydration
    2. Nitroglycerin
  8. Palliative factors: Decreased outflow obstruction
    1. Volume Resuscitation
    2. Alpha agonists (e.g. Phenylephrine)
  • Signs
  1. Loud S4 gallup
  2. Fixed or paradoxical split S2 Heart Sound
  3. Harsh, crescendo-decrescendo Systolic Murmur at apex (30-40%)
    1. Results from Mitral Regurgitation and mitral valve leaflets migrating anteriorly into LV outflow tract
    2. Radiates along Left Sternal Border into sternal notch
    3. Sounds like flow murmur
    4. Accentuated with standing, Valsalva Maneuver
    5. Diminished with squatting
  4. Biphasic pulse
  5. Brisk carotid upstroke
  6. Hyperdynamic (or split) point of maximal apical impulse (PMI)
  • Diagnostics
  1. Electrocardiogram (changes seen in 90% of cases, may detect HCM before Echocardiogram)
    1. Left Ventricular Hypertrophy
      1. Large voltage R Waves in the anterior and lateral leads (I, aVL, V4-6)
    2. Inferior and Lateral Q waves
      1. Deep, dagger-like, narrow Qs in inferior (II, III, avF) and lateral (I, aVL, V5-6) leads
      2. Absent history of Coronary Artery Disease (and HCM Qs are narrower than CAD Q waves)
    3. Septal T-Wave Inversion (variable)
    4. Cardiac Ischemia
    5. High voltage overall
  2. Echocardiogram
    1. Definitive test for diagnosis
    2. Septum wider than 15mm confirms diagnosis
    3. Left venticular hypertrophy
    4. Reduced ventricular chamber volume
  • Management
  1. Management goals
    1. Decrease exertional Dyspnea and Chest Pain
    2. Prevent Sudden Cardiac Death
  2. General
    1. Avoid intensive Exercise
    2. Light aerobic activities (e.g. hiking, non-competitive swimming) are typically allowed
    3. Admit HOCM patients presenting with arrhythmia (and consider for ICD)
  3. Pharmacologic
    1. See Systolic Dysfunction
    2. Beta Blockers
      1. First-line therapy for symptomatic Hypertrophic Cardiomyopathy
      2. Improve symptoms
      3. Does not reduce risk of Sudden Cardiac Death
    3. Nondihydropyridine Calcium Channel Blockers (e.g. Verapamil)
      1. May be used as alternative if Beta Blockers are not tolerated
    4. Exercise caution with Diuretics
      1. Hypertrophic Cardiomyopathy requires higher filling pressures
    5. Avoid nitrates
  4. Devices
    1. Implantable Defibrillator (ICD)
      1. Consider in any patient at high risk for Sudden Cardiac Death
      2. Indicated for history of Ventricular Fibrillation or sustained Ventricular Tachycardia
    2. Biventricular pacing
      1. Consider in Heart Failure
  5. Obstructive Hypertrophic Cardiomyopathy with Heart Failure refractory to medical management
    1. Surgical myomectomy or Septal myomectomy
      1. First-line management
    2. Septal Alcohol ablation
      1. Consider at very high surgical risk
    3. Heart Transplant
      1. Severe Systolic Heart Failure
  • Prevention
  1. No competitive sports participation until complete evaluation
  2. Consider screening family members of those with Hypertrophic Cardiomyopathy
    1. Up to annual Echocardiogram, Electrocardiogram and physical is recommended in Europe
  • Complications
  1. Heart Failure
  2. Dynamic outflow obstruction by mitral valve (common)
  3. Arrhythmia
    1. Atrial Fibrillation (most common, from progressive atrial enlargement)
    2. Ventricular Tachycardia
  4. Sudden Cardiac Death risk is 2-3% per year
    1. Typically due to Ventricular Tachycardia
    2. May be the presenting finding