Hypertrophic Cardiomyopathy

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

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II. Definition

  1. Left Ventricular Hypertrophy without chamber dilation

III. 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 (up to 1 in 200 in some studies in U.S.)
    1. Most common Primary Cardiomyopathy in United States
  3. More common in males
  4. Most common cause of Sudden Cardiac Death in young people

IV. Pathophysiology

  1. Previously known as Idiopathic Hypertrophic Subaortic Stenosis (IHSS)
  2. Pathogenesis
    1. Idiopathic in 50% of patients (no known risk factors)
    2. Familial (30 to 60% of patients)
      1. Autosomal Dominant with variable penetrance (not everyone is affected)
      2. Conferred by 11 mutant genes and over 500 transmutations related to SarcomereProteins
  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

V. 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]

VI. 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)

VII. 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)

VIII. 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. Reduced ventricular chamber volume
    4. Left venticular hypertrophy (based on maximal left ventricular end diastolic wall thickness at any point)
      1. Adult: Thickness >15 mm at any point (>13 mm if HCM Family History) or
      2. Child: Thickness > 2 stadard deviations (SD) above mean for age

IX. Evaluation

  1. Screening Indications
    1. See Risk Factors above
    2. Hypertrophic Cardiomyopathy Family History
    3. New cardiac murmur
    4. Abnormal EKG
  2. Approach
    1. Three generation Family History
    2. Prolonged cardiac monitoring
      1. Dysrhythmia
      2. Paroxysmal Atrial Fibrillation
    3. Dynamic cardiac examination
      1. Murmur increases with Valsalva Maneuver or squat to stand maneuver
      2. Autonomic Dysfunction
    4. Electrocardiogram
      1. See Diagnostic findings as above
      2. Myocardial Ischemia
    5. Echocardiogram
      1. See diagnostic findings as above
      2. Left Ventricular Outflow Obstruction (75% of cases)
      3. Mitral Regurgitation
      4. Diastolic Dysfunction

X. Differential Diagnosis

  1. See Cardiomyopathy
  2. Hypertensive Cardiomyopathy
  3. Athletic Heart Syndrome
  4. Aortic Valve Disorders (Aortic Stenosis, Aortic Regurgitation)
  5. Metabolic disorders
    1. Amyloidosis
    2. RASopathy (e.g. Costello syndrome, Legius syndrome, Neurofibromatosis type 1, Noonan Syndrome)
    3. Glycogen Storage Disease
    4. Lysosomal Storage Disease

XI. Management

  1. Refer all patients to center specializing in Hypertrophic Cardiomyopathy for best outcomes
  2. Management goals
    1. Decrease exertional Dyspnea and Chest Pain
    2. Prevent Sudden Cardiac Death
  3. General
    1. Admit HOCM patients presenting with Arrhythmia (and consider for ICD)
  4. Sports
    1. Light aerobic activities (e.g. hiking, non-competitive swimming) are typically allowed
    2. Avoid intensive Exercise
      1. However use Shared Decision Making
      2. Ventricular Arrhythmias occur in patients regardless of competitive sport activity
      3. AICD is not recommended as a measure to allow for sports participation
  5. Work Certification in Hypertrophic Cardiomyopathy
    1. Truck Driver Certification criteria (DOT Physical)
      1. No implantable cardiac Defibrillator (AICD) and
      2. No major risks of Sudden Cardiac Death (see below)
    2. Commerical Pilot Certification (Commercial Flight Physical)
      1. Low risk of Sudden Cardiac Death (see below) and
      2. Completes a treadmill stress test at 85% of peak Heart Rate
  6. Pregnancy
    1. Pregnancy is considered safe in Hypertrophic Cardiomyopathy
    2. HCM related Sudden Cardiac Death in pregnancy and delivery is rare
    3. Beta Blockers (other than Atenolol) may be continued in pregnancy
    4. HCM-related pregnancies are associated with adverse outcomes of 3-4% regardless of delivery method
  7. Monitoring
    1. Periodic repeat testing includes EKG, Echocardiogram and continuous cardiac monitoring
    2. Diagnosed HCM
      1. Child: Perform every 1 to 2 years
      2. Adult: Perform every 3 to 5 years
    3. Family History of HCM
      1. Child: Perform every 1 to 3 years (if relative was diagnosed as a child)
      2. Adult: Perform every 3 to 5 years (if relative was diagnosed as an adult)
  8. Pharmacologic
    1. See Systolic Dysfunction
    2. Beta Blockers
      1. First-line therapy for symptomatic Hypertrophic Cardiomyopathy
      2. Improves symptoms by slowing Heart Rate and reducing Left Ventricular Outflow Obstruction (LVOTO)
      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
      2. Do not use in combination with Beta Blockers (choose one)
    4. Left Ventricular Outflow Obstruction (LVOTO)
      1. Avoid Diuretics
      2. Avoid ACE Inhibitors
      3. Avoid Angiotensin Receptor Blockers
      4. Avoid nitrates
      5. Avoid Hypotension
    5. Exercise caution with Diuretics
      1. Hypertrophic Cardiomyopathy requires higher filling pressures
      2. Avoid Diuretics if findings of obstruction on Echocardiogram
      3. Diuretics improve Dyspnea if volume overload is present
    6. Systolic Dysfunction (EF <50%) and NO LVOTO
      1. Treat as Systolic Dysfunction
    7. Refractory symptoms (not controlled with Beta Blocker or Calcium Channel Blocker)
      1. Consider Disopyramide (Norpace)
        1. Combine with AV nodal blocking agent (e.g. Beta Blocker) to prevent Atrial Fibrillation
      2. Consider septal reduction procedures (e.g. myomectomy) as below
  9. Devices
    1. Implantable Defibrillator (ICD)
      1. Consider in any patient at high risk for Sudden Cardiac Death (see below)
      2. Indicated for history of Ventricular Fibrillation or sustained Ventricular Tachycardia
    2. Biventricular pacing
      1. Consider in Heart Failure
  10. Obstructive Hypertrophic Cardiomyopathy with Heart Failure refractory to medical management
    1. Surgical myomectomy or Septal myomectomy
      1. First-line management
      2. Improves symptoms but does not prevent disease progression
    2. Septal Alcohol ablation
      1. Consider at very high surgical risk
      2. Improves symptoms but does not prevent disease progression
    3. Heart Transplant
      1. Severe Systolic Heart Failure

XII. 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

XIII. Complications: General

  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

XIV. Complications: Sudden Cardiac Death

  1. Typically due to Ventricular Tachycardia
  2. May be the presenting finding
  3. Incidence
    1. Risk is 2-3% per year overall
    2. Occurs in 10% of patients who are diagnosed in childhood
  4. Risk Factors
    1. Highest risk is at a younger age
    2. Family History of Hypertrophic Cardiomyopathy related sudden death
    3. Very severe Left Ventricular Hypertrophy with wall thickness >=30 mm
    4. Unexplained Syncope
    5. Left Systolic Dysfunction with ejection fraction <50%
    6. Left ventricular apical aneurysm
    7. Cardiac MRI with late gadolinium enhancement
    8. Nonsustained Ventricular Tachycardia on ambulatory monitoring

XV. References

  1. Joshi and Dermark (2016) Crit Dec Emerg Med 30(8):3-12
  2. Schauer et al. (2016) Crit Dec Emerg Med 30(9):13-9
  3. Brieler (2017) Am Fam Physician 96(10):640-6 [PubMed]
  4. Gersh (2011) Circulation 124(24): e783-831 [PubMed]
  5. Kelly (2007) Am J Emerg Med 25(1): 72-9 [PubMed]
  6. Ommen (2020) Circulation 142(25):e558-631 +PMID:33215931 [PubMed]
  7. Wexler (2009) Am Fam Physician 79(9): 778-84 [PubMed]

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