Hypertrophic Cardiomyopathy

Epidemiology

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Etiology

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Physiology

General Comments

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Left Ventricular Outflow Tract-Aorta Pressure Gradient

  • Incidence: pressure gradient between the left ventricular outflow tract and the aorta is present in 75% of hypertrophic cardiomyopathy cases (either at rest or with provocation)
  • Dynamic Nature of Outflow Tract Gradients: gradients fluctuate from day to day (based on factors which alter myocardial contractility and loading (such as dehydration, ethanol ingestion, or large meals)

Pathophysiologic Manifestations

  • Diastolic Dysfunction (see Congestive Heart Failure, [[Congestive Heart Failure]])
  • Left Ventricular Outflow Tract Obstruction
  • Mitral Regurgitation (MR) (see Mitral Regurgitation, [[Mitral Regurgitation]])
  • Myocardial Ischemia

Diagnosis

Echocardiogram (see Echocardiogram, [[Echocardiogram]])

  • Morphologic Variants
    • Asymmetric Septal Hypertrophy (ASH)
    • Biventricular Hypertrophy
    • Left Ventricular Wall Thinning with Low Ejection Fraction and Bi-Atrial Enlargement
    • Midcavity Hypertrophy with Midcavity Obstruction
    • Mild-Moderate Septal Hypertrophy
    • Predominant Apical Left Ventricular Hypertrophy
    • Predominant Free Wall Hypertrophy: unusual pattern
    • Severe Concentric Left Ventricular Hypertrophy with Cavity Obliteration
    • Sigmoid Septum: more common in older adults

Exercise Stress Echocardiogram

  • Preferred Method to Determine if Outflow Tract Gradient is Present: mimics the conditions under which gradient might occur during normal daily activities

Dobutamine Stress Echocardiogram

  • Alternative to Exercise Stress Echocardiogram: although is less reliable than exercise stress echocardiogram

Valsalva Manuever with Echocardiogram

  • May Induce Gradient: although is less reliable than exercise stress echocardiogram

Clinical Manifestations

Cardiovascular Manifestations

  • Angina/Chest Pain (see Chest Pain, [[Chest Pain]])
  • Arrhythmias
  • Left Ventricular Aneurysm (see Left Ventricular Aneurysm, [[Left Ventricular Aneurysm]])
  • Mitral Regurgitation (see Mitral Regurgitation, [[Mitral Regurgitation]])
    • Mechanism: due to systolic anterior motion (SAM) of the mitral valve or papillary muscle/chordae tendineae abnormalities -> abnormal mitral valve leaflet coaptation (usually with a posteriorly-directed jet)
    • Characteristics of Murmur: mid-late systolic murmur
      • In contrast, primary mitral valve disease usually presents with a central-directed jet with holosystolic murmur, loudest at the apex and radiating to the axilla
    • Radiation: may radiate toward the base of the heart (due to the eccentric jet)
  • Other Findings Related to Hypertrophic Cardiomyopathy Itself
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  • Palpitations (see Palpitations, [[Palpitations]])
  • Pre-Syncope/Syncope (see Syncope, [[Syncope]])
    • Risk Factors
      • Age <30 y/o
      • Small Left Ventricular End-Diastolic Volume/Small Left Ventricular Cavity Size
      • Episodes of Non-Sustained Ventricular Tachycardia (on 72 hr Ambulatory EKG Monitoring)
    • Mechanisms
      • Atrial Fibrillation
      • Conduction Abnormalities/Atrioventricular Heart Blocks
      • Exertional Myocardial Ischemia
      • Left Ventricular Outflow Tract Obstruction
      • Ventricular Baroreflex Activation with Inappropriate Vasodilation
  • Systolic Murmur Due to Left Ventricular Outflow Tract Obstruction
    • Mechanism: due to combination of left ventricular septal hypertrophy and systolic anterior motion (SAM) of the mitral valve
      • May reflect both mitral regurgitation and aortic outflow obstruction in patients with a large gradient
    • Characteristics: harsh crescendo-decrescendo murmur (begins slightly after S1) heard best at apex and left lower sternal border
    • Radiation: left axilla and base (usually not to the neck)
    • Maneuvers Which Increase Intensity of Murmur: due to increased obstruction
      • During More Forceful Contraction Following Compensatory Pause After Premature Ventricular Contraction: increases murmur
      • Nitroglycerin: increases murmur
      • Going From Squatting/Sitting/Supine Positions -> Standing : increases murmur
      • Valsalva: increases murmur
    • Maneuvers Which Decrease Intensity of Murmur: due to decreased obstruction
      • Going to Standing -> Sitting/Squatting Position: decreases murmur
      • Handgrip: decreases murmur
      • Passive Elevation of Legs: decreases murmur
  • Sudden Cardiac Death (se Sudden Cardiac Death, [[Sudden Cardiac Death]])

Pulmonary Manifestations

  • Exertional Dyspnea (see Dyspnea, [[Dyspnea]]): most common presenting symptom (occurs in >90% of cases)

Other Manifestations

  • Fatigue (see Fatigue, [[Fatigue]])
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Treatment

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References

  • Nonobstructive Hypertrophic Cardiomyopathy with Left Ventricular Aneurysm. Tex Heart Inst J. 2013; 40(4): 465–467 [MEDLINE]