Hypertrophic cardiomyopathy

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Background

  • Genetically-linked (AD) hypertrophy of cardiac muscle - can but does not always cause outflow obstruction
  • "HOCM"
  • Abnormal LV diastolic function due to decreased compliance
  • Historically, obstructive forms known as:
    • Idiopathic hypertrophic subaortic stenosis (IHSS)
    • Asymmetric septal hypertrophy (ASH)
  • Yamaguchi syndrome, an atypical HCOM, in which only 1% are non-Japanese

Diagnosis

  • Sx: Syncope or sudden death most common
    • Also exertional dyspnea, chest pain, syncope, dizzyness, palpitations, or CHF
  • Systolic murmur that increases w/ maneuvers that decrease preload (e.g. valsalva, transitioning from squatting to standing, etc.).
  • EKG
    • Nonspecific/normal.
    • Or, high voltage/LVH, deep narrow Q waves in 1, avL, V5, V6 = "daggers of death"

Work-Up

  1. EKG
    1. May show signs of:
      1. LVH
      2. "Needle-like" Q waves
  2. CXR
  3. ECHO

Differential Diagnosis

Cardiomyopathy

Chest pain

Critical

Emergent

Nonemergent

Treatment

Definitive = Myomectomy

Decompensated

  • Consider primary insult, which usually is preload issue (fluid depletion, bleed, etc.)
  • If decompensated presents as hypotensive CHF
    • Preserve preload
      • Careful hydration
      • Avoid high airway pressure if intubate
    • Limit tachycardia
      • Beta blockers
    • Avoid vasodilators (no nitrates)
    • Maintain sinus rythm (i.e. cardiovert A. fib)
    • Increase afterload (hypotensive only)
      • Phenylephrine, max dose range depending on source
        • Start at 100 mcg/min (~1.5 mcg/kg/min for average adult)
        • Range usually 0.5 - 6.0 mcg/kg/min, with efficacy minimal beyond 6 mcg/kg/min)[1]
        • Max phenylephrine infusion before other pressors
        • Fix acid-base disorder as acidosis may prevent pressor efficacy
        • Consider maxing vasopressin next
          • Pressor effects more preserved in hypoxia and acidosis[2]
          • Preferred over pressors with beta agonism
      • Push dose pressor while waiting for IV drip:
        • Place 1mL of 10mg/mL phenylephrine in 100mL NS
        • Final concentration 100mcg/mL
        • Use 1-2mL q2-5min (100-200mcg) in 10mL syringe
        • Onset 1min; duration 20min

Pharmacologic Management

  • Per Amer Coll of Cardiology 2011 recommendations[3]
  • Class I
    • BBs for angina or dyspnea in adults in HCM regardless of obstructive physiology - use with caution in sinus brady or conduction abnormality
    • Titrate BB dose to symptoms, may increase BB dose to resting HR to 60 bpm
    • PO verapamil titrated up to 480 mg/d if pt unresponsive or cannot tolerate BBs - caution in advanced HF, hypotension, sinus brady, high LVOT gradients
    • IV phenylephrine for acute hypotension unresponsive to fluids
  • Class IIa
    • Reasonable to add disopyramide with BB or verapamil if unresponsive to BB or CCB alone in obstructive HCM
    • Reasonable to add oral diuretics in nonobstructive HCM when symptoms persist despite BB or CCB
  • Class III (harm)
    • Avoid nifedipine and other dihydropyridine CCB
    • Avoid digitalis
    • Avoid disopyramide alone w/o BB or CCB
    • Avoid positive inotropic vasopressors (dopamine, dobutamine, norepi, epi)

See Also

Source

  • Tintinalli
  • Adapted from ....Rosen, Mattu (lecture)
  • Houston BA, Stevens GR. Hypertrophic Cardiomyopathy: A Review. Clinical Medicine Insights Cardiology. 2014;8(Suppl 1):53-65. doi:10.4137/CMC.S15717.
  1. Global RPH in reference to Micromedex. 12/2014. http://www.globalrph.com/phenylephrine_dilution.htm
  2. Overgaard CB and Dzavik V. Contemporary Reviews in Cardiovascular Medicine: Inotropes and Vasopressors - Review of Physiology and Clinical Use in Cardiovascular Disease. Circulation. 2008; 118: 1047-1056.
  3. American College of Cardiology. 2011. http://content.onlinejacc.org/article.aspx?articleid=1147838