Hypertrophic cardiomyopathy

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Background

  • Genetically-linked (AD) hypertrophy of cardiac muscle - can but does not always cause outflow obstruction
  • Up to 30% of patients will have no family history[1]
  • Average age of diagnosis between 30-40 years of age
  • Diastolic heart failure
    • Abnormal LV function due to decreased compliance
  • Historically, obstructive forms known as:
    • Idiopathic hypertrophic subaortic stenosis (IHSS)
    • Asymmetric septal hypertrophy (ASH)
    • Hypertrophic obstructive cardiomyopathy (HOCM)
  • Yamaguchi syndrome, an atypical HCOM, in which only 1% are non-Japanese
HOCM

Clinical Features

  • Syncope, chest pain, dyspnea
  • Symptoms made worse by exertion
    • Increasing ventricular contractility further narrows outflow as volume is lost
  • Systolic murmur increases with valsalva
    • Decreased blood return to heart
  • Systolic murmur decreases with squat/fist clench
    • Increased peripheral resistance increases aorta and reduces obstruction

Differential Diagnosis

Cardiomyopathy

Chest pain

Critical

Emergent

Nonemergent

Evaluation

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

Work-Up

  • ECG abnormalities in ~90%, but mostly nonspecific
    • High voltage ECG (which may produce abnormal T-waves)
    • LVH
    • Left atrial enlargement
    • Tall R-wave in V1, mimicking posterior MI
    • "Needle-like" Q waves, especially in lateral leads, mimicking infarction Q waves
  • CXR may be normal as LV is non-dilated
  • Echo[2]
    • Unexplained wall thickness > 15 mm in any myocardial segment
    • Septal/posterior wall thickness ratio:
      • >1.3 in normotensive pts
      • >1.5 in hypertensive pts
    • Systolic anterior motion by M mode in PSL window, worsened by Valsalva
    • Mitral regurgitation
    • EF may be preserved until acute decompensation
    • Formal echo should include tissue Doppler imaging

Management

  • Avoid exertion
  • ICD +/- pacer for ventricular arrhythmias
  • Definitive treatment is 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)[3]
        • 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[4]
          • 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[5]
  • Class I
    • beta-blockers 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 480mg/d if patient unresponsive or cannot tolerate beta-blockers - 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 with out BB or CCB
    • Avoid positive inotropic vasopressors (dopamine, dobutamine, norepinephrine, epi)

Disposition

  • Admit for echo and cardiology evaluation
  • If unable to admit, home on beta blocker, instructions for no exertion, follow up echo and cardiology outpt

See Also

References

  1. ↑ Gersh BJ, Maron BJ, Bonow RO, Dearani JA, Fifer MA, Link MS, Naidu SS, Nishimura RA, Ommen SR, Rakowski H, Seidman CE, Towbin JA, Udelson JE, Yancy CW. 2011 ACCF/AHA Guideline for the Diagnosis and Treatment of Hypertrophic Cardiomyopathy: Executive Summary. A report of the American College of Cardiology Foundation/American Heart Association Task Force of Practice.
  2. ↑ Mitevksa IP. Focus on echocardiography in hypertrophic cardiomyopathy - fourth in series. ESC Council for Cardiology Practice. Vol.13,N°20 - 14 Apr 2015.
  3. ↑ Global RPH in reference to Micromedex. 12/2014. http://www.globalrph.com/phenylephrine_dilution.htm
  4. ↑ 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.
  5. ↑ American College of Cardiology. 2011. http://content.onlinejacc.org/article.aspx?articleid=1147838
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