Hypertrophic cardiomyopathy

Background

HOCM
  • 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

Cardiomyopathy

Clinical Features

History

  • Syncope, chest pain, dyspnea, dizziness
  • Symptoms made worse by exertion
    • Increasing ventricular contractility further narrows outflow as volume is lost

Physical

  • Harsh midsystolic crescendo-decrescendo murmur
    • Increases in intensity with valsalva and standing up
      • Due to decreased blood return to the heart
    • Decreases with squatting and Trendelenburg
      • Due to increased peripheral resistance increases aorta and reduces obstruction

Differential Diagnosis

Syncope (peds)

Chest pain

Critical

Emergent

Nonemergent

Evaluation

Needle-like Q-waves
HOCM[2]

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[3]
    • 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

Diagnosis

  • Typically via echo

Management

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
    • Avoid vasodilators (no nitrates)
    • Maintain sinus rhythm (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)[4]
        • 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[5]
          • 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[6]
  • 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
    • Verapamil PO 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 digoxin
    • Avoid disopyramide alone with out BB or CCB
    • Avoid positive inotropic vasopressors (dopamine, dobutamine, norepinephrine, epi)


Medication Dosing

Phenylephrine 100mcg/min infusion (range 0.5-6mcg/kg/min) or 100-200mcg IV push q2-5min IV — Avoid vasodilators; max phenylephrine before adding other pressors

Disposition

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

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. ↑ http://www.thepocusatlas.com/pediatrics/
  3. ↑ Mitevksa IP. Focus on echocardiography in hypertrophic cardiomyopathy - fourth in series. ESC Council for Cardiology Practice. Vol.13,N°20 - 14 Apr 2015.
  4. ↑ Global RPH in reference to Micromedex. 12/2014. http://www.globalrph.com/phenylephrine_dilution.htm
  5. ↑ 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.
  6. ↑ American College of Cardiology. 2011. http://content.onlinejacc.org/article.aspx?articleid=1147838
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