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 β-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