Hypertrophic cardiomyopathy

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
• 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

• Dilated cardiomyopathy
• Hypertrophic cardiomyopathy
• Restrictive cardiomyopathy
• Peripartum cardiomyopathy
• Takotsubo cardiomyopathy
• Arrhythmogenic right ventricular dysplasia

Chest pain

Critical

• Acute Coronary Syndromes
  • STEMI
  • Non-STEMI
  • Unstable angina
• Aortic Dissection
• Cardiac Tamponade
• Pulmonary Embolism
• Tension Pneumothorax
• Boerhhaave's Syndrome
• Coronary Artery Dissection

Emergent

• Pericarditis
• Myocarditis
• Pneumothorax
• Mediastinitis
• Cholecystitis
• Pancreatitis
• Cocaine-associated chest pain

Nonemergent

• Stable angina
• Asthma exacerbation
• Valvular Heart Disease
• Aortic Stenosis
• Mitral valve prolapse
• Hypertrophic cardiomyopathy
• Pneumonia
• Pleuritis
• Tumor
• Pneumomediastinum
• Esophageal Spasm
• Gastroesophageal Reflux Disease (GERD)
• Peptic Ulcer Disease
• Biliary Colic
• Muscle sprain
• Rib Fracture
• Arthritis
• Chostochondirits
• Spinal Root Compression
• Thoracic outlet syndrome
• Herpes Zoster / Postherpetic Neuralgia
• Psychologic / Somatic Chest Pain
• Hyperventilation
• Panic attack

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
  • 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)
      • 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
        • 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
• 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

• Cardiomyopathy
• Amal Mattu July 30, 2012 case

References

Authors

Kevin Lu, Ross Donaldson, Daniel Eggeman, Mark Basso, Michael Holtz, Jordan Swartz, Neil Young, Claire, Daniel Ostermayer