Hypertrophic Cardiomyopathy
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More Specific Terms
Etiology
-
- onset < 10 years of age
- no associated hypertension
- genetic
- autosomal dominant, variable phenotypic presentation
- mutation in myosin heavy-chain 7 (beta) gene ( chromosome 14)
- troponin T mutations less common than myosin heavy chain mutations
- subtle ventricular hypertrophy
- few symptoms
- ominous prognosis
- alpha-tropomyosin mutation ( chromosome 15)
- acquired form in elderly patients with a long history of hypertension
Pathology
- myocardial hypertrophy is
- typically predominant in the ventricular septum
- may involve all ventricular segments equally
- left ventricular outflow obstruction
- may occur at rest
- secondary to thickened interventricular septum
- obstruction increased by:
- increased left ventricular contractility
- decreased preload ( nitrates diuretics, Valsalva)
- decreased afterload ( vasodilators, ACE inhibitors)
- obstruction decreased by:
- increased afterload ( handgrip)
- decreased contractility
- increased preload (fluid)
- ventricular diastolic dysfunction
- delayed ventricular relaxation
- decreased ventricular compliance
- pulmonary congestion
- myocardial oxygen supply/demand mismatch
- endomyocardial ischemia may occur despite normal coronary arteries
- systolic motion of anterior leaflet of mitral valve
- cardiac arrhythmias may result from aberrant conduction
Clinical-manifestations
- clinical presentation varies considerably
- exertional dyspnea
- angina pectoris
- palpitations/ arrhythmias
- syncope
- heart failure
- sudden death during physical exertion
- most common in children & young adults age 10-35
- commonly during periods of strenuous exercise
- bifid carotid pulse
- forceful, double or triple apical impulse
- coarse late-peaking systolic murmur of mitral regurgitation
-
- reduce preload
- reduce afterload
- increased myocardial contractility
- systolic anterior motion of mitral valve
- left ventricular hypertrophy generally remains stable in older patients; progressive disease with dilatation in 5-10%
- Brockenbrough's sign Special Laboratory:
- electrocardiogram
- left ventricular hypertrophy & strain
- increased voltage
- ST segment & T wave changes
- Q waves may mimic myocardial infarction [2]
- W waves, II, III, aVF & lateral leads (I, avL, V4- V6)
- p waves suggesting LAE
- conduction delay, ventricular ectopy
- left axis deviation
- left ventricular hypertrophy
- interventricular septum thickening diproportionately greater than ventricular free wall
- mitral valve function
- screen all first degree relatives [2]
- 48-72 hour HOLTOR monitoring ( risk stratification)
- exercise stress testing [2]
Complications
-
- major risk factors [2]
- ventricular fibrillation, prior cardiac arrest
- sustained ventricular tachycardia
- family history of sudden death in 1st degree relative < 40 years of age
- minor risk factors [2]
- unexplained syncope (> 2 episodes within 1 year)
- non- sustained ventricular tachycardia
- systolic blood pressure increase of < 20 mm Hg on exercise stress testing
- significant left ventricular outflow obstruction
- left ventricular septal wall thickness > 30 mm in diastole
- microvascular disease
- age < 30 years at diagnosis
- malignant genotype
Differential-diagnosis
Management
- relief of symptoms
- avoid strenuous physical activities, including most competitive sports
- pharmacologic therapy
-
- LVEF >= 50%, dyspnea &/or angina pectoris
- reduce myocardial contractility
- reduce heart rate
- propranolol 160-320 mg/day
- second line agents
- increased left ventricular diastolic filling
- diltiazem
- verapamil: may be used, may cause sudden hemodynamic deterioration in patients with high resting left ventricular outflow tract obstruction
- avoid dihydropyridines because of vasodilatory effect
- avoid diuretics
- may improve symptoms of pulmonary congestion
- excessive preload reduction
- may worsen LV outflow obstruction
- avoid nitrates & vasodilators
- includes avoid ACE inhibitors
- may increase left ventricular outflow obstruction
- unless LV systolic dysfunction develops [2]
- common
- supraventricular arrhythmias
- DC cardioversion if patient is unstable
- atrial fibrillation
- poorly tolerated
- cardioversion if possible
- digoxin relatively contraindicated
- inotropic agent
- potential to increase outflow obstruction
- control ventricular response prior to cardioversion with:
- suppression of chronic atrial fibrillation
-
- increased risk of cardiac arrest
- benefit of therapy not establish
- treat symptomatic ventricular tachycardia
- implantable defibrillator
- prophylaxis for bacterial endocarditis recommended prior to guidelines of 2007
- anticoagulation for paroxysmal or chronic atrial fibrillation
- Dual chamber pacing - right ventricular pacing used to alter ventricular activation sequence may reduce left ventricular outflow obstruction due to asymmetric septal hypertrophy
- implantable cardioverter-defibrillator ( ICD) for patients at risk for sudden death
- family history of sudden death
- diagnosis < 30 years of age
- recurrent non- sustained ventricular tachycardia
- extreme LV hypertrophy
- wall thickness > 20 mm
- significant outflow-tract gradient
- malignant genotype
- exercise-induced hypotension
- outflow tract gradient > 50 mm Hg
- symptoms despite maximal medical management
- useful in treatment of symptoms
- has not been demonstrated to improve survival
- procedures
- septal myotomy or myectomy (Morrow procedure)
- mitral valve replacement ( MVR)
- genetic couseling for all patients
More General Terms
Additional Terms
- Brockenbrough's sign
- myosin heavy chain 7; myosin-7; myosin heavy chain, cardiac muscle beta isoform; MyHC-beta; myosin heavy chain slow isoform; MyHC-slow (MYH7, MYHCB)
- troponin-T
References
- Manual of Medical Therapeutics, 28th ed, Ewald & McKenzie (eds), Little, Brown & Co, Boston, 1995, pg 132-33
- Medical Knowledge Self Assessment Program (MKSAP) 11, 14, 15 American College of Physicians, Philadelphia 1998, 2006, 2009
- Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed) Lippincott-Raven, Philadelphia, 1998, pg 104-108
- National Guideline Clearinghouse
- UpToDate 14.1 [1]
