Epidemiology
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Etiology
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Physiology
General Comments
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Left Ventricular Outflow Tract-Aorta Pressure Gradient
- Incidence: pressure gradient between the left ventricular outflow tract and the aorta is present in 75% of hypertrophic cardiomyopathy cases (either at rest or with provocation)
- Dynamic Nature of Outflow Tract Gradients: gradients fluctuate from day to day (based on factors which alter myocardial contractility and loading (such as dehydration, ethanol ingestion, or large meals)
Pathophysiologic Manifestations
- Diastolic Dysfunction (see Congestive Heart Failure, [[Congestive Heart Failure]])
- Left Ventricular Outflow Tract Obstruction
- Mitral Regurgitation (MR) (see Mitral Regurgitation, [[Mitral Regurgitation]])
- Myocardial Ischemia
Diagnosis
Echocardiogram (see Echocardiogram, [[Echocardiogram]])
- Morphologic Variants
- Asymmetric Septal Hypertrophy (ASH)
- Biventricular Hypertrophy
- Left Ventricular Wall Thinning with Low Ejection Fraction and Bi-Atrial Enlargement
- Midcavity Hypertrophy with Midcavity Obstruction
- Mild-Moderate Septal Hypertrophy
- Predominant Apical Left Ventricular Hypertrophy
- Predominant Free Wall Hypertrophy: unusual pattern
- Severe Concentric Left Ventricular Hypertrophy with Cavity Obliteration
- Sigmoid Septum: more common in older adults
Exercise Stress Echocardiogram
- Preferred Method to Determine if Outflow Tract Gradient is Present: mimics the conditions under which gradient might occur during normal daily activities
Dobutamine Stress Echocardiogram
- Alternative to Exercise Stress Echocardiogram: although is less reliable than exercise stress echocardiogram
Valsalva Manuever with Echocardiogram
- May Induce Gradient: although is less reliable than exercise stress echocardiogram
Clinical Manifestations
Cardiovascular Manifestations
- Angina/Chest Pain (see Chest Pain, [[Chest Pain]])
- Arrhythmias
- Atrial Fibrillation (AF) (see Atrial Fibrillation, [[Atrial Fibrillation]])
- Ventricular Tachycardia (VT) (see Ventricular Tachycardia, [[Ventricular Tachycardia]])
- Left Ventricular Aneurysm (see Left Ventricular Aneurysm, [[Left Ventricular Aneurysm]])
- Mitral Regurgitation (see Mitral Regurgitation, [[Mitral Regurgitation]])
- Mechanism: due to systolic anterior motion (SAM) of the mitral valve or papillary muscle/chordae tendineae abnormalities -> abnormal mitral valve leaflet coaptation (usually with a posteriorly-directed jet)
- Characteristics of Murmur: mid-late systolic murmur
- In contrast, primary mitral valve disease usually presents with a central-directed jet with holosystolic murmur, loudest at the apex and radiating to the axilla
- Radiation: may radiate toward the base of the heart (due to the eccentric jet)
- Other Findings Related to Hypertrophic Cardiomyopathy Itself
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- Palpitations (see Palpitations, [[Palpitations]])
- Pre-Syncope/Syncope (see Syncope, [[Syncope]])
- Risk Factors
- Age <30 y/o
- Small Left Ventricular End-Diastolic Volume/Small Left Ventricular Cavity Size
- Episodes of Non-Sustained Ventricular Tachycardia (on 72 hr Ambulatory EKG Monitoring)
- Mechanisms
- Atrial Fibrillation
- Conduction Abnormalities/Atrioventricular Heart Blocks
- Exertional Myocardial Ischemia
- Left Ventricular Outflow Tract Obstruction
- Ventricular Baroreflex Activation with Inappropriate Vasodilation
- Risk Factors
- Systolic Murmur Due to Left Ventricular Outflow Tract Obstruction
- Mechanism: due to combination of left ventricular septal hypertrophy and systolic anterior motion (SAM) of the mitral valve
- May reflect both mitral regurgitation and aortic outflow obstruction in patients with a large gradient
- Characteristics: harsh crescendo-decrescendo murmur (begins slightly after S1) heard best at apex and left lower sternal border
- Radiation: left axilla and base (usually not to the neck)
- Maneuvers Which Increase Intensity of Murmur: due to increased obstruction
- During More Forceful Contraction Following Compensatory Pause After Premature Ventricular Contraction: increases murmur
- Nitroglycerin: increases murmur
- Going From Squatting/Sitting/Supine Positions -> Standing : increases murmur
- Valsalva: increases murmur
- Maneuvers Which Decrease Intensity of Murmur: due to decreased obstruction
- Going to Standing -> Sitting/Squatting Position: decreases murmur
- Handgrip: decreases murmur
- Passive Elevation of Legs: decreases murmur
- Mechanism: due to combination of left ventricular septal hypertrophy and systolic anterior motion (SAM) of the mitral valve
- Sudden Cardiac Death (se Sudden Cardiac Death, [[Sudden Cardiac Death]])
Pulmonary Manifestations
- Exertional Dyspnea (see Dyspnea, [[Dyspnea]]): most common presenting symptom (occurs in >90% of cases)
Other Manifestations
- Fatigue (see Fatigue, [[Fatigue]])
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Treatment
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References
- Nonobstructive Hypertrophic Cardiomyopathy with Left Ventricular Aneurysm. Tex Heart Inst J. 2013; 40(4): 465–467 [MEDLINE]