Sandbox/HCM

# Overview
Hypertrophic cardiomyopathy (HCM), is a heterogeneous cardiac muscle disease characterized by unexplained LV hypertrophy associated with nondilated ventricular chambers in the absence any underlying disease that is capable of producing hypertrophy, or without overt hypertrophy in the presence of the HCM genetic substrate (genotype positive/phenotype negative or subclinical HCM).  HCM is caused by autosomal dominant mutations in sarcomere genes which encode components of the contractile apparatus of the heart.  The clinical manifestations of HCM individuals depends upon the site and extent of cardiac hypertrophy, having asymptomatic normal life expectancy without disability to severe symptomatic presentation due to LV outflow obstruction, heart failure, myocardial ischemia, arrhythmia, mitral regurgitation or sudden cardiac death.  The diagnosis of HCM is made with cardiac imaging (echocardiography or cardiac MRI), showing maximal LV wall thickness  15 mm in adults or thickness  2 SD above the mean for age, sex, body size in children and with genetic testing.  The management of HCM involves risk stratification to ascertain which patients are at risk for sudden cardiac death, treatment of comorbidities, ICDs for secondary or primary prevention, pharmacological therapy to control heart failure, surgical options for progressive and drug-refractory heart failure symptoms due to LV outflow tract (LVOT) obstruction and heart transplantation for systolic dysfunction with severe unrelenting symptoms.

# Classification

## Obstructive form of HCM
Defined when peak instantaneous LV outflow gradient 30 mm Hg under basal (resting) conditions. or with physiologic provocation.

## Non-obstructive form of HCM
Defined when peak instantaneous LV outflow gradient <30 mm Hg at rest and with provocation.

# Causes

## Life Threatening Causes
Hypertrophic cardiomyopathy can be a life-threatening condition and must be treated as such irrespective of the underlying cause.

## Common Causes
- Congenital: Autosomal dominant mutation in genes that encode sarcomere proteins or sarcomere-associated proteins.
Beta myosin heavy chain
Myosin binding protein C
Troponin T
Troponin I
Alpha tropomyosin
Actin
Regulatory light chain
Essential light chain
Actinin 
Myozenin
- Beta myosin heavy chain
- Myosin binding protein C
- Troponin T
- Troponin I
- Alpha tropomyosin
- Actin
- Regulatory light chain
- Essential light chain
- Actinin
- Myozenin

# FIRE: Focused Initial Rapid Evaluation
A Focused Initial Rapid Evaluation (FIRE) should be performed to identify patients in need of immediate intervention.
Boxes in red color signify that an urgent management is needed.

# Complete Diagnostic Approach to Hypertrophic Obstructive Cardiomyopathy
A complete diagnostic approach should be carried out after a focused initial rapid evaluation is conducted and following initiation of any urgent intervention.

# Treatment

# Complete Diagnostic Approach to Mitral Regurgitation
A complete diagnostic approach should be carried out after a focused initial rapid evaluation is conducted and following initiation of any urgent intervention.
Abbreviations: EKG: Electrocardiogram; LVOT: Left ventricle outflow tract;

# Treatment

# Do's
However in equivocal cases, cardiac catheterization with isoproterenol infusion may further aid in eliciting a provocable gradient (82). Otherwise, routine invasive cardiac catheterization to document outflow gradients is necessary only when there are discordant data from Doppler echocardiography and the physical examination

# Don'ts
Provocation with dobutamine infusion during Doppler echocardiography is no longer recommended as a strategy to induce outflow gradients in HCM.
- Don't perform genetic testing for relatives when the index patient does not have a definitive pathogenic mutation (Class IIb Level of Evidence:B).