Cardiomyopathies are diseases that affect the structure and function of the heart muscle (myocardium) in the absence of secondary causes (e.g., coronary artery disease, hypertension, valvular disease, and congenital heart disease).
- Incidence and prevalence difficult to estimate due to inconsistent reporting
- Second most common cause of sudden death after ischemic heart disease
- Both sporadic and familial forms exist.
- No clear gender or racial predominance
- Infectious diseases
- Inflammatory/autoimmune conditions
- Endocrinologic disorders
- Nutritional deficiencies
- Deposition diseases
- Familial storage diseases
- Genetic neurologic and neuromuscular disorders
- Hematologic/oncologic disorders
- Cardiovascular disorders
- Endomyocardial diseases
- Genetic (gene mutations)
Approximately ⅓ of cases have a genetic cause.
- Dilated cardiomyopathy (DCM):
- Heart appears enlarged.
- Muscle is thinned.
- Restrictive cardiomyopathy (RCM):
- Heart is normal size (or smaller).
- Muscle is stiffened.
- Hypertrophic cardiomyopathy (HCM)
- Heart is enlarged.
- Muscle is thickened.
- Arrhythmogenic right ventricular cardiomyopathy/dysplasia
- Unclassified cardiomyopathy
- Primary: arises from an exclusively cardiac issue
- Mixed (nongenetic/genetic)
- Secondary: caused by or associated with a known underlying systemic condition
- Disorders of connective tissue
- Muscular dystrophies
- Autoimmune disease
- Infections of the heart muscle
- Infiltrative diseases (hemochromatosis, sarcoidosis, or amyloidosis)
- Endocrine disorders (thyroid conditions, diabetes)
- Chronic substance abuse (especially alcohol or cocaine)
- Myocardium: thickest layer of the heart
- Specialized form of striated muscle
- Composed of cardiomyocytes connected by intercalated discs
- Structure, size, and arrangement of muscle fibers and heart chambers optimized for pumping force
- End effect of cardiomyopathies: structural change in heart muscle
- May cause hypertrophy or dilation of one or both of the heart ventricles
- Changes shape and capacity of ventricles
- Cause systolic or diastolic dysfunction, depending on the disease process
- Systolic dysfunction is characterized by a decrease in heart muscle contractility.
- Diastolic dysfunction is characterized by a decrease in left ventricular relaxation and ability to fill with blood and is often associated with increased filling pressures.
- Net end effect is inability to pump blood efficiently:
- Heart failure
- Volume overload
Diagnostic approach varies based on the type of cardiomyopathy. Physicians must have a high index of suspicion for disorders of the myocardium in patients with heart failure.
- Echocardiography with Doppler:
- Used in evaluation of all cases
- Assesses cardiac size, anatomy, structure, and function
- Cardiac MRI:
- Advanced imaging technique
- Allows greater characterization of cardiac structure and function
- Used to determine extent of myocardial damage, infiltration, and fibrosis
- Low sensitivity for diagnosis of cardiomyopathies
- Used to identify abnormal heart rhythms, such as associated arrhythmias or conduction delays
- Optimize cardiac output:
- Increase contractility.
- Allow for ventricular filling.
- Optimize ejection fraction.
- Treat or slow underlying disease progression.
- Manage symptoms of heart failure:
- Volume overload
- Blood pressure
- Manage symptoms caused by distortion of heart muscle:
- Arrhythmias: medication, pacemaker, or internal cardioverter–defibrillator (ICD)
- Blood clots: anticoagulants
In cases refractory to treatment, heart transplantation may be indicated.
- Heart failure
- Sudden cardiac death
Comparison of the Cardiomyopathies
|Dilated||Restrictive||Hypertrophic||Arrhythmogenic right ventricular CM|
|Physical exam findings|
|Ejection fraction||↓||↓ or normal||↑ or normal||↓|
|L ventricular diastolic dimension||↑||↑||↓||Normal|
|Left ventricular wall thickness||↓||Normal or ↑||↑↑||Normal|
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