Examples of Non-Ischemic Cardiomyopathy
Non-ischemic cardiomyopathies (NICMs) encompass five major variants: hypertrophic cardiomyopathy, restrictive/infiltrative cardiomyopathy, dilated cardiomyopathy, arrhythmogenic cardiomyopathy, and inflammatory cardiomyopathy. 1
Primary Classification of Non-Ischemic Cardiomyopathies
1. Hypertrophic Cardiomyopathy (HCM)
- Characterized by massive ventricular hypertrophy without obvious cause
- Impaired diastolic and systolic function
- High risk for sudden cardiac death (most common cause in young athletes)
- Often has familial propensity with genetic mutations (commonly in MYBPC3 and MYH7 genes) 2
- Prevalence: 1:250 to 1:500 in adults 1
2. Restrictive Cardiomyopathy (RCM)
- Characterized by restriction to ventricular filling due to restrictive forces in the endomyocardium
- Common causes include:
- Endomyocardial fibrosis (hypereosinophilic endomyocardial disease)
- Amyloidosis
- Sarcoidosis
- Hemochromatosis
- Glycogen storage diseases
- Fabry disease and other lysosomal storage disorders 2
3. Dilated Cardiomyopathy (DCM)
- Characterized by dilated ventricle and global systolic dysfunction
- Approximately 50% are idiopathic, more common in younger patients 1
- Other etiologies include:
- Toxins (alcohol, chemotherapeutic agents like anthracyclines)
- Familial/genetic inheritance
- Infections
- Autoimmune conditions
- Metabolic derangements
- Peripartum cardiomyopathy
- Muscular dystrophies 1
- Prevalence: 1:250 to 1:500 in adults 1
4. Arrhythmogenic Cardiomyopathy
- Primarily affects the right ventricle (ARVD/ARVC)
- Characterized by fibrofatty replacement of myocardium
- High risk for ventricular arrhythmias and sudden cardiac death
- Often caused by desmosomal protein mutations 2
- Prevalence: 1:2,000 to 1:5,000 in adults 1
5. Inflammatory Cardiomyopathy
- Acute or chronic myocarditis associated with cardiac dysfunction
- Caused by viral or microbial infection or autoimmune processes 3
- Can present with chest pain, elevated cardiac enzymes, and abnormal ECG 1
Unclassified Non-Ischemic Cardiomyopathies
1. Left Ventricular Non-Compaction (LVNC)
- Characterized by prominent trabeculations due to persistent embryonic sinusoids
- Leads to LV failure, thromboembolism, and arrhythmias 1
2. Stress-Induced (Takotsubo) Cardiomyopathy
- Transient LV systolic dysfunction attributed to catecholamine release
- Often follows a stressful event
- Presents similarly to acute myocardial infarction
- Accounts for approximately 2% of myocardial infarction with non-obstructive coronary arteries (MINOCA) 1
Clinical Significance
Non-ischemic cardiomyopathies have an approximate prevalence of 0.02% with an annual death rate of 25,000 in the United States 1, 2. Unlike ischemic cardiomyopathy, the pathophysiology is usually unclear and multifactorial, the functional consequences are global, the prognosis is generally better, and the therapeutic response is different 1.
Diagnostic Approach
Diagnosis typically involves:
- Clinical evaluation and family history
- Electrocardiography (ECG)
- Echocardiography (often the initial imaging test)
- Cardiac MRI (particularly valuable for tissue characterization)
- Genetic testing (recommended for both primary and secondary cardiomyopathies)
- Endomyocardial biopsy in selected cases 2
The MOGE(S) nosology system provides a comprehensive classification describing:
- Morphofunctional phenotype (M)
- Organ stratification (O)
- Genetic inheritance pattern (G)
- Etiological annotation (E)
- Functional status (S) 1
This classification system acknowledges that cardiomyopathies often don't fit into specific morphological and functional phenotypes due to tremendous genetic heterogeneity.