Cardiomyopathies: Pathological Essentials
Cardiomyopathies are defined as primary myocardial disorders classified based on structural and functional abnormalities.
1. Functional Classification
| Type | Key Pathological & Clinical Features |
|---|---|
| Dilated (DCM) | Systolic dysfunction. Four-chamber dilation. Causes: Alcohol, Beriberi, Coxsackie B, Doxorubicin, and Chagas disease. |
| Hypertrophic (HCM) | Diastolic dysfunction. Asymmetric septal hypertrophy. Often genetic (sarcomere proteins). Sudden death in young athletes. |
| Restrictive | Diastolic dysfunction. Decreased compliance. Causes: Amyloidosis, Sarcoidosis, Endomyocardial fibrosis (Löffler syndrome). |
2. Exam Must-Knows
- HCM Pathophysiology: Characterized by myofibrillar disarray on histology. The outflow tract obstruction is worsened by the Valsalva maneuver or standing (decreased preload) and improved by squatting (increased preload).
- Doxorubicin Toxicity: Classic cause of DCM; prevents topoisomerase-II-mediated DNA repair in cardiac myocytes.
- Löffler Syndrome: A restrictive cardiomyopathy associated with eosinophilia and endomyocardial fibrosis with prominent eosinophilic infiltrate.
- Amyloidosis: Classic cause of restrictive cardiomyopathy; look for “apple-green birefringence” on Congo red stain under polarized light.
3. Clinical Pearl
Diagnostic Distinction: DCM presents with heart failure signs (S3 gallop, dilated apex), while HCM is often identified by a harsh systolic murmur that increases with Valsalva and a paradoxical S4 gallop.