Histology · Year 1 · from Histology
Case 1: Hypertrophic Cardiomyopathy
Clinical Image
Source: Wikipedia - Hypertrophic Cardiomyopathy - CC BY-SA 3.0
Case Presentation
A 19-year-old college basketball player collapses during practice and is found to be in ventricular fibrillation. He is successfully resuscitated with an automated external defibrillator. In the hospital, his echocardiogram reveals asymmetric septal hypertrophy with the interventricular septum measuring 22 mm (normal <11 mm) and systolic anterior motion of the mitral valve causing left ventricular outflow tract obstruction. Family history reveals his father died suddenly at age 42 during a tennis match. Genetic testing identifies a mutation in the MYH7 gene encoding beta-myosin heavy chain. Histologically (from autopsy studies of similar cases), hypertrophic cardiomyopathy shows characteristic myocyte disarray - cardiomyocytes are hypertrophied and arranged chaotically rather than in parallel, with increased interstitial fibrosis. He is diagnosed with hypertrophic cardiomyopathy (HCM) and an implantable cardioverter-defibrillator (ICD) is placed. He is advised to discontinue competitive athletics.
Key Learning Points
- HCM is often caused by mutations in sarcomeric proteins (beta-myosin heavy chain, myosin-binding protein C, troponins)
- The mutations lead to abnormal sarcomere function, triggering compensatory hypertrophy
- Histologically, myocyte disarray and interstitial fibrosis create electrical instability, predisposing to fatal arrhythmias
- HCM is the leading cause of sudden cardiac death in young athletes
- Understanding cardiac muscle structure (sarcomeres, intercalated discs) explains how sarcomere protein mutations produce both mechanical and electrical dysfunction