Cardiomyopathies

Cardiomyopathies: Intro & Types - Heart's Structural Woes

Myocardial diseases with structural/functional abnormalities, not explained by CAD, HTN, valvular, or congenital heart disease (WHO/ESC criteria).

• Primary: Predominantly confined to heart muscle.
• Secondary: Myocardial involvement as part of systemic disease.

Main Morpho-functional Types:

• Dilated Cardiomyopathy (DCM): LV/RV dilation & systolic dysfunction.
• Hypertrophic Cardiomyopathy (HCM): Unexplained LV hypertrophy.
• Restrictive Cardiomyopathy (RCM): Impaired ventricular filling, diastolic dysfunction.
• Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy (ARVD/C): Fibrofatty replacement of RV myocardium.
• Unclassified: e.g., Takotsubo cardiomyopathy, Left Ventricular Non-compaction (LVNC).

⭐ Cardiomyopathies are diseases of the myocardium associated with cardiac dysfunction, leading to impaired heart performance and often heart failure or arrhythmias.

Dilated Cardiomyopathy: Big Baggy Chambers

• Pathophysiology: Systolic dysfunction with impaired contractility, ↓ ejection fraction (EF).
• Etiology: Primarily idiopathic; also alcohol, viral (Coxsackie B), genetic, peripartum.
  • 📌 Mnemonic (ABCCCD): Alcohol, Beri-beri, Coxsackie B, Cocaine, Chagas, Doxorubicin.
• Key Findings:

  • CXR: Cardiomegaly (classic 'water bottle' sign), pulmonary venous hypertension, pleural effusion.

  • Echocardiography: Hallmark: LV dilation, global hypokinesia, ↓EF < 45%; often functional MR/TR.

  • Cardiac MRI: Assesses LV dilation & dysfunction; LGE (mid-myocardial linear or absent) helps differentiate etiology.

⭐ Dilated cardiomyopathy is the most common type of cardiomyopathy and a leading indication for heart transplantation.

Hypertrophic Cardiomyopathy: Thickened Heart Walls

• Etiology: Autosomal dominant genetic disorder (sarcomeric protein mutations, e.g., MYH7, MYBPC3).
• Pathophysiology:
  • Diastolic dysfunction (impaired LV relaxation/filling).
  • Dynamic LV Outflow Tract Obstruction (LVOTO) due to:
    • Asymmetric Septal Hypertrophy (ASH): Septum > free wall.
    • Systolic Anterior Motion (SAM) of mitral valve.
• Imaging:
  • CXR: Often normal; may show LA enlargement, LVH signs.
  • Echocardiography: LVH ≥15mm (in absence of other cause); ≥13mm in relatives. Shows ASH, SAM, LVOTO gradient, diastolic dysfunction.
  • Cardiac MRI: Gold standard for morphology, hypertrophy distribution, fibrosis (Late Gadolinium Enhancement - LGE at RV insertion points), crypts.

⭐ Hypertrophic cardiomyopathy is the most common genetic cardiovascular disease and a leading cause of sudden cardiac death in young athletes.

Restrictive & ARVC: Stiff Walls & Fatty Scars

• Restrictive Cardiomyopathy (RCM): Stiff Ventricles
  • Causes: 📌 ASHES To ASHES (Amyloid, Sarcoid, Hemochromatosis, Endomyocardial fibrosis, Scleroderma), idiopathic.
  • Patho: Stiff ventricles, impaired diastolic filling, preserved EF (early).
  • Echo: Biatrial enlargement, normal/small LV, thick walls (infiltrative), diastolic dysfunction; 'sparkling' (amyloid).
  • MRI: LGE (amyloid: diffuse subendocardial/transmural; sarcoid: patchy).
• Arrhythmogenic RV Cardiomyopathy/Dysplasia (ARVC/D): Fatty Scars
  • Cause: Genetic (desmosomal proteins).
  • Patho: RV fibrofatty replacement.
  • MRI (key): RV dilation, akinesia/dyskinesia, wall thinning, fatty infiltration, RV LGE.

⭐ ARVC/D classically involves the 'triangle of dysplasia' in the right ventricle (RV inflow, RV outflow, and RV apex).

High‑Yield Points - ⚡ Biggest Takeaways

• HCM: Asymmetric septal hypertrophy (ASH), LVOTO, SAM. Apical HCM: "ace-of-spades".
• DCM: Global LV dilatation, systolic dysfunction, ↓EF.
• RCM: Impaired diastolic filling, biatrial enlargement. Amyloidosis: diffuse LGE.
• ARVD/C: Fibrofatty replacement of RV, RV dilatation/aneurysms.
• LVNC: Prominent trabeculations, NC/C ratio >2.3:1.
• Takotsubo: Apical ballooning, transient dysfunction, normal coronaries.
• Cardiac MRI LGE: Differentiates types (e.g., mid-myocardial in HCM, diffuse in amyloid).