Cardiomyopathy


Table of Contents

  1. Table of Contents
  2. Overview
  3. Epidemiology
  4. Pathophysiology
  5. Etiology and Risk Factors
  6. Clinical Presentation
  7. Diagnosis
  8. Treatment
  9. Complications
  10. Prognosis
  11. Prevention
  12. Recent Research and Advances
  13. Research Papers
  14. Connections
  15. Featured Videos

Table of Contents

  1. Overview
  2. Epidemiology
  3. Pathophysiology
  4. Etiology and Risk Factors
  5. Clinical Presentation
  6. Diagnosis
  7. Treatment
  8. Complications
  9. Prognosis
  10. Prevention
  11. Recent Research and Advances
  12. References
  13. Featured Videos

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1. Overview

Cardiomyopathy refers to a heterogeneous group of diseases of the myocardium associated with mechanical and/or electrical dysfunction that usually (but not invariably) exhibit inappropriate ventricular hypertrophy or dilatation, arising from a variety of causes that are frequently genetic. Cardiomyopathies are the leading cause of heart failure in younger patients and a major cause of sudden cardiac death.

The 2006 AHA classification divides cardiomyopathies into primary (predominantly involving the heart) and secondary (myocardial involvement as part of generalized systemic disease). Primary cardiomyopathies are further classified as genetic, mixed (genetic + non-genetic), and acquired. The 2008 European Society of Cardiology (ESC) classification uses a morphofunctional approach identifying four major subtypes:

The 2023 AHA/ACC Guideline on Cardiomyopathies provides the most current framework, introducing the concept of Stage A (at risk) through Stage D (advanced) cardiomyopathy progression for DCM and HCM.


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2. Epidemiology

Cardiomyopathies collectively represent a significant burden of cardiovascular disease worldwide:


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3. Pathophysiology

Dilated Cardiomyopathy (DCM)

DCM is characterized by progressive dilatation of one or both ventricles with impaired systolic function (EF <50%). At the molecular level, genetic mutations in sarcomeric, cytoskeletal, and nuclear envelope proteins disrupt force generation, calcium handling, and structural integrity. TTN (titin) truncating variants are the most common cause, accounting for 25% of familial DCM and 18% of sporadic DCM. Other culprit genes include LMNA (lamin A/C), MYH7, TNNT2, SCN5A, and PLN (phospholamban).

Mechanistically, cardiomyocyte loss (apoptosis, necrosis, autophagy) triggers a maladaptive repair response including: reactive fibrosis (TGF-β/SMAD pathway activation), neurohormonal activation (RAAS, sympathetic nervous system upregulation), and ventricular remodeling — progressive dilation and wall thinning — leading to worsening systolic dysfunction in a vicious cycle.

Hypertrophic Cardiomyopathy (HCM)

HCM results from autosomal dominant mutations in sarcomeric protein genes — most commonly MYH7 (beta-myosin heavy chain, 35–40%) and MYBPC3 (myosin-binding protein C, 40–50%). Mutant sarcomeres exhibit increased ATPase activity and calcium sensitivity, leading to hypercontractility, energy depletion, and disordered calcium flux. This triggers compensatory hypertrophy mediated by calcineurin-NFAT, PI3K-Akt-mTOR, and MAPK signaling cascades.

The hallmark histologic features are myocyte hypertrophy, myofibrillar disarray, and interstitial fibrosis. Asymmetric septal hypertrophy (ASH) — particularly of the basal interventricular septum — creates dynamic left ventricular outflow tract obstruction (LVOTO) in 70% of patients during exercise (resting LVOTO in 25%). The Venturi effect from abnormal anterior mitral valve leaflet systolic anterior motion (SAM) exacerbates LVOTO and contributes to mitral regurgitation.

Arrhythmogenic Cardiomyopathy (ARVC)

ARVC results from mutations in desmosomal proteins — predominantly PKP2 (plakophilin-2, 45%), DSP (desmoplakin), DSG2 (desmoglein-2), DSC2, and JUP (plakoglobin) — disrupting cardiomyocyte cell-to-cell adhesion. Mechanical stress (exercise) triggers cardiomyocyte detachment and apoptosis, replaced by fibro-fatty infiltration predominantly in the right ventricular free wall, apex, and infundibulum (the "triangle of dysplasia").

Fibro-fatty replacement creates slow conduction zones supporting reentrant ventricular tachycardia circuits, explaining the exercise-provoked ventricular arrhythmias and sudden cardiac death risk in ARVC patients.

Restrictive Cardiomyopathy (RCM)

RCM is characterized by impaired ventricular filling with normal or reduced diastolic volumes, normal or mildly reduced systolic function, and elevated filling pressures. The pathophysiologic basis depends on etiology: infiltration (amyloid fibrils, glycolipids in Fabry disease), endomyocardial fibrosis (hypereosinophilic syndrome, radiation), or storage diseases (hemochromatosis — iron deposition impairs mitochondrial function and contractility).

Cardiac amyloidosis (transthyretin [ATTR] or light-chain [AL] amyloid) causes amyloid fibril deposition in the extracellular matrix, increasing myocardial stiffness and impairing diastolic filling. ATTR amyloid also impairs sodium channel function, contributing to conduction abnormalities.


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4. Etiology and Risk Factors

Dilated Cardiomyopathy — Causes

Hypertrophic Cardiomyopathy — Risk Factors

Secondary Cardiomyopathy Causes


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5. Clinical Presentation

Dilated Cardiomyopathy

DCM typically presents with progressive heart failure symptoms: exertional dyspnea (NYHA Class I–IV), orthopnea, paroxysmal nocturnal dyspnea, fatigue, and reduced exercise tolerance. Physical examination reveals displaced/diffuse PMI, S3 gallop, functional mitral regurgitation murmur, elevated JVP, pulmonary crackles, and peripheral edema in advanced disease. Arrhythmias (AF, ventricular tachycardia) and conduction abnormalities are common, particularly in LMNA-related DCM.

Hypertrophic Cardiomyopathy

The triad of exertional dyspnea, chest pain, and syncope (particularly exertional syncope — a warning sign for SCD) characterizes HCM. Many patients are asymptomatic, identified by family screening or incidental ECG/echocardiography findings. Physical examination with LVOTO reveals:

Arrhythmogenic Cardiomyopathy (ARVC)

ARVC typically presents in young adults (15–40 years) with palpitations, syncope, or sustained ventricular tachycardia (left bundle branch block morphology, suggesting RV origin). Sudden cardiac death — often exercise-triggered — can be the first manifestation. Physical examination is often normal early; signs of RV failure develop in advanced disease.

Restrictive Cardiomyopathy

RCM presents with symptoms of biventricular failure: severe exercise intolerance (dominant complaint), dyspnea, lower extremity edema, and ascites. Examination reveals elevated JVP with prominent x and y descents (Kussmaul's sign — failure of JVP to fall with inspiration), S3/S4 gallop, hepatomegaly, and peripheral edema. In cardiac amyloidosis, additional features include macroglossia (AL amyloid), periorbital purpura (AL amyloid — pathognomonic), carpal tunnel syndrome, and bilateral low-voltage ECG despite thick walls on echocardiography (classic "voltage-wall thickness discordance").


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6. Diagnosis

Electrocardiography

Echocardiography

The primary imaging modality for initial evaluation:

Cardiac Magnetic Resonance Imaging (CMR)

CMR is the gold standard for myocardial characterization, tissue quantification, and ARVC evaluation:

Additional Diagnostic Testing


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7. Treatment

Dilated Cardiomyopathy

DCM treatment follows guideline-directed medical therapy (GDMT) for HFrEF (see Heart Failure guidelines):

Hypertrophic Cardiomyopathy

Arrhythmogenic Cardiomyopathy (ARVC)

Cardiac Amyloidosis (ATTR)


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8. Complications


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9. Prognosis


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10. Prevention

Primary Prevention

Secondary Prevention


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11. Recent Research and Advances

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Research Papers

The following PubMed topic searches return current peer-reviewed literature relevant to this condition. Each link opens a live PubMed query.

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Connections

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Hypertrophic Cardiomyopathy Explained: Symptoms, Causes & Treatments

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Cardiomyopathy Overview Restrictive, Dilated, Hypertrophic pathophysiology, symptoms

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Hypertrophic cardiomyopathy - signs and symptoms, causes, pathophysiology, treatment

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Dilated Cardiomyopathy - causes, symptoms, pathophysiology and treatment

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Cardiomyopathy treatment | Circulatory System and Disease | NCLEX-RN | Khan Academy

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Understanding the Symptoms of Hypertrophic Cardiomyopathy

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Takotsubo Cardiomyopathy (Broken heart syndrome) - pathophysiology, diagnosis and treatment

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Cardiomyopathy Overview - types (dilated, hypertrophic, restrictive), pathophysiology and treatment

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Cardiomyopathy | Clinical Medicine