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Cardiomyopathies

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Cardiomyopathies - The Big Three

  • Overview: Diseases of the heart muscle leading to impaired cardiac function.
FeatureDilated (DCM)Hypertrophic (HCM)Restrictive (RCM)
Systolic/DiastolicSystolic DysfunctionDiastolic DysfunctionDiastolic Dysfunction
EF↓↓ (< 40%)Normal or ↑Normal
VentricleDilated, thin wallThickened wallRigid, non-dilated
Key CauseIdiopathic, AlcoholGenetic (AD)Amyloidosis, Sarcoid
Heart SoundsS3 GallopS4 GallopS3 Gallop

HCM Murmur: Murmur intensity decreases with maneuvers that ↑ preload/afterload (e.g., squatting, handgrip).

Cardiomyopathy Classification Table

Dilated Cardiomyopathy - Stretched & Weak

  • Pathophysiology: Impaired contractility (systolic dysfunction) → ↓ ejection fraction (<40%) → ventricular dilation. Most common cardiomyopathy.
  • Etiologies: Mostly idiopathic. 📌 ABCCCD
    • Alcohol (reversible)
    • Beriberi (wet), Bug (Chagas disease)
    • Cocaine, Coxsackie B
    • Chemotherapy (Doxorubicin)
    • Dystrophy (muscular)
  • Clinical: S3 gallop, mitral/tricuspid regurgitation, balloon-like heart on CXR.
  • Diagnosis: Echo is key → shows LV dilation & ↓ EF.

Reversible Causes: Key reversible causes include alcohol toxicity, thyroid dysfunction, and tachycardia-induced cardiomyopathy. Always consider these in new-onset HF.

Interstitial Expansion and Pathological Hypertrophy in Heart

Hypertrophic Cardiomyopathy - Thick & Obstructed

  • Etiology: Autosomal dominant mutation in sarcomere protein genes (e.g., MYH7, MYBPC3).
  • Pathophysiology: Asymmetric left ventricular hypertrophy (LVH), particularly the septum, leading to dynamic LV outflow tract (LVOT) obstruction and severe diastolic dysfunction.
  • Clinical: Exertional dyspnea, angina, and syncope. Major cause of sudden cardiac death in young athletes.
  • Auscultation: Harsh crescendo-decrescendo systolic murmur at the left sternal border.

Exam Favorite: Maneuvers that decrease LV cavity size (↓ preload) like Valsalva or standing, worsen the obstruction and increase the murmur. Maneuvers that increase LV cavity size (↑ preload/afterload) like squatting or handgrip, decrease the murmur.

  • Dx: Echocardiogram shows septal wall thickness > 15 mm.
  • Rx: β-blockers, verapamil. Avoid preload-reducing agents (diuretics, nitrates).

Restrictive Cardiomyopathy - Stiff & Stubborn

  • Pathophysiology: Rigid, non-compliant ventricles lead to impaired diastolic filling and bi-atrial enlargement, with preserved systolic function initially.
  • Etiology: Primarily infiltrative diseases.
    • Amyloidosis: Most common cause; associated with multiple myeloma, chronic inflammation.
    • Sarcoidosis: Non-caseating granulomas infiltrate the myocardium.
    • Hemochromatosis: Iron deposition.
  • Clinical: Resembles constrictive pericarditis. Predominantly right-sided HF symptoms (JVD, peripheral edema, ascites). Kussmaul's sign (paradoxical ↑JVP with inspiration) may be present.
  • Diagnosis:
    • ECG: Low-voltage QRS complexes.
    • Echocardiogram: Thickened ventricular walls, sparkling "granular" appearance in amyloidosis.

Exam Favorite: The combination of low voltage on ECG despite thickened myocardium on echo is a classic finding for cardiac amyloidosis.

Amyloid deposition in restrictive cardiomyopathy

High‑Yield Points - ⚡ Biggest Takeaways

  • Dilated cardiomyopathy, the most common form, presents with systolic dysfunction and is often idiopathic or due to alcohol abuse.
  • Hypertrophic cardiomyopathy is an autosomal dominant condition causing diastolic dysfunction; its murmur increases with Valsalva.
  • Restrictive cardiomyopathy results from infiltrative diseases like amyloidosis or sarcoidosis, leading to diastolic dysfunction.
  • Arrhythmogenic RV cardiomyopathy involves fibrofatty infiltration of the right ventricle, causing arrhythmias.
  • Takotsubo cardiomyopathy ("broken-heart syndrome") is a stress-induced, reversible apical ballooning.

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Practice Questions: Cardiomyopathies

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A 43-year-old woman presents to her primary care provider with shortness of breath. She reports a 4-month history of progressively worsening difficulty breathing with associated occasional chest pain. She is a long-distance runner but has had trouble running recently due to her breathing difficulties. Her past medical history is notable for well-controlled hypertension for which she takes hydrochlorothiazide. She had a tibial osteosarcoma lesion with pulmonary metastases as a child and successfully underwent chemotherapy and surgical resection. She has a 10 pack-year smoking history but quit 15 years ago. She drinks a glass of wine 3 times per week. Her temperature is 98.6°F (37°C), blood pressure is 140/85 mmHg, pulse is 82/min, and respirations are 18/min. On exam, she has increased work of breathing with a normal S1 and loud P2. An echocardiogram in this patient would most likely reveal which of the following?

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Flashcards: Cardiomyopathies

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Assessing _____ can help distinguish cardiac disease from hepatic disease in a patient presenting with bilateral lower extremity edema and ascites

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Assessing _____ can help distinguish cardiac disease from hepatic disease in a patient presenting with bilateral lower extremity edema and ascites

hepatojugular reflux

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