#55 – Cardiomyopathies



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Definitions

  • 1980 – WHO characterized cardiomyopathies as “heart muscle diseases of unknown causes”
    • Distinguish between non-cardiovascular pathologies (HTN, coronary disease, valvular disease)
  • 1995 – WHO and International Society and Federation of Cardiology (ISFC) developed a task force specifically looking at the definition and classifications of cardiomyopathies
    • Definition they developed was “disease of the myocardium associated with cardiac dysfunction”
      • Dilated cardiomyopathy (DCM)
      • Hypertrophic cardiomyopathy (HCM)
      • Restrictive cardiomyopathy (FCM)
      • Arrhythmogenic right ventricular cardiomyopathy (ARVC)
      • Unclassified cardiomyopathy
  • 2006 – AHA released a statement to update to a more contemporary definition with two major categories
    • Primary cardiomyopathies (predominantly involving the heart)
      • Genetic
        • HCM, ARVC
      • Mixed
        • DCM, RCM
      • Acquired
        • Myocarditis, stress-induced, peripartum, tachy-induced
    • Secondary cardiomyopathies (other system involvement)
  • 2008 – European Society of Cardiology (ESC) updated the WHO/IFSC classification of cardiomyopathies as
    • “a disorder in which the heart muscle is structurally and functionally abnormal in the absence of coronary artery disease, HTN, valvular disease, and congenital heart disease”
      • Meant to more clinically useful
    • Further subcategorized into familial and non-familial causes, as well as removing CAD, vavlvular, congenital heart disease, and ion channelopathies as causes

Echographic Evaluation

  • Systolic
    • Decrease in myocardial contractility resulting in a decrease in left ventricular ejection fraction
      • To compensate, cardiac output is maintained by LV enlargement (increase stroke volume)
    • As a result, systolic dysfunction is most commonly characterized by a dilated cardiomyopathy
  • Diastolic
    • Dysfunction in LV relaxation resulting in abnormal filling and elevated filling pressures
      • Mostly affected by compliance and distensibility of the myocardium
    • As a result, diastolic dysfunction is most commonly characterized by restrictive cardiomyopathy

Current Classifications

Dilated

  • Definition
    • Dilation and impaired contraction of one or both ventricles resulting in an increase in total cardiac mass
  • Numbers
    • Incidence – 5-8 cases per 100,000 population
    • Prevalence – 36 per 100,000
    • STRONG HEART Study (20021) – Up to 14% of middle-aged and elderly may have asymptomatic LV dysfunction
  • Causes
  • Signs and Symptoms
    • Progressive dyspnea on exertion
    • Impaired exercise capacity
    • Orthopnea
    • Paroxysmal nocturnal dyspnea
    • Peripheral edema
    • Cardiomegaly
      • Radiographic
        • > 50% cardiothoracic ratio
      • Clinical
        • Displaced PMI
        • S3 with gallop
  • Classic Echocardiographic Findings
    • Left ventricular cavitary spherical dilation
    • Normal to decreased wall thickness
    • Reduced inward systolic motion
    • Left > Right atrial enlargement and dysfunction

Hypertrophic

  • Definition
    • Increased Left > Right ventricular wall thickness in the absence of pathologic causing conditions
  • Numbers
    • Prevalence – 1:500 of the adult population
  • Causes
    • Primarily genetic
      • Autosomal dominant with incomplete penetrance
      • 60-70% of patients have mutations in the beta myosin heavy chain and cardiac myosin-binding protein C genes
  • Signs and Symptoms
    • Atypical angina (25-30%)
    • Presyncope and syncope during or immediately after exertion (15-20%)
      • More common in patients < 30yo
    • Palpitations
    • Dyspnea on exertion
    • Fatigue
    • Clinical
      • LVOT obstruction
        • S4
        • Harsh crescendo-decrescendo systolic murmur after S1 best heard at apex and lower left sternal border
          • Accentuated by squatting and standing quickly
          • Diminished by standing and squatting quickly or with handgrip
        • Mitral regurgitation murmur
  • Classic Echocardiographic Findings
    • LV wall thickness > 15mm
    • LV outflow obstruction > 30mmHg
    • Asymmetric septal hypertrophy
    • Systolic anterior motion of the mitral valve (SAM)

Restrictive

  • Definition
    • Non-dilated, nonhypertrophied ventricles with moderate to marked biatrial enlargement
  • Numbers
    • ~5% of all cases of cardiomyopathies
  • Causes
    • Infiltrative
      • Amyloidosis, sarcoidosis
    • Non-infiltrative
      • Diabetic, scleroderma
    • Storage Disease
      • Hemochromatosis, Fabry, Gaucher
    • Endomyocardial
      • Cancer/Cancer therapy, pharmacologic
  • Signs and Symptoms
    • Dyspnea
    • Peripheral edema
    • Palpitations
    • Fatigue
    • Weakness
    • Exercise intolerance
    • Clinical
      • Elevated JVP with a prominent y descent
      • S3
      • Hepatosplenomegaly and ascites
  • Classic Echocardiographic Findings
    • Difficult and often requires doppler interrogation
      • Elevated peak mitral inflow velocity
      • Rapid early mitral inflow deceleration
      • Reduced annular velocity
    • Normal to low diastolic volume
    • Normal to low reduced LVEF
    • Atrial enlargement

The Cottage Physician (1893)



References

  1. Report of the WHO/ISFC task force on the definition and classification of cardiomyopathies. British heart journal. 1980; 44(6):672-3. [pubmed]
  2. Richardson P, McKenna W, Bristow M, et al. Report of the 1995 World Health Organization/International Society and Federation of Cardiology Task Force on the Definition and Classification of cardiomyopathies. Circulation. 1996; 93(5):841-2. [pubmed]
  3. Maron BJ, Towbin JA, Thiene G, et al. Contemporary definitions and classification of the cardiomyopathies: an American Heart Association Scientific Statement from the Council on Clinical Cardiology, Heart Failure and Transplantation Committee; Quality of Care and Outcomes Research and Functional Genomics and Translational Biology Interdisciplinary Working Groups; and Council on Epidemiology and Prevention. Circulation. 2006; 113(14):1807-16. [pubmed]
  4. Elliott P, Andersson B, Arbustini E, et al. Classification of the cardiomyopathies: a position statement from the European Society Of Cardiology Working Group on Myocardial and Pericardial Diseases. European heart journal. 2008; 29(2):270-6. [pubmed]
  5. Dec GW, Fuster V. Idiopathic dilated cardiomyopathy. The New England journal of medicine. 1994; 331(23):1564-75. [pubmed]
  6. Devereux RB, Roman MJ, Paranicas M, et al. A population-based assessment of left ventricular systolic dysfunction in middle-aged and older adults: the Strong Heart Study. American heart journal. 2001; 141(3):439-46. [pubmed]
  7. Felker GM, Thompson RE, Hare JM, et al. Underlying causes and long-term survival in patients with initially unexplained cardiomyopathy. The New England journal of medicine. 2000; 342(15):1077-84. [pubmed]
  8. Maron BJ, Gardin JM, Flack JM, Gidding SS, Kurosaki TT, Bild DE. Prevalence of hypertrophic cardiomyopathy in a general population of young adults. Echocardiographic analysis of 4111 subjects in the CARDIA Study. Coronary Artery Risk Development in (Young) Adults. Circulation. 1995; 92(4):785-9. [pubmed]
  9. Maron BJ. Clinical Course and Management of Hypertrophic Cardiomyopathy. The New England journal of medicine. 2018; 379(7):655-668. [pubmed]
  10. Richard P, Charron P, Carrier L, et al. Hypertrophic cardiomyopathy: distribution of disease genes, spectrum of mutations, and implications for a molecular diagnosis strategy. Circulation. 2003; 107(17):2227-32. [pubmed]
  11. Nienaber CA, Hiller S, Spielmann RP, Geiger M, Kuck KH. Syncope in hypertrophic cardiomyopathy: multivariate analysis of prognostic determinants. Journal of the American College of Cardiology. 1990; 15(5):948-55. [pubmed]
  12. Muchtar E, Blauwet LA, Gertz MA. Restrictive Cardiomyopathy: Genetics, Pathogenesis, Clinical Manifestations, Diagnosis, and Therapy. Circulation research. 2017; 121(7):819-837. [pubmed]
  13. Ammash NM, Seward JB, Bailey KR, Edwards WD, Tajik AJ. Clinical profile and outcome of idiopathic restrictive cardiomyopathy. Circulation. 2000; 101(21):2490-6. [pubmed]
  14. Kushwaha SS, Fallon JT, Fuster V. Restrictive cardiomyopathy. The New England journal of medicine. 1997; 336(4):267-76. [pubmed]

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