hypertrophic obstructive cardiomyopathy (hocm)

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  • 1.Hypertrophic Obstructive Cardiomyopathy Dr KURIAN JOSEPH JOURNAL PRESENTATION

2. Historical Perspective

  • HCM was initially described by Teare in 1958
      • Found massive hypertrophy of ventricular septum in small cohort of young patients who died suddenly
  • Braunwald was the first to diagnose HCM clinically in the 1960s
  • Many names for the disease
      • Idiopathic hypertrophic subaortic stenosis (IHSS)
      • Muscle subaortic stenosis
      • Hypertrophic obstructive cardiomyopathy (HOCM)

3. Background

  • Prevalence of HCM: 1:500 to 1:1000 individuals
      • This occurrence is higher than previously thought, suggesting a large number of affected but undiagnosed people
  • Men and African-Americans affected by almost 2:1 ratio over women and Caucasians
  • Global disease with most cases reported from USA, Canada, Western Europe, Israel, & Asia

4. Pathophysiology of HCM

  • The pathophysiology of HCM involves 4 interrelated processes:
    • Left ventricular outflow obstruction
    • Diastolic dysfunction
    • Myocardial ischemia
    • Mitral regurgitation

5. 6. Systolic Anterior Motion -SAM

  • Subaortic outflow obstruction is caused by systolic anterior motion (SAM) of the mitral valve - leaflets toward the ventircular septum
  • SAM is generated by
  • Venturi effect
  • A drag effect

7. LV Outflow Obstruction in HCM

  • Physiological Consequences of Obstruction
    • Elevated intraventricular pressures
    • Prolongation of ventricular relaxation
    • Increased myocardial wall stress
    • Increased oxygen demand
    • Decrease in forward cardiac output

8. 9. 10. Maron MS et al. NEJM.2003;348:295. 11. Pathophysiology of HCM

  • Diastolic Dysfunction
    • Contributing factor in 80% of patients
    • Impaired relaxation
      • High systolic contraction load
      • Ventricular contraction/relaxation not uniform
    • Accounts for symptoms of exertional dyspnea
      • Abnormal diastolic fillingincreased pulmonary venous pressure

12. Pathophysiology of HCM

  • Myocardial Ischemia
    • Often occurs without atherosclerotic coronary artery disease
    • Postulated mechanisms
      • Abnormally small and partially obliterated intramural coronary arteries as a result of hypertrophy
      • Inadequate number of capillaries for the degree of LV mass

13. Pathophysiology of HCM

  • Mitral Regurgitation
    • Results from the systolic anterior motion of the mitral valve
    • Severity of MR directly proportional to LV outflow obstruction
    • Results in symptoms of dyspnea, orthopnea in HCM patients

14. Integrated Pathophysiology Braunwald.Atlas of Heart Diseases: Cardiomyopathies, Myocarditis, and Pericardial Disease .1998. 15. Microscopy

  • The microscopy of HOCM demonstrates
    • Myocyte hypertrophy
    • Myocardial fibre disarry
    • Interstitial and perivascular fibrosis
    • Intimal and medial hypertrophy in intramural arteries.
    • These changes lead to LV diastolic dysfunction by impairing relaxation and reducing compliance and scarring of the myocardium.

16. Massive left ventricular hypertrophy, mainly confined to the septum Histopathology showingsignificant myofiberdisarray and interstitialfibrosisCell Research.2003;13(1):10. 17. Genetic Basis of HCM

  • Autosomal dominant trait
  • Mutations usually in
  • B-myosin heavy chain, Myosin binding proteinC and cardiac troponin T.
  • >450 mutations in 13 cardiac sarcomere & myofilament-related genes identified

Alcalai et al.J Cardiovasc Electrophysiol.19(1): Jan 2008. 18. Genetics of HCM Alcalai et al.J Cardiovasc Electrophysiol 2008;19:105. 19. Clinical Presentation

  • Dyspnea on exertion (90%), orthopnea, PND
  • Angina (70-80%)
  • Syncope (20%), Presyncope (50%)
    • outflow obstruction worsens with increased contractility during exertional activities
  • Sudden cardiac death
    • HCM is most common cause of SCD in young people, including athletes

20. Physical Examination

  • Carotid Pulse
      • Bifid short upstroke & prolonged systolic ejection
  • Jugular Venous Pulse
      • Prominenta wave decreased ventricular compliance
  • Apical Impulse
      • Double or triple
  • Heart Sounds
      • S4 usually present due to hypertrophy

21. Physical Examination

  • Murmur
      • Medium-pitch crescendo-decrescendo systolic murmur along LLSB without radiation
      • Dynamic maneuvers
        • Murmur intensity increases with decreased preload (i.e. Valsalva)
        • Murmur intensity decreases with increased preload (i.e. squatting, hand grip)

22. Dynamic murmur of HOCM

  • Smaller LV volume brings septum closer to anterior MV leaflet: more obstruction andlouder murmur.
  • Larger LV volume separatesupper septum from anterior MV leaflet: less obstruction and softer murmur.

23. How to alter LV volume

  • Increase LV volume
    • Squatting
    • Isometric handgrip
    • Beta Blockers
    • Phenylephrine
    • Passive leg lifting
    • Slow heart rate
    • IV volume infusion
  • Decrease LV volume
    • Stand (after squatting)
    • Valsalva maneuver
    • Amyl nitrate
    • Nitroglycerin
    • Increase heart rate
    • Volume depletio n
    • Isoproterenol
    • Exercise

24. Physical Examination in HCM Braunwald E.Atlas of Internal Medicine .2007. 25. Diagnostic Evaluation

  • Electrocardiogram
  • Echocardiogram
  • Catheterization

26. Electrocardiogram in HCM 27. Echocardiography in HCM 28. Transesophageal Echo 29. Coronary Angiography Hyperdynamic systolic function results in almost complete obliteration of the LV cavityCoronary angiography demonstrateSeptal bulge on LV cavity. 30. Cardiac Magnetic Resonance

  • CMR demonstrates myocardial scarring, which differentiate HCM from other LV hypertrophies
  • CMR is indicated when ECHO views are limited due to unusual distribution of hypertrophy, or to detect milder magnitudes of hypertrophy.
  • CMR with gadolinium enhancement imaging will detect myocardial scarring in about two thirds of HOCM patients.

31. Sudden Cardiac Death

  • Unfortunately, SCD can be the first clinical manifestation.
  • Occur in 15% of patients with HOCM
  • SCD is seen more in young patients during and after physical exercise.
  • High SCD association is seen in
  • Prior cardiac arrest
  • First degree relative with HOCM and SCD
  • Multiple syncope associated with syncope
  • Non sustained VT
  • Treatment of choice is ICD.
  • Strenuous sports should be avoided.
  • No evidence that medical Rx reduces the rick of SCD

32. Clinical Course of HCM

  • Heart Failure
    • Only 10-15% progress to NYHA III-IV
    • Only 3% will become truly end-stage with systolic dysfunction
  • Endocarditis
    • 4-5% of HCM patients
    • Usually mitral valve affected
  • Atrial Fibrillation
    • Prevalent in up to 30% of

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