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Bio-Med 350

Bio-Med 350

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Bio-Med 350

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  1. Bio-Med 350 Normal Heart Function and Congestive Heart Failure

  2. Basic Concepts: • The Cardiac Cycle • Myocardial Filling -- “Diastole”ComplianceLeft ventricular filling curves • Myocardial Emptying -- “Systole” Cardiac OutputFrank-Starling Performance Curves • The relationship of filling and emptying:Pressure - Volume Loops

  3. Cardiac Output is defined as: Stroke Volume X Heart Rate Blood Pressure is defined as: Cardiac Output X Systemic Vascular Resistance Basic Definitions What happens to each of these during: Exercise? When LV filling is impaired?? When systolic function is impaired???

  4. What happens to the runner during exercise? OR “Why the jogger didn’t blow his top!”

  5. Basic Definitions • Cardiac Output is defined as: Stroke Volume X Heart Rate • Blood Pressure is defined as: Cardiac Output X Systemic Vascular Resistance

  6. Basic Concepts: #1 • The Cardiac Cycle

  7. The Normal Cardiac Cycle • Components of Diastole: Isovolumic relaxationRapid Ventricular filling Atrial contraction (“kick”) • Components of Systole Isovolumic contraction L.V. Ejection

  8. Volume change during LV filling

  9. The Normal Cardiac Cycle • Let’s take a look at the cycle in some depth............

  10. The Cardiac Cycle

  11. Basic Concepts: #2 • The Cardiac Cycle • Myocardial Filling -- “Diastole”ComplianceLeft ventricular filling curves • Myocardial Contractility -- Systole Frank-Starling Performance Curves • The relationship of filling and emptying:Pressure - Volume Loops

  12. Left ventricular filling curves • Relationship of pressure to volume defines L.V. “stiffness” or “non-compliance” • At low pressures, almost linear

  13. “Compliance” is proportional to change in volume over change in pressure “Stiffness” is the inverse. Stiffness is proportional to change in pressure over change in volume Relationships to Remember

  14. Normal vs “non-compliant” LV

  15. Basic Concepts: #3 • The Cardiac Cycle • Myocardial Filling -- “Diastole”ComplianceLeft ventricular filling curves • Myocardial Emptying -- “Systole” Cardiac OutputFrank-Starling Performance Curves • The relationship of filling and emptying:Pressure - Volume Loops

  16. Mediators of Cardiac Output

  17. Relationships to Remember • “Preload” and “afterload” are defined as the wall tension during diastole and systole, respectively • Wall tension is defined as: P x r 2h (where h = wall thickness)

  18. Preload • Is the wall tension during ventricular filling • Is defined as P x r 2h during diastole!!!

  19. Why is volume the most important determinant of ventricular preload?? (Hint: look at the cardiac cycle)

  20. The Cardiac Cycle

  21. Afterload • Is the wall tension during ventricular ejection • Is defined as: P x r 2h during systole!!!

  22. Why is systolic pressure the most important determinant of ventricular afterload??? (Hint: look again at the cardiac cycle)

  23. The Cardiac Cycle

  24. How do we relate myocardial performance to: • Loading conditions: i.e. preload and afterloadAnd how does “myocardial contractility” relate to all of the above??

  25. Frank - Starling Curves • L.V. “performance” curves relating: • L.V.E.D.P. (i.e." preload”) • L.V. “performance” (i.e. cardiac output)

  26. Frank-Starling Curves in CHF

  27. Heart rate Blood pressure Cardiac output Vascular resistance When: LV filling falls LV systolic function is impaired The LV is non-compliant Afterload increases What happens to:

  28. How do we measure..... ? • Blood pressure • Cardiac output • Stroke volume • LVEDP • Systemic vascular resistance

  29. The Swan-Ganz Catheter

  30. Werner Forssman – 1929

  31. Right heart catheterization

  32. Right Heart Catheterization

  33. Fick Method -- O2 consumptionA-V O2 difference Thermodilution method --“The Black Box” Measuring Cardiac Output

  34. The Fick Principle Lungs O2 Body

  35. Measuring O2 consumption The Waters Hood

  36. The Thermodilution Method • Similar in principle to the Fick method • Uses change in temperature per unit time, rather than change in O2 saturation • Requires a thermal probe in the right side of the heart

  37. Construction of Starling Curve for an individual patient

  38. Pressure - Volume Loops • Relate L.V. pressure to L.V. volume in a single cardiac cycle • Can be used to explore the effects of various therapies on stroke volume and L.V.E.D.P. Pressure (mm Hg)

  39. Pressure - Volume Loops • Holding afterload and contractility constant • Varying “preload”, measured as end-diastolic volume

  40. Heart Failure Forward Failure: Inability to pump blood forward to meet the body’s demands Backward Failure: Ability to meet the body’s demands, at the cost of abnormally high filling pressures

  41. Systolic vs. Diastolic Dysfunction • Systolic dysfunction • Decreased stroke volume • Decreased forward cardiac output • Almost always associated with diastolic dysfunction as well • Diastolic Dysfunction • One third of patients with clinical heart failure have normal systolic function – i.e. “pure” diastolic dysfunction

  42. Left Heart Failure

  43. Left Heart Failure

  44. Left Heart Failure

  45. Left Heart Failure

  46. Diastolic Dysfunction • Impaired early diastolic relaxation (this is an active, energy dependent process) • Increased stiffness of the left ventricle (this is a passive phenomenon) • LVH • LV fibrosis • Restrictive or infiltrative cardiomyopathy

  47. Diastolic dysfunction due to LVH

  48. Diastolic dysfunction:Pressure – Volume Loop

  49. Left Heart Failure

  50. Compensatory Mechanisms for Heart Failure • Frank – Starling Mechanism • Neuro-humoral alterations • Left ventricular enlargement • LV Hypertrophy ↑ contractility • LV “remodeling” ↑ stroke volume