Bio-Med 350 - PowerPoint PPT Presentation

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Bio-Med 350

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Normal Heart Function and Congestive Heart Failure Basic Concepts: The Cardiac Cycle Myocardial Filling -- Diastole Compliance Left ventricular filling curves ... – PowerPoint PPT presentation

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Title: Bio-Med 350


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
    Output Frank-Starling Performance Curves
  • The relationship of filling and emptying
    Pressure - Volume Loops

3
Basic Definitions
  • Cardiac Output is defined as Stroke
    Volume X Heart Rate
  • Blood Pressure is defined as
  • Cardiac Output X Systemic Vascular
    Resistance

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 didnt 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
    relaxation Rapid Ventricular filling Atrial
    contraction (kick)
  • Components of Systole Isovolumic
    contraction L.V. Ejection

8
Volume change during LV filling
9
The Normal Cardiac Cycle
  • Lets 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-Starli
    ng 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
Relationships to Remember
  • 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

14
Normal vs non-compliant LV
15
Basic Concepts 3
  • The Cardiac Cycle
  • Myocardial Filling -- Diastole
    ComplianceLeft ventricular filling curves
  • Myocardial Emptying -- Systole Cardiac
    Output Frank-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
What happens to
  • Heart rate
  • Blood pressure
  • Cardiac output
  • Vascular resistance
  • When
  • LV filling falls
  • LV systolic function is impaired
  • The LV is non-compliant
  • Afterload increases

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
Measuring Cardiac Output
  • Fick Method -- O2 consumptionA-V O2 difference
  • Thermodilution method --The Black Box

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
    bodys demands
  • Backward Failure
  • Ability to meet the bodys 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 dysfunctionPressure 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

51
Frank Starling mechanism
52
Neuro-humoral mediators
53
Neuro-humoral mediators
54
Left Ventricular enlargement
  • Eccentric hypertrophy (cavity dilation and
    hypertrophy)
  • Seen in volume-overload states
  • Seen after acute MI (post-infarction
    remodeling)
  • Increased stroke volume at the expense of
    increased wall stress, oxygen demand and LVEDP
  • Concentric LVH
  • Increased LVEDP
  • Increased incidence of backward failure
  • Decreased wall stress at expense of increased
    oxygen demand and increased LVEDP

55
End results of compensatory mechanisms
56
Left Heart Failure
57
Pseudo Left Heart Failure Abnormally high
filling pressure (PCW pressure) despite
normal LV function and LVEDP
58
Right Heart Failure
  • Very commonly a sequela of Left Heart Failure
  • LVEDP
  • PCW
  • PA pressure
  • Right heart pressure overload
  • Cardiac causes
  • Pulmonic valve stenosis
  • RV infarction
  • Parenchymal pulmonary causes
  • COPD
  • ILD
  • Pulmonary vascular disease
  • Pulmonary embolism
  • Primary Pulmonary hypertension

59
Right heart vs. Left heart failure
  • Left Heart failure
  • Pulmonary congestion
  • Reduced forward cardiac output
  • Fatigue
  • Renal insufficiency
  • Cool extremities
  • Decreased mentation
  • Right Heart failure
  • Neck vein distension
  • Hepatic congestion
  • Peripheral edema
  • Also may result in reduced forward cardiac
    output, but with clear lung fields
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