Bio-Med 350

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Bio-Med 350

• Normal Heart Function
• and
• Congestive Heart Failure

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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

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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???
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What happens to the runner during exercise?

• OR
• Why the jogger didnt blow his top!

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Basic Definitions

• Cardiac Output is defined as Stroke
  Volume X Heart Rate

• Blood Pressure is defined as
• Cardiac Output X Systemic Vascular
  Resistance

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Basic Concepts 1

• The Cardiac Cycle

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The Normal Cardiac Cycle

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

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Volume change during LV filling
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The Normal Cardiac Cycle

• Lets take a look at the cycle in some
  depth............

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The Cardiac Cycle
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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

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Left ventricular filling curves

• Relationship of pressure to volume defines L.V.
  stiffness or non-compliance
• At low pressures, almost linear

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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

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Normal vs non-compliant LV
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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

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Mediators of Cardiac Output
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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)

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Preload

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

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Why is volume the most important determinant of
ventricular preload??
(Hint look at the cardiac cycle)
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The Cardiac Cycle
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Afterload

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

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Why is systolic pressure the most important
determinant of ventricular afterload???
(Hint look again at the cardiac cycle)
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The Cardiac Cycle
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How do we relate myocardial performance to

• Loading conditions i.e. preload and
  afterloadAnd how does myocardial
  contractility relate to all of the above??

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Frank - Starling Curves

• L.V. performance curves relating
• L.V.E.D.P. (i.e." preload)
• L.V. performance (i.e. cardiac output)

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Frank-Starling Curves in CHF
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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

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How do we measure.....
?

• Blood pressure
• Cardiac output
• Stroke volume
• LVEDP
• Systemic vascular resistance

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The Swan-Ganz Catheter
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Werner Forssman 1929
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Right heart catheterization
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Right Heart Catheterization
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Measuring Cardiac Output

• Fick Method -- O2 consumptionA-V O2 difference

• Thermodilution method --The Black Box

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The Fick Principle
Lungs
O2
Body
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Measuring O2 consumption
The Waters Hood
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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

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Construction of Starling Curve for an individual
patient
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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)
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Pressure - Volume Loops

• Holding afterload and contractility constant
• Varying preload, measured as end-diastolic
  volume

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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

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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

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Left Heart Failure
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Left Heart Failure
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Left Heart Failure
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Left Heart Failure
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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

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Diastolic dysfunction due to LVH
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Diastolic dysfunctionPressure Volume Loop
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Left Heart Failure
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Compensatory Mechanisms for Heart Failure

• Frank Starling Mechanism
• Neuro-humoral alterations
• Left ventricular enlargement
• LV Hypertrophy ? ? contractility
• LV remodeling ? ? stroke volume

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Frank Starling mechanism
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Neuro-humoral mediators
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Neuro-humoral mediators
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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

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End results of compensatory mechanisms
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Left Heart Failure
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Pseudo Left Heart Failure Abnormally high
filling pressure (PCW pressure) despite
normal LV function and LVEDP
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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

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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