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

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Normal Heart Functionand

Congestive Heart Failure

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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

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Basic Definitions

Cardiac Output is defined as:

Stroke Volume X Heart Rate

Blood Pressure is defined as:

Cardiac Output XSystemic 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 didn’t 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 XSystemic 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 fillingAtrial contraction (“kick”)

Components of SystoleIsovolumic contractionL.V. Ejection

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Volume change during LV filling

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The Normal Cardiac Cycle

Let’s 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 -- SystoleFrank-Starling 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

0

10

20

30

40

V o lum e (m l)

Pre

ssur

e (m

m H

g)Y

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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 OutputFrank-Starling Performance Curves

The relationship of filling and emptying: Pressure - Volume Loops

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Mediators of Cardiac Output

H e art R ate

Pre lo ad A f te rlo ad C o ntractil i ty

S trok e V o lu m e

C A R D IA C O U TPU T

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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 r2h

(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 afterload

And how does “myocardial contractility” relate to all of the above??

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Frank - Starling Curves

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L .V . end -d iasto lic p ressureor end-d iasto lic vo lum e

Car

dia

c O

utp

ut

or

stro

ke v

olu

me

L.V. “performance” curves relating:

1. L.V.E.D.P. (i.e." preload”)

2. 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

Body

O2

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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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L .V . end -d iasto lic p ressureor end-d iasto lic vo lum e

Car

dia

c O

utp

ut

or

stro

ke v

olu

me

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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.

Volume (ml)

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 body’s demands

Backward Failure:

Ability to meet the body’s 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

Impaire d Contrac tility

1. Myoc ardial Infarc tion2. Trans ie nt myoc ardial is c he mia3. Chronic Volume ove rload4. Dilate d Cardiomyopathy

L.V. Dias tolic dys func tion

1. Le ft ve ntric ular hype rtrophy2. Hype rtrophic c ardiomyopathy3. Re s tric tive c ardiomyopathy4. Trans ie nt myoc ardial is c he mia

Pre s s ure Ove rload

1. Aortic Ste nos is2. Unc ontrolle d hype rte ns ion

Obs truc tion of L.V. filling

1. Mitral Ste nos is2. Pe ric ardial c ons tric tion or tamponade

L.V. Sys tolic dys func tion

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Left Heart Failure

Impaired Contractility

1. Myocardial Infarction 2. Transient myocardial ischemia 3. Dilated Cardiomyopathy 4. Chronic Volume overload

L.V. Dias tolic dys func tion

1. Le ft ve ntric ular hype rtrophy2. Hype rtrophic c ardiomyopathy3. Re s tric tive c ardiomyopathy4. Trans ie nt myoc ardial is c he mia

Pre s s ure Ove rload

1. Aortic Ste nos is2. Unc ontrolle d hype rte ns ion

Obs truc tion of L.V. filling

1. Mitral Ste nos is2. Pe ric ardial c ons tric tion or tamponade

L.V. Sys tolic dys func tion

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Left Heart Failure

Impaire d Contrac tility

1. Myoc ardial Infarc tion2. Trans ie nt myoc ardial is c he mia3. Chronic Volume ove rload4. Dilate d Cardiomyopathy

L.V. Dias tolic dys func tion

1. Le ft ve ntric ular hype rtrophy2. Hype rtrophic c ardiomyopathy3. Re s tric tive c ardiomyopathy4. Trans ie nt myoc ardial is c he mia

Pre s s ure Ove rload

1. Aortic S te nos is2. Unc ontrolle d hype rte ns ion

Obs truc tion of L.V. filling

1. Mitral Ste nos is2. Pe ric ardial c ons tric tion or tamponade

L.V. Sys tolic dys func tion

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Left Heart Failure

Impaire d Contrac tility

1. Myoc ardial Infarc tion2. Trans ie nt myoc ardial is c he mia3. Chronic Volume ove rload4. Dilate d Cardiomyopathy

L.V. Dias tolic dys func tion

1. Le ft ve ntric ular hype rtrophy2. Hype rtrophic c ardiomyopathy3. Re s tric tive c ardiomyopathy4. Trans ie nt myoc ardial is c he mia

Pre s s ure Ove rload

1. Aortic S te nos is2. Unc ontrolle d hype rte ns ion

Obs truc tion of L.V. filling

1. Mitral Ste nos is2. Pe ric ardial c ons tric tion or tamponade

L.V. Sys tolic dys func tion

L.V. Diastolic dysfunction

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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 dysfunction:Pressure – Volume Loop

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Left Heart Failure

Impaire d Contrac tility

1. Myoc ardial Infarc tion2. Trans ie nt myoc ardial is c he mia3. Chronic Volume ove rload4. Dilate d Cardiomyopathy

L.V. Dias tolic dys func tion

1. Le ft ve ntric ular hype rtrophy2. Hype rtrophic c ardiomyopathy3. Re s tric tive c ardiomyopathy4. Trans ie nt myoc ardial is c he mia

Pre s s ure Ove rload

1. Aortic Ste nos is2. Unc ontrolle d hype rte ns ion

Obs truc tion of L.V. filling

1. Mitral Ste nos is2. Pe ric ardial c ons tric tion or tamponade

L.V. Sys tolic dys func tion

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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

Concentric LVH• Increased LVEDP• Increased incidence

of backward failure• Decreased wall

stress at expense of increased oxygen demand and increased LVEDP

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

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End results of “compensatory mechanisms”

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Left Heart Failure

Impaire d Contrac tility

1. Myoc ardial Infarc tion2. Trans ie nt myoc ardial is c he mia3. Chronic Volume ove rload4. Dilate d Cardiomyopathy

L.V. Dias tolic dys func tion

1. Le ft ve ntric ular hype rtrophy2. Hype rtrophic c ardiomyopathy3. Re s tric tive c ardiomyopathy4. Trans ie nt myoc ardial is c he mia

Pre s s ure Ove rload

1. Aortic Ste nos is2. Unc ontrolle d hype rte ns ion

Obs truc tion of L.V. filling

1. Mitral S te nos is2. Pe ric ardial c ons tric tion or tamponade

L.V. Sys tolic dys func tion

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“Pseudo” Left Heart FailureAbnormally high filling pressure (PCW pressure) despite normal LV function and LVEDP

Obstruction of L.V. filling

Mitral Stenosis

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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