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PATHOPHYSIOLOGY OF

HEART FAILURE

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Notes to heart physiologyEssential functions of the heart

to cover metabolic needs of body tissue(oxygen, substrates) by adequate blood supply

to receive all blood comming back from the tissueto the heart

Essential conditions for fulfilling these functions

normal structure and functions of the heartadequate filling of the heart by blood

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Essential functions of the heart are securedby integration of electrical and mechanical

functions of the heartCardiac output (CO) = heart rate (HR) x stroke vol.(SV)

- changes of the heart rate

- changes of stroke volumeControl of HR:

- autonomic nervous system

- hormonal(humoral) control

Control of SV:

- preload

- contractility

- afterload

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Adaptive mechanisms of the heart

to increased load

Frank - Starling mechanism

Ventricular hypertrophyincreased mass of contractile elements strength

of contraction

Increased sympathetic adrenergic activityincreased HR, increased contractility

Incresed activity of RAA system

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Preload

Stretching the myocardial fibers during diastole by increasing end-

diastolic volume force of contraction during systole =Starlings law

preload = diastolic muscle sarcomere length leading to increased

tension in muscle before its contraction (Fig.2,3)

-venous return to the heart is importantend-diastolicvolume is influenced

-stretching of the sarcomere maximises the numberof actin-myosin bridges responsible for development of force

- optimal sarcomere length 2.2 m

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Myocardial contractility

Contractility of myocardium

Changes in ability of myocardium to develop the forceby contraction that occur independently on thechanges in myocardial fibre length

Mechanisms involved in changes of contractility

amount of created cross-bridges in the sarcomereby of Ca ++iconcentration

- catecholamines Ca++icontractility- inotropic drugs Ca++icontractility

contractilityshifting the entire ventricular functioncurve upward and to the left

contractilityshiffting the entire ventricular functioncurve (hypoxia, acidosis) downward and to the right

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Pressure volume loops recorded under differentconditions

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It is expressed as tension which must be developed in the wall

of ventricles during systole to open the semilunar valves andeject blood to aorta/pulmunary artery

Laplace law:

intraventricular pressure x radius of ventriclewall tension = --------------------------------------------------------

2 x ventricular wall thickness

afterload:due to - elevation of arterial resistance- ventricular size- myocardial hypotrophy

afterload:due to - arterial resistance- myocardial hypertrophy

- ventricular size

Afterload

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Heart failure

Definition

It is the pathophysiological process in whichthe heart as a pump is unable to meet

the metabolic requirements of the tissue for

oxygen and substrates despite the venous

return to heart is either normal or increased

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Explanation of the terms

Myocardial failure = abnormalities reside in the myocardium and leadto inability of myocardium to fulfilling its function

Circulatory failure= any abnormality of the circulationresponsible for the inadequacy in body tissueperfusion, e.g. decreased blood volume, changesof vascular tone, heart functiones disorders

Congestive heart failure= clinical syndrome which is developeddue to accumulation of the blood in front

of the left or right parts of the heart

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General pathomechanisms involved in heartfailure development

Cardiac mechanical dysfunction can develop asa consequence in preload, contractility and afterload

disorders

Disorders of preload

preloadlength of sarcomere is more than optimal strength of contractionpreloadlength of sarcomere is well below the optimal strength of contraction

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Important:failing ventricle requires higher end-diastolic volumeto achieve the same improvement of CO that normal

ventricle achieves with lower ventricular volumes

Disorders of contractility

In the most forms of heart failure the contractility of myocardium

is decreased (ischemia, hypoxia, acidosis, inflammation, toxins,

metabolic disorders... )

Disorders of afterload due to:

fluid retention in the body

arterial resistancevalvular heart diseases ( stenosis)

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Characteristic features of systolic dysfunction

(systolic failure)

ventricular dilatation

reducing ventricular contractility (either generalized

or localized)

diminished ejection fraction (i.e., that fraction of end-diastolic

blood volume ejected from the ventricle during each systolic

contraction les then 45%)

in failing hearts, the LV end-diastolic volume (or pressure)

may increse as the stroke volume (or CO) decreases

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Characteristic features of diastolic dysfunctions

(diastolic failure)

ventricular cavity size is normal or small

myocardial contractility is normal or hyperdynamic

ejection fraction is normal (>50%) or supranormal

ventricle is usually hypertrophied

ventricle is filling slowly in early diastole (during the periodof passive filling)

end-diastolic ventricular pressure is increased

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Causes of heart pump failure

A. MECHANICAL ABNORMALITIES

1. Increased pressure load

central (aortic stenosis, aortic coarctation...)

peripheral (systemic hypertension)

2. Increased volume loadvalvular regurgitation

hypervolemia

3. Obstruction to ventricular fillingvalvular stenosis

pericardial restriction

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B. MYOCARDIAL DAMAGE

1. Primary

a) cardiomyopathy

b) myocarditis

c) toxicity (e.g. alcohol)

d) metabolic abnormalities (e.g. hyperthyreoidism)

2. Secondary

a) oxygen deprivation (e.g. coronary heart disease)

b) inflammation (e.g. increased metabolic demands)

c) chronic obstructive lung disease

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C. ALTERED CARDIAC RHYTHM

1. ventricular flutter and fibrilation

2. extreme tachycardias

3. extreme bradycardias

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Pathomechanisms involved in heart failure

A. Pathomechanisms involved in myocardial failure

1. Damage of cardiomyocytescontractility,complianceConsequences:

defect in ATP production and utilisationchanges in contractile proteins

uncoupling of excitation contraction process

number of cardiomyocytesimpairment of relaxation of cardiomyocytes with decrease

compliance of myocardium

impaired of sympato-adrenal system (SAS) number of1-adrenergic receptors on the surface of cardiomycytes

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2. Changes of neurohumoral control of the heartfunction

Physiology:SNScontractilityHRactivity of physiologic pacemakersMechanism: sympathetic activity cAMP Ca ++icontractility

sympathetic activity influenceof parasympathetic system on the heart

Pathophysiology: normal neurohumoral control ischanged and creation of pathologic

neurohumoral mechanisms are present

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Important:

Catecholamines and system RAA = compensatory mechanisms

heart function and arterialBP

The role of angiotensin II in development of heartfailure

vasoconstriction ( in resistant vesels) retention of Na blood volumereleasing of arginin vasopresin peptide (AVP )

from neurohypophysis

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Pathophysiology of diastolic heart failure

systolic heart failure= failure of ejecting function of the heart

diastolic heart failure= failure of filling the ventricles,resistance to filling of ventricles

But, which of the cardiac cycle is real diastole ?

Diastolic failure is a widely recognized clinical entity

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Definition of diastolic heart failure

It is pathophysiological process characterized by symptoms andsigns of congestive heart failure, which is caused by increased filling

resistance of ventricles and increased intraventricular diastolic

pressure

Primary diastolic heart failure

-no signs and symptoms of systolic dysfunction is present

- ! up to 40% of patients suffering from heart failure!

Secondary diastolic heart failure

- diastolic dysfunction is the consequence of primarysystolic dysfunction

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Main causes and pathomechanisms of diastolicheart failure

1. structural disorderspassive chamber stiffness

a) intramyocardial

e.g. myocardial fibrosis, amyloidosis, hypertrophy,

myocardial ischemia...

b) extramyocardiale.g. constrictive pericarditis

2. functional disordersrelaxation of chamberse. g. myocardialischemia, advanced hypertrophy of ventricles,

failing myocardium, asynchrony in heart

functions

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Ventricular compliance is caused by structural abnormalitieslocalized in myocardium and in extramyocardial tissue

a) Intramyocardial causes: myocardial fibrosis, hypertrophy of

ventricular wall,restrictive cardiomyopathy

b. Extramyocardial causes :constrictive pericarditis

The role of myocardial remodelling in genesis ofheart failure

adaptive remodelling of the heartpathologic remodelling of the heart

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Main causes and mechanisms involved inpathological remodelation of the heart

1.Increased amount and size of myocytes=hypertrophyDue to:- volume and/or pressure load

(excentric, concentric hypertrophy)

- hormonal stimulation of cardiomyocytes by

norepinephrine, angiotenzine II

2. Increased % ofnon-myocytic cellsin myocardium

and their influence on structure and function of heart

a.endothelial cellsendothelins : mitogenic ability stimulation growth of smooth muscle cells of vessels, fibroblasts

b.fibroblasts- production of kolagens

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Symptoms and signs of heart failure

1. forward failure:symptoms result from inability of the heart to pump enoughblood to the periphery (from left heart), or to the lungs (from

the right heart)

a) forward failure of left heart:-muscle weakness, fatigue,dyspepsia, oliguria....

general mechanism:tissue hypoperfusionb) forward failure of right heart:- hypoperfusion of thelungs disorders of gas

exchange

-decreased blood supplyto the left heart

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2. backward failure:symptoms result from inability of the heart to accept

the blood comming from periphery and from lungs

a. backward failure of left heart:

increased pulmonary capillary pressuredyspnoea

and tachypnoea, pulmonary edema (cardiac asthma)

arterial hypoxemia and hypercapnia....

b. backward failure of right heart:increased pressure in systemic venous system

peripheral edemas, hepatomegaly, ascites nocturnal diuresis....

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DIAGNOSTIK

Fungsional

Anatomi

Penyebab/ etiologi

Irama

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