Pathophysio of Heart Failure

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PATHOPHYSIOLOGY OFPATHOPHYSIOLOGY OF

HEART FAILUREHEART FAILURE


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Notes to heart physiologyNotes to heart physiology

Essential functions of the heartEssential functions of the heart to cover metabolic needs of body tissueto cover metabolic needs of body tissue

(oxygen,(oxygen, substrates) by adequate blood supplysubstrates) by adequate blood supply

to receive all blood coming back from the tissue toto receive all blood coming back from the tissue tothe heartthe heart

Essential conditions for fulfilling these functionsEssential conditions for fulfilling these functions

normal structure and functions of the heartnormal structure and functions of the heart

adequate filling of the heartadequate filling of the heart


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

functions of the heartfunctions of the heart

Cardiac output (CO) = heart rate (HR) x strokeCardiac output (CO) = heart rate (HR) x strokevolume(SV)volume(SV) Determinants of cardiacDeterminants of cardiac

outputoutput- changes of heart rate- changes of heart rate

- changes of stroke volume- changes of stroke volume Control of HR:Control of HR:

- autonomic nervous system- autonomic nervous system

- hormonal(humoral) control- hormonal(humoral) control

Control of SV:Control of SV:

- preloadpreload- contractilitycontractility

- afterloadafterload


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PreloadPreload

tretching the myocardial fibers during diastole by increasitretching the myocardial fibers during diastole by increasind-diastolic volume will increase the force of contractionnd-diastolic volume will increase the force of contractionuring systole =uring systole = Starlings lawStarlings law

preloadpreload = diastolic muscle sarcomere length before= diastolic muscle sarcomere length beforecontractioncontraction (Fig.2,3)(Fig.2,3)

- venous return to the heart is important!- venous return to the heart is important!

- stretching of the sarcomere maximises the number of - stretching of the sarcomere maximises the number of actin-myosin bridges responsible for development of foractin-myosin bridges responsible for development of for

- optimal sarcomere length- optimal sarcomere length 2.22.2 mm


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Myocardial contractilityMyocardial contractility

ontractility of myocardiumontractility of myocardium CChanges in developed force by contraction that occuhanges in developed force by contraction that occuindependently on changes in myocardial fiber lengthindependently on changes in myocardial fiber length

Mechanisms involved in changes of contractilityMechanisms involved in changes of contractility amount of created cross-bridges in the sarcomeramount of created cross-bridges in the sarcomer byby changes of changes of [[CaCa ++++ ]]ii concentrationconcentration

-- catecholaminescatecholamines [[CaCa ++++ ]]ii contractilitycontractility- inotropic drugs- inotropic drugs [[CaCa ++++ ]]ii contractilitycontractility

contractilitycontractility shifting the entire ventricular functionshifting the entire ventricular functioncurve upward and to the leftcurve upward and to the left

contractilitycontractility shiffting the entire ventricular functioshiffting the entire ventricular functio

curve (hypoxia, acidosis) downward and to the righcurve (hypoxia, acidosis) downward and to the righ tt


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ItIt is expressed as tension which must beis expressed as tension which must bedevelopeddevelopedin the wall of ventricles during systole to openin the wall of ventricles during systole to openthethesemilunar valve and eject blood tosemilunar valve and eject blood to aorta/pulm.aorta/pulm.art.art.

Laplace law:Laplace law:

intraventricular pressure x radius of ventriclintraventricular pressure x radius of ventriclwall tension = --------------------------------------------------------wall tension = --------------------------------------------------------

2 x2 x ventricular wall thicknessventricular wall thickness

afterload:afterload: due to - elevation of arterial pressuredue to - elevation of arterial pressure-- ventricular sizeventricular size

afterload:afterload: due to -due to - arterial pressurearterial pressure- myocardial hypertrophy- myocardial hypertrophy

AfterloadAfterload


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Heart failureHeart failure

efinitionefinition

It is the pathophysiological process in whichIt is the pathophysiological process in which

the heart as a pump is unable to meetthe heart as a pump is unable to meetthe metabolic requirements of the tissue fothe metabolic requirements of the tissue for

oxygen and substrates despite the venousoxygen and substrates despite the venous

returnreturn to heartto heart is either normal or increasedis either normal or increased


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Terms explanationTerms explanation

Myocardial failureMyocardial failure = abnormalities reside in the myocard= abnormalities reside in the myocardand lead to decreased function of and lead to decreased function of myocardiummyocardium

Circulatory failureCirculatory failure = any abnormality of the= any abnormality of the

circulationcirculation responsible for the inadequacy inresponsible for the inadequacy inbodybody

tissue perfusion, e.g. decreasedtissue perfusion, e.g. decreasedbloodblood

volume, changes of vascular tone,volume, changes of vascular tone,heart disorders.heart disorders.

Congestive heart failureCongestive heart failure = clinical syndrome which is developed= clinical syndrome which is developed

due to accumulation of the blood indue to accumulation of the blood in frfrof the left or right parts of the heartof the left or right parts of the heart


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General pathomechanisms involved in heartGeneral pathomechanisms involved in heartfailure developmentfailure development

Cardiac mechanical dysfunctionCardiac mechanical dysfunction can develop as acan develop as aconsequence in preload, contractilityconsequence in preload, contractility andand afterloadafterloaddisordersdisorders

Disorders of preloadDisorders of preload

preloadpreload length of sarcomere is more than optimallength of sarcomere is more than optimal strength of contractionstrength of contraction

preloadpreload length of sarcomere is well below the optimalength of sarcomere is well below the optimal strength of contractionstrength of contraction


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Causes of heart pump failureCauses of heart pump failure

A. MECHANICAL ABNORMALITIESA. MECHANICAL ABNORMALITIES

1. Increased pressure load1. Increased pressure load cc entral (aortic stenosis)entral (aortic stenosis)

pp eripheral (systemic hypertension)eripheral (systemic hypertension)

2. Increased volume load2. Increased volume load- valvularvalvularregurgitationregurgitation hypervolemia 3. Obstruction to ventricular filling3. Obstruction to ventricular filling

- valvular stenosis- valvular stenosis- pericardial restriction- pericardial restriction


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B. MYOCARDIAL DAMAGEB. MYOCARDIAL DAMAGE1. Primary1. Primary

a)a) cc ardiomyopathyardiomyopathyb)b) mm yocarditisyocarditis

c)c) tt oxicity (alcohol)oxicity (alcohol)

d)d) mm etabolic abnormalities (hyperthyreoidism)etabolic abnormalities (hyperthyreoidism)

2. Secondary2. Secondary

a)a) oo xygen deprivation (coronary heart disease)xygen deprivation (coronary heart disease)

b)b) iinflammation (increased metabolic demands)nflammation (increased metabolic demands)

c)c) cc hronic obstructive lung diseasehronic obstructive lung disease


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C. ALTERED CARDIAC RHYTHMC. ALTERED CARDIAC RHYTHM

1.1. vv entricular fibrilationentricular fibrilation

2.2. ee xtreme tachycardiasxtreme tachycardias

3.3. ee xtreme bradycardiasxtreme bradycardias


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sensitivity of vessel wall to norepinephrinesensitivity of vessel wall to norepinephrine

mitogenic effect on smooth muscles in vessels and onmitogenic effect on smooth muscles in vessels and oncardiomyocytescardiomyocytes hypertrophyhypertrophy

constriction of vas efferens ( in glomerulus )constriction of vas efferens ( in glomerulus )

sensation of thirstsensation of thirst

secretion of aldosteron from adrenal glandsecretion of aldosteron from adrenal gland

mesangial conctractionmesangial conctraction glomerular filtration rateglomerular filtration rate

facilitation of norepinephrine releasing from sympathetifacilitation of norepinephrine releasing from sympathetinerve endingsnerve endings


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Pathophysiology of diastolic heart failurePathophysiology of diastolic heart failure

systolic heart failuresystolic heart failure = failure of ejecting function of the he= failure of ejecting function of the he

diastolic heart failurediastolic heart failure == failure of filling the ventriclesfailure of filling the ventricles filling resistance of ventriclesfilling resistance of ventricles

Which of the cardiac cycle isWhich of the cardiac cycle is realreal diastole ?diastole ?


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Definition of diastolic heart failureDefinition of diastolic heart failure

is pathophysiological processis pathophysiological process characterized by symptocharacterized by symptod signs of congestive heart failure, which is causedd signs of congestive heart failure, which is caused

creased filling resistance of ventriclescreased filling resistance of ventricles andand increasedincreasedtraventricular diastolic pressuretraventricular diastolic pressure

Primary diastolic heart failurePrimary diastolic heart failure

- no signs and symptoms of systolic dysfunction- no signs and symptoms of systolic dysfunction! up to 40%! up to 40% of of patients suffering from heart failure!patients suffering from heart failure!

Secondary diastolic heart failureSecondary diastolic heart failure

- diastolic dysfunction is the consequence of - diastolic dysfunction is the consequence of primaryprimarysystolicsystolic dysfunctiondysfunction


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Main causes and pathomechanisms of diastolicMain causes and pathomechanisms of diastolicheart failureheart failure

.structural disorders.structural disorders passive chamber stiffnesspassive chamber stiffness

a) intramyocardial e.g. myocardial fibrosis, amyloidosia) intramyocardial e.g. myocardial fibrosis, amyloidosihypertrophy, myocardial ischemiahypertrophy, myocardial ischemia

b) extramyocardial e.g. constrictive pericarditisb) extramyocardial e.g. constrictive pericarditis

2. functional disorders2. functional disorders relaxationrelaxation of chambersof chamberse. g. myocardial ischemia,e. g. myocardial ischemia,advanced hypertrophy of ventricleadvanced hypertrophy of ventriclefailing myocardium, asynchronyfailing myocardium, asynchrony


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Causes and mechanism participating on impaireCauses and mechanism participating on impaireventricular relaxationventricular relaxation

a) physiological changesa) physiological changes in chamber relaxationin chamber relaxation lead tolead to :: prolonged ventricular contractionprolonged ventricular contractionRelaxation of ventricles is not impairedRelaxation of ventricles is not impaired

b) pathological changesb) pathological changes inin chamber relaxationchamber relaxation lead tolead to :: impaired relaxation processimpaired relaxation process

delayed relaxation ( retarded )delayed relaxation ( retarded )

incomplete ( slowed ) relaxationincomplete ( slowed ) relaxation


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Consequences of impaired ventricular relaxatioConsequences of impaired ventricular relaxatio

- filling of ventricles is- filling of ventricles is more dependent on diastasismore dependent on diastasis anan systole of atriassystole of atrias

SSymptoms and signs:ymptoms and signs:

exercise intolerance = early sign of diastolic failureexercise intolerance = early sign of diastolic failure

coronary blood flow during diastolecoronary blood flow during diastole

Causes and mechanisms involved in developmeCauses and mechanisms involved in developmeof ventricular stiffnessof ventricular stiffness

ventricular compliance = passive property of ventricleventricular compliance = passive property of ventricle

Norm : resistance of cardiomyocytes and other heartNorm : resistance of cardiomyocytes and other hearttissue to stretchingtissue to stretching


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ventricular complianceventricular compliance is caused byis caused by structuralstructuralabnormalitiesabnormalities localizedlocalized in myocardiumin myocardium and inand inextramyocardial tissueextramyocardial tissue (Fig.11)(Fig.11)

a. Intramyocardial causesa. Intramyocardial causes : myocardial fibrosis,: myocardial fibrosis,hypertrophy of ventricular wallhypertrophy of ventricular wall,restrictive cardiomyopathyrestrictive cardiomyopathy

b. Extramyocardial causesb. Extramyocardial causes : constrictive pericarditis: constrictive pericarditis(Fig.12)(Fig.12)

The role of myocardial remodelling in genesis of The role of myocardial remodelling in genesis of

heart failureheart failure adaptive remodelling of the heartadaptive remodelling of the heart

pathologic remodelling of the heartpathologic remodelling of the heart


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ain causes and mechanisms involved in pathologicaain causes and mechanisms involved in pathologicaremodelation of theremodelation of the heartheart

Increased amount and sizeIncreased amount and size of cardiomyocytes = hypertropof cardiomyocytes = hypertropDue to:Due to: -- volume and/or pressure loadvolume and/or pressure load

(excentric, concentric hypertrophy)(excentric, concentric hypertrophy)

- hormonal stimulation of cardiomyocytes by- hormonal stimulation of cardiomyocytes bynorepinephrine, angiotenzine IInorepinephrine, angiotenzine II

. Increased percentage and influence. Increased percentage and influence of of non-myocytarnon-myocytarcellscells on structure of myocardiumon structure of myocardium

a.,a., endothelial cellsendothelial cells endothelins :endothelins : mitogenic abilitymitogenic ability stimulation growth of smooth muscle cells of vessels,stimulation growth of smooth muscle cells of vessels,fibroblastsfibroblasts

b.,b., fibroblastsfibroblasts -- production of kolagensproduction of kolagens


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Symptoms and signs of heart failureSymptoms and signs of heart failure

orward failure:orward failure: symptoms result fromsymptoms result from inability of the heainability of the hea to pump enough bloodto pump enough blood to theto the peripheryperiphery (from left heart ), or to the(from left heart ), or to the lungslungs

(from the right heart)(from the right heart)

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

generally:generally: tissue hypoperfusiontissue hypoperfusion

b) forward failure of right heart:b) forward failure of right heart: -- hypoperfusion of thehypoperfusion of thelungslungs disorders of gasdisorders of gasexchangeexchange

- decreased blood supply to the left heart- decreased blood supply to the left heart


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Pathophysio of Heart Failure

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