06_3 Cardiovascular System Heart Failure

8/2/2019 06_3 Cardiovascular System Heart Failure

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Coagulation

Disorders

Hypertension

Dysrhythmias

Shock,Anaphyl

axis

Heart

Failure

Angina,MI

LipidDisorder

Heart Failure

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HF Definition and risk

factors

Inability of the ventricles to pump enough blood to

meet the bodys metabolic demand

Weakening of heart muscle is due to ageing process

Heart failure is caused or worsened by other disorders:

Chronic hypertension

Diabetes

Mitral stenosis (inability of mitral valve to open fully)

Myocardial infarction (clot within coronary arteries)

Atherosclerosis of the coronary arteries


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Heart physiologyRight side of heart receives blood

from venous system

Send it to lungs to receive oxygen

and lose CO2

Blood returns to left side of heart

Heart sends the blood to other

parts of body through aorta

Volume blood received by right

side must be = received by left


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Heart physiology: Cardiac

output

Affected by:

Preload the degree to which the heart fibres are

stretched to fill the chamber with blood just prior to

heart contraction (systole)

Afterload the pressure in the aorta that must be

overcome for the blood to be ejected from the left

side of the heart

In heart failure:

If left myocardium becomes weak, excess blood

accumulates in the left ventricles. The walls of left

ventricles become thicker (hypertrophy). Blood

backs up into lung causes cough, shortness of

breath (esp. when lying down). Congestive heart


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Heart physiology:

Characteristics1.Heart contracts with a specific

strength (contractility)

Positive inotropic effect ability to increase

strength of contraction

Type of drug cardiac glycosides

2.Heart beats a certain rate (beats per

minute)


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HF Management

Lifestylechanges

Drugs

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HF Drugs (1/2)Cardiacglycoside

From plant digitalis

Used to be firstchoice, nowreplaced by ACEinhibitors

Increase force ofcontraction

(increase cardiacoutput)

Slow electricalconduction throughheart, resulting infewer beats/min

Combined theseeffects will increaseefficiency of heart

Therapeutic windowsmall

Side effectsvomiting, diarrhoea,

ACEinhibitors

Lower BP - reduce

blood volume byenhancing excretionof sodium andwater. Arterial bloodpressure is reduced,thus increasing

cardiac output Lower preload andreduce peripheraledema by dilatingthe veins that returnblood into heart

Combined theseeffects will decreaseworkload of heartthus increase itsefficiency

Reduce mortality

following acute MIwhen given early

Diuretics

Increase urine

flow, thusreducing bloodvolume andcardiacworkload, as

well as reducingedema andcongestion

Side effectelectrolyte

imbalance,especially iftaking cardiacglycosidestogether


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HF Drugs (2/2)Posphodiesterase

inhibitors(PDE3-I) Brief half-life

For short-termcontrol of acuteheart failure

Use only for 2 3days For patients not

responding toACE inhibitorsand cardiac

glycosides Eg: milrinone,

inamrinone,cilostazol

Vasodilators

High incidence ofside effects

For severe casesand cannot use

ACE inhibitors e.g. Hydralazineand Isosorbidedinitrate (Isordil)

adrenergicblockers Reduce

symptoms, slowprogression of HF

Produce negative

inotropic effectreduce heart rateand drop in bloodpressure, thusdecreaseafterload and

workload of heart Always used

together withother drugs

e.g. Carvediloland Metoprolol

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06_3 Cardiovascular System Heart Failure