Pathophysiology of Cardiac Failure

Question 1

what 3 factors affect SV?

Answer 1

• preload
• afterload
• contractility

Question 2

what is afterload?

Answer 2

• force contracting heart must generate to eject blood from heart
• heart is pumping against tension in the ventricle wall and the pressure in the aorta

Question 3

What will happen if the heart can’t generate sufficient wall tension?

Answer 3

decreased SV since not enough force to overcome the afterload

Question 4

how is heart failure graded?

Answer 4

1,2,3 and 4

Question 5

what is class 1 heart failure?

Answer 5

• no limitation of physical activity

- ordinary physical activity does not cause undue fatigue, palpitations or dyspnea

Question 6

what is class 2 heart failure?

Answer 6

• slight limitation to exercise

- ordinary exercise results in palpitations, dyspnea and fatigue

Question 7

what is class 3 heart failure?

Answer 7

• marked limitation of exercise

- less than ordinary exercise= fatigue, palpitations and dyspnea

Question 8

what is class 4 heart failure?

Answer 8

• cant exercise, experience symptoms at rest also

- discomfort increases by doing activity

Question 9

what is ejection fraction?

Answer 9

proportion of blood you can eject from your ventricle

Question 10

Describe the features of systolic ventricular dysfunction?

Answer 10

• impaired cardiac contractility
• ejection fraction decreased because heart muscle just doesn’t contract as well as it should
• the EDV is the same however

Question 11

describe the features of diastolic ventricular dysfunction?

Answer 11

• normal ejection fraction
• decreased filling occurring or impairment of ventricular relaxation
• EDV lower

Question 12

what is the overall similarity between diastolic and systolic ventricular dysfunction ?

Answer 12

lower SV and hence cardiac output is falling

Question 13

What conditions affect systolic dysfunction of the ventricle?

Answer 13

• contractility: ischaemic heart disease, cardiomyopathy
• volume overload- overstretched leading to problems with subsequent contractions
• pressure overload- valvular stenosis means you can’t push out as much blood, not ejecting same volume each stroke

Question 14

what can lead to impairments of relaxation which result in diastolic dysfunction?

Answer 14

• impedance of ventricular expansion
• extreme hypertrophy of chamber wall
• ischaemia of heart can reduce the hearts ability to relax during diastole and fill
• increased heart rate

Question 15

what is the effect of long term heart failure on the heart?

Answer 15

usually both sides of the heart eventually become affected

Question 16

where does blood come from to the right side of the heart? what effect does right heart failure therefore have?

Answer 16

• blood comes from the veins and peripheral tissues

- if unable to clear the blood it will accumulate downstream in tissues and organs= leads to oedema

Question 17

how does oedema arise as a result of R side heart failure?

Answer 17

increase in pressure in the veins since blood is not cleared therefore leads to an increase in hydrostatic pressure in vein.
more fluid pushed out along the entire length of the capillaries and this accumulates in soft tissue

Question 18

what effect does R heart failure have on the GI system?

Answer 18

problems with congestion in capillaries hence can’t absorb nutrients effectively from the GI tract: weight loss, anorexia

Question 19

what is the effect of liver congestion as a result of R sided heart failure?

Answer 19

liver is the site of detoxification= congestion of fluid and toxins in the liver will result in damaging the liver

Question 20

where does L heart pump blood? what is the effect of left heart failure on the body? what clinical signs are visible?

Answer 20

• systemic circulation
• decreased tissue perfusion since cable to provide the output to supply the tissues
• cyanosis and hypoxia signs become visible

Question 21

what congestion effect does L heart failure have?

Answer 21

pulmonary congestion since left side can’t beat to meet the demand of the R side which is normal

Question 22

what affect does pulmonary congestion have on the patient as a result of L heart failure?

Answer 22

• cough with a frothy sputum
• orthopnea- in recumbent position patient struggles to breath
• PND

Question 23

what is orthopnea?

Answer 23

• postural related
• in recumbent position the patient has issues with breathing
• lie down gravity effect lessened hence massive fluid return from legs to heart and backs up in lungs due to L heart failure

Question 24

what is PND?

Answer 24

• waking up gasping for breath in middle of night
• gravity effect=accumulation of fluid in ankles
• lie down fluid re-distributes back to heart but L can’t cope due to failure and fluid starts to accumulate in the pulmonary circulation

Question 25

how does left heart failure lead to right heart failure?

Answer 25

- blood not cleared from lungs - increases resistance to flow in the pulmonary circulation - R side has to work harder and will eventually lead to failure of R side since it can't cope

Question 26

What causes R ventricular dysfunction?

Answer 26

- pulmonary hypertension - valve damage, stenosis, incompetence - cardiomyopathies, infarction affecting the pumping abilities of the R ventricle - L knock on affect to right

Question 27

What leads to left ventricular dysfunction?

Answer 27

- hypertension- elevated total peripheral resistance, afterload increased - acute MI - aortic or mitral stenosis or regurgitation

Question 28

what are the compensatory mechanisms of the body trying to achieve during heart failure?

Answer 28

keep mean arterial blood pressure high.

Question 29

how can compensatory mechanisms worsen heart failure?

Answer 29

if heart is damaged it can't meet the O2 and energy demands and can't cope with further stress long term compensatory mechanisms put stress of heart up to meet demand

Question 30

what detects the heart failing and the cardiac output dropping?

Answer 30

decreased renal blood flow hence decreased volume getting filtered out into the urine

Question 31

how do kidneys respond to decreased CO? What effect does this have?

Answer 31

- renin release triggered= angiotensin 2 produced + aldosterone leading to sodium and therefore water retention - vascular volume increased to increase venous return increasing frank starling mechanism

Question 32

what other sensors detect drop in CO? what is their response to the drop?

Answer 32

- baroreceptors in aortic and carotid bodies - increase sympathetic nervous system increasing HR and TPR via vasoconstriction= increasing afterload in order to increase contractility of the heart

Question 33

how does the effect of the frank starling mechanism result in worsening heart failure?

Answer 33

- increased vascular volume increases EDV therefore increasing muscle stretch and O2 consumption - overstretching sarcomeres you start to see a decrease in force generated - increasing EDV only results in a slight increase in SV however increases the force on the heart

Question 34

How does sympathetic activity worsen heart failure?

Answer 34

- initially helpful= increased HR and contractility increases CO - increases heart workload and energy demand of the suffering heart tissue - increases TPR which heart pumping against - increases renin release

Question 35

what happens as a result of desensitisation of beta and adrenoreceptors?

Answer 35

- effects of sympathetic activity start to decrease - iontropy starts diminishing - cardiac activity drops

Question 36

how does the renin angiotensin system worsen heart failure?

Answer 36

- decreased blood flow through kidneys increases release of renin - angiotensin 2 results in increasing TPR and blood volume - deposition of fibroblasts and collagen in ventricles increase stiffness altering its contractility

Question 37

what is the strategy to treat heart failure?

Answer 37

- decrease preload and afterload to decrease cardiac work demand - relax smooth muscle - inhibit RAAS, prevent accumulation of fluid exasperating oedema - prevent inappropriate increase in HR