18 Heart Failure

Question 1

define heart failure

Answer 1

the inability of the heart to supply adequate blood flow and therefore oxygen delivery to peripheral tissues and organs

Question 2

What is the most common cause of heart failure?

Answer 2

post MI

Question 3

What happens to myocardium which does not receive blood flow?

Answer 3

hypoxia
hypercapnia
glycolytic and acidotic
nutrient depletion
risk of necrosis

Question 4

How does a myocardial infarct occur?

Answer 4

fibro-fatty plaques may rupture, releasing substances activating platelets

thrombus forms

Question 5

How is ischaemia visible on an ECG?

Answer 5

elevation of ST segment

Question 6

How is an MI treated acutely?

Answer 6

PCI

Question 7

What happens in a PCI?

Answer 7

catheter inserted into peripheral artery
goes to aorta - coronary vessel
punches through thrombus
balloon inflated
stent fitted

Question 8

How quickly after the MI do you want to do a PCI?

Answer 8

2 hours

Question 9

What is a PCI?

Answer 9

Percutaneous Coronary Intervention

Question 10

If you do nothing to treat an MI, how much of that area will die?

Answer 10

70%

Question 11

If you perform a PCI, how much of the area will die?

Answer 11

30%

Question 12

Why does a PCI not reduce ischaemia to 0%?

Answer 12

the act of re-introducing blood flow itself is detrimental to the heart (release of ROS)

Question 13

What might cause HF by pressure overload?

what is the trigger here?

Answer 13

HTN
aortic stenosis

pathological hypertrophy against a higher after-load

Question 14

What might cause HF by contractile dysfunction?

Answer 14

ischaemic heart disease

congenital cardiomyopathies

Question 15

what happens in ischaemic heart disease?

Answer 15

reduced blood flow to cardiomyocytes

don’t function as well

Question 16

What happens to SV in HF?

Answer 16

the peak and magnitude of SV are lower

Question 17

What is the effect of decreased SV on baroreceptor reflex?

Answer 17

decreases it

Question 18

How can a decreased baroreceptor reflex increase HR?

Answer 18

decreased vagal and increased symp tone to SA node

Question 19

How can a decreased baroreceptor reflex increase heart contractility?

Answer 19

increased symp activity to ventricular muscle

Question 20

How does an increase in contractility increase CO?

Answer 20

increases SV

Question 21

What happens in pathological hypertrophy?

Answer 21

cardiomyocytes enlarge
lose their shape
distance between capillaries and cardiomyocytes increases

Question 22

how does the baroreceptor reflex interact with the adrenal gland?

what is the clinical significance of this?

Answer 22

a decreased reflex increases catecholamine release

the increase in serum adrenaline is measurable

Question 23

What are the consequences of persistent adrenargic stimulation of the heart?

Answer 23

hyperphosphorylation of Ca2+ handling proteins

pathologcial hypertrophy

beta adrenoreceptor internalisation

Question 24

Why is hyperphosphorylation of Ca2+ a problem?

Answer 24

leads to…
dysfunctional Ca2+ homeostasis
contractile dysfunction
arrhythmia

Question 25

What sort of arrhythmia might we expect in HF?

Answer 25

delayed afterdepolarisation | DAD

Question 26

What happens in DAD?

Answer 26

spontaneous release of SR calcium during diastole

Question 27

How does calcium release cause DAD?

Answer 27

calcium removed by 3Na+ / Ca2+ transporter, so depolarises membrane

Question 28

How can DAD be made worse?

Answer 28

persistent stimulation - upregulation of PKA hyperphospharylation of ryanodine receptor, making the SR more leaky

Question 29

What might be used to treat DAD? How might they work?

Answer 29

beta-blockers | calcium channel blockers reduce SR Ca2+ load, making it less leaky

Question 30

How does a low ABP increase renin release?

Answer 30

increased sympathetic activity to kidney (baroreceptor) decreased wall tension in renal afferent arterioles decreased Na+ delivery to macula densa

Question 31

how does a reduction in cardiomyocyte function alter ABP?

Answer 31

decreases stroke volume | reduces ABP

Question 32

How does angiotensin II increase water intake?

Answer 32

increases thirst drive via hypothalamus

Question 33

How does angiotensin II increase water reabsorption?

Answer 33

ADH | Aldosterone

Question 34

What effect does angiotensin II have on blood volume?

Answer 34

it increases it

Question 35

Why is it important that we are able to increase EDV?

Answer 35

it helps us to maintain SV

Question 36

What are the consequences of blood volume loading?

Answer 36

persistent loading causes them to go beyond the plateau of the Starling curve and SV can no longer be sustained

Question 37

how does oedema occur in HF?

Answer 37

mismatch in LV and RV CO due to HF

Question 38

Why do lungs not accumulate fluid in normal pulmonary circulation?

Answer 38

because we are constantly breathing humidified air

Question 39

How does left HF cause pulmonary oedema?

Answer 39

increased hydrostatic pressure in pulmonary circulation

Question 40

What are the effects of pulmonary oedema?

Answer 40

increased diffusion distance arterial hypoxia dyspnea peripheral chemoreceptor activation

Question 41

What can hypoxia in the lung lead to?

Answer 41

hypoxic pulmonary vasoconstriction | pulmonary HTN

Question 42

How can you overcome pulmonary hypoxia acutely?

Answer 42

delivering 100% O2

Question 43

How might you treat pulmonary oedema chonically?

Answer 43

loop diuretics ACEi AT1R antagonists

Question 44

What is the effect of cardiac hypertrophy?

Answer 44

increases suceptibility to ischaemia increases incidence of arrhythmias increases incidence of sudden death