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Cardio > Pathophysiology > Flashcards

Pathophysiology Flashcards

1
Q

Cardiac dz affects what % of dogs in vet hospital population?

A

11%

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2
Q

What is the definition of heart failure

A

complex syndrome initiated by an inability of the heart to maintain a normal cardiac output at normal filling pressures

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3
Q

How does heart failure occur? (5)

A
  1. pump failure
  2. volume overload
  3. pressure overload
  4. arrhythmias
  5. diastolic heart failure
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4
Q

What do all heart diseases share?

A

the capacity to cause real or percieved underfilling of the arterial circulation -> initiates a cascade of events resulting in heart failure

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5
Q

What is pump failure?

A

when failure of systolic function of the myocardium results in inadequate stroke volume and fall in cardiac output

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6
Q

What are the primary diseases resulting in systolic/pump failure?

A

dilated cardiomyopathy (flappy heart)
coronary vascular disease (narrowing/blockage of coronary arteries)

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7
Q

What is volume overload?

A

when necessity for a cardiac chamber to chronically increase output can result in overwork and eventually failure of the heart

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8
Q

What are primary diseases resulting in volume overload?

A

valvular insufficiencies (mitral, aortic)(don’t close properly = backflow)
shunting diseases (VSD, PDA)
chronic anaemia

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9
Q

What is the problem with mitral insufficiency?

A

LV tries to pump out total stroke volume
which is the forward stroke volume + additional regurgitant stroke volume
Overworking to pump out excessive amounts of blood

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10
Q

What is pressure overload?

A

when there is a chronic increase of pressure against which a ventricle has to pump blood can eventually result in failure of myocardium

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11
Q

What are primary diseases resulting in pressure overload?

A

hypertension (systemic or pulmonary)
narrowing of outflow tract (pulmonary stenosis, aortic stenosis)

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12
Q

What are arrhythmias?

A

Abnormalities of cardiac rhythm that affect both cardiac filling and heart rate and can compromise output

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13
Q

What are the consequences of arrhythmias?

A

low HR results in drop of CO
very high HR = diastole is too short to allow adequate filling = fall of SV and CO
disorganised electrical activity

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14
Q

What is diastolic failure?

A

when inability of the heart to relax normally can compromise filling and result in fall of CO

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15
Q

What are primary diseases resulting in diastolic failure?

A

hypertrophic cardiomyopathy
dilated cardiomyopathy (myocardial fibrosis)
pericardial effusion (fluid around heart)

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16
Q

When there is an increase in blood volume what comes into play?

A

RAAS: angiotensin II, aldosterone
ADH
Renal autoregulation of flow (decreased renal flow = increased sodium retention)

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17
Q

When there is a decrease in blood volume, what comes into play?

A

Natriuretic peptides
Renal autoregulation of flow (increased renal flow = decreased sodium retention)

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18
Q

What are the short term effects of heart failure?

A

drop in CO = drop in arterial BP = arterial underfilling
sensed by baroreceptors
decrease parasympathetic activity + increase sympathetic activity
trying to restore BP with increased HR, contractility and vasc. resistance

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19
Q

What are the neural regulation of decreased CO?

A

Norepinephrine causes
increased HR
increased cardiac contraction
improved cardiac relaxation
stimulation of renin release and RAAS

20
Q

What are the endocrine system in HF (medium term)?

A

RAAS
ADH
Natriuretic peptides of vascular tone (Nitric oxide, prostaglandins, endothelin)

21
Q

What stimulates the release of renin?

A

renal sympathetic nerve stimulation
reduced pressure in afferent arteriole
reduced sodium in distal tubules

22
Q

What are the advantages of RAAS in HF?

A

increased circulating fluid volume, increased preload, increased CO
increased systemic vascular resistance improved BP

23
Q

What are the disadvantages of RAAS in HF?

A

long term stimulation = excessive fluid retention
excessive resistance to ventricular emptying
direct and indirect deleterious effects on myocardium

24
Q

What do we know about survival vs RAAS?

A

canine heart failure patients with pharmacological antagonism of RAAS have better long term survival

25
Q

What is the effect of enalapril on mortality in severe CHF?

A

lower probability of death

26
Q

What is the difference in HR in animals developing HF VS not?

A

with CHF all have increased HR over time

27
Q

How does ADH have an effect in HF?

A

only in severe HF
increases vascular resistance to protect BP, ultimately deleterious
increases fluid retention (but without sodium)

28
Q

What is a consequence of ADH in HF

A

hyponatraemia
retention of free water w/o sodium

29
Q

How do natriuretic peptides have an effect in HF?

A

counter regulatory hormones that are released in response to increased ventricular and atrial pressures
increased levels associated with HF = biomarker

30
Q

What is hypertrophy in HF?

A

long term alteration in pressure or volume loading of the ventricle that results in a structural adaptation of the ventricle

31
Q

What mediates hypertrophy in HF?

A

adrenergic stimuli
angiotensin II
aldosterone
intracellular calcium

32
Q

What are the 2 different hypertrophy patterns and their causes?

A

Concentric: thick walls, small chamber (pressure overload)
Eccentric: large chamber (volume overload)

33
Q

What are the consequences of hypertrophy in HF?

A

initially adaptive and allows patient to compensate
then increases myocardial oxygen demand and can result in fibrosis + hypoxia of myocardium
excessive hypertrophy is detrimental

34
Q

What characterizes HF in the short term?

A

alteration in autonomic tone: increased sympathetic + decreased parasympathetic

35
Q

What characterizes HF in the medium term?

A

stimulation of endocrine systems

36
Q

What characterizes HF in the long term?

A

hypertrophy

37
Q

What are the clinical signs of HF?

A

tachycardia (increased sympathetic)
poor peripheral perfusion (vasoconstriction)
fluid retention (RAAS, ADH)

38
Q

What is the clinical signs of left sided heart failure?

A

evelation in filling pressures in L side of heart
retained fluid within pulmonary circulation

39
Q

What is the clinical signs of right sided heart failure?

A

elevation in filling pressures in the R side of heart
retained fluid found within systemic veins

40
Q

What is the normal function of vasculature?

A

distribute cellular metabolic substrates around body
remove cellular metabolic waste products
maintain fluid homeostasis
primary homeostasis

41
Q

What are the signs of vascular disease?

A

Underperfusion (vascular obstruction)
increased vascular permeability (oedema or haemorrhage)
abnormal flow
abnormal pressures

42
Q

What are the types of disturbance in starling equilibrium?

A

increased hydrostatic pressures (CHF or venous occlusion)
increased vascular permeability (vasculitis)
decreased oncotic pressure (hypoproteinaemia)
decreased lymphatic drainage (lymphoedema)

43
Q

What are the types of vascular diseases?

A

Obstructive (thrombosis and embolism)
Degenerative
Inflammatory (vasculitis)
Malformations (congenital or acquired)

44
Q

What needs to be present for thromboembolism to form?

A

one or more:
disturbance of flow
disturbance of endothelial integrity
disturbance of haemostasis

45
Q

What are the causes of thromboembolism?

A

Cardiac dz
cushing’s dz
parasitic dz
protein losing nephropathies
neoplasia
autoimmune haemolytic anaemia

Cardio (11 decks)

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