Heart failure

Question 1

Common causes of heart failure

Answer 1

Coronary artery disease

High blood pressure

Cardiomyopathy

Heart valve disorders

Arrythmias

Question 2

Causes & effects of concentric cardiac hypertrophy

Answer 2

Cause:
Response to pressure overload on heart due to high blood pressure or narrowing of aortic valve
Increased resistance against which heart has to pump leads to thickening of heart muscle walls

Effects:
Ventricular wall muscles thicken resulting in smaller chamber
Allows heart to generate higher pressure to overcome resistance
Thickening reduces chambers ability to fill with blood
Leads to diastolic dysfunction (impaired filling)

Question 3

Causes & effects of eccentric cardiac hypertrophy

Answer 3

Cause:
Occurs in response to volume overload on heart
Caused by leaky valves or dilated cardiomyopathy
Heart muscle responds by stretching & enlarging to accommodate increased blood volume it needs to pump

Effects:
Heart chamber dilates allowing for greater blood volume
Allows heart to maintain stroke volume & compensate for increased volume
Increased wall stress & dilation lead to systolic dysfunction (impaired contraction) & reduced pumping efficiency

Question 4

Pathophysiological responses which occur in cardiac failure

Answer 4

Activation of sympathetic nervous system
Releases adrenaline to increase HR, constrict blood vessels & increase contractility
Initially helps maintain CO but contributes to heart muscle damage

Activation of renin angiotensin aldosterone system (RAAS)
Kidneys release renin in response to reduced blood flow & pressure
Leads to formation of angiotensin II which causes vasoconstriction, fluid retention & stimulates release of aldosterone
Aldosterone promotes sodium & water retention
Increases blood volume & peripheral resistance
Can worsen heart failure symptoms

Ventricular remodeling
Includes hypertrophy & dilation of heart chambers
Adaptations initially help compensate for reduced pumping ability
Over time impair contractility & disrupt normal heart architecture

Fluid retention
As CO decreases there is fluid retention in various parts of body
Leads to oedema in lungs, legs & ankles

Question 5

Clinical signs of heart failure

Answer 5

Dyspnoea

Weakness

Oedema

Irregular heart beat

Question 6

Describe mechanisms by which oedemas develop

Answer 6

Increased capillary hydrostatic pressure
Reduced CO leads to increase in pressure in blood vessels
Forces fluid out of capillaries into interstitial spaces

Sodium & water retention
RAAS activated in response to reduced CO
Results in water & sodium retention leading to expansion of circulating blood volume

Reduced capillary oncotic pressure
Reduced production of albumin (maintains COP)
Leading to reduced osmotic force that draws fluid into capillaries
Thus favoring movement if fluid into interstitial spaces

Lymphatic dysfunction
Lymphatic vessels become overwhelmed by increased fluid accumulation

Inflammation & endothelial dysfunction
Disrupted integrity & permeability of capillary walls allowing for leakage of fluid into interstitial spaces

Question 7

How is heart failure treated

Answer 7

Stage 1b
Asymptomatic, no cardiac remodelling
No treatment but consider weight control, regular re-assessment & client education

Stage 2b
Pimobendan (improves contractility)
Weight control, regular re-assessment, client education

Stage c
Remove fluid
Use vasodilator
Use pimobendan
This reduced blood pressure so need to compensate
Loop diuretics, furosemide, torasemide
Aldosterone antagonists, spironolactone