Pathophysiology of heart failure

Question 1

What is Starling’s Law?

Answer 1

States that stroke volume of the heart increases in response to an increase in the volume of blood in the ventricles before contraction (e.g. end diastolic volume), when all other factors remain constant

Question 2

What is the Starling equation?

Answer 2

Illustrates the role of hydrostatic and oncotic forces in the movement of fluid across capillary membranes (movement occurs as a result of either diffusion, filtration or oncotic pressure)

Question 3

How does hydrostatic pressure differ as fluid moves from arterioles to capillaries and then to venules?

Answer 3

Decreases as it travels through arterioles
Remains fairly steady (although still decreasing slightly) as it moves through capillaries
Decreases as it travels through venules

[Osmotic force, or protein concentration, remains constant]

Question 4

What is the clinical definition of heart failure?

Answer 4

A syndrome in which patients have typical symptoms (e.g. breathlessness, ankle swelling and fatigue) and signs (e.g. raised JVP, pulmonary crackles and a displaced apex beat) resulting from abnormality of cardiac structure or function

Question 5

What is the pathophysiological definition of heart failure?

Answer 5

Abnormality of cardiac structure or function leading to failure of the heart to deliver oxygen to the body at a sufficient rate to meet the metabolic demand

Question 6

How can heart failure be classified?

Answer 6

HFrEF = heart failure with reduced ejection fraction 
HFpEF = heart failure with preserved ejection fraction

Question 7

What conditions class heart failure as having reduced ejection fraction?

Answer 7

Typical HF symptoms
Typical HF signs
Reduced left ventricular ejection fraction

Question 8

What conditions class heart failure as having preserved ejection fraction?

Answer 8

Typical HF symptoms
Typical HF signs
Normal or mildly reduced left ventricular ejection fraction
Relevant structural heart disease (e.g. L ventricular hypertrophy or L atrium enlargement) and/ or diastolic dysfunction

Question 9

How do you calculate an ejection fraction?

Answer 9

Stroke volume / End diastolic volume

[SV = EDV-ESV]

Left ventricle used to determine heart failure

Normal = >55%

Question 10

What are the benefits of using echocardiography?

Answer 10

Cheap
Robust
Able to define cardiac structure and function

Question 11

How does the disease process differ between heart failure with reduced ejection fraction and without (preserved ejection fraction)?

Answer 11

Reduced ejection fraction = disease process affecting contraction of the heart (caused by myocardial injury or overload - increased preload or afterload)

Question 12

What is ventricular remodelling?

Answer 12

Remodelling aims to preserve stroke volume
Chronic pressure overload = hypertrophy
[Can often occur with ventricular dilation which is a result of myocardial injury or chronic volume overload]

Question 13

What macroscopic changes are seen in ventricular remodelling?

Answer 13

Loss of muscle mass
Hypertrophy or dilation of chamber size
Dys-synchronous contraction

Question 14

What microscopic changes are seen in ventricular remodelling?

Answer 14

Myocyte changes (cell thinning, lengthening, hypertrophy, necrosis, apoptosis) 
Disorganised muscle fibre orientation 
Extracellular matrix alterations and inflammatory changes

Question 15

What intracellular changes are seen in ventricular remodelling?

Answer 15

Contractile protein structure and functional derangements
Disorganised cytoskeleton 
Impaired communication between cells
Altered energy metabolism 
Deranged excitation

Question 16

What signs and symptoms may be present in right sided congestive heart failure?

Answer 16

Oedema/ ascites (due to congestion of peripheral tissues)
Impaired liver function (due to liver congestion)
Anorexia, GI distress, weight loss (due to GI tract congestion)

Question 17

What signs and symptoms may be present in left sided congestive heart failure?

Answer 17

Activity intolerance and signs of decreased tissue perfusion (e.g. increased capillary refill time) due to decreased cardiac output
Cyanosis/ hypoxia (due to impaired gas exchanged caused by pulmonary congestion)
Pulmonary oedema causing cough with frothy sputum, orthopnea (shortness of breath) and paroxysmal nocturnal dyspnoea

Question 18

How can heart failure be classified in terms of severity?

Answer 18

Stage 1: no limitation of physical activity
Stage 2: comfortable at rest with undue breathlessness, fatigue or palpitations on ordinary physical activity
Stage 3: comfortable at rest but less than ordinary physical activity results in undue breathlessness, fatigue or palpitations
Stage 4: unable to carry out any physical activity without discomfort, symptoms can be present at rest

Question 19

Why do you get oedema in heart failure?

Answer 19

Plasma excessively filtered in arterioles (where the hydrostatic pressure is higher) with minimal absorption in the venules (where hydrostatic pressure is lower) meaning that the net loss of fluid from plasma is greater than the gain meaning fluid is retained in the interstitial space

Question 20

What are the basic general treatment principles for acute decompensated heart failure?

Answer 20

ABCDE assessment 
O2 via re-breath bag 
GTN 
Diuretics 
Continuous positive airway pressure 
Inotropes 

[transplant rare for acute HF]

Question 21

What examination findings are indicative of heart failure?

Answer 21

Raised JVP >4cm
Displaced apex beat
Pulmonary crackles
Gallop rhythm on auscultation (presence of 3rd or 3rd/4th heart sounds)

Question 22

What do the normal heart sounds (I and II) indicate?

Answer 22

Heart sound I = closing of mitral and tricuspid valves

Heart sound II = closing of semilunar valves

Question 23

What does a third heart sound indicate?

Answer 23

‘Galloping rhythm’ heard in congestive heart failure
Caused by sudden deceleration of blood flow from the left atrium into the left ventricle
Anatomically, left ventricle may be thin-walled and dilated with generalised decreased vigor of contraction

Question 24

What does a fourth heart sound indicate?

Answer 24

‘Galloping rhythm’ heard in coronary heart disease
Can be caused by stiffness in the left ventricle due to scar formation or a greatly thickened left ventricular wall (e.g. in essential hypertension or aortic stenosis)

[Never heard in AF as atrial contraction is ineffective]

Question 25

What does presence of both a third and fourth heart sound indicate?

Answer 25

Often seen in improvement of heart failure symptoms (e.g. S3 pattern gives way to an S3 S4 pattern)

Question 26

What is an echocardiogram?

Answer 26

Ultrasound used to look at the heart and associated blood vessels

Question 27

How does the RAAS system affect heart failure?

Answer 27

Decreased perfusion to kidneys results in Macula Densa cells in the JGA responding to low BP by activating RAAS system - this results in increased Angiotensin II and Aldosterone action further increasing work of heart