Pathophysiology of heart failure

Question 1

Define heart failure

Answer 1

Inability of the heart to meet the demands (deliver blood volume that allow body tissues to function) of the body
-Reduced CO, tissue hypo-perfusion, increased pulmonary pressures and tissue congestion

Question 2

What is the most common cause of heart failure?

Answer 2

Ischaemic heart disease

-myocardial dysfunction e.g. through fibrosis, remodelling of muscle

Question 3

What are other causes of heart failure?

Answer 3

• Hypertension (increased afterload and accelerates atherosclerosis)
• Aortic stenosis
• Cardiomyopathies
• Arrhythmias
• Other valvular or myocardial structural disease
• Pericardial diseases

Question 4

What are some rare causes of heart failure

Answer 4

From grossly elevated demand on cardiac output

e.g. sepsis, severe anaemia, thyrotoxicosis

Question 5

Equation to measure the ability of the heart to meet demands of the body

Answer 5

CO = SV x HR

Question 6

What is the usual stroke volume for a 70kg man?

Answer 6

~70-75ml

Question 7

What are the 3 factors that affects stroke volume?

Answer 7

• Pre-load (increased pre-load increases SV)
• Myocardial contractility (increases SV)
• After-load (increased after-load decreases SV)

Question 8

What links pre-load and myocardial contractility?

Answer 8

Frank-Starling’s law

Question 9

What does the Frank-Starling’s law suggest?

Answer 9

The greater stretch there is, the greater force of contraction up to a point

Question 10

What happens to the contractility of heart with increased sympathetic activity (inotropic)?

Answer 10

Increased contractility

Question 11

How is cardiac output reduced in heart failure?

Answer 11

Reduced stroke volumes from…

• Reduced pre-load = impairing of ventricle during diastole
• Reduced myocardial contractility = muscle not able to produce same force of contraction for a given volume within ventricle
• Increased after-load = increased pressure which ventricle contracts against

Question 12

What are the two classes of heart failure based on ejection fraction?

Answer 12

1) Heart failure with reduced ejection fraction (HFrEF)

2) Heart failure with preserved ejection fraction (HFpEF)

Question 13

Describe heart failure with reduced ejection fraction

Answer 13

• Systolic dysfunction; contractility problems
• Space in ventricle not reduced
• Can’t pump with enough force
• Muscle walls thin/fibrosed, chambers enlarged, abnormal myocardial contraction
• Reduced ejection pressure starting from 40% below

Question 14

Describe heart failure with preserved ejection fraction

Answer 14

• Diastolic dysfunction; filling problem
• Ventricular volume/capacity for blood is reduced
• Ventricular chambers too stiff/not relaxing enough, hypertophy
• Space in ventricles decreases

Question 15

What is the usual ejection fraction for a normal functioning heart?

Answer 15

~60%

Question 16

What is the equation for ejection fraction?

Answer 16

Amount of blood pumped out of the ventricle / Total amount of blood in ventricle

Question 17

How is ejection pressure not reduced in HFpEF?

Answer 17

Maintained ejection fraction as there’s a decrease in stroke volume but also to the space in the ventricles (denominator and nominator both reduced)

Question 18

How else is heart failure classified apart from ejection fraction?

Answer 18

Which ventricle(s) is involved

• Right
• Left
• Biventricular

Question 19

What is the consequence of reduced cardiac output?

Answer 19

• Activation of neuro-hormonal response
• RAAS = ADH + vasoconstriction + Aldosterone = increased blood pressure
• Baroreceptors = increased sympathetic drive

-Increased cardiac demand and further reduction in stroke volume

Question 20

What are the signs and symptoms of heart failure?

Answer 20

• Fatigue/lethargy
• Breathlessness
• Leg swelling
• Raised jugular venous pressure (RV)
• Basal pulmonary crackles (LV)