19. Pathophysiology Of Heart Failure

Question 1

What is heart failure?

Answer 1

Inability of heart to meet the demands (deliver a blood volume that allows body tissues to function as required) of the body

Question 2

What is the most common cause of heart failure?

Answer 2

Ischaemic heart disease (coronary heart disease)

Question 3

What are some other causes of heart failure?

Answer 3

Hypertension
Arrhythmias
Aortic stenosis
Other valvular or myocardial structural diseases
Cardiomyopathies
Pericardial diseases

Question 4

What is fraction ejected?

Answer 4

Stroke volume/end diastolic volume

Question 5

What influences stroke volume?

Answer 5

Pre-load - volume in ventricle at end of diastole
Myocardial contractility
After-load - total peripheral resistance

Question 6

What is Frank-Starling’s Law?

Answer 6

More ventricular distension during diastole = greater volume ejected (SV) during systole

Question 7

How can contractility of the heart change?

Answer 7

Contractility of the heart can increase with sympathetic activity

Question 8

Why is cardiac output reduced in heart failure?

Answer 8

Stroke volume can be reduced due to reduced pre load, reduced myocardial contractility or increased afterload

Question 9

What is a filling problem (diastolic) with the heart?

Answer 9

Ventricular volume/capacity for blood is reduced due to:

• ventricular chambers too stiff/not relaxing enough
• ventricular walls thickened

Question 10

What is a contractility (ejection) problem (systolic) with the heart?

Answer 10

Can’t pump with enough force due to:

• muscle walls thin/fibrosed
• chamber enlarged
• abnormal or uncoordinated myocardial contraction

Question 11

What is HFrEF?

Answer 11

Heart failure with reduced ejection fraction
Systolic dysfunction
Contractility problem
Most common type

Question 12

What is HFpEF?

Answer 12

Heart failure with preserved ejection fraction
Diastolic dysfunction
Filling problem

Question 13

What is the normal ejection fraction?

Answer 13

> 50%, typically >60%

Question 14

How can a heart be failing if EF is maintained?

Answer 14

Ventricle ejects less volume in a heartbeat as less volume to begin with
Fraction of what is available to eject is still >50%
Hence ejection fraction is maintained

Question 15

Which ventricle is usually involved in heart failure? What is involvement of both ventricles called?

Answer 15

Usually left ventricle, but with subsequent involvement of the right ventricle
Involvement of both ventricles is biventricular (congestive) heart failure

Question 16

Describe Frank-Starling’ curve in heart failure

Answer 16

Increased LV filling in failing heart leads to a very little increase in CO
Eventually it leads to worsening CO
Markedly increased LVEDP result in falling CO and development of pulmonary congestion

Question 17

What does the drop in cardiac output trigger to try and correct the falling CO?

Answer 17

Damaged ventricular tissue
Reduction in efficiency of ventricular contraction
Reduced stroke volume
Reduced cardiac output
Neurohormonal activation

Question 18

How is cardiac work increased when cardiac output is decreased?

Answer 18

Blood pressure decreases leading to 2 pathways:

1. Baroreceptors sense, increased sympathetic drive (inc. heart rate, inc. peripheral resistance)
2. Activation of renin-angiotensin-aldosterone pathway, increases circulating volume due to Na+ and water retention, stimulates ADH, vasoconstriction, enhances sympathetic pathway

Question 19

What are the clinical signs and symptoms of heart failure?

Answer 19

Symptoms: fatigue/lethargy, breathlessness, leg swelling
Many signs and symptoms due to increased interstitial fluid (oedema) in:
- pulmonary tissues
- peripheral tissues

Question 20

How is tissue fluid formed?

Answer 20

Gradient between hydrostatic and oncotic pressure governs movement of fluid out of or back into capillaries
Higher hydrostatic in arterial end, higher oncotic pressure at venule end

Question 21

How does tissue oedema form?

Answer 21

Increased capillary hydrostatic pressures leads to less fluid being drawn back intravascularly at venule end

Question 22

Why is raised jugular venous pressure important?

Answer 22

Measurement of the pressure in the right internal jugular vein can be used as a direct reflection of pressures in the right side of heart