L17 - the pathophysiology of heart failure

Question 1

What is heart failure?

Answer 1

An inability of the heart to meet the demands of the body (adequate blood volume delivering an adequate supply of oxygen and nutrients)

Question 2

Conditions which affect the ability of the heart muscle to function, the chamber size and the valves can cause heart failure, but what is the most common cause?

Answer 2

Ischaemic heart disease (coronary artery disease) - it is the same thing

Question 3

IHD causes heart failure through fibrosis (scarring) of the muscle. What are three other major causes of heart failure?

Answer 3

Hypertension (increases afterload)/ aortic stenosis (increases afterload)/cardiomyopathies (hypertrophic heart means more heart muscle to supply)/arrythmias/valvular diseases/pericardial diseases

Also HF can occur if the demand is greatly increased e.g. sepsis, severe anaemia (this is high output heart failure)

Know these

Question 4

CO = SV X HR, remembering this equation can remind you of things that could lead to heart failure. Stroke volume is the volume ejected in a single beat. Bearing this in mind what is the ejection fraction?

Answer 4

The proportion that the stroke volume is of the end diastolic volume (SV/EDV) remember that the heart doesn’t empty its ventricles completely on pumping, residual blood is left over

Question 5

What is meant by preload and afterload?

What affects stroke volume

Answer 5

Preload - volume in ventricle at the end of diastole (EDV)
Afterload - total peripheral resistance

Myocardial contractility, preload and afterload

Question 6

Heart failure is down to one of three things affecting stroke volume (ignoring high output HF): increased afterload (hypertension/aortic stenosis), reduces myocardial contractility or reduced preload. What do the following things mean?
A) HFpEF
B) HFrEF

Answer 6

Heart failure with reduced ejection fraction - the space in the ventricle is NOT reduced it is the result of poor ventricular contraction. More remains in ventricle than should be

Hear failure with preserved ejection fraction - the space in the ventricle is reduced. Ejection fraction is the same but stroke volume is less because not enough blood is filling the chamber

Question 7

Congestive (biventricular) heart failure is when both ventricles are involved. The left ventricle is most commonly involved with subsequent involvement of the right ventricle. Although the most common cause of RV failure is LV failure, give an example of when RV failure can occur in isolation

Answer 7

Secondary to chronic lung diseases

Question 8

Pulmary congestion (increases pulmonary pressures) occur due to back up of blood in the pulmonary circulation due to reduced cardiac output. T/F

Answer 8

T

Question 9

A reduced cardiac output and blood pressure stimulates normally beneficial systems in the body to try to rectify these things but it causes the heart to work harder which is detrimental to patients with heart failure. What are these systems?

Answer 9

Decreased co -> decreased BP -> baroceptors -> increases SYM activation -> increases HR and peripheral resistance -> afterload -> increases cardiac work

Renin angiotensin aldosterone system -> increases water retention and vasoconstriction which increase preload and afterload respectively thus increasing cardiac work

Question 10

What are the common signs and symptoms of HF and briefly explain them

Divide them in to general and LV and RV specific

Answer 10

Fatigue
Breathlessness
leg oedema

RV
breathlessness
Peripheral oedema - due to backflow of pressure from RV failing
raised JVP (indicative of raised venous pressure)
hepatomegaly (due to liver congestion)

LV
exertional breathlessness
Pulmonary oedema - due to backflow of pressure from LV failing - causes Orthopnoea (breathlessness on lying down - see slide for expl)
paroxysmal nocturnal dysopnoea - Waking up at night due to breathlessness
basal pulmonary crackles
Cardiomegaly - displaced apex beat

Question 11

What is the typical ejection fraction for a healthy heart?

Answer 11

> 50% typically 60%

Question 12

How is ejection fraction measured?

Answer 12

Echocardiogram

Question 13

In heart failure then will be a lower CO at a given LVEDP, T/F?

Answer 13

T

Question 14

What two factors does the frank-starling curve compare?

Answer 14

LVEDP and cardiac output

Question 15

What three factors have an affect on stroke volume?

Answer 15

Pre-load/contractility/afterload

Question 16

Compare the macroscopic appearances of hearts with HFpEF and HFrEF

Answer 16

HFpEF - Thick hypertrophied ventricular wall

HFrEF - thin, fibrosed walls with enlarged chambers

Question 17

Typically below what ejection fraction is considered HFrEF?

Answer 17

40%