Session 10- The Pathophysiology of Heart Failure Flashcards
What features of the heart have to be affected in order for there to be impairment of cardiac function
- functioning muscle
- chambers size
- one-way valves
What is cardiac output
Stroke volume x heart rate
Stroke volume
Volume of blood ejected by a single ventricle in a single beat
What is ejection fraction
Fraction ejection in a single heart beat of total volume available (EDV)
How do you calculate ejection fraction
Stroke volume/ end diastolic volume
Amount if blood pumped out of ventricle/ total amount of blood in ventricle
What is ejection fraction typicallly
> 50% typically 60-70%
What determines ability to increase stroke volume
Pre-load
Myocardial contractility
After-load
What is pre-load
Volume in ventricle at end of diastole
The stretch on the ventricle just before contraction
What is after load
Force ventricles have to contract against
Total peripheral resistance
What is the relationship between pre-load and stroke volume
Increasing blood volume in ventricle at the end of diastole causes increased stretch
More ventricle stretch during diastole = greater stroke volume ejected in systole
Relationship between myocardial contractility and stroke volume
Contractility improves with greater stretch afforded by the increase in EDV
Contractility of the heart also improves with increasing sympathetic activity
-greater SV for a give end diastolic volume: if increase in SV so does CO
What is heart failure
A clinical syndrome of reduced cardiac output, tissue hypoperfusion, increased pulmonary pressures and tissue congestion
What is the most common cause of heart failure
Ischaemic heart disease
Causes of heart failure
- hypertension
- valvular disease e.g. aortic stenosis
- cardiomyopathies (e.g. hypertrophic/dilated) - arrhythmias
What is remodelling
The loss of myocytes and fibrosis of cardiac tissue in response to these conditions changing ventricular function and ventricular shape/size
What can remodelling lead to
Impairment of ventricular filling- chamber size
Impairment of ventricular ejection- emptying
What will cause contractility problem
Ejection problems
Muscle walls thin/fibrosed
Chamber space enlarged (overstretched sarcomere)
Abnormal or uncoordinated myocardial contraction
What will cause a filling problem
Diastolic
Ventricular volume/ capacity for blood is reduced
- ventricular chambers too stiff/ not relaxing enough
- ventricular walls thickened (Hypertrophied/ concentric remodelling)
What is an ejection problem
Space available in ventricle not reduced but poor ventricular contraction so unable to empty it as well
What is a filing problem
Space available in ventricle is reduced therefore EDV is reduced
How do you determine if its an ejection issue
Drop in ejection fraction
EF<40%
HFrEF
How do you determine if its a filling issue
EF> 50%
HFpEF
Which ventricle s more commonly involved in heart failure
Left however failure of one inevitable leads to failure of the other
Symptoms of heart failure
Dyspnoea
Fatigue
Due to tissue hypoperfusion
As well as tissue fluid retention
