Session 10.1 Flashcards
What is heart failure?
The inability of the heart to meet the demands of the body
I.e deliver blood volume that allows body tissue to function as required
It’s a clinical syndrome of reduced cardiac output, tissue hypopergfusion, increased pulmonary pressure and tissue congestion
What are some causes of heart failure?
- most common = ischaemic heart disease
- hypertension
- cardiomyopathies
- arrhythmia
- pericardial disease
- arterial stenosis
How can you calculate the fraction of Blood ejected?
SV/EDV
What influences stroke volume?
1) Preload - volume in ventricles at end of diastole (EDV)
2) myocardial contractility
3) afterload - the pressure against the heart must work to eject blood (TPR).
Nb: get a high afterload due to a stenosis valve = more pressure. Has a negative effect on stroke volume
Why is cardiac output reduced in heart failure?
Reduction in stroke volume
- reduced preload (EDV) due to impaired filling, perhaps due to hypertrophy
- reduced myocardial contractility - cant produce the same force for contraction of the EDV
- increased afterload = heart needs to work against an increased pressure e.g secondary to aortic stenosis or chronic severe hypertension
What is heart failure due to?
1) a filling problem (diastole)
- ventricular chambers too. Stiff
- hypertrophied ventricular chambers
2) a contractility (ejection) problem (systole)
- cant pump with enough force for EDV
- e.g muscle walls thin/ fibrosis, overstretched sarcometes, abnormal/uncoordinated contraction
What is the difference between systolic and diastolic heart failure??
Systolic
- Heart failure with reduced ejection fraction (HFrEF)
Ejection problem. Weakened heart muscle cant squeeze as well (wall of LV is thin) so filling capacity is good but cant empty
Diastolic
- heart failure with preserved ejection fraction (HFpEF)
Filling problem e.g LV hypertrophy = lower EDV.
What’s a normal ejection fraction and whats reduced?
Normal is 50% or more. Typically 60%. As long as it doesn’t drop below 50, its HFpEF.
Reduced is less than 40 = diagnosis of HFrEF.
What’s biventricular heart failure?
Involvement of ventricles = congestive heart failure.
What’s the most common for RV heart failure?
LV heart failure
What kind of physiological mechanisms are needed to restore co?
Neural hormonal activation by reduced cardiac output accounts for the Symptoms of heart failure.
This mechanism however leads to an increased cardiac demand and further reduction of stroke volume = condition gets worse
What physiological mechanisms occur in response to reduced CO?
Reduced CO= reduced BP so get -
1) activation of RAAS pathway
- ADH increases circulating volume due to Na+ and eater retention
- vasoconstriction
- enhances sympathetic pathway
2) Baroreceptors
- increase sympathetic drive
- increase HR and TPR
What are the symptoms of heart failure?
- fatigue/lethargy
- breathlessness (due to pulmonary oedema)
- maybe leg swelling (peripheral oedema)
Many signs arise as a result of oedema in both pulmonary and peripheral tissue.
How does oedema occur due to heart failure?
Failing right or left ventricle = higher pressure in venous circulation means less fluid being drawn back intravascularly at venule end.
How will someone with RV heart failure present?
- fatigue/lethargy
- breathlessness
- peripheral pitting oedema
- raised jugular venous pressure
- tender, smooth enlarged liver (liver congestion)
