18. Heart Failure Flashcards
What is the simple definition of heart failure?
inability of the heart to meet the demands of the body
What is the ESC definition of heart failure?
Clinical syndrome of:
- reduced cardiac output,
- tissue hypoperfusion,
- increased pulmonary pressures
- and tissue congestion
What are the most common cause of heart failure?
• Ischaemic Heart Disease(coronary heart disease)
- myocardial dysfunction e.g. through fibrosis (scarring), remodelling of muscle
What are other causes of heart failure?
- myocardial infarction
- Hypertension (increased afterload & accelerates atherosclerosis)
- Arrhythmias
- Aortic stenosis (increased afterload)
- Other valvular or myocardial structural diseases
- Cardiomyopathies (e.g. hypertrophic/dilated)
- Pericardial diseases
• Rarely, can occur if a grossly elevated demand on cardiac output e.g. sepsis, severe anaemia, thyrotoxicosis [high output heart failure]
How do we measure the ability of the heart to meet demands of the body?
Ejection fraction
What is the ejection fraction?
SV/EDV
What influences stoke volume?
- Preload
This refers to the stretch on the ventricle just before contraction in systole. It’s affected by the EDV, the volume in the ventricle at the end of diastole. - Afterload
This refers to the total peripheral resistance - Myocardial contractility
This refers to the myocytes ability to contract
Describe Frank-Starlings Law of the heart
Starling’s law says that the stroke volume of the left ventricle will increase as the left ventricular volume increases.
This is due to increased stretch of the myocytes which causes a more forceful contraction in systole.
Essentially the more the cardiac muscle is stretched the stronger the contraction up to a certain point
Give a factor that can cause the Frank-Starling curve to vary
Frank-Starling curves can vary depending on the inotropic state of the heart.
It can be influenced by sympathetic activity, an increase in synthetic activity can cause an increase in the contractility of the heart.
This causes the curve to shift upwards and to the left.
It means that for an increase in the left ventricular end diastolic pressure should get an increase in CO.
Why is cardiac output reduced in heart failure?
Stroke volume can be reduced due to
– Reduced pre load (reduced EDV)
• Impaired filling of ventricle during diastole
– Reduced myocardial contractility
• Muscle not able to produce same force of contraction for a given volume within ventricle
– Increased afterload
• ↑pressure against which ventricle contracting e.g. aortic stenosis, chronic
What are the 2 reasons that heart can fail?
- A filling problem (diastolic)
Ventricular volume/capacity for blood is reduced
• Ventricular chambers too stiff/not relaxing enough
• Ventricular walls thickened (hypertrophied) - A contractility (ejection) problem (systolic)
Can’t pump with enough force (for a given EDV)
• Muscle walls thin/fibrosed,
• Chambers enlarged (overstretched sarcomeres)
• Abnormal or uncoordinated myocardial contraction
What are the two ways of classifying heart failure according to ejection fracture?
- Heart Failure with reduced Ejection Fraction (HFrEF)
– [systolic dysfunction]
– Contractility problem
– Most common type - Heart Failure with preserved Ejection Fraction (HFpEF)
– [diastolic dysfunction]
– Filling problem
What is the normal ejection fraction?
Normal >50% (typically 60% +)
- abnormal if below 40%
How can a heart be “failing” if EF is maintained…?
“filling problem”..
- Ventricle ejects less volume in a heartbeat (SV reduced) as less volume to begin with
- Fraction of what is available to eject is still >50%
- Hence “Ejection Fraction” is ‘preserved’
Which ventricle is most commonly affected in heart failure?
Left ventricle most commonly involved
• But with subsequent involvement of the right ventricle
What is congestive/biventricular heart failure?
Involvement of both ventricles (biventricular)
What is the most common cause of right ventricular failure?
Left ventricular failure
When might right ventricular heart failure occur in isolation?
Secondary to chronic lung diseases (cor pulmonale)
Explain the presentation circumstances which lead to the development of left ventricular failure,
The left side of the heart receives oxygen-rich blood from the lungs and pumps it forward to the systemic circulation. However failure of the left side of the heart causes blood to back up (be congested) into the lungs, causing respiratory symptoms as well as fatigue due to insufficient supply of oxygenated blood.
Explain the presentation circumstances which lead to the development of right ventricular failure
The most common cause for RV heart failure is LV heart failure.
However right-sided heart failure can also occur in isolation often caused by pulmonary heart disease (cor pulmonale), which is typically caused by difficulties of the pulmonary circulation, such as pulmonary hypertension or pulmonic stenosis.
There’ll be a backward failure of the right ventricle which cause blood to flow back into the venous system.
This leads to congestion of systemic capillaries and generates excess fluid accumulation in the body.
Explain the presentation circumstances which lead to the development of biventricular failure
In biventricular heart failure both ventricles are involved,
It results in the development of symptoms seen for both right and left sided heart failure.
Describe the Frank-Starling’s Curve in Heart Failure
- Increased LV filling in the healthy heart leads to big increase in CO (gradient of curve)
- Increased LV filling in failing heart leads to a very little increase in CO…(gradient of curve)
- Eventually it leads to worsening CO (curve dips)
- Markedly increased LVEDP [in attempts to increase SV] result in falling CO and development of pulmonary congestion
Explain the pathophysiology of heart failure
Heart failure is caused by any condition that reduces the efficiency of the heart muscle,through damage or overloading.
It causes a decrease in CO.
the decreased CO causes a decreased BP (BP = CO x TPR).
This results in the activation of neuro-hormonal systems.
This is an attempt to increase the BP but in this reality culminates in an increased after-load and pre-load which puts even more strain on the failing heart.
Explain the circumstances that results in Heart Failure with reduced Ejection Fraction (HFrEF)
In HFrEF you have systolic dysfunction .
There’s a problem with heart contraction and therefore the heart can’t pump with enough force. This means you have a contractility problem.
Causes include:
Thin/ fibrosed walls, enlarged chambers , abnormal/ uncoordinated contraction.
This is the most common type of heart failure