Session 11 - Heart failure Flashcards
Define heart failure
‘a state in which the heart fails to maintain an adequate circulation for the metabolic needs of the body despite an adequate filling pressure’.
Give five causes of chronic right heart failure
- Pulmonary hypertension
- Arrythmias
- Chronic lung disease
- Left to right shunt
- Left heart failure
Give six causes of chronic left heart failure?
- Systemic hypertension
- Arrythmias
- Coarctation of the aorta
- Anaemia
- Thyrotoxicosis
- Ischaemic heart disease
Give two causes of acute right heart failure
- Pulmonary embolism
- Rupture of tricuspid valve cusp
Give two causes of acute left heart failure
- Myocardial infarction
- Rupture of mitral or aortic valve
Give three causes of congestive heart failure
- Thyrotoxicosis
- Lesions of the aortic and mitral valves
- Anaemia
Give six compensatory mechanisms for heart failure
- Activation of sympathetic nervous system
- Activation of the renin-angiotensin-aldosterone system
- Anti-diuretic hormones
- Nitric oxide
- Prostaglanding E2 and I2
- Hypertrophy of cardiac muscle
How is sympathetic nervous system activated in heart failure?
Fall in blood pressure and blood volume detected by baroreceptors in the aortic arch and carotid sinus
How does activation of sympathetic nervous system compensate for heart failure?
- Increased heart rate and contractility to increase cardiac output - increases the work load of the heart
- Vasoconstriction of arterioles - increases blood pressure but also increases the afterload
- Renin secretion by the kidneys
How does activation of renin-angotensin-aldosterone system occur?
- Reduced renal blood flow
- SNS induction of renin secretion
- Secretion of endothelin by vascular endothelial cells, causes renal vasoconstriction > renin-angotensin-aldosterone system activated
Give the sequence of events which leads to RAAS activation
Angiotensin –> (renin) –> Angiotensin 1 –> (Angiotensin Converting Enzyme) –> Angiotensin 2
What does angiotensin 2 do?
Activated by RAAS sequence
Promotes vasoconstriction and release of aldosterone from adrenal cortex
Causes increased blood pressure and salt and water retention by kidneys, increasing blood volume and increasing venous return and stroke volume
How do anti-diuretic hormones compensate for heart failure?
- HF increases ADH secretion resulting in water retention and increased blood volume
- Reduced urine output by kidneys contributes to weight gain and oedema fluid
What happens to nitric oxide to compensate for HF?
A powerful vasodilators which is inhibited in heart failure
How do prostaglands E2 and I2 compensate for HF?
Act as vasodilators on afferent renal arterioles to attenuate effects of Na+/RAAS
What effect does hypertrophy of heart muscle have in compensation for heart failure?
- Response to increased demand
- Decreases ventricular volume which exacerbates reduced cardiac output
- The heart may remodel and dilate
- Increasing venous pressure may push heart to the right of starling’s curve resulting in damage to myocardium Results in reduced stroke volume for a given venous pressure..
Give five main symptoms of left heart failure
Fatigue Exertional dyspnoea Pulmonary oedema Displaced apex beat and cardiomegaly Tachcardia
Why do you get fatigue in left heart failure?
Cardiac output does not meet metabolic needs, meaning some tissues insufficiently perfused - acidocis may ensue
- Pulmonary oedema impars gas exchange causing a state of hypoxia
Why do you get exertional dyspnoea in left heart failure?
Heart is unable to meet the increasing metabolic demand of tissues during exercise, acidosis may occur
Why do you get pulmonary oedema in left heart failure?
Increased venous pressure results in increased hydrostatic pressure in the mpulmonary capillaries. Fluid moves into the interstitium resulting in oedema.
What are pulmonary crackles?
Fluid collects in base of the lungs > pulmonary crackles
What is orthopnoea?
Whilst lying down fluid distributes across base of lungs, causing breathlessness due to impaired gas exchange
What is the result of breathlessness?
Impairment of gas exchange
What is cyanosis?
Result of imparied gas exchange leading to hypoxaemia
