Flashcards in Session 11 - Heart failure Deck (40):
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
- Chronic lung disease
- Left to right shunt
- Left heart failure
Give six causes of chronic left heart failure?
- Systemic hypertension
- Coarctation of the aorta
- 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
- Rupture of mitral or aortic valve
Give three causes of congestive heart failure
- Lesions of the aortic and mitral valves
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
Displaced apex beat and cardiomegaly
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
Why do you get displaced apex beat and cardiomegaly in left ventricular heart failure?
Left ventricular hypertrophy
Why tachcyardia in LVHF?
Sympathetic response to falling CO
What are five signs and symptoms of right heart failure?
Peripheral oedema 'pitting oedema'
Why does fatigue occur in RVHF
Decreased flow to the lungs results in hypoxaemia due to a ventilation/perfusion mismatch. Insufficient oxygen for metabolic needs.
What happens in breathlessness in in RVHF?
Decreased oxygenated blood enters systemic circulation. Hyperventilation results in order to increase the partial pressure of oxygen.
Why do you get raised JVP in RVHF?
Failure of right side of the heart to pump causes a rise in venous pressure and distension of the jugular veins.
What is peripheral oedema in RVHF?
Increased venous pressure also raises capillary pressure. Increased hydrostatic pressure causes fluid to move into the interstitium.
Oedema causes weight gain
What is hepatomegaly in RHVF?
Back up of blood in the inferior vena cava causes congestion of the hepatic veins leading to hepatic engorgment.
Name four targets of drugs for manipulation of cardiac output?
Kidneys - Regulate blood volume
Arterioles- regulate bp
Myocardium - regulates force of contraction - the force is developed in a muscle fibre,
SAN - regulates heart rate
Give three life style changes which can be used to tackle heart failure?
Reduce alcohol consumption
Increase aerobic exercise
Give three anti-hypertensives that can be used to treat HF
Diuretics e.g. loop diurteics, spironolactone
Give a drug which causes reduction of cardiac workload
Give a positive inotropic drug
Digoxin - increases intracellular calcium
Give three anti-arrhymic drugs which can be used to treat HF
Calcium channel blocker
Give four types of drugs which can be given for HF
Reduction of cardiac workload
Anti arrhythmic drugs