11. Heart Failure Flashcards
What is the definition of heart failure?
State in which the heart fails to maintain an adequate circulation for the needs of the body, despite an adequate filling pressure
What is the primary cause of systolic heart failure (left sided heart failure)?
Ischaemic heart disease
What is the main marker that changes from class I to IV heart failure?
From no symptomatic limitation of physical activity to inability to carry out any physical activity without symptoms
What is the average stroke volume of the heart?
75ml/beat
What 4 factors affect cardiac output?
HR
Venous capacity (LV preload)
Aortic and peripheral impedance (after load)
Myocardial contractility
What happens the more cardiac muscle fibres are stretched after a certain point?
Cardiac output decreases as force with which the fibres can contract decreases
What is the difference between heart failure due to left ventricular systolic dysfunction (left sided HF) and heart failure with preserved ejection fraction (right sided HF)?
Left ventricular systolic function - loss of muscle results in reduced ability of the heart to contract with enough force.
HFpEF - reduced LV compliance and therefore impaired myocardial relaxation.
What does the ejection fraction of the heart need to be below to be considered as heart failure?
40%
What is normally present in left ventricular systolic dysfunction?
Increased LV capacity Reduced LV cardiac output Thinning of the myocardial wall (fibrosis, necrosis, proteinase) Mitral valve incompetence Neuro-hormonal activation Cardiac arrhythmias
What is congestive heart failure? What normally leads to this?
When both ventricles are affected by heart failure.
Left-sided heart failure raises pulmonary arterial pressure, leading to additional right sided heart failure.
What two neuro-hormonal pathways are activated in heart failure? What affect do they have?
RAAS and sympathetic nervous system. Make heart work even harder (eg due to vasoconstriction)
What group of drugs are used in the treatment of heart failure due to their affect on the RAAS system? How do they work?
ACE inhibitors - prevent production of angiotensin II to reduce vasoconstriction and release of aldosterone from the adrenal cortex, thus reducing salt and water retention.
Why are diuretics used as a treatment in heart failure?
Reduce blood volume and therefore oedema
What type of oedema occurs in left sided heart failure? Why?
Pulmonary oedema. Left sided heart failure raises left atrial pressure, so pressure increases in vessels of pulmonary system, these vessels have low resistance, so pulmonary artery pressure increases, and fluid leaks out of capillaries causing oedema.
What type of oedema occurs in right-sided heart failure? Why?
Peripheral oedema. Right side of heart cannot pump effectively, raising pressure in right side of heart and therefore increasing venous pressure and capillary pressure. Increased capillary hydrostatic pressure causes water to move out of capillaries.
