MP323 - HEART FAILURE Flashcards
heart failure
characterised by impaired cardiac pumping such that the heart is unable to pump adequate amount of blood to meet metabolic needs
signs and symptoms of HF
shortness of breath
excessive tiredness
leg swelling
congestive HF - left-sided failure
- most common form
- blood backs up through the left atrium into the pulmonary veins
- pulmonary congestion and oedema
congestive HF - right-sided failure
- rare
- associated with pulmonary hypertension
stroke volume
the volume of blood pumped from one ventricle of the heart with each beat
the difference between end-diastolic volume (EDV) and end-systolic volume (ESV)
increased preload on SV
preload increased
EDV increases
increased stroke volume
increased afterload on SV
afterload increased
ESV increased
decreased stroke volume
increased contractility on SV
contractility increased
ESV reduced
increased stroke volume
effect of HR on cardiac output
higher the heart rate, the higher the cardiac output
HR x SV = CO
preload
- the amount of fibre stretch in the ventricles at the end of diastole (before next contraction)
- directly related to ventricular filling
- higher end-diastolic volume implies higher preload
preload increases with…
- increased in blood volume
- vasoconstriction
preload decreases with…
- loss in blood volume
- vasodilation
Starling’s law
- relationship between preload and cardiac output
excessive preload = excessive stretch - reduced contraction - reduced SV and CO
afterload
- the resistance against which the ventricle must pump
excessive afterload = difficult to pump blood - reduced SV and CO
afterload increases with…
hypertension
vasoconstriction
afterload decreases with…
vasodilation
contractility
- ability of the heart muscle to contract
- relates to the strength of contraction
contractility increases with…
positive inotropes
contractility decreases with…
infarcted tissue - no contractile strength
ischaemic tissue - reduced contractile strength
myocardial hypertrophy
walls of heart thicken to provide more muscle mass - stronger contraction
how does vasoconstriction worsen heart failure
increases the resistance against which heart has to pump (increases afterload), and therefore decreases CO
how does Na+ and water retention worsen heart failure
increases fluid volume, which increases preload
if too much stretch (too much fluid) there is a decrease in strength of contraction and decreased CO
how does excessive tachycardia worsen heart failure
decreases diastolic filling time - decreases ventricular filling - decreases SV and CO
