heart failure Flashcards
what is heart failure?
marked reduction in ventricular contractility
prognosis of heart failure
high mortality
50% death within 5 years
how to calculate stroke volume?
left ventricular end diastolic volume - left ventricular end systolic volume
average systolic volume
70ml
average cardiac output
5L/min
what is ejection fraction?
the proportion of the left ventricular end diastolic volume that is ejected. Measures how effective the heart is as a pump
normal ejection fraction
70%
how to calculate ejection fraction
stroke volume/left ventricular end diastolic volume
ejection fraction in heart failure
reduced to below 60%
affects tissue perfusion
unable to sustain adequate circulation of blood to the tissues
which side of the heart more commonly fails?
left because of higher resistance to pump against
higher workload
pressure volume relationship left ventricular work
area under the curve
aspects to left ventricular pressure-volume relationship
- filling
2. ejecting
filling of left ventricle
diastolic compliance - how well it fills
healthy heart is very compliant
limited by pericardium
ejecting of left ventricle
systolic contraction - strength of contraction
contractility of left ventricle
more stretched the myocardium the more it will recoil and eject harder
limited by overlap of myocardial filaments
greater contact of actin/myosin interaction and increased sensitivity of myofibrils to Ca2+ affects systolic contraction ability
what are the types of heart failure?
systolic or diastolic dysfunction
systolic dysfunction definition
heart failure with reduced ejection fraction
diastolic dysfunction
heart failure with preserved ejection fraction
features of systolic dysfunction
impaired myocardial contraction so heart cannot empty properly
flabby, weak ventricle
systolic contraction falls
stroke volume falls
to compensate and maintain cardiac output tachycardia which puts more pressure on heart long-term
features of diastolic dysfunction
impaired myocardial relaxation so heart cannot fill properly
stiff fibrotic ventricle - cardiomyopathy and collagen deposits
diastolic compliance drops
high pressures at lower volumes of filling
left ventricular end diastolic pressure rises
stroke volume falls
compensation increases systolic contraction
increased pressure on heart
upstream effects of heart failure
inability to keep up with returning venous flow so increased upstream pressure in circulation
increased pressure in lungs
downstream effects of heart failure
inadequate perfusion of vital organs - kidneys
reduced perfusion of kidneys sensed by juxtaglomerular apparatus
activation of RAAS
vasoconstriction increases SVR and BP
ADH release
aldosterone release
water and sodium retention
blood volume increased despite normal blood volume in response to reduced perfusion
what happens to stroke volume?
decreased due to increased afterload and SVR from vasoconstriction
effect of rise in upstream pressure in heart failure
hydrostatic pressure increased due to increases blood volume so increased loss of fluid from circulation into interstitium causing oedema
fluid accumulates in alveoli/lungs and causes pulmonary oedema
role of hydrostatic pressure
major determinant of fluid movement at capillary level
hydrostatic pressure gradient pushes fluid out of blood vessels into interstitium
osmotic pressure/oncotic pressure gradient pulls fluid from interstitium into intravascular space
left ventricular heart failure
pulmonary oedema - upstream effect
drop in renal function - poor perfusion
activation of RAAS
right ventricular heart failure
less common
when does right ventricular heart failure occur?
raised pulmonary vascular resistance
what does right ventricular heart failure cause?
back up of pressure from RV - raised JVP/CVP
peripheral oedema - ankles
hepatomegaly - raised hydrostatic pressure causes liver engorgement
what is congestive heart failure?
biventricular heart failure
prolonged left ventricular failure can progress to right sided failure due to increased pulmonary resistance
how do patients present?
fluid congestion - wet, none = dry
hypoperfusion - cold, well perfused = warm
worst prognosis = cold and wet
presentation of fluid congestion
raised JVP
pulmonary/systemic oedema
orthopnoea
presentation of hypoperfusion
low BP
reduced renal function
cold
cold
cyanotic and not well-perfused
causes of heart failure
ischaemic heart failure valvular disease arrhythmias hypertension intra-cardiac shunts drugs cardiomyopathy fluid overload
how do arrhythmias cause heart failure
reduced CO
poor ejection of atria into ventricles and poor preload
how does hypertension cause heart failure?
increased SVR
increased afterload
how do drugs cause heart failure?
changes to sympathetic NS
beta blockers can worsen heart failure
perfusion of the heart itself
rise in left ventricular wall pressure during systole occludes coronary vessels running through the ventricle
therefore most perfusion occurs during diastole
perfusion of heart during exercise
during exercise time spent in systole increases and time spent in diastole reduces
therefore there is reduced coronary blood flow
less effect on right ventricle because there is a lower pressure
ischaemic and heart failure
rising wall tension from cardiac failure will worsen coronary flow and myocardial ischaemia
tachycardia will worsen coronary flow/myocardial ischaemia even more because will reduce total time spent in diastole
mortality after heart failure diagnosis
10% in 30 days
30% in 1 year
50% in 50 years
why does heart failure cause increased urination at night?
lying down reduces peripheral oedema so fluid is reabsorbed into vasculature
volume intravascularly increases so there is a response to counteract this and increase water loss
