acute heart failiure Flashcards
define heart failiure
inability to provide adequate cardiac output to support tissue needs or doing so at expense of an increased filling pressure
what are the average pressures in normal circulation, systemic veins, right ventricle, pulmonary artery, pulmonary veins, aorta
5,30,8,100
in right heart failure where does the pressure change
blood collects in RV so JVP is raised CVP increases, systemic vein pressure increases. only place where pressure changes
where does right sided heart failure cause ooedma
ankles
why does increased bp in systemic veins during right sided heart failiure not backup into ateries
but circulatory reflexes tend to maintain mean pulmonary
artery pressure, left-ventricular end-diastolic pressure and aortic pressure at virtually
normal levels.
where does the pressure change in left sided heart failure
aorta is maintained due to circulatory reflexes, the whole pulmonary system increases in pressure and right ventricle is put under stress. eventually right side will fail too
what is it called when both the right and left side of the heart are failing
congestive heart failiure
what are the 3 main causes of heart failure
pressure overload, volume overload, contractile dysfunction
what factors could contribute to pressure overload on the heart
hypertension, aortic stenosis
what factors could contribute to volume overload on the heart
aortic or mitral valve regurgitation
what factors could contribute to contractile dysfunction on the heart
ischaemic heart disease, pregnancy , congenital cardiomyopathies
state the law of laplace and rerrange it for the heart
p equals 2sw divided by r
for heart
s equals p times r divided by 2w
for a fixed wall strength a smaller heart can generate more pressure than a larger one true or false
true due to laplace law
describe what happens in the compensated and decompensated stages of heart faliure with regards to pressure overload
During severe aortic stenosis or hypertension, the acute effect is an
increase in wall stress. The heart responds by thickening its wall so that, during the
compensated phase, wall stress is normalised by concentric hypertophy. However, when
dilation (sometimes referred to dilatation) develops, R increases and wall stress rises. This has
a number of deleterious consequences which will be discussed later
Cardiomyopathy: Note the contrast between the two types of cardiomyopathy in the initial
phases.
Compensated concentric hypertrophy leads to a normal relation between wall thickness
and wall stress, whereas the development of dilation leads to myocardial failure. In dilated
cardiomyopathy, there is an initial compensated phase when hypertrophy is proportional to the
degree of chamber enlargement, followed by excessive chamber enlargement and inadequate
hypertrophy.
