cardio 4 Flashcards
what is afterload
the resistance that the heart has to pump against
what determines afterload
arteriolar pressure and peripheral resistance
what is preload
stress on ventricular wall before systole
what is equal to preload
left ventricle end-diastolic pressure
what is the formula for cardiac output
Stroke volume x heart rate
what should cardiac output ideally be equal to
venous return
which is larger, venous capacitance or arterial capacitance
venous
what is cardiac output proportional to
rate and force of contraction
what are the two regulations of cardiac performance
intrinsic and extrinsic
what relationship guides the intrinsic regulation of cardiac performance
frank starling
what is the frank starling relationship
force of contraction is proportional to initial fiber length
what is a good measure of initial fiber length
LVEDP
the strength of heart pumping is dependent on
the amount of blood
in heart failure, what is the issue
more blood in heart does not increase the force of contraction
what is involved in the extrinsic regulation of the heart
sympathetic parasympathetic baroceptor reflex
what occurs if BP increases
carotid sinus baroceptors, CNS, increased vagal flow, decrease HR
what occurs if BP decreases
less carotid sinus baroceptor to CNS, decrease in vagal outflow, increase in sympathetic outflow, increase heart rate and vasoconstriction
what are the 3 causes of heart failure
infarct, ischemia, increased pressure or volume load
what are signs of heart failure
reflex tachycardia
enlarged heart
oedema
dyspnea
elevated venous pressure
swollen ankles
swollen neck veins
how does failure to pump affect sympathetic outflow?
how does this effect glomerular filtration?
increased
decreased
what does enhances sympathetic outflow lead to
circulatory congestion
what causes enlarged neck veins
pooling of blood in venous side of circulation
how does sympathetic outflow affect venous pressure
increased
what does increased venous pressure result in
fluid expelled from blood = edema and dyspnea
what is the term for an enlarged and inefficient heart
maladaptive hypertrophy
what are the 3 key ways to treat heart failure
enhance contracitilty
reduce fluid intake and increase fluid loss
reduce cardiac workload
what cardiac glycoside is useful in treating HF
digoxin
what are the 3 benefits of using cardiac glycosides in chronic EF
positive inotropic
negative chronotropic
edema reduced
is arterial BP preserved with the use of cardiac glycosides
yes
where do cardiac glycosides have indirect effects
supraventricular tissue
baroceptors
vagal tone
where do cardiac glycosides have direct effects
purkinje fibres
ventricular myocardium
where do cardiac gylcosides have effects
SA AV purkinje and ventricles
how do cardiac glycosides effect vagal outflow
increased
how do cardiac glycosides affect purkinje fibres
automaticity anf excitabilty
how do cardiac glycosides affecrt ventricles
(+ ) INOTROPIC
how can cardiac glycosides cause problems in the AV node
AV block
what are catecholamine positive inotropic agents?
dopamine and dobutamine
what receptor for dopamine and dobutamine act on
beta 1
what effect do phosphodiesterase inhibitors
positive inotropic
how do phosphodiesterase inhb=itors increase contracility
inhibit breakdown of cAMP, increased Ca through L, increased contractility
what are the two phosphodiesterase inhibitors
amrinone and milrinone
what is one more class of drug that has positive inotropic effects
changes to angiotensin II
what is the SGLT2 inhibitor of interest
empagliflozin
