1 - Cardiac Fn Overview Flashcards
3 key determinants of fiber shortening
preload, afterload, contractility
2 reasons the beat following a premature beat is stronger than normal
increased preload, better contractility
which events occur first and last during diastole?
first - isovolumic relaxation
last - atrial kick
how do the apex and base move relative to each other during heartbeat?
apex moves up towards base and closer to chest wall (PMI), base stays still pretty much
how does wall stress indirectly affect fiber shortening?
affects afterload > affects fiber shortening
what is the key determinant of cardiac performance?
preload
starling’s law
more tension due to greater preload > more forceful contraction
2 key determinants of stroke volume
fiber shortening and ventricular size
4 determinants of preload
intravascular volume
venous return
atrial contraction
pericardial function
how does mitral regurgitation improve cardiac performance?
decreased afterload due to low resistance leading back into the left atrium
LaPlace law
wall stress = P*R/(2h)
h is wall thickness
eccentric vs concentric hypertrophy
eccentric has increased wall stress in results in dilated thin walls. Caused by volume overload
concentric has decreased wall stress and a thickened wall. Caused by pressure overload
difference between contractility and ejection fraction
contractility is load independent, EF is load dependent
positive inotropic effect
cardiac performance improves with greater contractility provided preload and afterload don’t change
relative durations of diastole and systole
diastole is twice as long as systole (2/3 of cycle)
