11 terms

CO & cardiac cycle

With a-flutter, a-fib, or junctional rhythms a portion of the left ventricular filling is lost, what % of LVEDV is normally contributed by atrial contraction (kick)?
Passive diastolic filling accounts for 75% of left ventricular filling, with the atrial contraction causing an additional 25% filling of ventricles.
Define EF
The ratio of SV (end-diastolic volume minus end-systolic volume) to end-diastolic volume. EF = SV/EDV = (EDV-ESV)/EDV
Normal EF range
0.6-0.8 or 60-80%
What are the 2 determinants of CO?
What is cardiac index (CI)
CO divided by body surface area (BSA) in meters squared
Normal CI range
2.4-4.0 L/min/m2
When the ventricle fills more during diastole, more blood is ejected during systole. Whose law is this?
Starling's law of the heart relates ventricular filling during diastole to what?
To the amount of blood ejected during systole. The greater the ventricular filling during diastole (the greater the preload) the greater the quantity of blood pumped into the aorta during systole.
Describe the process that causes ventricular myocyte relaxation
Ventricular myocyte contraction requires increased intracellular Ca. For the myocyte to relax, intracellular Ca must be reduced back to resting levels. Ca is sequestered in the SR thru energy dependent processes.
Describe where isovolumetric relaxation occurs on the left ventricular pressure volume loop.
Occurs from closure of the aortic valve to opening of the mitral valve
Describe where isovolumetric contraction occurs on the left ventricular pressure volume loop.
Occurs from closure of the MV to the opening of the AV.