Contractility & Cardiac Output Flashcards
Define SV and its equation
The vol of blood ejected by LV in a single beat
SV = EDV - ESV
Define EF and its equation
Fraction of the EDV ejected with each SV
EF = SV/EDV
What is a normal EF
55%
Define CO and its equation
Total vol. ejected by the ventricle per unit time
CO - SV x HR
An increase in afterload means what in terms of velocity of contraction
Decreased velocity and more ESV
Define the FSL
Col. of blood ejected by the LV is = to the vol. present in the ventricle at the end of diastole (EDV)
An increase in VR means what
An increase in EDV and an increase in SV and pressure on LV
Positive inotropic stimulation means what in terms of SV and LVEDV
Increased SV and increased EDV
What is the most accurate definition of EDV? What is another way of determining this
The amount of wall tension in LV just before contraction
Another way is the pressure in the chamber just before contraction
Increased VR means what in terms of EDV and pressure and SV
Increased EDV and increased P and increased SV
What happens in increased after-load
LV must generate higher pressure in IV Contraction to overpower Ao. Pressure and open AoSLV
LV become hypertrophic which leads to heart failure and increased ESV
Does EDV increase with increased contractility
Yes
Cardiac work is directly proportional to what
Pressure work
Define stroke work and give the equation
Work done per each beat
SW = SV x AoP
Define cardiac minute work and give the equation
Work per unit time
CMW = CO x AoP
CO is considered external work while AoP is considered internal (pressure) work
Myocardial O2 consumption correlates directly with what
CMW
Pressure work (AoP) is what compared to external work
More costly in O2 demand than in CO
So we burn more O2 in OV Contraction than in actual ejection of blood from the heart
How would Ao. Stenosis affect myocardial O2 demand
Ao. Stenosis means increased Aop which means an increased O2 demand
What receptor innervates the myocytes for sympathetic innervation
B1
The parasympathetic N.S innervates which part of the heart only
The atria
Atrial systole takes place when in the EKG
IV Contraction
Rapid Ven. EJ
IV Relaxation
Rapid Vent Filling
PR
QRS with S1
ST segment
Post T wave with S2
Way post T wave
A decreased mean systolic pressure means what in terms of CO
A decreased CO
What is indicated at the equilibrium point
CO = Preload = EDV = VR
At extremely high pressures, what happens to CO
It levels off and does not increase anymore
Define the mean systemic pressure
RA pressure where VR = 0
What two things influence MSP
Blood volume
Distribution of blood between unstressed and stressed volumes
If Blood Vol is higher than normal, unstressed vol. is already “full”, so what happens to remaining volume and what does this mean for MSP and intersection point
Shifted to the stressed volume
MSP is increased, and intersection point shifts R causing a higher CO
If blood volume is decreased, what does this mean for the stressed and unstressed volume and the equilibrium
A decreased MSP and a shift left, causing a decreased CO
What does a positive and negative inotropic effect cause in terms of the equilibrium and the MSP and CO and pressure
Positive:
Left shift due to increased contraction and thus an increased SV
Negative:
Right shift with a decreased SV
What happens in cardiac failure in regards to inotrpoy, compliance, and Blood volume
Decreased inotropy which means decreased vascular compliance, but increased blood volume and increased resistance
