cardiac output

Question 1

cardiac output

equation and 4 determinants

Answer 1

co = HR x SV with SV being volume at beginning of systole in LV to volume at it’s end
1) preload 2) afterload 3) HR 4) contractility

Question 2

what is the importance of the frank-starling

Answer 2

-investigates the fact that the end diastolic volume can stretch the ventricle to a point where it can’t stretch further and this is the cause of heart failure- not enough strength in the ventricle to push it all out

Question 3

what happens with you decrease heart rate

Answer 3

• you increase SV by increasing the amount of time the heart can fill before it ejects (longer diastole and increased end diastolic vol)
• co= SV x HR

Question 4

what happens with you increase heart rate

Answer 4

-decrease the amount of time to fill so decrease diastole, decrease SV and decrease the end diastolic vol
CO = SV x HR

Question 5

on the frank-starling lV pressure vs volume diagram, walk through the whole cycle

Answer 5

(ck slide 12)
A- mitral valve opens building LV volume and pressure leading to …
B- closure of the MV giving us the END DIASTOLIC VOLUME/PRESSURE FOR LV
B to C- give isovolumic contraction (all valves closed)
C- aortic valve opens when ventricle pressure higher than aortic pressure
D- aortic valve closes
D to A- isovolumic relaxation (all valves closed)

Question 6

if you increase peripheral vascular resistance, what happens to strove volume

Answer 6

-decreases because need more pressure to generate enough pressure to overcome the change

Question 7

what do Sarnoff curves prove

Answer 7

that if you increase the heart’s ability to contract, you can increase stroke volume ie. not just heart rate determines SV

Question 8

what does a positive ionotropic agent do to after load

Answer 8

-it shifts the afterload curve up and thus it increases the SV

Question 9

what are some things that can actually cause systolic dysfunction

Answer 9

• myocardial infarction
• ischemia
• dilated cardiomyopathy
• volume overload

Question 10

what occurs in diastolic dysfunction? describe what occurs via frank-starling graph

Answer 10

• the pressure of the LV is increased at B (the end diastolic LV pressure)
• reason is that when the ventricles get bigger, due to hypertrophy, it can’t comply with the filling that needs to be done and so you get this diastolic dysfunction and an upward shift of the line going from A to b

Question 11

what does an increase in blood volume do to the mean systemic filling pressure

Answer 11

-increases it…. opposite is true for loss of bv

Question 12

what does vaso dilation do to the venous return

Answer 12

-increases venous return, not the mean systemic filling pressure

Question 13

what does vasoconstriction do to the venous return

Answer 13

-decreases venous return, not the mean systemic filling pressure

Question 14

how does the sympathetic nervous system effect the cardiac output

Answer 14

-increases Ca permeability in nodal cells to increase the slope of the phase 4 depolarization thus increasing the SA/AV stimulation
-increases permeability of Ca in myocytes causing a chronotropic effect
-norepi also starts glycogenolysis that helps with CO
=increase CO by increasing heart rate (nodal cells) and stroke volume (Ca on myocytes)

Question 15

what does the parasympathetic nervous system do to the cardiac output

Answer 15

• decreases heart rate via Ach on sa and av nodes

thus decreases CO

Question 16

sympathetics-wise, what occurs IN SYSTOLE in the heart during acute exercise?

Answer 16

*systole- increase glycogenolysis to increase energy mobilization and create an enhanced substrate for contraction
-increased cellular permeability to calcium to have more ca during phase 2 and an increased in contractility
-increase in HR and decrease in filling time
INCREASE CO

Question 17

*sympathetics-wise, what occurs IN DIASTOLE in the heart during acute exercise?

Answer 17

• increased HR and decreased filling time-decreased diastole
• enhanced Ca efflux
• increased Ca sequestration
• shorter relaxation time BUT more efficient and faster filling rate

Question 18

what is the equilibrium point

Answer 18

when CO and Venous return are have matching inflow and outflow (cross on CO of Ven return vs RA) graph

Question 19

how do you measure cardiac output

Answer 19

• have oxygen put into pt
• divide that by difference between arterial sample (post lungs) and venous blood at PA

or

-insert dye and see what comes out other end

or thermal dilution

Question 20

what increases CO

Answer 20

• hyperthyroidism
• anemia (more watery so less viscosity holding it back, need more oxygen so increase HR and CO)
• reduced peripheral vascular resistance
• AV shunt

Question 21

what decreases CO

Answer 21

• heart damage- coronary blockage and valve disease
• decreased blood vol
• acute venous dilation and venous obstruction
• decreased tissue mass or tissue metab