Cardiac Performance

Question 1

Cardiac Output eqn

Answer 1

CO = HR x SV

heart rate x stroke volume

Question 2

Stroke Voulme eqn

Answer 2

SV = EDV - ESV

Question 3

Regulation of EDV and ESV determine what?

Answer 3

cardiac performance

Question 4

3 regulators of Cardiac Performance

Answer 4

1) preload
2) afterload
3) contractility

Question 5

Preload is?

Answer 5

Vol of blood inside and tension of heart chamber before contraction.

Wall stress at end diastole

Question 6

Frank-Starling Law

Answer 6

↑ stretch = ↑ contraction force

stretch depends on preload

Question 7

Summation and recruitment do not occur in which type of mm?

Answer 7

cardiac

Question 8

Cardiac mm does or does not fxn at the peak of length-tension?

Answer 8

Does not

Question 9

Stretch causes ↑ tension how? (3)

Answer 9

1) overlap of think/thin filaments (lines myosin up with correct location on actin)
2) ↑ Ca2+ sensitivity (stretch of troponin ↑ desire to bind Ca2+)
3) ↑ Ca2+-induced Ca2+ release by activating stretch-activated Ca2+ channels

Question 10

Stiffness of cardiac mm affects tension how? (2)

Answer 10

1) high resting tension
2) small ∆ in length produces large ∆ in tension

Question 11

↑ in LV End Diastolic Fiber Length will ↑ what?

Answer 11

Stroke Volume

Question 12

Preload influenced by? (3)

Answer 12

1) vent filling time
2) vent compliance
3) atrial systole

Question 13

Preload dictates?

Answer 13

vent filling pressure

Question 14

↑ heart rate affects vent filling time how?

Answer 14

↓ length of reduced filling phase = ↓ EDV and ↓ SV

Question 15

Mechanism that preserves SV when HR ↑?

Answer 15

Contractility (via sympathetic stim)

Question 16

Compliance is? Compliance eqn?

Answer 16

Heart’s ability to distend under pressure.

C=∆vol/∆pressure

Question 17

Inability for Compliance leads to?

Answer 17

↓ ED fiber length, ↓ SV

Question 18

Atrial Systole fills vent how much at rest?

Answer 18

10-20%

Question 19

Atrial Systole most important for?

Answer 19

↑ HR (e.g. exercise).

Contributes ~40% of SV

Question 20

Afterload is?

Answer 20

Mean Aortic Pressure

Pressure req’d for vent to eject blood

Question 21

Afterload affected by? (3)

Answer 21

Factors that oppose vent ejection:

1) Peripheral Resistance
2) Blood Viscosity
3) Valvular Dysfxn (e.g. stenosis, insufficiency)

Question 22

↑ Afterload means ↑ pressure needed to do what?

Answer 22

pressure req’d to eject blood

Question 23

Mean Aortic Pressure eqn

Answer 23

MAP = Pdia + 1/3 (Psys-Pdia)

Question 24

Pressure-Vol loops provide info about what?

Answer 24

Vent performance

Question 25

4 phases of Press-Vol loop?

Answer 25

1) Isovolumetric contraction (contr against closed chamber)
2) Vent ejection
3) Isovol relaxation
4) Vent filling

Question 26

Isovolumetric Contraction set up

(Pressure-Volume Loop)

Answer 26

Mitral and Aortic valves closed

Fixed vol of blood (vol is constant)

Huge LVP ↑

Question 27

Vent Ejection set up

(Pressure-Volume Loop)

Answer 27

Mitral valve closed

LVP > aortic pressure Ѧ aortic valve opens

LVP stays ↑ thru contraction

LV vol ↓ significantly

Question 28

Isovolumetric Relaxation set up

(Pressure-Volume Loop)

Answer 28

Systole ends Ѧ vent relaxes

LVP pressure < aortic pressure

Ѧ aortic valve closes

Closed valves = fixed ESV

Question 29

Vent Filling set up

(Pressure-Volume Loop)

Answer 29

(Passive filling during vent and atrial diastole)

Myocardium relaxed LV press < atrial press

Mitral valve opens

Vent fills (passive & atrial contraction)

L vent vol ↑ back to EDV

Question 30

What change can be made in P-V Loop to ↑ Preload?

Answer 30

↑ venous return -> ↑ LV filling and ↑ stretch

Ѧ ↑ SV (Frank-Starling mechanism)

Question 31

What change can be made in P-V Loop to ↑ Afterload?

Answer 31

↑ aortic press (HTN) -> LV must eject against ↑ aortic press

Ѧ LV press must ↑ even more ->

aortic valve opens later and closes sooner

Ѧ ESV ↑, SV ↓

Question 32

What change can be made in P-V Loop to ↑ Contractility?

Answer 32

Symp Stim -> ↑ LV press

Ѧ LV ejects more blood during systole (↑ SV)

Ѧ ESV ↓

Question 33

Compliance allows vent to what?

Answer 33

Allows vent to have large ∆ in vol w/ small ∆ in pressure.

Question 34

Cardiac performance dependent on regulation of what two things?

Answer 34

EDV and ESV

Question 35

Pressure Volume Loop

Answer 35