Cardiac Mechanics - Pressure-volume relationships

Question 1

ESP

Answer 1

aortic pressure = afterload

Question 2

EDP

Answer 2

venous pressure = preload

Question 3

Preload

Answer 3

load on heart during diastole (before contracting), RAP, CVP, Pv, EDV, EDP

Question 4

Afterload

Answer 4

load on heart during systole (while contracting), TPR, MAP

Question 5

Preload (EDP)^

Answer 5

ESV constant, SV^, CO ^

Question 6

Frank Starling law

Answer 6

as the heart fills up with more blood during diastole (EDV^), it contracts harder and pumps out more blood during systole –> SV^

Question 7

Afterload (ESV/ESP^)

Answer 7

SV decreases and CO decreases

Question 8

Contractility

Answer 8

Depends upon intrinsic strength of the muscle [Ca++] inside cell
Depends upon the total amount of heart muscle which is fixed in the short term but can change with aerobic exercise
Increases with sympathetic stimulation

Question 9

Ejection fraction ^

Answer 9

(SV/EDV)^

Question 10

At any given EDP and ESP

Answer 10

as contractility ^, SV^

Question 11

Stroke work

Answer 11

deltaP * deltaV = work performed by the heart to eject a volume of blood (stroke volume) at a specific pressure (mean arterial pressure)

Question 12

Total energy required

Answer 12

External work + Internal work

Question 13

External work

Answer 13

SV * MAP

Question 14

Internal work

Answer 14

1/2 * MAP * ESV

Question 15

Efficiency

Answer 15

work accomplished (SW)/ total energy used

Question 16

As PV area increases

Answer 16

need more O2

Question 17

During systole

Answer 17

Pcoronary - Pheart = 0

Question 18

Flow in coronary arteries is

Answer 18

greatest during diastole, and very low during systole

Question 19

If aortic valve leaks

Answer 19

no isovolumic contraction, LVV ^, always leaking blood from aorta into ventricles

Question 20

Aortic stenosis

Answer 20

valve doesn’t completely open –> increase velocity in order to get blood out through smaller opening, large pressure drop across the valve, must ^LVP to account for pressure loss

Question 21

Cardiac output

Answer 21

= venous return

Question 22

As preload (EDP)^

Answer 22

stretch the ventricular muscle so that [Ca++]^ resulting in a stronger contraction

Question 23

As afterload (ESP)^

Answer 23

heart needs to pump against a higher pressure to eject. Valves close sooner, leaving more blood in the heart (ESV^ so SV decreases)

Question 24

Vascular system affects

Answer 24

EDP and ESP and consequently CO