2.3

Question 1

why is it known as a left ventricular pressure volume loop

Answer 1

graph forms a complete loop, representing one complete cardiac cycle, which (typically) ends at same pressures and volumes at which it began

Question 2

what are plotted on same graph

Answer 2

a theoretical passive pressure-volume relationship and an active pressure-volume relationship

Question 3

what do passive pressure-volume and active pressure-volume relationships reflect

Answer 3

the passive and active length-tension relationships of strips of cardiac muscle as they would be reflected in the whole heart

Question 4

during each cardiac cycle

Answer 4

the heart operated within the limits imposed by these relationships

Question 5

what does the passive or diastolic P-V relationship determine

Answer 5

the relationship between pressure and volume in the intact heart during diastole

Question 6

example of diastolic P-V relationship

Answer 6

during diastole in the LV, pressure in LV increases, stretching LV (and thus increasing sarcomere length)

Question 7

resulting relationship between pressure and volume reflect

Answer 7

length-tension relationship of the left ventricular cells

Question 8

in diastole P-v relationship how is relationship expressed graphically

Answer 8

substitution of ventricular systolic pressure for force and of end diastolic ventricular volume for myocardial resting fiber (sarcomere) length

Question 9

why is the pressure-volume curve in diastole initially quite flat (compliant)

Answer 9

indicating that large increases in volume can be accomodated with only small rises in pressure

Question 10

systolic pressure development on p-v relationship is

Answer 10

considerable at the lower filling pressures

Question 11

the ventricle becomes … with greater filling

Answer 11

much less distensible

Question 12

how is the ventricle becoming less distensible with greater filling shown

Answer 12

sharp rise of the diastolic curve at large intraventricular volumes

Question 13

in intact heart, what is peak force attained at

Answer 13

filling pressure of 12mmHg

Question 14

what is the sarcomere length at intraventricular diastolic pressure of 12mmHg

Answer 14

2.2 um

Question 15

the resistance to stretch of the myocardium at high filling pressure probably resides in

Answer 15

the noncontractile constituents of the tissue (connective tissue) and serve as a safety factor protecting against overloading of the heart in diastole

Question 16

usually ventricular diastolic pressure is

Answer 16

0 to 7 mmHg

Question 17

usually average diastolic sarcomere length is

Answer 17

about 2.2 um

Question 18

where does normal heart operate on Frank-starling curve

Answer 18

ascending portion

Question 19

the upper curve represents the theoretical

Answer 19

peak presssure that could be developed by the ventricle during systole at each degree of filling

Question 20

what does the upper curve arise from

Answer 20

the frank-starling relationship of initial myocardial fiber length (or initial volume) to peak isovolumic force (or pressure) development by the ventricle

Question 21

experimentally the P-V relationship can be obtained by

Answer 21

closing off the aorta and thereby forcing the LV of an isolated heart to contract isovolumically

Question 22

in case of LV contracting isovolumically

Answer 22

the ventricle would develop the max pressure which it is capable, given its initial volume

Question 23

contractility represents the performance of the heart at a given

Answer 23

preload and afterload, and it depends on teh state of the excitation-contraction coupling processes within cells

Question 24

contractility can be augmented by

Answer 24

certain drugs such as norepinephrine and digitalis, and by an increase in contraction frequency (tachycardia)

Question 25

positive inotropic effect

Answer 25

increasse in contractility

Question 26

the increased contractility produced by intervention is reflected by

Answer 26

incremental increases in developed force and velocity of contraction

Question 27

a reasonable index of myocardial contractility in the contracting heart can be obtained

Answer 27

from the contour of ventricular pressure curves

Question 28

a hepodynamic heart is characterized by

Answer 28

elevated EDP, and slowly rising ventricular pressure, and a somewhat reduced ejection phase (curve c)

Question 29

a hyperdynamic heart (such as one stimulated by norepineophrine) shows

Answer 29

reduced EDP, fast rising ventricular pressure, and a brief ejection phase (curve B)

Question 30

max dP/dt

Answer 30

change in pressure over time
greater the change in pressure over shorter change in time, greater the contractility

Question 31

slope of the ascending limb of the ventricular pressure curve indicated

Answer 31

the maximal rate of force development by the ventricle (max rate of pressure change with time)

Question 32

the slope is maximal (greater dP/dt) during

Answer 32

the isovolumic phase of systole (before ejection)

Question 33

at any given degree of ventricular filling, the slope provides

Answer 33

an index of the initial contraction velocity, and hence contractility

Question 34

the contractile state of the myocardium can be obtained from the

Answer 34

max velocity of blood flow in the ascending aorta during the cardiac cycle

Question 35

the ejection fraction

Answer 35

EDV-ESV/EDV

Question 36

The p-v loop is a

Answer 36

time-independent representation of the passive and active length-tension relationship of the LV

Question 37

Contractility is defined by

Answer 37

dP/dt and characterizes the dynamic state of the heart