Heart 8

Question 1

Shape of the P-V loop segment of the pressure-volume loop

Answer 1

Not a flat line: the afterload is not constant

Question 2

What is the ejection fraction of the ventricle?

Answer 2

EF=[(EDV-ESV)/EDV]*100

Question 3

What is the ejection fraction?

Answer 3

Fraction of blood ejected during one stroke of the heart in relation to the total left ventricular end-diastolic volume

Question 4

What is a normal ejection fraction?

Answer 4

Around 60%

Question 5

Effects of increased preload (with respect to the length-tension relationship)

Answer 5

Increased resting tension and shortening, but no change in maximum tension development

Question 6

Effects of increased preload (with respect to left ventricular pressure and volume)

Answer 6

Increased end diastolic pressure, increased stroke volume

Question 7

`Effects of increased afterload (with respect to left ventricular pressure and volume)

Answer 7

Increased amount of pressure development before ejection, increased energy consumption; decreased stroke volume

Question 8

Effects of contractility (tension/length curve)

Answer 8

Increased contractility shifts curve upward and left since there is more shortening and muscle length does not increase as much, but is more tense

Question 9

Effects of conractility (left ventricular pressure/volume)

Answer 9

Increased ejection velocity and stroke volume

Question 10

What three things should be changed to maximize shortening of muscle or stroke volume in the heart?

Answer 10

Increase preload
Decrease afterload
Increase contractility

Question 11

Definition of heart failure

Answer 11

Condition in which the heart fails to provide cardiac output sufficient to meet the needs of the body

Question 12

Systolic heart failure

Answer 12

Decreased ventricular capacity

Question 13

Diastolic heart failure

Answer 13

Decreased ventricular compliance

Question 14

Three things that will decrease ventricular filling

Answer 14

Increase in end-diastolic pressure
Decrease in ventricular compliance
Loss of atrial function

Question 15

What will decrease ventricular filling time?

Answer 15

Increase in heart rate

Question 16

Three things affecting contractility

Answer 16

Sympathetic nerve activity
Drugs (inotropic agents, like digitalis)
Disease

Question 17

Two things that will increase ventricular outflow tract resistance

Answer 17

Valvular stenosis; subaortic stenosis

Question 18

Dilated heart has what effect on the heart?

Answer 18

Heart stretches, producing higher wall tension and larger afterload

Question 19

Heart rate’s affect on contractility and refill time

Answer 19

Increases contractility, decreases time for ventricular filling

Question 20

Factors influencing ventricular rate

Answer 20

Pacemaker function, AV nodal conduction, and ventricular arrhythmias