Cardiovascular Performance

Question 0

What is preload in the normal heart?

Answer 0

Preload is the end-diastolic volume of the heart

Question 1

What is the preload force?

Answer 1

The force applied to a muscle before the onset of contraction

Question 2

What is the driving force of ventricular contraction?

Answer 2

It is the preload

Question 3

What is the Frank Starling curve?

Answer 3

A graph that plots end-diastolic volume against ventricular pressure.
It has one convex curve on top representing peak systolic pressure and a concave sort of curve on the bottom representing end diastolic pressure. The area between the two is the strength of ventricular contraction which increases with volume

Question 4

What principle is behind the preload being the driving force of ventricular contraction?

Answer 4

The length-tension relationship of muscle which shows that with an increase in length there is an increase in tension due to the increase of cross-bridges formed between the contractile muscle elements

Question 5

What is CVP?

Answer 5

It is the pressure in the superior vena cava and is equivalent to the right atrial pressure and (in the absence of tricuspid valve disease) it is also equal to right ventricular end diastolic pressure

Question 6

What is pulmonary artery wedge pressure?

Answer 6

It is equivalent to left atrial pressure and left ventricular end diastolic pressure in the absence of mitral valve disease

Question 7

What is the equation for ventricular compliance?

Answer 7

Change in EDV/Change in EDP

Question 8

How does compliance influence EDV?

Answer 8

If there is a decrease in compliance, the EDP will be overestimated

Question 9

What is the change in EDP in diastolic heart failure?

Answer 9

Higher

Question 10

What is the change in EDP in systolic heart failure?

Answer 10

High

Question 11

What is the EDV in systolic heart failure?

Answer 11

High

Question 12

What is the EDV in diastolic heart failure?

Answer 12

Low EDV (can’t distend to fill)

Question 13

What is the EF in systolic heart failure?

Answer 13

Low

Question 14

What is the EF is diastolic heart failure?

Answer 14

Normal

Question 15

Where should the transducer be for an accurate CVP reading?

Answer 15

At the level of the right atrium (mid axillary line and fourth intercostal space supine)

Question 16

Where is the level of the right atrium when a person is sitting up to 60 degrees?

Answer 16

5 cm below the sternal angle

Question 17

When should CVP and wedge pressure be measured?

Answer 17

At the end of expiration

Question 18

Why should CVP and wedge pressure be measured at the end of expiration?

Answer 18

Because that is when the intrathoracic pressure equals zero, so the measure of transmural pressure will be accurate since it is the difference between the intra vascular pressure and the intrathoracic pressure

Question 19

What is the influence of intrathoracic pressure on CVP.

Answer 19

May cause a change in the measured pressure of the veins with respiratory variations but not in ventricular filling.
Take CVP at lowest point of tracing during ventilation
Take CVP at highest point with normal breathing

Question 20

What does peep do to the cardiac filling pressures at end expiration?

Answer 20

Falsely elevates them because the intrathoracic pressure does not equal zero at the end of expiration

Question 21

What is afterload?

Answer 21

The force applied to muscle after the onset of contraction

Question 22

What is afterload in the normal heart?

Answer 22

The peak tension developed across the walls of the ventricles during systole

Question 23

What is the law of Laplace?

Answer 23

Wall tension = pressure X radius / 2 X wall thickness

Question 24

What are the components of afterload?

Answer 24

Preload
Pleural pressure
Vascular impedance
Peripheral vascular resistance