Lecture 2: Cardiac and Vascular Function:

Question 1

Wiggers Diagram

Answer 1

Learn

Question 2

What happens to ventricular volume at the VE/IVR time period and why?

Answer 2

Ventricular volume becomes negative as their is negative flow (backwards) because E aorta is less than E ventricle. (some back flow)

Question 3

How can the phases filling and ejection be divided in the wiggers diagram?

Answer 3

Into rapid and reduced time periods.

Question 4

What does an echocardiogram show in terms of ventricular wall thickness during the cardiac cycle?

Answer 4

Ventricular wall thickness varies between systole and diastole.

Question 5

What sort of motion do the atrioventricular valves reform during ejection?

Answer 5

A ripple like effect as blood is ejected.

Question 6

What is the general difference between left and right ventricles in terms of pressures and valve sequences?

Answer 6

Pressure is lower in the right ventricle therefore timing is slightly different.

Question 7

What does the RV pump blood through?

Answer 7

The low resistance lungs

Question 8

What does the LV pump blood through?

Answer 8

The entire system circuit

Question 9

Describe the timing of the mitral and tricuspid valves

Answer 9

The tricuspid valve opens before the mitral

The mitral valve closes just before the mitral valve

i.e LV has less filling time

Question 10

Describe the timing of the aortic and pulmonary valve

Answer 10

The pulmonary valve opens before the aortic valve

Aortic closes before the pulmonary valve

i.e LV has less ejection time

Question 11

Why do the AV and semilunar valves have different timings between the left and right sides of the heart?

Answer 11

RV valves open sooner and close later because:

• Differences in electrical activation and pressures (takes less time to generate pressure in the RV.)

Question 12

Describe the pressure of the RA

Answer 12

~3mmHg

Question 13

Describe RV pressures

Answer 13

(s) 18mmHg

d) 0mmHg (i.v.r

Question 14

Describe PA pressures

Answer 14

(s) 18mmHg

(d) 12mmHg

Question 15

Describe PA wedge pressures (cap)

Answer 15

8mmHg average

Question 16

Describe LA pressures

Answer 16

8 mmHg average

Question 17

Describe LV pressures

Answer 17

(s) 130 mmHg

(d) 0 mmHg

Question 18

Describe the systemic aortic pressure

Answer 18

(s) 130 mmHg

(d) 75 mmHg

Question 19

Whats the components of CO?

Answer 19

CO = HR x SV

Question 20

What are the determinants of SV?

Answer 20

• Preload
• Afterload
• Ionotropy

Question 21

How does HR affect CO?

Answer 21

HR directly influences CO and also indirectly acts via the determinants of SV particularly preload and inotropic state.

Question 22

Describe the main factors of CO;

Answer 22

CO = SV x HR

SV = EDV - ESV

EDV influenced by Preload
ESV influenced by Afterload and Inotropic state

HR influences preload and Inotropic state

Question 23

How does HR influence preload?

Answer 23

Reduced preload by reducing the time of ventricular filling therefore redoing SV

Question 24

How does HR influence inotropic star?

Answer 24

HR relates to the force frequency relationship that plays a minor role in ionotropy.

Question 25

What are the relaxants graphs for ventricular performance?

Answer 25

``` PV loop Ejection Fraction Peak dP/dT Ventricular function curve CO/VR MRAP curve a.k.a guyton VP graph ```

Question 26

What does the linear line on the P-V graph represent?

Answer 26

Potential pressure of the chamber This is never achieved as the valves open once threshold pressure is reached

Question 27

Potential pressure increases linearly with and represents what relationship?

Answer 27

EDV This clearly reflects the force-sarcomere length relationship.

Question 28

When is the length tension relationship for sarcomeres exhibited?

Answer 28

During isometric or fixed length muscle contraction

Question 29

Why can sarcomeres generate varying levels of tension at a fixed resting length?

Answer 29

Inotropic state accounts for this and means that sarcomeres can generate more force from an unchanged resting length

Question 30

What can be obtained from a P-V loop?

Answer 30

The ventricular work performed each cardiac cycle (stroke work) SW = SV x TPR (P xV)

Question 31

What are the four determinants of cardiac performance?

Answer 31

Preload Afterload Inotropic state Chronotropic state

Question 32

What is preload?

Answer 32

The tension produced by the degree of stretch of myocyte filaments - L-T relationship - Length dependant activation (a) - Increased stretch increases troponin C sensitivity to Ca (b) - Increased stretch increases the activation of stretch sensitive Ca channels

Question 33

What is Afterload?

Answer 33

The pressure of which the ventricle must pump against Increased in hypertension.

Question 34

What is inotropic state?

Answer 34

The degree of activation of contractile proteins by Ca in the myocyte sarcomere.

Question 35

What influences ionotropy?

Answer 35

- AP plateau phase (excitation contraction coupling) - External ion gradient (NCX and Na/K ATP ase transporters) - Force frequency relationship - ANS - Drugs \ Caffiene, inhibits PDE prevents cAMP breakdown \ Digoxin, cardiac glycoside inhibits Na/K ATPase, NCX reverses \ Verapamil, Ca channel inhibitor - Heart failure

Question 36

How does chonrotropic state influence CO?

Answer 36

- HR increases, CO increases - Force frequency relationship - High HR reduces SV, decreasing CO

Question 37

What does the equilibrium between CO and VR represent on the venous return/ CO curve?

Answer 37

This is the steady state equilibrium at which the heart works with some transient deviations. The MRAP at this point = mean systemic filling pressure

Question 38

What are normal values for Ejection Fraction?

Answer 38

``` Rest = ~50% Exercise = ~85% ```

Question 39

What are the two types of ventricular function curves?

Answer 39

Stroke volume vs preload | Stroke Work vs preload

Question 40

Why is stroke volume vs preload not used?

Answer 40

Stroke volume is difficult to measure and not independent of afterload

Question 41

Why is stroke work vs preload good?

Answer 41

Not susceptible to changes in after load If MAP increases, SV decreases keeping SW constant.

Question 42

What does a ventricular function curve represent?

Answer 42

Summery of the P-V and frank-starling relations

Question 43

A family of curves on the ventricular function curve represents?

Answer 43

Different inotropic states

Question 44

What does a ventricular function curve account for?

Answer 44

Preload After load Inotropic state

Question 45

Describe how LA pressure is obtained?

Answer 45

A fluid filled catheter with a ballon tip is passed through the femoral vein via the heart into the PA. Ballon inflates and measures the pre-capillary pressure which is representative of the LA pressure mostly... This can measure both pulmonary artery pressure and pulmonary wedge pressure.

Question 46

What are two methods of CO measurement?

Answer 46

Ficks Method | Thermodilution

Question 47

What is Ficks method?

Answer 47

Based on conservation of mass. Using a known quantity of bolus i.e O2 injected prior to the heart and over time the concentration is measured down stream. The rate of dilution is representative of CO

Question 48

What are the prerequisite of ficks method?

Answer 48

1) Mixed venous blood (whole body average of O2 concentration 2) All the measured substance must be collected, none lost 3) Steady state must exist, Ventilation and CO

Question 49

What is thermodilution?

Answer 49

Using this indicator dilution technique. - Cold saline is used as indicator - Measured downstream temperature change to indicate the rate of dilution and thus CO

Question 50

What are the advantages of thermodilution?

Answer 50

- No arterial puncture needed - No toxicity - Recirculation is negligible / ignored

Question 51

Check 205 notes

Answer 51

Now