Cardiac Performance I

Question 1

Stages to the cardiac cycle. What is the state of the valves at each stage?

Answer 1

1. Isovolumic relaxation

• AV valves closed
• Semilunar valves closed

2. Inflow: (Ventricular filling)

• AV valves open
• Semilunar valves closed

3. Inflow: (Ventricular filling with Atrial systole)

• AV valves open
• Semilunar valves closed

4. Isovolumic contraction

• AV valves closed
• Semilunar valves closed

5. Ejection: Ventricular ejection

• AV valve closed
• Semilunar valves open

Question 2

Which factors affect preload?

Answer 2

• Amount and rate of venous return
• Exercise
• Increase in blood volume
• Sympathetic activity

Question 3

Preload is affected by which two cardiac pumps? How?

Answer 3

• Respiratory Pump
  
  • ​Intrapleural pressure decreases during inspiration and abdominal pressure increases, squeezing local abdominal veins, allowing thoracic veins to expand and increase blood flow towards the right atrium.
• Skeletal muscle pump
  
  • ​In the deep veins of the legs, surrounding muscles squeeze veins and pump blood back towards the heart. This occurs most notably in the legs. Once blood flows past valves it cannot flow backwards and therefore blood is “milked” towards the heart.

Question 4

S1 heart sounds corrrespond to the closing of which valves?

Answer 4

Tricupsid and mitral

Question 5

S2 heart sounds corrrespond to the closing of which valves?

Answer 5

Aortic and pulmonary

Question 6

What does S3 correspond to and when is it heard?

Answer 6

S3 correspons to the passive filling of the ventricle, heard if the ventricle is full or if the circulation is hyperdynamic

Question 7

What does S4 correspond to?

Answer 7

The atrial systole against a stiff ventricle

Question 8

The delay of T1 (clsing of tricupsid valve) even more than normally causes the split S1 which is heard in a _____________.

Answer 8

right bundle branch blockage

REMEMBER: The mitral valve typically closes slightly before the tricupsid valve. But a significant difference can cause a split sound that is heard in right bundle branch blockage.

Question 9

A split S2 has a _________ pitch.

Answer 9

High

*Split S2 is when the aortic valve closes substaintally before the pulmonary valve

Question 10

S3 sound has a ________ pitch.

Answer 10

Low

Question 11

Stroke work

Answer 11

The work done by the ventricle to eject a volume of blood (i.e., stroke volume). The force that is applied to the volume of blood is the intraventricular pressure. Therefore, ventricular stroke work can be estimated as the product of stroke volume and mean systolic pressure during ejection.

Question 12

Frank- Starling Law

Answer 12

The stroke volume of the heart increases in response to an increase in the volume of blood in the ventricles, before contraction, when all other factors remain constant.

Question 13

What is the diffence between the stroke volume on the right and left sides of the heart?

Answer 13

The only difference from left and right, the left is 8x higer than right in terms of pressure. You eject the same volume, but the left has to eject from higher pressure than the right. Your left is ejecting against a high peripheral restiance.

Question 14

Indicators of cardiac performance

Answer 14

• Load-dependent
  
  • ​Indicators of performance change as you change the end diastolic volume
• Load- independent
  
  • ​End systolic volume, so contractility doesn’t deoend in the load at all

Question 15

Examples of indicatiors of cardiac performance that are load-dependent.

Answer 15

Stroke volume

Cardiac output

Ejection fraction

Maximal rate of pressure

Question 16

Examples of indicatiors of cardiac performance that are load-independent.

Answer 16

End-systolic elastance (measure of contractility)

Pre-load recruitable stroke work

Question 17

Normal ejection fraction

Answer 17

55-65%

*Stroke volume/ end diastolic volume x100

Question 18

Cardiac index

Answer 18

Cardiac output/ BSA

*BSA is body surface area in m²

Question 19

Determinants of cardiac performance

Answer 19

1. Loading conditions: Preload, afterload, Frank-Starling mechanism
2. Heart Rate
3. Contractile state

Question 20

What is the relationship between pressure and EDV in patients with diastolic heart failure?

Answer 20

• In normal patients, filling their heart to 120 mL produces pressure of 8 mmHg
• In patients with diastolic heart failure, if the EDV increases filling heart to 120 mL produces a pressure of 30 mmHg, this is because there is stiffen in the heart but you still have the same volume. This causes an increase in the pressure.

Question 21

As afterload increases, cardiac output __________ (increases/ decreases).

Answer 21

decreases

Question 22

How does the heart reduce wall stress?

Answer 22

By thickening the wall

Question 23

Force frequency relationship

Answer 23

Question 24

Heart rate affects cardiac contractility through the ____________ relationship.

Answer 24

Force- frequency

Question 25

How is the cardiac cycle affected by an increase in heart rate?

Answer 25

An increase in heart rate leads to a reducton in the duration of the cardiac cycle that mostly affects the duration of diastole. Ventricular filling is then affected by heart rate.

Question 26

Although cardiac performance depends on loading, ____ does not.

Answer 26

Contractility

Question 27

Shortening against a constant load is _________ contraction.

Answer 27

Isotonic

Question 28

Lusitropy

Answer 28

rate of myocardial relaxation \*The increase in cytosolic calcium of cardiomyocytes via increased uptake leads to increased myocardial contractility (positive inotropiceffect), but the myocardial relaxation, or lusitropy, decreases.

Question 29

Relaxion of the heart is negatively impacted by which factors?

Answer 29

* **Calcium overload** – too much intracellular calcium * **Reduced rate of calcium removal from myocyte** through pumps if calcium is not removed from the cell quickly enough. * Plasma membrane Calcium ATPase * Sodium-Calcium (Na/Ca) exchanger * **Impaired Sarco-Endoplasmic Reticulum Calcium ATPase (SERCA)** this primary active transporter pumps calcium from the cytoplasm of the myocyte into its sarco-endoplasmic reticulum.

Question 30

Relaxion of the heart is positively impacted by which factors?

Answer 30

* Increased catecholamine

Question 31

dP/dt

Answer 31

Maximal rate of rise of left ventricular pressure (LVP), but it is determined by myocardial contractility and the loading conditions on the ventricle, thus it is an imperfect and sometimes incorrect predictor of the inotropic state (myocardial contractility).

Question 32

Maximal dP/dt depends on ___ and \_\_\_\_\_\_\_\_.

Answer 32

Heart rate ; loading

Question 33

% of it cardiac muscle metabolism uses _____ for 70% of its metabolic energy requirements.

Answer 33

Fatty acids **NOTE:** Anaerobic glycolysis takes over under stress and ischemic conditions, because using glucose is mroe efficient

Question 34

What parameters does diastolic function depend on?

Answer 34

Passive ventricular stiffness Elastic recoil after end- systole Relaxation (active process) Heart rate (which mainly affects the duration of diastole)

Question 35

Diastolic function depends on which extraventricular factors?

Answer 35

Reight ventricle interaction with left ventricle Pericardium

Question 36

Minimal dP/dt

Answer 36

A negative value during isovolumic relaxation. The more negative this value is, the better the relaxation is

Question 37

Tau

Answer 37

Time constant of the relaxation process where the pressure decay over time is "curve-fitted" \*Echo is the best imaging method