Cardiac Output and Contractility Flashcards
1
Q
- What is the effect of a positive inotropic agent?
A
Increase in contractility
- Increase in EDV
- Increase in CO
- Increase in SV
2
Q
- What is the effect of a positive chonotropic agent?
A
- Increase in HR
3
Q
- What is the effect of a negative inotropic agent?
A
- Decrease contractility
4
Q
- What is the effect of a negative chonotropic agent?
A
- Decrease HR
5
Q
- What is preload? (General sense)
A
- End Diastolic Volume
6
Q
- What is preload in a more detailed sense?
A
- Amount of wall tension in RV or LV just before contraction is initiated
7
Q
- What is afterload (in a general sense)?
A
- Aortic diastolic pressure
8
Q
- What is afterload in a more detailed sense?
A
- The amount of diastolic pressure in the aorta/pulmonary arteries that must be exceeded for semilunar valves to open
9
Q
- How are afterload and velocity related?
A
- They are inversely related
- Increase in afterload leads to a decrease in velocity of contraction/shortening of muscle fibers
10
Q
- How do you calculate stroke volume ?
A
- SV=EDV-ESV
- Note that in normal conditions, this is approx 70 mL
- Represents volume of blood ejected by ventricle with each beat
11
Q
- How do you calculate ejection fraction?
A
- EF%=SV/EDV
- Usually around 55%
- Represents the fraction of EDV that is ejected in each stroke volume
12
Q
- How do you calculate cardiac output?
A
- CO=HR x SV
- Volume of blood ejected by the ventricle per minute
- Normal=5 L/min
13
Q
- What does the Frank Starling relationship tell us?
A
- The volume of blood ejected by the ventricle depends on the volume present in the ventricle at the end of diastole (EDV)
- Note that EDV relates to venous return (more venous return, larger EDV)
- In a steady state CO=venous return
14
Q
- Will a chonotropic effect have an inotropic effect?
A
- Yes
- Positive chonotropic effect will have positive effect on inotropy and vice versa
15
Q
What is represented by points 1-2 in the following pressure volume curve?

A
- Isovolumetric contraction
16
Q
- What is represented by points 2-3 in the pressure volume loop?

A
- Ejection of blood
17
Q
- What is represented from points 3-4 in the pressure volume loop?

A
- Isometric relaxation
18
Q
- What is represented by points 4-1 in the pressure volume loop?

A
- Ventricular filling
19
Q
- Which point on the curve represents preload?

A
- 1
- Remember preload=EDV
20
Q
- Which point on the loop represents afterload?

A
- 2
- Remember that afterload is the aortic pressure that must be exceeded in order for the aortic valve to open and blood to be ejected from the ventricle
21
Q
- On which points of the loop are the AV valves opening and closing?
- On which points of the loop are the semilunar valves opening and closing?
A
- AV valves open during 4
- AV valves close during 1
- Semilunar valves open at 2
- Semilunar valves close during 3
22
Q
- What are the effects of increased pre-load on the pressure volume loop?
A
- Increase in EDV
- Afterload and contractility remain constant
- Increased stroke volume

23
Q
- What are the effects of increased afterload on the pressure volume loop?
A
- Greater pressure in aorta
- Reduced SV
- Reduced EF%

24
Q
- What are the effects of increased contractility on pressure volume loop?
A
- Increased SV
- Increased aortic pressure
- Decreased ESV

25
* What type of effect does sympathetic stimulation have on CO?
* Via what receptors does this act?
* Via what NTX does this act?
* What are the biochemical effects that occur as a result of sympathetic stimulation?
* **Positive inotropic effect**
* **Beta 1 adrenergic receptors**
* **NE**
* **Phosphorylation of sarcolemma Ca2+ channels (leads to increased intracellular Ca2+ concentrations)**
* **Phosphorylation of phospholamban (increased sequestering of Ca2+ in the SR; important for subsequent contractions)**
* **Phosphorylation of Troponin I (Inhibits troponin i so that troponin c can bind to Ca2+ and help enable cross bridge formation)**
26
* What type of effect does the parasympathetic nervous system have on cardiac output?
* Through which receptor does it work?
* What biochemical events occur as a result?
* **Negative inotropic effect in ATRIA ONLY**
* **Muscarinic receptor activation**
* ****Decreases inward Ca2+ current during plateau
* AcH increases outward K+ current via K+-ACh channel (hyperpolarizes membrane)
27
* How does increasing HR affect contractility?
* Positive chonotropic effect increases HR and increased HR increases contractility (positive inotropic effect)
* **Positive staircase effect (Bowditch staircase)**
* **More Ca2+ enters into cell and taken up into SR**
* **Postextrasystolic potentiation (arrythmia, extra beat)**
28
* What is volume work equivalent to?
* What is pressure work equal to?
* Which is greater?
* Cardiac output
* Aortic pressure
* Pressure work
29
* **What is minute work?**
**Minute work=CO x aortic pressure (pressure work)**
30
* **What is stroke work?**
* **Performed by the LV**
* **Stroke Work=SV X aortic pressure**
* **Represents the area within the pressure volume loop**
31
* What is the **Fick principle?**
* **Cardiac output=O2 consumption/([O2]pulmonary vein-[O2]pulmonary artery)**
32
* What is the relationship between CO and venous return at a steady state?
* **At a steady state, the volume of blood ejected by Lv (CO)=venous return**
33
* Changing what factor will shift which part of the cardiac curve ONLY?
Inotropy
34
* Changes in what parameter will change the vascular function curve only?
* **Changes in blood volume**
35
* **What parameter affects both Cardiac and Vascular function curves?**
**TPR**
36
What is represented by the blue dot in the following figure?

Equilibrium-where CO=venous return
37
What is represented by the arrows in the following diagram?
* 1st arrow=equilibrium where CO=venous return
* 2nd arrow=Mean systemic pressure; proportional to blood volume and preload\*\*
38
* What parameter is causing the changes in the cardiac function curve?

* Left represents a **positive inotropic effect (increased inotropy, increased HR, increased afterload)**
* Left represents a **negative inotropic effect (decreased inotropy, decreaed heart rarte, increased afterload)**
39
* **Changing what parameter has caused the shifts in the following figures?**

* Right
* Increasing blood volume
* Decreasing systemic vascular resistance (SVR)
* Decreasing mean circulatory filling pressure/mean systemic pressure
* Left
* Decreasing blood volume
* Increasing systemic vascular resistance
* Increasing mean circulatory filling pressure/mean systemic pressure
40
* **_What parameter has been changed to cause the shifts in the diagrams below?_**

* TPR
* **Left diagram shows an increase in TPR** **which leads to a right shift of the cardiac function curve and a left shift of the vascular function curve**
* **Right diagram shows a decrease in TPR which leads to a left shift of the cardiac function curve and a right shift of the vascular function curve**
41
* What is the relationship between CO and venous return in an individual with heart failure?
* Decreased inotropy
* Decreased vascular complaince
* Increased blood volume
* Increased SVR