Lecture - CVS (Bevin ECG) Flashcards
Using the terms “negatively/positiely” and “inside/outside” - describe the following and maybe even draw it out in your head what’s happening
- RMP
- Atrial depolarisation
- Ventricular depolarisation
- Ventricular repolarisation
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ECG vectors
What’s the basic principle of ECGs that referes to the direction of the wave of potential change?
At any given electrode, the polarity of the voltage change depends on the direction in which the wave of potential change is moving
So Shape of ECG depends where you look at it on the skin - th shape of it depensd where you look at the heart from so this diagram is one particular place you can keep the wires (standardised places)
ECG vectors
- What does depol towards + electrode create?
- Depol away away from + electrode?
- Repol away from + electrode?
- No depol/reopl, no pot difference aka i____ line - what does it look like on ECG?
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Standard limb leads (I, II and III)
- There are 4 electordes - where are they placed?
- In the Einthoven lead system, the heart is considered to lie in the centre of a triangle formed by what? Which plane is it oreintated in?
- In this traingle, draw the arrow of the direction of depolarisation
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Standard limb lead II:
- Where is the positive electrode and where is the negative electrode?
- Okay so SA nodal cells depolarise spontaneously: what depolarises from this, in what direction is the wave, so what sort of deflection will you see?
- In the ventrcular septum, the overall direction of the depol is where? So what do we see next?
- In the ventricles, the depol occurs from where to where so what direction and what do you see? Big and fast so big and narrow
- The last portion of the ventricles - how do they depol so what do you see?
- Then the repol of ventricles occurs from where to where so what direction so what do you see?
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Slide 32: what sorta stuff can you see on ECG?
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Characterisitcs of ECG:
- What are the waves?
- What are the segments?
- What’s the ST segment? When does it change?
- What are intervals?
- What does the PR (PQ) interval denote? How long is it normally?
- QS interval - time taken for what? How long is it usually?
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Back to Standard limb leads
- Recordings are made between what?
- A combination of 2 electodres is called a what?
- What does Lead I record? So where are the + and - placed? Draw the purple arrow on the triangle
- Lead II we’ve already done but how is that positioned? What does it record the pot diff between?
- WHat about lead III?
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Augmented limb leads - I think these are three more ways to arrange the wires
- What electrodes are used?
- How many electrodes are + and how many -?
- What are the three arrangements?
- What does ‘aV’ refer to?
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- What’s the hexaxial reference system?
- Are aV bipolar or unipolar? What about limb leads? What plane f the body do both work in?
- In your head, draw out the 6
- What leads is the deflection negative for?
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- What is the mean QRS axis?
- SO the mean QRS axis usually lies within what quadrants?
- Corresponds to what?
- If any of the leads I, II and III have negative deviation - what does that say about the mean QRS?
- What is right and left axis deviation?
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- What are chest leads?
- What are they called?
- What are the negative electodes? SO the poisitive must be where?
- What is earthed?
- Why do the chest leads give large ECG deflections?
6 What plane do the chest leads examine the heart?
- For the following active electrodes, what area in the heart are they sorta over and what is their main QRS delfection?
- Draw the 6 in your head
- So if those are the -ve then the positive are the 6 on the chest? Like one at a time, they’ll be put on and give the recording
- Because they’re closest to heart so bigger deflections
Go read yellow paper for the “how to interpret a 12-lead ECG”
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