ECG 1: The Basics Flashcards Preview

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Flashcards in ECG 1: The Basics Deck (123)
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1

What is moving in the process of depolarization?

Positive ion into cell
Negative ion out of cell

2

What is moving in the process of depolarization?

Positive ion out of cell
Negative ion into cell

3

What is the baseline electrical state of myocytes?

Negatively charged

4

What direction is the voltage change in depolarization?

Postitive

5

What direction is the voltage change in repolarization?

Negative

6

What do the electrodes detect?

Change in polarization, ie charges that are moving (not still)

7

What makes a lead (ECG)?

2 electrodes; voltage is compared between them

One is designated + and one - by convention

8

What is voltage?

Electrical potential difference

Voltage is what makes electric charges move. It is the 'push' that causes charges to move in a wire or other electrical conductor.

9

What direction does the reading deflect when a positive charge moves toward the positive electrode?

Upward

10

What direction does the reading deflect when a positive charge moves away from the positive electrode?

Downward

11

What direction does the reading deflect when a positive charge moves diagonally toward the positive electrode?

Upward, but smaller (than if it were moving directly toward it)

12

If a charge is moving roughly perpendicular to the lead, what is the deflection on ECG?

Extant but tiny

13

Where are the limb electrodes placed?

One on each shoulder, and one on a leg

14

What does Lead I measure?

Electrical current from right to left (at level of shoulders)

15

What does Lead II measure?

Electrical current from R shoulder to feet

16

What does Lead II measure?

Electrical current from L shoulder to feet

17

What are the aVF, aVR, and aVL leads based on?

One electrode & average of the two others

Electrode end is +, averaged end is -

18

What plane do the limb leads assess current in?

All limb leads assess electrical activity in the coronal plane

Measure activity that is up-down or right-left, but NOT front-back

19

What do aVF, aVL, and aVR stand for?

augmented Vector Foot, Left, and Right

The F/L/R indicates the + end, and is the non-calculated one (- end of this lead is the average between the other two electrodes)

20

What does "augmented" mean, in the limb leads?

Historical note: these leads have a little "a" in the name to mean "augmented". The word "augmented" arose because originally the active electrode was compared to an average of all three electrodes. When they removed the active electrode from the "averaged electrodes" the electrical deflection became greater and thus "augmented"

21

What is the positive end of the precordial leads?

Theoretical ground, from sum of the 3 limb electrodes

Theoretically corresponds to centre of chest

22

What are bipolar vs unipolar leads?

Bipolar: limb leads. Based on 2 electrodes, or 1 & avg of the other 2

Unipolar: precordial leads. Based on 1 electrode, & avg of limb leads

23

What plane do precordial leads measure activity in?

Coronal plane: front-back, and right-left

24

Describe the pattern of electrical movement in the heart

Starts in the RA, spreads to LA

SA node activated

Charge starts down bundle of His as atria start repolarizing

Charge is at end of septum and starts travelling up walls around when atria are done repolarizing

Signal travels through myocardium; depolarizes

Myocardium slowly repolarizes

25

Which bundle branch depolarizes the septum?

Left bundle branch

26

Which depolarizes first, endocardium or epicardium?

Endocardium: Purkinje fibres are close to the endocardium

(Inside before outside)

27

Which repolarizes first, endocardium or epicardium?

Epicardium

Heart depolarizes outside-in
(myocytes near outside have shorter plateau phase)

28

How big is a small square of ECG paper?

1mm

29

How big is a large square of ECG paper?

5mm

30

What speed are ECGs recorded?

25mm/s