Lecture 04: ECG: Fundamental Theory (Hayward) Flashcards Preview

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Flashcards in Lecture 04: ECG: Fundamental Theory (Hayward) Deck (26):
1

Electrocardiography

study and interpretation of the electrical activity in the heart, as evidenced by differences in the electrical potential measured on the surface of the body

2

ECG

measurement of voltage changes on body over time. Displays deflections through thorax. A record of the electrical activity of the heart with respect to time.

3

How is dipole established for ECG?

Current flows from depolarized cells to those that are at rest, causing a difference in membrane potential, which creates electrical field/dipole on the surface. Electrical difference is recorded by electrodes

4

Negative wave approaching + pole is reflected on ECG as

upward (positive) deflection

5

repolarization

process by which cell returns to the original resting sate after being depolarized.

6

What are potential differences at rest?

none

7

what does ECG read when whole cell is depolarized?

nothing

8

negative wave moving towards negative pole is reflected on ECG as

downward (negative) deflection

9

measurement on ECG if repolarization occurs from same place that depolarization started

negative deflection

10

which is longer: depolarization repolarization?

repolarization

11

measurement on ECG if repolarization occurs in opposite direction as depolar.

positive (positive T wave deflection)

12

measurement on ECG if wave of depolarization moves at right angle to positive electrode

small or absent deflection

13

P wave represents

atrial depolarization (from RA to LA)

14

QRS complex represents

ventricular depolarization

15

T wave represents

ventricular repolarization

16

most common lead system

bipolar (leads on RA, LL)

17

flat line b/w P and QRS represents

conduction delay as depolarization passes through the AV node, Bundle of His, Bundle branches

18

LBB or RBB activates first?

LBB because it's larger

19

Q wave represents

depolarization across the ventricular septum from L to R side

20

definition of R wave on ECG in lead II

first upward deflection, whether or not there's a Q wave

21

Why is R always positive in lead II?

ventricles depolarize outward toward epicardium, especially on L side towards + lead

22

definition of S wave on ECG in lead II

downward deflection following the R wave. Reflects final depolarization of the base or back wall of the heart (neg. deflection)

23

Flat line b/w QRS and T wave represents

time of total ventricular depolarization before repolarization

24

T wave represents

ventricular repolarization. Occurs slowly and in variable directions

25

ATRIAL repolarization on ECG

produces low amplitude wave that typically occurs during the QRS complex and typically NOT observed

26

Normal sequence of activation in the heart and intervals on ECG

1) SA node
2) SA node through atrial myocardium (150 msec)
3) AV node (80-100 ms)
4) AV bundle, bundle branches, purkinje network (80 ms)
5) ventriculr myocardium (80 ms)

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