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

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

Electrocardiography

A

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
Q

ECG

A

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
Q

How is dipole established for ECG?

A

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
Q

Negative wave approaching + pole is reflected on ECG as

A

upward (positive) deflection

5
Q

repolarization

A

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

6
Q

What are potential differences at rest?

A

none

7
Q

what does ECG read when whole cell is depolarized?

A

nothing

8
Q

negative wave moving towards negative pole is reflected on ECG as

A

downward (negative) deflection

9
Q

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

A

negative deflection

10
Q

which is longer: depolarization repolarization?

A

repolarization

11
Q

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

A

positive (positive T wave deflection)

12
Q

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

A

small or absent deflection

13
Q

P wave represents

A

atrial depolarization (from RA to LA)

14
Q

QRS complex represents

A

ventricular depolarization

15
Q

T wave represents

A

ventricular repolarization

16
Q

most common lead system

A

bipolar (leads on RA, LL)

17
Q

flat line b/w P and QRS represents

A

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

18
Q

LBB or RBB activates first?

A

LBB because it’s larger

19
Q

Q wave represents

A

depolarization across the ventricular septum from L to R side

20
Q

definition of R wave on ECG in lead II

A

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

21
Q

Why is R always positive in lead II?

A

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

22
Q

definition of S wave on ECG in lead II

A

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

23
Q

Flat line b/w QRS and T wave represents

A

time of total ventricular depolarization before repolarization

24
Q

T wave represents

A

ventricular repolarization. Occurs slowly and in variable directions

25
Q

ATRIAL repolarization on ECG

A

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

26
Q

Normal sequence of activation in the heart and intervals on ECG

A

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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