Exam #2: Electrocardiography Flashcards Preview

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Flashcards in Exam #2: Electrocardiography Deck (42):
1

What is depolarization?

Switching of charges on the cell membrane; positive outside relative to negative inside

2

How is current related to depolarization & repolarization? How is this related to the ECG tracing?

- Current only flows when there is a depolarization or repolarization event
- The ECG electrode can only detect current

3

By convention, flow of a positive ion away from the positive pole of an electrode appears as what? What about the opposite?

- Away= negative deflection
- Toward= positive deflection

Away= down
Toward= up

4

What is the electrocardiogram?

A summation of all the depolarizations and repolarizations occurring in cardiac cells

5

What is the p-wave? What is the normal duration of the p-wave?

- A summation of atrial myocyte depolarization
- 0.06-0.11 sec

6

What step theoretically comes before atrial depolarization?

SA node generation of impulse that CANNOT be seen on ECG

7

What does the PR interval correspond to? What is the normal duration of a PR interval?

- Atrial myocyte plateau phase (Ca++ IN & K+ OUT)
- 0.12-0.2 sec

8

What causes the QRS complex? What is the normal duration of a QRS complex?

- Ventricular depolarization
- 0.03-0.12 sec

9

What is the Q of the QRS? Define Q-wave.

Septal depolarization, which is positive current moving away from the positive electrode

Any negative defection before the R-wave is a Q-wave

10

What is the R of the QRS?

Ventricular muscle depolarization spreading toward electrode

11

What is the S of the QRS?

Ventricular muscle depolarization spreading away from the electrode

12

What is the ST segment?

Plateau phase of the ventricular myocyte

13

What is the T-wave?

Ventricular myocyte repolarization

14

Is atrial repolarization viewed?

NO, it is buried in the QRS

15

What is the chart speed of an ECG tracing?

25 mm/sec

16

How much time passes between 5mm?

0.2 sec (1 large box)

17

How much time passes between 1mm?

0.04 sec (1 small box)

18

What corresponds to 1.0 mV?

10mm (2x large boxes vertically)

19

Where is lead I?

+ left arm to - right arm

20

Where is lead II?

+ left foot to - right arm

21

Where is lead III?

+ left foot to - left arm

22

Where the standard limb leads bipolar or unipolar? What about the augmented limb leads?

Standard= bipolar
Augmented= unipolar

23

Where is aVR?

+ right arm

24

Where is aVL?

+ left arm

25

Where is aVF?

+ left foot

26

Draw the hexaxial lead system.

N/A

27

List the placement of the precordial leads.

V1= R. sternal border 4th intercostal space
V2= L. sternal border, 4th intercostal space
V4= Midclavicular, left 5th intercostal space
V3= between V2 & V4
V5= anterior axillary line, in line with V4
V6= in line with V4 & V5, midclavicular

28

List the R-R rate as determined by counting "large boxes."

1= 300
2= 150
3= 100
4= 75
5= 60
6= 50
7= 42

29

What causes left axis deviation?

End of deep expiration
Supine
Obesity
Hypertrophy (systemic, valvular disease, congenital)
LBBB (occurs with wide QRS)

30

What causes right axis deviation?

End of deep inspiration
Moving to standing
Tall
Hypertrophy (pulmonary valve stenosis, pulmonary HTN, congenital)
RBBB (with wide QRS)

31

What is the normal PR-interval?

0.12-0.2 seconds
3-5 small boxes

32

What is the normal QRS duration?

0.03-0.12 seconds
<1-3 small boxes

33

What is the normal QT interval?

asdf

34

What causes increased voltage of QRS?

Hypertrophy
Thin chest

35

What causes decreased voltage of QRS?

Previous MI
Fluid in pericardium or pleural space
Large chest

36

What are the clinical manifestations of hyperkalemia on ECG?

Tall, peaked T-waves

37

What are the clinical manifestations of hypokalemia on ECG?

Decreased T-wave amplitude
Inverted T-wave
U-waves

38

What is the pathophysiology underlying a PR interval that is longer than normal?

1st degree AV block

39

What is the pathophysiology underlying a PR interval that is shorter than normal?

Junctional rhythm or accessory pathway between the atria & ventricles

40

What is the pathophysiology underlying a few very large & wide QRS complexes appearing in a lead with mostly normal QRS complexes?

PVCs

41

What is the pathophysiology underlying all very large & wide QRS complexes?

Ventricular rhythm
Extreme hyperkalemia

42

What is the pathophysiology underlying a p-wave that occurs without a subsequent QRS complex?

AV Block

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