EKG

Question 1

Describe the electrical status of a myocardial cell at rest?

Answer 1

The interior of the cell in negative while the exterior is positive with the membrane acting as an insulator.

Question 2

When the myocardial cell is at rest, what is the resulting electrical status called?

Answer 2

Polarized, since the positive and negative charges are on opposite sides or ends.

Question 3

What happens to the myocardial cell during depolarization?

Answer 3

Positive (Na+) ions move INTO the cell

Question 4

What is a lead axis?

Answer 4

A straight line drawn between a positive and negative lead.

Question 5

What type of lead measurement is involved in Einthoven’s Triangle?

Answer 5

Bipolar as the leads measure the potential between two limbs, not a single site

Question 6

Which leads are bipolar?

Answer 6

I, II, III

Question 7

What are the unipolar leads?

Answer 7

VR, VL, VF and precordial leads

Question 8

Placement of leads V1, V2

Answer 8

Sternal border at 4th intercostal space

Question 9

Placement of V3

Answer 9

Midpoint between V2 and V4

Question 10

Placement of V4

Answer 10

Left MCL, 5th ICS

Question 11

Placement of V5

Answer 11

“Anteroaxiallry line even with V4 (5th ICS)

Question 12

Placement of V6

Answer 12

Midaxillary line at the 5th ICS

Question 13

In what plane do the unipolar chest leads measure the cardiac vector?

Answer 13

Horizontal

Question 14

In what plane do the Bipolar leads and augmented leads measure the cardiac vector?

Answer 14

Frontal

Question 15

On an EKG tracing, what does the vertical axis measure?

Answer 15

Voltage

Question 16

On an EKG tracing, what does the horizontal axis measure?

Answer 16

Time

Question 17

What is the measurement of the “small” squares? (distance)

Answer 17

1mm

Question 18

What is the measurement of the “big” squares? (distance)

Answer 18

5mm

Question 19

In regards to time, what does one small square equal?

Answer 19

0.04 seconds OR 40 milliseconds (ms)

Question 20

In regards to time, what does one big square equal?

Answer 20

0.2 seconds or 200ms

Question 21

In regards to time, what does 5 large squares equal?

Answer 21

1 second or 1000ms

Question 22

How long is the rhythm strip?

Answer 22

10 seconds

Question 23

What does the T wave represent?

Answer 23

repolarization of the ventricles

Question 24

What does the QRS wave represent?

Answer 24

depolarization of the ventricles

Question 25

What does the P wave represent?

Answer 25

Depolarization of the atria

Question 26

What determines the measurement of the cardiac axis?

Answer 26

The mean QRS vector

Question 27

What 2 leads are used to determine axis?

Answer 27

I, and aVF

Question 28

Normal PR interval in ms and boxes

Answer 28

0.12-.20 or 3-5 small boxes

Question 29

Normal QRS in ms and boxes

Answer 29

0.06-0.12 ms or 1.5-3 small boxes

Question 30

Normal QT interval in ms and boxes

Answer 30

0.36-.44 or 9-11 small boxes

Question 31

Describe the “1500 Method” or determining rate?

Answer 31

In a REGULAR rythm, count the number of small boxes between R waves and divide that INTO 1500 to equal the rate per minute.
EX: 37.5 small boxes
1500/37.5= 40 bpm

Question 32

If the QRS complex in Lead I and aVF are positive, what is the axis deviation?

Answer 32

Normal

Question 33

If QRS complex in Lead I is positive and aVF is negative, what is the axis deviation?

Answer 33

Left

Question 34

If QRS complex in Lead I is negative and aVF is positive, what is the axis deviation?

Answer 34

Right

Question 35

If QRS complex in Lead I is negative and aVF is negative, what is the axis deviation?

Answer 35

Extreme axis leftward and upward (-90-180)

Question 36

Causes of Left axis deviation (4)

Answer 36

1. LVH
2. LBB/LFB
3. Inferior wall MI
4. Raised Diaphragm (ascites, pregnancy, organomegaly)

Question 37

Causes of Right axis deviation?

Answer 37

1. RV overload
2. RBB
3. Lateral wall MI
4. emphysema
5. RV strain (PE, pulmonary stenosis, pulmonary HTN, chronic lung disease)