Electrocardiogram

Question 1

what does an ECG show?

Answer 1

sum of APs in many cardiac cells

Question 2

how many seconds are the small boxes on an ECG?

Answer 2

0.04

Question 3

how many seconds are the large boxes on an ECG?

Answer 3

0.2 (5 little boxes)

Question 4

what does the P-R interval represent?

Answer 4

atrial depolarization followed by atrial contraction

Question 5

what does the Q-T interval represent?

Answer 5

ventricular depolarization followed by contraction

Question 6

what does the T wave represent?

Answer 6

ventricular repolarization

Question 7

why is atrial repolarization not seen on an ECG?

Answer 7

hidden by ventricular depolarization

Question 8

what does the R-R interval represent?

Answer 8

heart rate

Question 9

what is the equation to determine heart rate?

Answer 9

(60sec/min)/(x sec/beat)

Question 10

how do you read ‘X’ from an ECG strip to determine HR?

Answer 10

count small boxes between R-R and multiply by 0.04sec

Question 11

what is a normal PR interval?

Answer 11

0.12 - 0.20 sec

Question 12

what is a normal QRS duration?

Answer 12

0.08 - 0.10 sec

Question 13

what is a normal QT interval?

Answer 13

0.4 - 0.43 sec

Question 14

what is a normal RR interval?

Answer 14

0.6 - 1.0 sec

Question 15

where are the negative and positive electrodes for lead 1?

Answer 15

right arm/wrist = -/ve
left arm/wrist = +/ve

Question 16

where are the negative and positive electrodes for lead 2?

Answer 16

right arm/wrist = -/ve
left leg/ankle = +/ve

Question 17

where are the negative and positive electrodes for lead 3?

Answer 17

left leg/ankle = +/ve
left arm/wrist = -/ve