ECG basics - Johnston

Question 1

times for:
PR interval
QRS duration
QT interval 
R-R interval

Answer 1

PR interval - 0.12 - 0.20 sec
QRS duration - 0.05 - 0.1 sec
QT interval - up to 0.43
R-R interval - 0.6 - 1 sec

Question 2

P ave upright/ inverted/ variable

Answer 2

upright in: 1,2, V4-6, AVF

inverted: AVR
variable: 3, AVL, other chest leads

Question 3

normal Q wave morphology

Answer 3

Q waves

Question 4

1/2 mm ST depression indicates

Answer 4

subendocardial injury/ ischemia

Question 5

1/2 mm ST elevation indicates

Answer 5

subepicardial/ transmural injury or ischemia

Question 6

T wave normal morphology

Answer 6

upright in 1,2, V3-V6
inverted: AVR
variable: 3, AVL, AVF, V1-V2
shape: slightly rounded and asymmetrical
height -

Question 7

QT duration and elements in terms of MI

Answer 7

T wave - ischemic pattern associated with inverted T waves
ST elevation - pattern of injury
Q wave/ QS complex- pattern of necrosis or infarction

Question 8

U wave

Answer 8

His/ Purkinje repolarization

Question 9

determines normal axis

Answer 9

positive defleciton in leads I and aVF

Question 10

determines LEFT axis

Answer 10

positive in lead 1

negative in aVF

Question 11

determines RIGHT axis

Answer 11

negative in lead I

positive in aVF

Question 12

right superior axis deviation

Answer 12

Lead I negative

Lead aVF negative

Question 13

0 to - 30 axis

Answer 13

lead I positive
lead II positive
aVF negative

Question 14

-30 to -90 axis

Answer 14

lead I positive
lead II negative
aVF negative

Question 15

breathing effect on HR

Answer 15

HR increases when you inspirate

HR decreases when you expirate