4 - ECG Review

Question 1

How to measure heart rate

Answer 1

R waves in 30 large squares X 10
or
R waves in 15 large squares X 20

Question 2

What does the P wave represent and what is normal length

Answer 2

Atrial depolarisation

80ms

Question 3

What is the PR interval

What is the normal length

Answer 3

Time to cross AV node ang propagate to ventricles

120-200ms

Question 4

What does a prolonged PR interval indicate

Answer 4

Heart block (over 200)
Hypokalemia
Acute rheumatic fever

Question 5

What is the QRS complex and what is the normal length

Answer 5

Synchronisation of the contraction of the ventricles

less than 120ms

Question 6

Normal rate

Answer 6

60-100bpm

Question 7

Sinus bradycardia

Answer 7

HR less than 60 bpm
normal in athletes
Can be seen in pts with BB

Question 8

Sinus tachycardia

Answer 8

HR above 100bpm

Question 9

Ventricular tachycardia

Answer 9

Prolonged QRS
No P wave
180-190bpm

Question 10

Ventricular Fibrillation

Answer 10

Irregular rhythm
300+bpm
No QRS or P wave

Question 11

First degree heart block

Answer 11

PR interval fixed >200ms

Regular rate

Question 12

Second degree heart block - Type 1 (Wenkenbach)

Answer 12

Regularly irregular
Each successive impulse more difficult to pass the AV node
PR interval gets longer till not followed by QRS

Question 13

Second degree heart block - Type 2

Answer 13

AV node randomly fails to respond to impulses

Irregularly irregular

Question 14

Third degree heart block

Answer 14

Impulses from atria do not connect with ventricles
P waves not synchronised
bradycardia

Question 15

Atrial Fibrillation

Answer 15

Irregularly irregular
No P wave
Tachycardia (100-160)
Many sites in atria generating electrical impulses

Question 16

Atrial flutter

Answer 16

110bpm, regular rhythm, multiple F waves, 300bpm

Question 17

Junctional rhythm

Answer 17

1:1 P wave, inverted in lead I
Damage to SA node so AV node takes over as pacemaker
Bradycardia
Normal QRS
absent P wave

Question 18

Supraventricular Tachycardia (SVT)

Answer 18

140-220bpm
P wave absent
Abnormality near AV node
high freq of impulses at AV node

Question 19

AV nodal reentrant tachycardia

Answer 19

AVNRT is most common regular supraventricular tachycardia

reentry circuit within AV node

Question 20

What does the ST segment represent?

Answer 20

Time when both ventricles are fully depolarised
80-120ms
Usually isoelectric

Question 21

Depressed ST

Answer 21

Coronary ischemia or hypokalemia

Question 22

STEMI

Answer 22

ST Elevation Myocardial Infarct

MI with elevated ST

Question 23

What does a person have to have to qualify as a STEMI?

Answer 23

New ST elevation in 2 or more adjacent ECG leads

Question 24

NSTEMI

Answer 24

MI without ST elevation

less seious where ischaemia but not muscle death

Question 25

What leads do you look at to determine the electrical axis?

Answer 25

Leads I and aVf

Question 26

What is the electrical axis if QRS are both positive

Answer 26

Normal quadrant

Question 27

What is the electrical axis if QRS for Lead I is positive but aVF is negative

Answer 27

Left axis deviated

Question 28

What is the electrical axis if QRS in lead I and aVF are both negative

Answer 28

Right axis deviated

Question 29

How many leads must ST be elevated for STEMI

Answer 29

2 leads