Interpretation of ECG

Question 1

how is a regular rate on an ECG calculated?

Answer 1

300/number of big squares per R-R interval

Question 2

what is a normal rate?

Answer 2

60-100 bpm

Question 3

what is a sinus rhythm?

Answer 3

• normal P waves
• normal QRS complexes
• one P wave per QRS complex
• regular rhythm

Question 4

how is atrial fibrillation seen on an ECG trace?

Answer 4

• no discernable P waves

- irregular QRS complexes

Question 5

how is arterial flutter seen on an ECG trace?

Answer 5

• p waves seen at a rate of 300 per minute

- p waves have a saw toothed appearance

Question 6

what is Junctional tachycardia? how is junctional tachycardia seen on ECG?

Answer 6

• impulses arriving from AV node

- normal QRS complexes yet absent P waves

Question 7

what is ventricular tachycardia?

Answer 7

• after 2 sinus beats rate increases to 150 bpm

- QRS complexes become broad and T waves are difficult to identify

Question 8

what is a P wave? What is its normal form on an ECG?

Answer 8

• time for atrial depolarisation

- less than 0.25 mv should be upright in 2,3 and aVF

Question 9

what is P-mitrale?

Answer 9

• bifid P wave

- L atrial hypertrophy

Question 10

what is P pulmonale?

Answer 10

• peaked P wave greater than 0.25 mv

- R atrial hypertrophy

Question 11

what is the PR interval? what is the normal range?

Answer 11

• time between atrial and ventricular depolarisation

- 0.12 s-0.2 s

Question 12

what does an abnormal length PR interval mean?

Answer 12

prolonged interval implies delayed AV conduction hence a 1st degree heart block

Question 13

what is QRS complex? what is the normal range?

Answer 13

• time for ventricular depolarisation

- normally is less than or equal to 0.12s

Question 14

what is normal Q wave?

Answer 14

less than 0.04s and less than 2mm in depth

Question 15

what is an abnormal QRS complex? What is it indicative of?

Answer 15

• greater than 0.12s

- ventricular conduction defects- left or right Bundle Branch Block

Question 16

what does it mean if the voltage of the QRS complex is less than 5mv?

Answer 16

• hypothyroidism
• COAD
• Myocarditis
• precarditis and pericardial effusion

Question 17

how is L ventricular hypertrophy seen on an ECG?

Answer 17

R wave in V5 greater than 25mv

Question 18

how is R ventricular hypertrophy seen on ECG trace?

Answer 18

dominant R wave in V1 or deep S wave in V6

Question 19

what features define a significant Q wave?

Answer 19

• interval greater than 0.04s

- depth greater than 2mv

Question 20

what does an abnormal Q wave in lead 3 indicate?

Answer 20

Pulmonary embolism

Question 21

what is QT interval?

Answer 21

• measured from start of Q to end of T

- ventricular depolarisation then repolarisation

Question 22

how is corrected QT calculated?

Answer 22

QTc= QT/ square route of RR interval

Question 23

what is normal range for the QT interval?

Answer 23

0.38-0.42 s

Question 24

why is the corrected QT interval used?

Answer 24

any change in heart rate alters QT interval and the heart rate is not constant

Question 25

what can cause prolonged QT interval?

Answer 25

-acute myocardial ischaemia
-myocarditis
-bradycardia
-head injury
-hypothermia
-urea and electrolyte imbalance
congenital
-drugs

Question 26

what is the the ST segment?

Answer 26

time from end of ventricular depolarisation to start of ventricular repolarisation

Question 27

what is a normal ST segment?

Answer 27

isoelectric

Question 28

what does ST elevation indicate? what defines ST elevation?

Answer 28

• 1mm in 2 adjacent limb leads

- infarction

Question 29

what does depression of ST segment indicate?

Answer 29

ischaemia

Question 30

what are T waves representative of?

Answer 30

ventricular repolarisation

Question 31

where are T waves most likely to be inverted?

Answer 31

aVR and V1

Question 32

where is it abnormal for T waves to be inverted? What is this indicative of?

Answer 32

• lead 1 or 2 and V4-V6

- ischaemia or infarction

Question 33

what effects does digoxin have on T waves?

Answer 33

• T wave inversion

- St segment slopping depression

Question 34

what 3 changes happen to ECG trace in Acute MI?

Answer 34

• T wave peaking followed by T wave depression
• ST segment elevation
• appearance of new Q waves

Question 35

how is an anterior infract identified on an ECG?

Answer 35

• sinus rhythm
• Q waves in leads V2-V4
• inverted T waves leads V4-V6

Question 36

how is an anterolateral infarct seen in an ECG?

Answer 36

• sinus rhythm
• Q waves in leads 1, 2 aVL
• raised ST segments V2-V6

Question 37

how is an inferior infract seen on an ECG?

Answer 37

• sinus rhythm
• Q waves leads 3 and aVF
• depressed ST segment in aVL and V6

Question 38

how is a posterior infarct identified from an ECG?

Answer 38

V1- ST segment depression and tall R wave

Question 39

How can a pulmonary embolism be identified from an ECG?

Answer 39

• large S wave in lead 1
• deep Q wave in lead 3
• inverted T wave in lead 3

Question 40

what are the features of hyperkalaemia on an ECG?

Answer 40

• Tall, tented T wave

- widened QRS

Question 41

what are the ECG features of hypokalaemia?

Answer 41

• small T wave

- prominant U wave

Question 42

what is the features on an ECG of hypercalcaemia?

Answer 42

short QT interval

Question 43

what are the 2 features on an ECG identifying hypocalcaemia?

Answer 43

• long QT interval

- small T waves