Basic Features

Question 1

What are the two ways to calculate heart rate?

Answer 1

1. Count QRS on rhythm strip and times by 6
2. Divide number of large squares between R-R interval by 300

Question 2

What is the rate if there is an interval of 2 large squares?

Answer 2

300/2=150 bpm

Question 3

What is the HR if there is an interval of 1 large square?

Answer 3

300/1=300

Question 4

What is the heart rate is there is an interval of 3 large squares?

Answer 4

300/3=100 bpm

Question 5

What is the HR if there is an interval of 4 large squares?

Answer 5

300/4=75 bpm

Question 6

What is the HR if there is an interval of 5 large squares?

Answer 6

300/5=60 bpm

Question 7

How do you work out the HR if it is irregular?

Answer 7

1. Count QRS spikes on rhythm strip and x 6
2. Use the 300/large sq interval to determine the range of HR using smallest and longest intervals

Question 8

How do you know if the strip is in sinus rhythm?

Answer 8

1. P waves that look largely the same within each lead
   2 a. Upright P wave in lead II
   b. Inverted P wave in lead aVR

Question 9

How do you determine if the axis is normal?

Answer 9

Normal if both leads I and aVF are positive

Question 10

What is the diagram for the anatomy of the limb leads?
(Imagine a circle)

Answer 10

AVR. AVL

                                 Lead I

Lead III. Lead II

          AVF

Question 11

Which leads are septal?

Answer 11

V1 and V2

Question 12

Which leads are anterior?

Answer 12

V3 and V4

Question 13

Which leads are lateral?

Answer 13

V5 and V6

Leads I and aVL are ‘high lateral’

Question 14

Which leads are inferior?

Answer 14

Leads II, III and aVF

Question 15

What is the ECG axis?

Answer 15

The average direction of electrical activity as the ventricles activate
(Should be down and to the left = right when you are looking at the patient!!)

Question 16

What does the p wave represent?

Answer 16

Atrial depolarisation

Question 17

What does the p wave look like with enlarged RA?

Answer 17

1. Taller wave (>2.5mm)

Question 18

What does the p wave look like with enlarged LA?

Answer 18

Bifid (second peak occurs as larger left atrium starts to depolarise)

Question 19

What happens during the PR interval?

Answer 19

Atria depolarisation (p wave) and contraction throughout rest of PR interval.

AV node holds up ventricular contraction to allow atrial contraction to complete

Question 20

What might be occurring if the p wave is short (<3mm)?

Answer 20

Accessory pathway present between atria and ventricles that BYPASS THE AV NODE

= ventricular contraction is not paused (to allow complete atrial contraction) and occurs too early

Question 21

What does the QRS complex represent?

Answer 21

Ventricular depolarisation

Question 22

What are the 3 main characteristics of the QRS complex?

Answer 22

Width - time taken
Height - voltage generated
Shape - conduction pathway followed

Question 23

What is important to remember about the ST segment when the QRS is broad?

Answer 23

Anything that affects depolarisation affects repolarisation. Therefore the ST and T following a broad QRS will likely be abnormal as a result of the broad QRS

Question 24

What

Question 25

How can you tell if changes in the ST and T segments are primary?

Answer 25

Narrow QRS - therefore ST and T should be normal (not affected by broad QRS)

Question 26

What does a wide QRS signify?

Answer 26

Conduction happening out of sync - not using the usual efficient pathways

Question 27

What does a tall QRS signify?

Answer 27

Higher voltage = enlarged tissue

Question 28

What might a short QRS signify?

Answer 28

Blockage of conduction signal, eg in pericardial effusion

Question 29

Where is it NORMAL to see Q waves?