ECG

Question 1

What does ECG show?

Answer 1

Changes in voltage over time

Question 2

What does a small/big square represent?

Answer 2

Small square- 40ms
Big square- 0.2 seconds

Question 3

How long is the PR interval?

Answer 3

120-200ms

Question 4

How long is QT intercal?

Answer 4

440ms- men
460ms- women

Question 5

How long QRS complex?

Answer 5

100ms

Question 6

Are P and T waves positvie or negative? Why?

Answer 6

P waves- positive all leads except avR (-ve)

Due impulse going R.atrium to L.atrium
From aVR moving away meaning -ve.

Question 7

Are leads positive or negative in QRS complex?

Answer 7

QRS complexes:
- V1 and V2 anterior
- Conduction goes down ventricle
- L.V more muscle than right so peak is –ve
- Going away

• V3-V6 QRS +ve becomes more anterior

Question 8

What is investigated when looking slow HR?

Answer 8

PR interval
Normal 3-5 squares

Question 9

Define QT interval?

Answer 9

Time taken ventricular depolarisation and repolarisation

Question 10

Define ST segment?

Answer 10

Interval between depolarisation and repolarisation
Isoelectric- not elevated or depressed

Question 11

Explain bipolar leads?

Answer 11

Form triangle between wrists and left leg
Right leg- ground electrode

Question 12

How do bipolar leads work?

Answer 12

Negative poles- reference electrodes
Positive poles- recording electrodes

Question 13

Explain unipolar leads? Positive or negative?

Answer 13

aVR, aVL, aVF\Bisect angles of triangles
Combine 2 electrodes as reference
All positive

Question 14

Where are 6 unipolar chest leads positioned?

Answer 14

V1: R of sternum- 4th intercostal space
V2: L of sternum- 4th intercostal space
V4: R of sternum- 5th intercostal space
V3: between V2 and V4
V5: 5th intercostal space- anterior axillary line
V6: 5th intercostal space- midaxillary line

Question 15

What occurs P wave?

Answer 15

Atrial depolarisation
Small- atria less muscle

Question 16

What occurs QRS?

Answer 16

Ventricular depolarisation
Quick- specialised fibres

Question 17

Why is there ;ength between start P wave and start QRS wave?

Answer 17

Delay at AV node

Question 18

What happens ST segment?

Answer 18

Interval between depolarisation and repolarisation

Question 19

What occurs during T wave?

Answer 19

Ventricular repolarisation

Question 20

Define tachycardia?

Answer 20

High HR
Greater 100
Narrow QRS

Question 21

Define brachycardia?

Answer 21

Low HR
Less 60

Question 22

Explain Right Bundle Branch Block RBBB

Answer 22

Conduction AV node- His-Purkinje
Left/Right bundle
Block
Delay depolarisation ventricles- QRS wider

Question 23

Explain Left Bundle Branch Block LBBB

Answer 23

LBBB damaged
RV depolarised before LV
Big R wave

Question 24

What causes broad QRS complex?

Answer 24

LBBB and RBBB

Question 25

What does ST segment represent?

Answer 25

Interval between V depolarisation and V Repolarisation
Normally isoelectric

Question 26

What does elevated ST segment represent?

Answer 26

Heart attack

Question 27

What does right axis deviation indicate?

Answer 27

Delay depolarisation right side

Question 28

What does fibrosis in RV cause?

Answer 28

Delay electrical activity going left