ECG (Tutorial)

Question 1

how many leads does a 12 lead ECG have? What are they?

Answer 1

10 leads

• 6 chest leads: V1-V6
• 4 limb leads: 1,2,3, Earth on Right Leg also aVF, aVR, aVL

Question 2

what forms Einhovens triangle?

Answer 2

lead 1- L and R arms +ve Left arm
lead 2- R arm L Leg +ve at left leg
Lead 3- R arm and leg +ve at the leg

Question 3

how do lead traces become larger?

Answer 3

if electrical activity is in the same direction as the orientation of the lead it will be larger (more parallel)

Question 4

what determines whether traces are up or down?

Answer 4

if depolarisation is towards the positive end of the lead the trace goes up

Question 5

what trace is negative? why?

Answer 5

• aVR

- depolarisation is towards the positive

Question 6

on a ECG trace what is the value for 1 5mm box and a small 1 mm box?

Answer 6

• 200ms or 0.2s

- 40ms or 0.04s

Question 7

what is the normal range for PR interval? what is most of the delay due to?

Answer 7

• 120-200 ms

- AV node 100-150ms is range taken for electrical conduction to pass through

Question 8

what is the normal range for QRS complex?

Answer 8

60-120 ms

Question 9

what is the normal range for the QT interval?

Answer 9

less than 440ms

Question 10

what can second degree heart blocks progress to?

Answer 10

• 3rd degree heart block

- ventricular asystole

Question 11

what can a third degree heart block progress to?

Answer 11

• ventricular fibrillation

- asystole

Question 12

what is ventricular asystole? what does it progress to?

Answer 12

• atria are pulsating but ventricle remain stationary

- circulatory arrest