ECG

Question 1

How many large squares pass through per minue on an ECG?

Answer 1

300

Question 2

What is a normal PR length?

Answer 2

0.12-0.2 seconds

Question 3

What is a normal QRS length?

Answer 3

0.08-0.12 seconds

Question 4

What is a normal QT interal length?

Answer 4

0.35-0.43 seconds

Question 5

What may cause a prolonged QT interal?

Answer 5

Drugs

Electrolyte abnormalities (hypokalaemia, hypocalcaemia etc.)

Question 6

What can cause deviation in the QRS complex?

Answer 6

Venticular hypertrophy (either left or right)

Question 7

Deviation in the QRS complex is best seen in which leads?

Answer 7

I, II and III

Question 8

Which distinctive patterns will be present on the ECG for right axis deviation?

Answer 8

• Increases in lead III QRS
• Negative deflection in lead I QRS

The right ventricle now has more influence on the QRS than the left

Question 9

Which conditions are likely to cause right axis deviation and why?

Answer 9

Pulmonary conditions

e.g. PE

These put strain on the right side of the heart so lead to hypertrophy

Question 10

How does left axis deviation present on an ECG?

Answer 10

Negative QRS complex in lead III

Negative QRS complex in lead II

Question 11

What causes left axis deviation?

Answer 11

LVH or a conduction defect

Question 12

Which area of the heart do leads V1 and V2 “look” at and which pattern do they nrmally observe?

Answer 12

Right ventricle

• Small upward deflection (R wave - septum depolarised)
• Large downward deflection (Q wave - main muscle mass depolarised)

Question 13

Which area of the heart do leads V5 and V6 “look” at and which pattern do they nrmally observe?

Answer 13

Left ventricle

• Small initial downward deflection (septal Q wave)
• Large upward deflection (R wave - main muscle mass depolarised)

Question 14

How is it possible to tell on an ECG where the interventricular septum is present?

Answer 14

When R and S waves are roughly equal

That happens around V3/4

Question 15

How is an ECG reported on? (6)

Answer 15

1. Verify patient details
2. Check date and time of ECG
3. Check paper calibration
4. Determine axis
5. Look at rhythm strip for: Electrical activity, rhythm, P waves, PR interval, is each P wave followed by a QRS complex, is the QRS of normal duration
6. Look at individual leads for volatge criteria changes or ST or T wave changes