Principles of Electrocardiography

Question 1

1. What is an electrocardiogram (ECG)?

Answer 1

• Recording of the electrical activity of the heart (and other muscles).

Question 2

2. Outline very simply how an ECG works

Answer 2

Sensors attached to the skin are used to detect signals produced by the heart each time it beats.

Question 3

3. Name the axis of the graph produced by an ECG

Answer 3

voltage vs time

Question 4

4. What is a galvanometer?

Answer 4

(an instrument used to measure the size & direction of small electric currents)

Question 5

6. What is a dipole?

Answer 5

where there is a difference in charge between one bit of membrane and another

Question 6

8. When all of the heart muscle is polarised (E.g. at rest), is there a dipole or not?

Answer 6

there is no dipole

Question 7

9. When part of the heart muscle is depolarised, is there a dipole or not?

Answer 7

a dipole exists

Question 8

10. When all of the muscle is depolarised (E.g. contracting), is there a dipole or not?

Answer 8

there is no dipole

Question 9

11. What does 12 ECG leads allow?

Answer 9

Looking at the heart from 12 angles

Question 10

61. What is ventricular ectopics?

Answer 10

Premature ventricular contractions

Question 11

60. Where does Type 1 2nd degree heart block occur?

Answer 11

• It occurs in the AV node above the bundle of his

Question 12

59. What is Type 1 2nd degree heart block?

Answer 12

P-R interval progressively longer until a P wave is blocked. Cycle begins after blocked P wave.

Question 13

58. What is sinus tachycardia?

Answer 13

• Sinus rhythm is faster than 100bpm but usually not faster than 130bpm. Conduction is normal.

Question 14

57. What is sinus bradycardia?

Answer 14

• Slowed sinus rhythm (lower than 60bpm but not lower than 40) but normal conduction.

Question 15

what causes a prolonged QRS complex

Answer 15

bundle branch blocks