ECG's

Question 1

what are the squares representative of in an ECG?

Answer 1

small square = 40ms

big square = 0.2s secs

Question 2

how many bipolar leads are there and what do they do?

Answer 2

3 leads
record electrical activity in 2 directions
(wrist, wrist, ankle)

Question 3

how many unipolar arm leads are there and what do they do?

Answer 3

3 leads
looks at electricity going too?
(shoulder, shoulder, abdomen)

Question 4

how many unipolar chest leads are there and what do they do?

Answer 4

6 leads

looks at incoming electrical activity, starts on the right and moves down and to the left

Question 5

which leads assess electricity within the lateral myocardial territory?

Answer 5

leads 1, aVL, V5 and V6

Question 6

which lead is usually inverted compared to anterior and inferior leads?

Answer 6

aVR

Question 7

what are the 3 main peaks of the ECG waveform?

Answer 7

P = atrial depolarisation
QRS = ventricular depolarisation (+ve if travelling toward, -ve if moving away)
T = ventricular repolarisation

Question 8

which waves are always positive except on the aVR?

Answer 8

P waves and T waves except on the aVR.

Question 9

QRS waves face upwards on which side?

Answer 9

the left (positive)

Question 10

QRS waves face downwards on which side?

Answer 10

the right (negative)

Question 11

what is the P wave?

Answer 11

atrial depolarisation, SA node sends an impulse into the atria causing a contraction.
AV node sends a signal to the ventricles down His-Purkinje systems, slows conduction causing the PR interval.

Question 12

what is the QRS complex?

Answer 12

takes up to 120ms (3 small squares) shows ventricular depolarisation.

Question 13

what is the ST segement?

Answer 13

represents interval between depolarisation and repolarisation.

Question 14

what is the T wave?

Answer 14

represents ventricular repolarisation

Question 15

what is the QT interval?

Answer 15

represents time of depolarisation + repolarisation