ECG

Question 1

P wave

Answer 1

Atrial depolarisation <0.12s

Question 2

QRS complex

Answer 2

Ventricular deoplarisation about 1 second

Question 3

T wave

Answer 3

Ventricular repolarisation

Question 4

PR Interval

Answer 4

Largely AV node delay 0.12-0.2

Question 5

ST Segment

Answer 5

Ventricular systole, end of QRS to start of T wave

Question 6

TP Interval

Answer 6

Diastole (ventricles relax)

Question 7

what is the pacemaker potential?

Answer 7

slow depolarisation of membrane potential to a threshold

Question 8

what is the pacemaker potential due to?3

Answer 8

• decrease in K efflux
• Na influx (funny current)
• Transient Ca influx through T type Ca channels

Question 9

what causes a rising phase of action potential in pacemaker cells?

Answer 9

activation of L type Ca channels which causes a Ca influx

Question 10

what causes repolarisation in pacemaker cells?

Answer 10

Inactivation of L type Ca channels and activation of K efflux

Question 11

what is in the intercalated disc between cardiac myocytes?

Answer 11

desmosomes and gap junctions

Question 12

what is the resting membrane potential of atrial and ventricular myocytes?

Answer 12

-90mV

Question 13

what happens when depolarization moves away from the recording electrode?

Answer 13

upwards deflection on ECG

Question 14

position of the standard limb lead?

Answer 14

I : RA to LA
II : RA TO LL
III : LA to LL

Question 15

QT interval

Answer 15

start of QRS to end of T wave, 0.44-.46 seconds

Question 16

what are the lateral leads?

Answer 16

I and aVL

Question 17

what are the inferior leads?

Answer 17

II, III, aVF

Question 18

which leads look at

• inter ventricular septum?
• anterior of the heart
• lateral aspect of the heart

Answer 18

V1 and V2
V3 and V4
V5 and V6

Question 19

Khogali’s 6 step ECG analysis?

Answer 19

1. Verify patient details: name and date of birth
2. Check date and time ECG was taken
3. Check the calibration of the ECG paper
4. Determine the axis, if possible
5. Workout the rate and rhythm – use the rhythm strip and ask yourself the following 7 questions:
   1 Is electrical activity present?
   2 Is the rhythm regular or irregular?
   3 What is the heart rate?
   .4 P-waves present?
   5 What is the PR interval?
   6 Is each P-Wave followed by a QRS complex?
   7 Is the QRS duration normal?
6. Look at individual leads for voltage criteria changes OR any ST or T-wave changes