Practical points on the ECG

Question 1

what does the ST segments of the ECG represent?

Answer 1

ventricle contraction (systole)

Question 2

what does the TP segment represent?

Answer 2

ventricle relaxation (diastole)

Question 3

what is the PR interval?

Answer 3

largely AV nodal delay

Question 4

what is the normal time for PR?

Answer 4

0.12-0.2 seconds

Question 5

what is responsible for the QT interval ?

Answer 5

depolarisation and re-polarisation of the ventricles

Question 6

what is the normal time for QT?

Answer 6

0.36- 0.44 at a heart rate of 60. It NEEDS to be corrected for heart rate

Question 7

what is the paper speed of an ECG?

Answer 7

25mm/sec

Question 8

how do you calculate heart rate?

Answer 8

300/number of large squares between beats

Question 9

what is the ECG rhythm strip?

Answer 9

prolonged recording of one lead

Question 10

which lead is normally used for the rhythm strip?

Answer 10

lead 2

Question 11

why is a rhythm strip useful?

Answer 11

allows you to detect rhythm disturbance

Question 12

why do we need 12 leads?

Answer 12

leads allow you to look at the heart from different directions

Question 13

what does this 12 lead ECG allow you to do?

Answer 13

determine the axis of the heart in the thorax

look for any segment or T wave changes in relation to specific regions of the heart. This is curtail e.g. in diagnosing ischaemic heart disease

look for any voltage criteria changes. This is curtail in diagnosing e.g. chamber hypertrophy

Question 14

get a practical approach to analysing the ECG

Answer 14

determine the rhythm from the rhythm strip

Is electrical activity present?
Is the rhythm regular or irregular?
What is the heart rate?
P-waves present?
What is the PR interval?
Is each P-Wave followed by a QRS complex? 
Is the QRS duration normal? 

Then look at individual leads for voltage criteria changes
OR any ST or T-wave changes

Question 15

which diseases does a normal ECG not exclude?

Answer 15

MI

intermittent rhythm disturbance

stable angina

Question 16

what may an MI cause on an ECG but equally not always cause?

Answer 16

ST elevation

Question 17

what ECG should be done for intermittent rhythm disturbance?

Answer 17

If suspected do ambulatory ECG recording for 24 hrs or 7 days

Question 18

what should be done if the person has stable angina?

Answer 18

) If suspected do Exercise ECG. Look for ST changes during/after exercise. Usually absent during rest!