Physiology: ECG

Question 1

What is the principle of ECG

Answer 1

To record the cardiac action potential at body surface

Question 2

What waves are detected by the ECG machine

Answer 2

Depolarisation & repolarisation wave

Question 3

What is 2 T wave abnormalities

Answer 3

1. Peaked T wave indicate hyperkalaemia
2. Inverted T wave indicated ischaemia or digoxin

Question 4

What is 2 ST segment abnormalities

Answer 4

1. ST elevation indicate recent infarction
2. ST depression & T wave inversion indicate MI

Question 5

What is the 2 QRS complex abnormalities

Answer 5

1. Significant Q wave indicate old infarction
2. M like appearance indicate bundle branch block

Question 6

What is 3 P wave abnormalities

Answer 6

1. Absent indicate no sinus rhythm & AV node takes over
2. Peaked indicate right atrial enlargement
3. Double peak indicate left atrial enlargement

Question 7

What is 4 PR interval abnormalities

Answer 7

1. Prolonged PR interval indicate 1st degree heart block
2. Increased PR interval & dropped beat indicate 2nd degree heart block Mobitz type 1
3. Non-conducted P wave indicate 2nd degree heart block Mobitz type 2
4. Complete AV dissociation w/ no QRS complex/T wave indicate 3rd degree heart block

Question 8

What does the different parts of the ECG indicated

Answer 8

GRAPH
P wave: atrial depolarisation
Q wave: interventricular septal depolarisation
R wave: ventricle depolarisation at apex
S wave: ventricle depolarisation at base
QRS – ventricular depolarization (mask atrial repolarisation)
T wave: ventricular repolarization
PR segment: AV delay
ST segment: ventricle completely depolarized

Question 9

What is the 3 leads

Answer 9

1. Limb
2. Augmented
3. Chest
   add placements