ECGs

Question 1

ECG square dimension (time)

Answer 1

small square: 1mm, 0.04 sec
big square: 5mm, 0.20 sec

Question 2

what does the p wave represent

Answer 2

atrial depolarisation, conduction from SAN throughout atria

Question 3

PR interval represents

Answer 3

time for electrical activity to go from atria to ventricles through the AVN

Question 4

what does QRS complex represent

Answer 4

ventricular depolarisation

Question 5

what does ST segment represent

Answer 5

time taken after depolarisation finishes for repolarisation to begin

Question 6

what does t wave represent

Answer 6

ventricular repolarisation

Question 7

what does qt interval represent

Answer 7

time for ventricles to depolarise then repolarise

Question 8

what does rr interval represent

Answer 8

time between two QRS complexes, time for one complete heart cycle

Question 9

normal pulse

Answer 9

60-100 bpm

Question 10

what is sinus rhythm

Answer 10

p wave starting each qrs complex

Question 11

how to calculate rate if regular

Answer 11

1500/number of small squares
300/number of large squares

Question 12

which leads are used to assess cardiac axis

Answer 12

I, II, aVF

Question 13

how to assess cardiac axis

Answer 13

if II is +ve and I is +ve then cardiac axis normal
if II is -ve and I is +ve then left axis deviation
If II is +ve and I is -ve then right axis deviation
if aVF is -ve and I is -ve then there is extreme axis deviation

Question 14

is axis deviation always pathological

Answer 14

no. LAD seen in short fat ppl and RAD in tall thin ppl

Question 15

how should p waves look

Answer 15

+ve in leads I, II
inverted in aVR
biphasic in V1

Question 16

how can p waves be abnormal

Answer 16

absent
sawtooth
p pulmonale (right atrial enlargement)
p mitrale (left atrial enlargement)
p wave inversion

Question 17

what does a wide QRS indicate

Answer 17

ventricles not correctly depolarised

Question 18

how does calcium affect qt interval

Answer 18

hypercalcaemia shortens it
hypocalcaemia prolongs it

Question 19

atrial fibrillation ECG

Answer 19

irregularly irregular rhythm
absent p waves
narrow QRS

Question 20

rule of thumb for if activity is from atria or ventricles

Answer 20

if the activity is starting at or above AVN then narrow QRS
broad QRS implies ventricular origin or aberrant conduction

Question 21

atrial flutter ECG

Answer 21

regularly irregular rhythm
absent p waves with sawtooth baseline
narrow QRS

Question 22

Supraventricular tachycardias ECG

Answer 22

any tachyarrythmia above bundle of His
retrograde p waves (after QRS)
p wave could be in T waves or look like double t waves

Question 23

1st degree heart block ECG

Answer 23

prolonged PR interval
can be seen in healthy ppl

Question 24

Mobitz type 1 heart block ECG

Answer 24

also 2nd degree heart block type 1 or Wenckeback phenomenom
usually benign

starts with shorter PR interval
gets longer each cycle
eventually p wave without QRS
then cycle begins again

represents increased delay at AVN

Question 25

Mobitz type 2 heart block ECG

Answer 25

aka 2nd degree heart block type 2 PR interval constant when QRS present some p waves not followed by QRS represents damage to conduction tissue below AVN - always pathological could be broad or narrow QRS

Question 26

3rd degree heart block ECG

Answer 26

complete cessation of AV conduction p waves and qrs independent can be broad or narrow qrs patient usually bradycardic

Question 27

Wolff-Parkinson-White ECG

Answer 27

accessory pathway from atria to ventricles typically connecting left atria to left ventricle short pr interval broad QRS with slurring of start

Question 28

ventricular fibrillation ECG

Answer 28

incompatible with life rapid, broad, irregular, chaotic ventricular depolarisation no discernible waves

Question 29

monomorphic VT ECG

Answer 29

most common VT fast HR broad, consistent ventricular complexes loss of other features sometimes occasional normal cycles

Question 30

left bundle branch block ECG

Answer 30

damage to left bundle branch, usually pathological broad QRS deep S wave in V1 notched R wave in V6 can also see notched top in other lateral leads new LBBB consistent with STEMI

Question 31

right bundle branch block ECG

Answer 31

damage to right bundle branch usually pathological broad QRS RSR in V1 and adjacent leads wide slurred S wave in V6 ST depression and t wave inversion v1-3

Question 32

Torsades de Pointes (TdP)

Answer 32

type of polymorphic VT broad QRS changing amplitude beat to beat twisting appearance

Question 33

NSTEMI ECG

Answer 33

subendocardial ischaemia (sub-total occlusion) widespread ST depression T wave inversion

Question 34

pericarditis ECG

Answer 34

widespread concave ST elevation (often saddle shaped) widespread PR depression may be tachycardic

Question 35

hyperkalaemia ECG

Answer 35

potassium >5.5 tented T waves

Question 36

hypokalaemia ECG

Answer 36

potassium <3.5 ST depression T wave inversion and U waves