ECG interpretation

Question 1

P wave represents

Answer 1

represents the wave of depolarisation that spreads from the SA node throughout the atria

Question 2

What does the isoelectric period after the P wace represent?

Answer 2

the time in which the impulse is travelling within the AV node

Question 3

How long should a normal P wave last?

Answer 3

• 0.08-0.1 seconds
• 80-100 milliseconds

Question 4

P-R interval

Answer 4

time from the onset of the P wave to the beginning of the QRS complex

represents the time between onset of atrial depolarisation and onset of ventricular depolarisation

Question 5

Normal P-R interval usually lasts?

Answer 5

• 0.12-0.20 seconds
• 3-5 little squares

Question 6

QRS complex

Answer 6

represents ventricular depolarisation

Question 7

QRS complex normal time

Answer 7

upto 3 little squares
no more than 120 ms

Question 8

ST segment

Answer 8

• isoelectric period following QRS
• represents the period in which the entire ventricle is depolarised and roughly corresponds to the plateau phase of ventricular action potential

Question 9

T wave

Answer 9

represents ventricular repolarisation

longer in duration than depolarisation

Question 10

U wave

Answer 10

a small ppositive U wave may follow the T wave which represents the last remnants of repolarisation

Question 11

Q-T interval

Answer 11

represents the time for both ventricular depolarisation and repolarisation to occur, therefore roughly estimates the duration of a ventricular action potential

Question 12

Normal Q-T duration

Answer 12

0.2-0.4 seconds depending on heart rate

Question 13

at high heart rates Q-T segment will

Answer 13

shorten
ventricular action potentials shorten in duration

Question 14

Names of 12 lead ECG

Answer 14

• 1,2,3, aVR, aVL, aVF, (frontal plane)
  V1,V2,V3,V4,V5,V6 (horizontal plane)

Question 15

Normal PQRST waves label

Answer 15

insert diagram
may not always see all waves in QRS

Question 16

degree of heart standards ecg leads

Answer 16

insert

Question 17

chest lead positions

Answer 17

insert

Question 18

vertical and horizontal calibration markers

Answer 18

• vertical: 10 mV
  
  • generally, 1 small = 1mV, 1 big =
    5 squares
• horizontal: 1 small = 40ms, 5 small squares = 200 seconds, 5 big sqaures = 1 second

Question 19

initial analysis of ecg

Answer 19

• check calibration is 2 high 1 wide
• rate
• QRS axis
• rhythm

Question 20

calculation of heart rate from an ECg:

Answer 20

• count the squares between complexes:
  
  • 5 large = 60bpm
  • 4 large = 75 bpm
  • 3 large = 100 bpm
  • 2 = 150 bpm
  • 6 = 50bpm
• for an irregular rhythm:
  
  • count number of complexes in 30 large squares and multiply by 10
  • 30 large squares = 6 seconds (in uk)

Question 21

How to calculate the (mean frontal) QRS axis?

Answer 21

• overall direction of the electrical signal in the FRONTAL plane (not V leads)
• find the most isoelectric complex (goes up as much as it goes down) from leads: 1,2,3,aVF,aVR,aVL
• axis is 90 degrees from this
• normal QRS axis is between -30 and +120 degrees
• going toward which side?

Question 22

Insert mean frontal QRS axis question

Answer 22

insert
- lead II is most isoelectric
- 90 degrees either side is +150 or -30
- look at AVL and lead I both have QRS waves upwards
- lead three has QRS downwards
- hence must be -30

Question 23

Cardiac Rhythm (sinus)

Answer 23

• sinus rhythm = norm = atria contract before ventricles
• 1 p wave infront of every QRS complex
• resting generally between 60-90bpm

Question 24

Tachycarda (3 common)

Answer 24

• fast heart
• atrial fibrillation
• supraventricular tachycardia
• ventriculary tachycardia

Question 25

Atrial fibrillation on ECg

Answer 25

no p waves irregular multiple short circuits in atria hence very irregular to AV node

Question 26

Supraventiruclar tachycardia on ECG

Answer 26

regular, narrow complexes short circuuit that runs regularly in atria fairly bengin

Question 27

Ventricular tachycardia

Answer 27

regular, broad complexes short circuit that runs regularlry in ventricle very dangerous

Question 28

insert ecg what does it show

Answer 28

atrial fibrillation

Question 29

insert ecg what does it show

Answer 29

supraventricular tachycardia 150bpm

Question 30

insert ecg what does it show

Answer 30

ventricular tachycardia broad regular complexes

Question 31

Bradycardia (2)

Answer 31

slow heart rate - problems at AV node = heart block, doesnt get to ventricle - sinus node dysfunction

Question 32

insert ecg what does it show

Answer 32

complete heart block (AV node problem) 30bpm

Question 33

Heart Block ECG features

Answer 33

number of QRS complexes, ten square gap, 30 bpm, lots of p waves at normal rate not getting through AV node

Question 34

insert ecg what does it show

Answer 34

sinus node dysfunction intermittent p waves

Question 35

Sinus node dysfunction ecg features

Answer 35

- no p waves on first because no sinus beat - second and third have p waves - 30 bpm

Question 36

Tall complexes on ecg show signify

Answer 36

ventriculr hypertrophy

Question 37

broad complexes on ecg signify

Answer 37

bundle branch block more than 3 squares wide QRS

Question 38

ST elevation on ecg signify

Answer 38

MI or pericarditis

Question 39

ST depression/ T wave inversion signifies

Answer 39

many causes

Question 40

insert ecg what does it show

Answer 40

left ventricular hypertrophy (complexes go off the page or run into each other) T waves may also be inverted when complexes are big

Question 41

insert ecg what does it show

Answer 41

left bundle branch block broad complexes V1 lead generally will go downwards eight squares between p and QRS still attached tho so first degree heart block

Question 42

insert ecg what does it show

Answer 42

triphasic large downwards qrs V1 and V2 mostly above baseline right bundle branch block

Question 43

insert ecg what does it show

Answer 43

st segment elevated above baseline on standard leads st segment elevated v leads st segment is depressed, reciprocal change sixth complex is an ectopic beat acute inferior ST segment elevation myocardial infarc (acute inferior STEMI)

Question 44

Q wave MI

Answer 44

deeply inverted Q waves virtually no R waves T waves may be inverted - extensive damage to myocardium