ECG

Question 1

PR interval

Answer 1

Start of P to start of Q

3-5 boxes

Question 2

PR segment

Answer 2

End of P to start of Q

Question 3

QT interval (idea and number)

Answer 3

Start of Q to end of T

9-11.5 boxes

Question 4

ST segment

Answer 4

End of S to start of T

Question 5

QRS complex (number)

Answer 5

2-3 boxes (30-120ms)

Question 6

Number of leads

Answer 6

3 bipolar leads - I, II, III (frontal plane)
3 augmented leads
6 precordial leads

Question 7

Where is Lead II put

Answer 7

Positive electrode on left leg
Negative electrode on right arm
Ground on right leg

Question 8

Speed of contraction in different cells

Answer 8

AV node: 0.05m/s
Purkinje fibres: up to 5m/s
Conduction via bundles: 1m/s
AV node delays signal by 0.1-0.2 seconds
Slower conduction between contractile myocytes (0.5m/s)

Question 9

What is happening at each part of an ECG

Answer 9

P wave: depolarisation of the atria
PR segment: delay of AV node
QRS complex: depolarisation of ventricles
T wave: repolarisation of ventricles
ST segment - beginning of repolarisation in the ventricles

Question 10

Calculate Rate

Answer 10

300 divided by the number of big boxes

Or if irregular - number of P waves in a 10 second interval, and times this by 6 - bpm

Question 11

First Degree Heart Block

Answer 11

PR interval is more than 5 little boxes
usually asymptomatic
In young people
Delayed AV node transmission

Question 12

Mobitz type 1 (Wenckebach)

Answer 12

PR interval gets longer and longer until a QRS fails to follow P wave
Cause: AV node damage

Question 13

Mobitz Type II (Hay)

Answer 13

Some P waves are blocked and not followed by a QRS
PR interval remains the same
Likely cause: problem with bundle of His
Implant pacemaker

Question 14

Third degree Heart Block

Answer 14

Atrial signals consistently fail to arrive at the ventricles
Ventricular rate is consistent - 30-40 bpm
Time between atrial and ventricular beats is variable
PR interval varies rapidly
Narrow-complex escape rhythms >40bpm
or Broad-complex escape rhythms - slower HR

Question 15

Respiratory sinus arrhythmia

Answer 15

Benign
When a person breathes in, heart beat increases
When a person breathes out, heart beat decreases

Question 16

Escape beats and premature beats

Answer 16

Premature beats triggered by irritable tissue
Escape beats triggered by natural rhythmicity of non-atrial tissue
Triggered in ventricular tissue or by AV node

Question 17

Premature Ventricular Contractions

Answer 17

Unusually wide and weird looking ventricular contractions
the 2 ventricles are electrically unsynchronised
No S wave, and a negative dip where the T wave should be

Question 18

Atrial Fibrillation

Answer 18

Disorganised electrical activity in atria - no P wave/wiggly line
Ventricular rate is fast and irregular
Very common in elderly
Can lead to thrombus formation in atria

Question 19

What is the ECG best for

Answer 19

Excellent for rate (Holter monitor 24/7)
Seeing when something is wrong, but is not a one stop diagnosis
Fast and affordable

Question 20

What are deep, large Q waves a sign of

Answer 20

Dead tissue - old MI

Question 21

What does 1 big/little box represent

Answer 21

1 big box: 200ms

1 small box: 40 ms