Chapter 2

Question 1

P wave is caused by…

Answer 1

the SA node (located at the top of the right atrium) initiating atrial depolarisation

Question 2

P wave amplitude…

Answer 2

< 0.25mV (2.5 small squares)

Question 3

P wave duration…

Answer 3

< 0.12s (3 small squares)

Question 4

P wave is positive in…

Answer 4

I and II

Question 5

Inverted p wave in I may suggest…

Answer 5

arm electrodes are placed wrong, dextrocardia or abnormal atrial rhythm

Question 6

P wave is inverted in…

Answer 6

aVR

Question 7

P wave in V1 can be…

Answer 7

biphasic

Question 8

PR interval =

Answer 8

The time between onset of atrial depolarisation and onset of ventricular depolarisation as the electrical impulse is conducted through the AV node, the bundle of His, bundle branches and Purkinje fibres

Question 9

Duration of PR interval =

Answer 9

0.12 – 0.20s (3-5 small squares)

Question 10

QRS complex =

Answer 10

Ventricular depolarisation

Question 11

QRS duration =

Answer 11

< 0.10s (2.5 small squares)

Question 12

Delays in ventricular depolarisation e.g. bundle branch block =

Answer 12

wide QRS (>0.12s, 3 small squares)

Question 13

The left side of the septum depolarises first and then the impulse travels towards the right…

Answer 13

Lead V1 lies immediately to the right of the septum = an initial small positive deflection (R wave) is caused as the depolarisation wave travels towards this lead

Question 14

When the wave of depolarisation travels away from the recording electrode…

Answer 14

the first deflection is negative = small Q wave

Question 15

normal Q waves =

Answer 15

<2 small squares deep, <1 small square wide and <25% of the amplitude of the R wave

are often present in lateral leads (I, aVL, V5, V6)

Question 16

Precordial lead QRS morphology changes depending on whether the depolarisation forces are moving towards or away from a lead:

Answer 16

V1 = small positive (R) wave followed by large negative deflection (S wave)

R wave increases in amplitude from V1-V6 (usually <27mm in V5-V6)

S wave depth decreases from V1-V6 (V1 = <30mm, often absent in V5-V6)

QRS complex changes from being predominantly negative in V1 to being predominantly positive in V6 (the transition zone lies between V3 and V4)

Question 17

ST segment =

Answer 17

Period between end of ventricular depolarisation and the begging of repolarisation

Question 18

ST segment in V1-V3 =

Answer 18

rapidly ascending S wave merges with T wave (high-take off)

Question 19

Non-pathological ST elevation can be associated with…

Answer 19

benign early repolarisation (common in young men, athletes and black people)

Question 20

T waves =

Answer 20

Ventricular repolarisation

Question 21

T waves are…

Answer 21

Asymmetrical - first half more gradual slope than the second half

Inverted in aVR, sometimes in III and V1 (occasionally in V2 as well as V1 – isolated V2 inversion is abnormal)

If symmetrical and inverted suggests myocardial ischemia

Question 22

Tall T waves?

Answer 22

?acute myocardial ischemia or hyperkalaemia

Question 23

QT interval is…

Answer 23

Total time taken for depolarisation and repolarisation of the ventricles

Question 24

QT interval duration =

Answer 24

0.35-0.45s

Question 25

U waves =

Answer 25

Small deflection that follows the T wave

Generally upright (except in aVR)

Most prominent in V2-V4

Results from repolarisation of mid-myocardial cells (those between the endocardium and epicardium) and His-Purkinje system

seen in athletes, hypokalaemia and hypercalcemia