QRS abnormalities

Question 1

Criteria for LVH

Answer 1

– In limb leads: [R in lead I] + [S in lead III] > 25mm
– In chest leads: any of the following:
* R in V5-6 >25mm
* S in V1-3 > 25mm
* [S in lead V1] + [R in lead V5 or 6] > 35mm (>40yrs old)
* [Tallest R] + [deepest S] > 45mm
– LVH may also show evidence of ‘strain’ in L-sided leads: ST
segment depression + T wave inversion

Question 2

Criteria for RVH

Answer 2

[dominant R in V1] + [R axis deviation] + [deep S in V5-6] +/-
RBBB

‘strain’: ST segment depression, T wave inversion in V1-2

Question 3

How do we inspect for Posterior infarction?

Answer 3

what appears as a dominant R-wave in V1 is in fact a reciprocal
view of a pathological Q wave

Question 4

What is a definite sign of a BBB?

Answer 4

wide QRS, that is always preceded by a P wave.

Question 5

What is BBB common confused with and how can we distinguish from it?

Answer 5

Ventricular pace makers (wide QRS) but no preceding P wave

Question 6

Criteria for RBBB.

Answer 6

rSR pattern in V1
– preceded by P
– followed by abN repolarization pattern
– Wide ‘slurred’ S wave in V6
– If R Axis Deviation: RBBB is part of RVH
Wide QRS

Question 7

Causes of RBBB

Answer 7

Ischaemia
Cardiomyopathy

Question 8

Criteria for LBBB.

Answer 8

– ‘M’ pattern in V6
– preceded by P
– followed by abN repolarization (T-waves)
– In V1, S-wave may look slurred (notch is not always obvious)
Wide QRS

Question 9

Causes of LBBB.

Answer 9

Acute MI and Hypertension

Question 10

Criteria for L ant Hemi-block.

Answer 10

LAD and V6 R small

Question 11

Criteria for PAC.

Answer 11

Shorter PP interval preceding it.
Also opposite direction.

Question 12

Criteria for PJC.

Answer 12

Not preceded by a P wave.
Shorter RR interval

Question 13

Describe a PVC.

Answer 13

Earlier than expected p wave
Wide QRS
Short RR interval and compensatory pause

Question 14

Characteristics of a Physiological Pacemaker

Answer 14

Primary pacemaker
too slow/stopped
Wave arises after a
prolonged pause
Is an electrical
safety back-up

Question 15

Premature complexes

Answer 15

Superimposed on
underlying rhythm
Wave premature
Electrical Abnormality

Question 16

What is an abnormal Q wave?

Answer 16

– Q > 2mm deep
– Q >40ms wide
– Q > 25% of height of following R-wave
– Present in V1-V3

Question 17

Criteria for ST elevation and depression.

Answer 17

– ST segment elevation: ST > 1mm in 2 or more contiguous limb
leads or > 2mm in 2 or more chest leads
– ST segment depression: ST > or equal to 0.5mm in 2 or more
contiguous leads