ECG Abnormalities

Question 1

List Conduction defects pathology on ECG

Answer 1

Heart block - 1st degree, 2nd degree, 3rd degree 
Right BBB
Left BBB
Bifrascular block 
Trifascular block

Question 2

What is the feature of 1st degree heart block

Answer 2

PR > 200 ms

Question 3

What are the features of 2nd degree heart block

Wenckebach / Mobitz 1

Answer 3

Progressive lengthening of PR interval
One non conducted p wave
Next conducted beat has a shorter PR interval

Question 4

Features of 2nd degree heart block mobitz 2

Answer 4

Constant PR
Occasional nonconducted p waves
Often wide QRS
-block is usually in bundle branches of Purkinje fibres

Question 5

Features of 2nd degree heart block 2:1

Answer 5

2 p wave per QRS

Normal consistent PR waves

Question 6

Features of 3rd degree heart block

Answer 6

P waves and QRS are at different rates there is dissociation
Abnormally shaped QRS ventricular origin 40bpm

Question 7

Features of right BBB

Answer 7

Wide QRS 
MaRRoW in v1 and v 6
rSR pattern in v1
Aetiology 
- Infarct inferior MI
- normal variation
- congenital -ASD, VSD, Tetralogy of Fallot 
- hypertrophy - RVH (PE, Cor pulmonale)
Spells INCH

Question 8

Features of left BBB

Answer 8

WiLLiaM 
Wide QRS notched at the top 
T wave inversion in the lateral leads
Aetiology 
- fibrosis 
- LVH - AS, HTN
- infarct - inf MI
- Coronary HD 
Spells FLIC

Question 9

Feature of a bifascular block

Answer 9

RBBB & LAD

Question 10

Features of a trifascular block

Answer 10

RBBB & LAFB & 1st degree AV block

Question 11

Types of escape rhythms and what are they

Answer 11

Atrial escape
Junctional escape
Ventricular escape

They appear late after the expected beat

Question 12

What features of an atrial escape

Answer 12

SAN fails to depolarise potentially due to a sinus node arrest or exit block so may be a long pause if the pause is long enough there will be an escape atrial rhythm at a rate correlating with the intrinsic automaticity of the atrial focus. May be a single atrial beat, multiple atrial complexes, or a sustained ectopic atrial rhythm due to an ectopic site
Rate is slower than sinus node and different p wave this depends on the location of the ectopic atrial focus
Abnormal P wave
Normal QRS
60-80 bpm q

Question 13

Features of a junctional escape

Answer 13

Usually no p waves
Occasionally after QRS
Normal QRS
40-60 bpm
They occur when there is a failure of upper pacemaker tissue (absence of impulse from SAN or atrial myocardium or AV block
They occur after a variable pause longer than sinus length
In this rhythm there are one or more QRS that are not preceded by a pwave
Occur sinus arrest or AV block in this case there are p waves that are dissociated with the QRS complexes and the PR interval are variable

Question 14

What are the features of a ventricular escape

Answer 14

Usually a result of complete AV block therefore there are regular p waves
Or may be due to SAN failure - no p waves
Wide QRS 20bpm

Failure of SAN and AV node to generate an impulse
Absence p wave
Associated with widened QRS that resembles premature ventricular contraction and occurs after a variable pause
In 2nd or 3 rd heart block there is SAN activity no AV node there are p waves dissociated from ventricular complexes and are faster