ECG

Question 1

Accelerated idioventricular rhythm (AIVR)

Answer 1

Ectopic ventricular pacemaker exceeds AV node
Rhythm: Regular
Rate: 50-120bpm
P wave: absent
PR-not measurable
QRS- wide >0.12 sec not normal looking

Question 2

Causes of Accelerated idioventricular rhythm

Answer 2

Reperfusion of acute MI
Beta-sympathomimetics such as isoprenaline or adrenaline
Drug toxicity, especially digoxin, cocaine and volatile anaesthetics such as desflurane
Electrolyte abnormalities
Cardiomyopathy, congenital heart disease, myocarditis
Return of spontaneous circulation (ROSC) following cardiac arrest

Question 3

Inferior STEMI. Leads and blood supply

Answer 3

Leads: II, III, aVF

Blood supply. RCA or LCx more commonly RCA

Question 4

Anterior STEMI Leads and blood supply

Answer 4

Leads: V2-V4

Blood supply: LAD

Question 5

Anteroseptal Leads and blood supply

Answer 5

Leads: V1-V4

Blood supply: LAD

Question 6

Lateral STEMI

Answer 6

I. aVL, V5,V6

LCx>LAD

Question 7

Left anterior fascicular block (LAFB)

Answer 7

Blockage means conduction to the left passes through the posterior fascicle. So vector down and right resulting in (due to right branch reaching first)
Small R waves in inferior leads
Small Q waves in lateral leads

Vector then spreads upwards and outwards to where anterior fascicle would usually supply so:

Large R waves in lateral leads
Large S waves in inferior leads

longer QRS,maybe normal 85-110 ms

Question 8

Left posterior fascicular block (LPFB)

Answer 8

Blockage means conduction runs through the anterior fascicle. So vector is upwards and left.
Small R waves in lateral
Small Q waves in inferior

Major wave then goes along LV wall so vector is downward and right

Large S waves in lateral
Large R waves in inferior

RAD, QRS normal or prolonged

Question 9

Right bundle branch block (RBBB)

Answer 9

Right ventricle delayed as impulse has to travel from the left ventricle
left ventricle is activated normally, meaning that the early part of the QRS complex is unchanged.

Delayed right ventricule results in a secondary R wave in v1-v3 and slurred S wave in lateral leads RSR’
QRS>120

Question 10

Left bundle branch block (LBBB)

Answer 10

Septal depolarisation is reversed R to L.
Eliminates normal small Q wave in lateral leads
Widens QRS >120ms
Tall R waves in the lateral leads (v5-v6)
Deep S waves in V1-3
LAD

Question 11

Bifascicular block

Answer 11

Usually RBBB and LAFB or LPFB. Means only one fascicle for heart impulses usually seen on ECG by RBBB with RAD
Most commonly due to ischaemic heart disease

Question 12

First degree block

Answer 12

PR > 200ms

Question 13

Second degree block Mobitz Type 1 (Wenckebach)

Answer 13

Progressive prolongation of PR followed by a missed QRS
P-P interval is constant

usually due to reversible conduction block at the level of the AV node

Question 14

Causes of mobitz type 1

Answer 14

Drugs: beta-blockers, calcium channel blockers, digoxin, amiodarone
Increased vagal tone (e.g. athletes)
Inferior MI
Myocarditis
Following cardiac surgery (mitral valve repair, Tetralogy of Fallot repair)

Question 15

Mobitz type II block

Answer 15

PR constant
intermittently missed conductions
Complete dissociation of P waves and QRS
Due to failure of His-Purkinje fibres. Structural damage

Question 16

Cause of mobitz type II

Answer 16

Anterior MI (due to septal infarction with necrosis of the bundle branches).
Idiopathic fibrosis of the conducting system (Lenegre’s or Lev’s disease).
Cardiac surgery (especially surgery occurring close to the septum, e.g. mitral valve repair)
Inflammatory conditions (rheumatic fever, myocarditis, Lyme disease).
Autoimmune (SLE, systemic sclerosis).
Infiltrative myocardial disease (amyloidosis, haemochromatosis, sarcoidosis).
Hyperkalaemia.
Drugs: beta-blockers, calcium channel blockers, digoxin, amiodarone.