Bundle Branch block

Question 1

Depolarisation waves travel through the heart’s septum via the ____ __ ___ and _____ ____ which are organised into left and right bundle branches

Answer 1

Bundle of His
Purkinje fibres

Question 2

The 2 bundle branches depolarise the respective ventricles s______

Answer 2

simultaneously

Question 3

Which bundle branch depolarises the septum?

Answer 3

Left bundle branch

Question 4

Ventricular depolarisation (QRS) is normally complete with ___ ms

Answer 4

120

Question 5

A broad QRS complex indicates…

Answer 5

abnormal ventricular depolarisation

Question 6

The main feature of bundle branch bocks is the ______ of ____ ______

Answer 6

broadening of QRS complexes

Question 7

What is the diagnostic criteria for Right bundle branch block?

Answer 7

Broad QRS complex longer than 120ms (3 small squares)

RSR’ pattern in V1-V3

Wide slurred S wave in lateral leads: I, aVL, V5-6

Question 8

What is the RSR’ pattern in Right BBB?

Answer 8

An intitial upward deflection (R wave), a larger downward deflection (S wave), then another large upward deflection (R’ wave)

Question 9

What mnemonic can be used to recognise left and right bundle branch blocks by looking at V1 and V6?

Answer 9

WiLLiaM
MaRRoW (V1 resembles M, V6 resembles W)

Question 10

In right bundle branch block the SAN acts as initial pacemaker. Depolarisation reaches the AVN but through the bundle of His only on the ____ bundle branch

Answer 10

left

Question 11

In right bundle branch block, is the septum depolarised?

Answer 11

Yes
(septum depolarised by left bundle branch)

Question 12

In right bundle branch block the left ventricular wall depolarises as normal but the right ventricular walls eventually depolarised by the left bundle branch block by a ____ less e____ pathway

Answer 12

slower, less efficient

Question 13

What is the diagnostic criteria for left bundle branch block?

Answer 13

Broad QRS complex (over 120ms or 3 small squares)
Dominant S wave in V1
Broad monophasic R wave in lateral leads: I, aVL, V5-V6
Absence of Q waves in lateral leads
Prolonged R wave over 60ms in leads V5-6

Question 14

How is the septum depolarised in left bundle branch block?

Answer 14

Abnormally from right to left

Question 15

The left ventricle has greater mass so LBBB can cause cardiac axis changes and the left bundle branch splits into _____ and ______ fascicles

Answer 15

anterior and posterior

Question 16

In LBBB there is block in both….

Answer 16

left anterior fascicule and left posterior fascicle

Question 17

If only the anterior fascicle is blocked, then there is ___ axis deviation

Answer 17

left

Question 18

Posterior fascicle block may cause ____ axis deviation

Answer 18

right
However, posterior fascicle does less work than anterior fascicle so may not have obvious ECG changes

Question 19

The right ventricular muscle doesn’t have enough mass to significantly d___ the c____ a___

Answer 19

deviate the cardiac axis

Question 20

What is bifascicular block?

Answer 20

Both the right bundle branch and one of the fascicles of the left bundle branch is blocked

Question 21

What is trifascicular block?

Answer 21

When a 3rd degree heart block exists alongside bifascicular block

Question 22

____ bundle branch block is always pathological and indicates significant damage to the cardiac conduction system

Answer 22

Left

Question 23

A broad complex tachycardia requires differentiation between v_____ tachycardia or s____ tachycardia with concurrent b___ b____ b____

Answer 23

ventricular
sinus
bundle branch block