heart block

Question 1

3 types of heart block

Answer 1

first degree
2nd degree
3rd degree (complete)

Question 2

what are the 2 places that can be blocked

Answer 2

Block in AVN or bundle of His = AV block

Block in lower conduction system = Bundle Branch Block (RBBB or LBBB)

Question 3

3 causes of heart block

Answer 3

1. Coronary artery disease
2. Cardiomyopathy
3. Fibrosis of conducting tissues (particularly in elderly people)

Question 4

what is first degree heart block

Answer 4

This is the result of delayed AV conduction (but still makes it to the ventricles) and is reflected by a prolonged PR interval (>0.22s) on the ECG

Question 5

4 causes of first degree heart block

Answer 5

1. LEV’s disease
2. IHD – scar tissue from myocyte death blocks conduction pathway
3. Myocarditis
4. Hypokalaemia

Question 6

management for first degree heart block

Answer 6

asymptomatic so no treatment required

Question 7

what is second degree heart block

Answer 7

This occurs when some atrial impulses fail to reach the ventricles

Question 8

2 forms of second degree heart block

Answer 8

1. Mobitz type 1 (Wenckebach)
2. Mobitz type II`

Question 9

what happens in mobitz type 1 heart block

Answer 9

1. Generally caused by AV node block and results in progressive PR interval prolongation until a P wave fails to conduct and a QRS is absent after the first P wave (dropped beat)
2. Eventually ventricle’s pacemaker cells kick in
3. The PR interval then returns to normal and the cycle repeats itself

Question 10

what does patient with mobitz type 1 heart block experience

Answer 10

light headedness, dizziness and syncope

Question 11

what happens in mobitz type 2 heart block

Answer 11

1. Caused by a block at an intra-nodal level so the QRS is widened and QRS complexes are dropped without PR prolongation
2. Fairly random dropped beats – no PR elongation

Question 12

what does patient with mobitz type 2 heart block experience

Answer 12

chest pain, SOB, syncope and postural hypotension

Question 13

what is third degree complete heart block

Answer 13

Occurs when there is complete dissociation between atrial and ventricular activity.

E.g. atrial BPM is 60, ventricular is 30 BPM

Question 14

3 causes of third degree heart block

Answer 14

CHD
Infection
Hypertension

Question 15

4 symptoms of third degree heart block

Answer 15

Syncope
Dyspnoea
Chest pain
Confusion

Question 16

what does ECG for third degree heart block show

Answer 16

P waves and QRS complexes occur independent

Ventricular contractions are sustained by spontaneous escape rhythm originating below the site of the block in 2 places

Question 17

what does ecg show if block is in his bundle

Answer 17

His bundle – gives rise to a narrow QRS complex at a rate of 50-60 BPM and is relatively reliable

Question 18

what does ecg show if block is in his purkinje system

Answer 18

i.e. distally – gives rise to a broad QRS complex at a rate of <40 BPM, often associated with dizziness and blackouts

Question 19

treatment for third degree heart block

Answer 19

IV atropine (acute) – increases HR

Permanent pacemaker insertion

Question 20

what is bundle branch block

Answer 20

Complete block of a bundle branch is associated with a wide QRS complex with an abnormal pattern and is usually symptomatic.

Question 21

causes of acute bundle branch block

Answer 21

Ischaemia and MI
Myocarditis

Question 22

causes of chronic bundle branch block

Answer 22

HTN
Cardiomyopathies

Question 23

2 types of bundle branch block

Answer 23

RBBB

LBBB

Question 24

what is RBBB bundle branch block

Answer 24

There is sequential spread of an impulse (i.e. LV then RV)

Results in an R wave in V1 and a slurred S wave in V5/6 (

Question 25

what does RBBB bundle branch block occur in

Answer 25

Occurs in PE, RV hypertrophy, IDH, congenital heart disease

Question 26

what is LBBB bundle branch block

Answer 26

Opposite of a RBBB
Slurred S wave in V1 and R wave in V5/6 (WiLLiaM)

Question 27

what does LBBB bundle branch block occur in

Answer 27

IHD, aortic stenosis, hypertension, aortic valve disease

Question 28

management for bundle branch block

Answer 28

Cardiac pacemaker