Atrioventricular block

Question 1

what results in AV block?

Answer 1

block in conduction in either the AV node or the bundle of his.

Question 2

How many forms of heart block are there?

Answer 2

Three.

Question 3

what is first degree AV block?

Answer 3

Prolongation of the PR interval to >0.22s. every atrial depolarisation is followed by conduction to the ventricles but with delay (every P wave is followed by a QRS)

Question 4

what is second degree AV block?

Answer 4

Some P waves conduct and others do not.

Question 5

what are the different forms of second degree AV block called?

Answer 5

Mobitz I block, Mobitz II block and 2:1 or 3:1 block

Question 6

what is Mobitz I AV block?

Answer 6

Progressive PR interval prolongation until a P wave fails to conduct. The PR interval before the blocked P wave is much longer than the PR interval after the blocked P wave.

Question 7

what is mobitz II AV block?

Answer 7

occurs when a dropped QRS complex is not preceded by progressive PR interval prolongation. usually has a wide QRS complex (>0.12s)

Question 8

What is 2:1 or 3:1 block?

Answer 8

occurs when every second or third P wave conducts to the ventricles

Question 9

what is third degree heart block?

Answer 9

complete heart attack occurs when all atrial activity fails to conduct to the ventricles

Question 10

what drug may be given to treat heart block?

Answer 10

IV atropine

Question 11

what are congenital causes of complete heart block?

Answer 11

• autoimmune

- structural heart disease

Question 12

what are idiopathic fibrosis causes of complete heart block?

Answer 12

• Lev’s disease

- Lenegre’s disease

Question 13

what are the ischaemic heart disease causes of complete heart block?

Answer 13

• acute myocardial infarct

- ischaemic cardiomyopathy

Question 14

what are the non-ischaemic heart disease causes of complete heart block?

Answer 14

• calcific aortic stenosis
• idiopathic dilated cardiomyopathy
• infiltrations (e.g. amyloidosis, sarcoidosis, neoplasia)

Question 15

what types of surgery may result in complete heart block?

Answer 15

aortic valve replacement, CABG, VSD repair

Question 16

what iatrogenic causes are there of complete heart block?

Answer 16

radiofrequency AV ode ablation and pacemaker implantatation

Question 17

what drugs could cause complete heart block?

Answer 17

digoxin, beta-blockers, non-dihydropyridine calcium-channel blockers, amiodarone

Question 18

what infections could cause complete heart block?

Answer 18

endocarditis, lyme disease and chagas’ disease

Question 19

what autoimmune rheumatic disease causes of complete heart block are there?

Answer 19

SLE, rheumatoid arthritis

Question 20

what neuromuscular disease causes complete heart block?

Answer 20

duchenne muscular dystrophy

Question 21

what is bundle branch conduction delay?

Answer 21

slight widening of the QRS complex (up to 0.11s).

Question 22

what is bundle branch conduction delay known as?

Answer 22

incomplete bundle branch block

Question 23

what is complete block of bundle branch?

Answer 23

associated with a wider QRS complex (>0.12s).

Question 24

what does the shape of the QRS depend on in complete BBB?

Answer 24

whether the right or the left bundle is blocked.

Question 25

How is right bundle branch block seen on the ECG?

Answer 25

deep S waves in leads I and V6 and as a tall late R wave in V1

Question 26

How is left bundle branch block seen on the ECG?

Answer 26

deep S wave in lead V1 and a tall late R wave in leads I and V6.

Question 27

what is hemiblock?

Answer 27

delay or block in the divisions of the left bundle branch produces a swing in the direction of depolarisation of the heart.

Question 28

what is bifascicular block?

Answer 28

a combination of a block of any two of the following - right bundle branch, the left antero-superior division and the left postero-inferior division.

Question 29

what symptoms may be seen for bundle branch block?

Answer 29

none. it is usually asymptomatic.

Question 30

what signs may be seen in bundle branch block?

Answer 30

Right BBB may cause splitting of the second heart sound. | left BBB may cause reverse splitting of the second heart sound.

Question 31

what symptoms may patients with intraventricular conduction disturbances complain of?

Answer 31

syncope

Question 32

what are the causes of right bundle branch block?

Answer 32

``` normal finding in about 5% of individuals. congenital cardiac disorders such as: - atrial and ventricular septal defects - pulmonary stenosis and Fallot's tetralogy - pulmonary embolism - pulmonary hypertension - MI - fibrosis of conduction tissue - chagas disease ```

Question 33

what are the common causes of left bundle branch block?

Answer 33

aortic stenosis hypertension MI severe coronary disease