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Cardiovascular > Atrioventricular block > Flashcards

Atrioventricular block Flashcards

1
Q

what results in AV block?

A

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

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2
Q

How many forms of heart block are there?

A

Three.

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3
Q

what is first degree AV block?

A

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)

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4
Q

what is second degree AV block?

A

Some P waves conduct and others do not.

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5
Q

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

A

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

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6
Q

what is Mobitz I AV block?

A

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.

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7
Q

what is mobitz II AV block?

A

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

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8
Q

What is 2:1 or 3:1 block?

A

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

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9
Q

what is third degree heart block?

A

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

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10
Q

what drug may be given to treat heart block?

A

IV atropine

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11
Q

what are congenital causes of complete heart block?

A
  • autoimmune

- structural heart disease

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12
Q

what are idiopathic fibrosis causes of complete heart block?

A
  • Lev’s disease

- Lenegre’s disease

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13
Q

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

A
  • acute myocardial infarct

- ischaemic cardiomyopathy

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14
Q

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

A
  • calcific aortic stenosis
  • idiopathic dilated cardiomyopathy
  • infiltrations (e.g. amyloidosis, sarcoidosis, neoplasia)
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15
Q

what types of surgery may result in complete heart block?

A

aortic valve replacement, CABG, VSD repair

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16
Q

what iatrogenic causes are there of complete heart block?

A

radiofrequency AV ode ablation and pacemaker implantatation

17
Q

what drugs could cause complete heart block?

A

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

18
Q

what infections could cause complete heart block?

A

endocarditis, lyme disease and chagas’ disease

19
Q

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

A

SLE, rheumatoid arthritis

20
Q

what neuromuscular disease causes complete heart block?

A

duchenne muscular dystrophy

21
Q

what is bundle branch conduction delay?

A

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

22
Q

what is bundle branch conduction delay known as?

A

incomplete bundle branch block

23
Q

what is complete block of bundle branch?

A

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

24
Q

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

A

whether the right or the left bundle is blocked.

25
Q

How is right bundle branch block seen on the ECG?

A

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

26
Q

How is left bundle branch block seen on the ECG?

A

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

27
Q

what is hemiblock?

A

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

28
Q

what is bifascicular block?

A

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.

29
Q

what symptoms may be seen for bundle branch block?

A

none. it is usually asymptomatic.

30
Q

what signs may be seen in bundle branch block?

A

Right BBB may cause splitting of the second heart sound.

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

31
Q

what symptoms may patients with intraventricular conduction disturbances complain of?

A

syncope

32
Q

what are the causes of right bundle branch block?

A 
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
33
Q

what are the common causes of left bundle branch block?

A

aortic stenosis
hypertension
MI
severe coronary disease

Cardiovascular (16 decks)

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