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ECG > Week 6 > Flashcards

Week 6 Flashcards

1
Q

What does the P-R interval represent?

A

Atrial depolarisation, AV node excitation, AV node delay - the time between atrial and ventricular depolarisation

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2
Q

In sinus rhythm, what is the duration of the P-R interval?

A

3-5 small boxes (0.12 - 0.2 seconds). Length should be consistent

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3
Q

Why is a delay between atrial and ventricular depolarisation important?

A

To allow optimal ventricular filling

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4
Q

What can a slow ventricular rate lead to?

A

Reduced CO - lightheadedness, hypotension and confusion

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5
Q

When analysing the PR interval, what 3 things should be asked?

A
  1. is the PR interval between 3-5 small boxes? 2. does the PR interval vary? 3. can it be measured?
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6
Q

List 4 causes of AV block

A
  1. ischemia 2. myocardial infarction (cell death) 3. exaggerated drug response (digoxin, calcium-channel blockers and beta-blockers). 3. congenital anomalies
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7
Q

How does ischemia effect conduction?

A

cell repolarise more slowly or incompletely.

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8
Q

What are the two main reasons for shortened PR interval?

A
  1. AV junctional rhythm (depolarisation spreads to atria and ventricles at the same time). 2. when an accessory pathway is present and bypasses AV junction. This pathway is fast-conduction.
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9
Q

Name the two accessory pathway syndromes

A
  1. Wolf-Parkinson-White, 2. Lown-Ganong-Levine (LGL)
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10
Q

What are the 3 junctional depolarisation sources?

A
  1. junctional rhythm, 2. junction ectopic, 3. AV re-entry tachycardia
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11
Q

What ECG characteristic signals retrograde conduction in the atria?

A

Inverted P wave in lead II

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12
Q

What is the accessory pathway in WPW called?

A

Bundle of Kent - fasting conducting than AV node. It connects the ventricles directly

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13
Q

What wave is seen on an ECG of WPW client?

A

Shortened PR interval and delta-wave (slurred QRS)

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14
Q

What dose the delta wave represent?

A

Slow depolarisation (myocyte-myocyte) of the ventricle. The rest of the ventricles depolarise normally shortly after via AV node and bundle branches.

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15
Q

Is WPW a contraindication to exercise testing?

A

yes

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16
Q

What can WPW and LGL lead to?

A

Paroxysmal tachycardia

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17
Q

What is the accessory pathway in LGL syndrome called?

A

Bundle of James

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18
Q

Where does the Bundle of James connect?

A

Connects the atria to the bundle of His, bypassing the AV node.

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19
Q

What is the characteristics of 1st degree AV block?

A

Prolonged PR interval (>0.2 seconds), constant delay, each P wave is followed by QRS. May be temporary.

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20
Q

List what may cause slowing of electrical conduction through the AV node.

A

Ischemia, injury, infarction, drugs (digoxin, calcium-channel blockers, beta-blockers), myocarditis, degenerative changes (fibrosis associated with age), lyme disease, hypokalemia

21
Q

What is the only substance a health and wellbeing physiologist can administer?

A

oxygen

22
Q

Is 1st degree heart block a contra-indication to exercise testing?

A

no

23
Q

How is 2nd degree block Type 1 identified?

A

The length of PR interval increases with each beat until a P wave fails to produce a QRS complex

24
Q

How is 2nd degree Type II identified?

A

The length of the PR interval is constant but occasionally P wave fails to produce QRS complex

25
Q

What is a block where every second P wave doesn’t produce a QRS?

A

2:1 AV block

26
Q

How is 3rd degree (complete) AV block distinguished?

A

If there is no relationship between the P and QRS waves - i.e they are being triggered independently

27
Q

Is 2nd degree type I block typically temporary?

A

yes

28
Q

Causes of 2nd degree type I block

A

periods of high vagal activity (e.g. during sleep), ischemia, inferior wall MI, rheumatic fever, drugs

29
Q

What blocks are contraindications to exercise testing?

A

2nd and 3rd degree

30
Q

What block is more common, 2nd degree type I or type II?

A

2nd degree type I

31
Q

What is the most common cause of 2nd degree type II block?

A

Inferior wall MI, severe CAD (ischemia), degenerated changes.

32
Q

Where in the conduction system is 2nd degree type II thought to arise?

A

at the level of the bundle branches or bundle of His

33
Q

Where in the conduction system is 2nd degree type I thought to arise?

A

at the AV node itself

34
Q

Is 2nd degree Type I or Type II more serious and why?

A

Type II - ventricular rate tends to be slow (reduce C0) and can progress without warning to 3rd degree block. A ratio of conducted beats less than 2:1 is more likely to be symptomatic.

35
Q

In 2nd degree heart block, is atrial and ventricular rhythm regular?

A

Atrial rhythm is regular and ventricular rhythm is irregular

36
Q

If the block is constant (2:1 or 3:1) is the rhythm regular?

A

Yes

37
Q

Do the atria and ventricles work independently in 3rd degree heart block?

A

Yes

38
Q

How do the ventricles know the contract in 3rd degree heart block?

A

They sometimes develop an escape rhythm at the level of the junctional tissue surrounding the AV node. Most commonly, escape rhythm originates at the level of the Purkinji fibres

39
Q

What is the rate of a junctional escape rhythm?

A

40-60bpm

40
Q

What is the rate of escape rhythm at level of Purkinji fibres?

A

20-40bpm

41
Q

3rd degree block at the AV node is most commonly caused by what?

A

Congenital condition

42
Q

Do clients with 3rd degree heart block lose atrial kick?

A

Yes (which is reduces blood flow by 30%).

43
Q

Bradycardia (20-40bpm) and broad QRS complex should alert you to what?

A

3rd degree heart block

44
Q

Can individuals with 3rd degree heart block tolerate exercise?

A

No

45
Q

What is the main determinant of the severity of symptoms due to heart block?

A

Ventricular rate - this determines CO.

46
Q

What may be given is rate is too slow?

A

Epinephrine, atropine, dopamine

47
Q

If escape rhythm originates in the Purkinji fibres, will the QRS complex be wide?

A

Yes

48
Q

3rd degree block in anterior wall MI is good/bad prognosis?

A

Bad - suggests extensive damage

49
Q

When is 1st degree block normal and why?

A

When it accompanies sinus bradycardia. Vagal tone reduces AV conduction

ECG (8 decks)

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