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BMS242 CVS Phys > L15 - ECG and Heart Blocks > Flashcards

L15 - ECG and Heart Blocks Flashcards

1
Q

Machine to measure ECG

A

Electrocardiograph

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2
Q

Read out of the ECG machine

A

Electrocardiogram

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3
Q

What does the ECG rely on

A

The summation of the cells repolarisation and depolarisation which gives resultant vectors

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4
Q

What about the hearts electrical activity can be sensed by predators

A

The small ammount which reaches the surface of the skin

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5
Q

Where are the three limb leads placed

What is this known as

A

Right arm, left arm, left leg

Einthovens triangle

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6
Q

Where is lead I

A

Right arm to left arm (+)

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7
Q

Where is lead II

A

Right arm to left leg (+)

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8
Q

Where is lead III

A

Left arm to left leg (+)

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9
Q

At rest what can be said about current flow

What is this point known as

A

No net current flow toward an electrode so no deflection on the ECG

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10
Q

What would net current flow toward an electrode cause

A

Upward deflection of the ECG trace

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11
Q

What deflection is seen when the atria depolarise

A

Net current movement toward II

Upward deflection in lead II

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12
Q

What deflection is seen when the septum is depolarised

A

Upward deflection in lead II

As current is moving in the same direction as lead II

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13
Q

What deflection is seen when the ventricles depolarise

A

Downward deflection in lead II

As current is moving in the opposite direction of lead II

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14
Q

Describe what is occuring at the P wave

A

Atrial depolarisation

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15
Q

Why is the p wave a relatively small deflection

A

Atria = small muscle mass = small deflection of the ECG trace

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16
Q

What does the flat line after the p wave represent

A

That atrial depolarisation is complete

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17
Q

Describe the QRS complex

A

Ventricular depolarisation begins at the apex

Large deflection as large muscle mass

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18
Q

Why is no wave seen for the repolarisation of the atria

A

Because it is masked by the QRS complex

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19
Q

What does the flat line after the QRS complex represent

A

Completion of ventricular depolarisation

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20
Q

What is happening to the blood at the flat line after the QRS complex

A

Blood being ejected from the ventricles into pulmonary and systemic circulations

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21
Q

What is shown by the t wave

A

Ventricular repolarisation - beginning at the apex

Occurs in the same direction as depolarisation so has an upward deflection

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22
Q

What is shown by the flat line after the t wave

A

Ventricular repolarisation is complete

Heart is ready for the next cycle

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23
Q

Normal PR interval

A

0.12-0.2

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24
Q

Normal QRS interval

A

0.08-0.1

25
Q

Normal QT interval

A

0.4-0.43

26
Q

Normal st interval

A

Average of about 0.32

27
Q

What is shown by the U wave

A

Possible repolarisation of the purkinje fibres/papilalry muscles

28
Q

What would a high P wave be indicative of

A

Atrial hypertrophy

greater muscle mass of the atria so more t depolarise

29
Q

What would a low T wave be indicative of

A

Ventricular hypoxia (not enough O2)

30
Q

What would a prolonged ST interval be indicative of

A

Acute myocardial infarction

31
Q

What is electromechanical dissociation

A

When the heart has been damaged, electrical activity is still conducted however the heart muscle is unable to respond - cardiac output is 0

This can be seen after death

32
Q

What is meant by arrhythmia

A

Lack of a rhythm

33
Q

What situations may cause natural variations in a hearts rhythm
What are these two variations called?
Is this normal?

A

Exercise, sinus arrhythmia
Bradycardia and tachycardia
Normal

34
Q

What occurs in sinus arrhythmia

A

Increase in HR by 15% on inspiration

Decrease in HR by 15% on expiration

35
Q

What is non-exercise tachycradia

A

Where HR is in the region of 150-200 and no exercise is being performed

36
Q

What HRs are achieve when the heart is in a flutter statee

A

200-300

37
Q

What HRs are seen when the heart is in fibrilation

A

300

38
Q

What is meant by a heart block

A

Impairment of the hearts conducting pathways

39
Q

What sort of things could cause a heart block

A

Heart disease/artery disease/infarction

40
Q

What is a first degree heart block

A

Block that occurs between the SA and AV nodes

Slowing SA –> AV node conduction

41
Q

What does a first degree heart block lead to on ECG

A

Increased PR interval

42
Q

What are the two types of second degree heart block

A

Mobitz I

Mobitz T2

43
Q

Describe a mobitz type 1 second degree heart block

A

Some SA impulses fail to evoke QRS complex

PROGRESSIVE PROLONGATION of the PR interval leads to a non conducting p-wave

44
Q

In a mobitz 1 when is the PR interval longest

A

Immediately prior to the dropped beat

45
Q

In a mobitz 1 when is the PR interval shortest

A

Immediately after the dropped beat

46
Q

Describe a mobitz type 2 second degree heart block

A

Intermittent non conducted beats remain constant
PR interval in conducted beats REMAINS CONSTANT
(P waves march through at a constant rate)
PR interval is an exact multiple of the preceeding PR interval (ie. double if one beat is dropped)

47
Q

What causes a mobitz type 2 heart block

A

Failure at the level of the purkinje system (below the AV node)

48
Q

What is a mobitz 2 likely to be caused by

A

Structural damage to the conducting system

49
Q

Why is mobitz 2 described as ‘all or nothing’

A

His-purkinje cells suddenly and unexpectedly stop working

No pattern or fixed relationship

50
Q

What is a type 3 heart block caused by

A

Complete absence of AV conduction

None of the supraventricular impulses are connected to the ventricles

51
Q

Is perfusing rhythm maintained in a type 3 heart block

A

Yes at rest

BUT not under stress

52
Q

What are the consequences of 1st degree heart block

A

Benign

Only usually noticed in athletes

53
Q

What are the consequences of 2nd degree heart block

A

Mobitz 1 usually benign (beat dropped and then recovery)

54
Q

What is the most common form of arrhythmia

A

Atrial fibrillation

55
Q

Describe atrial fibrillation

A

Rapid beating of the atria

Starts with a brief episode that becomes more constant

56
Q

What are the symtpoms of atrial fibrillation

A

Usually is asymptomatic but some symptoms associated with a high HR are often seen
Congestive symptoms

57
Q

Treatments of atrial fibrillation

A 
Flecanidide 
B-blockers 
Amidrarone 
Dronedarone 
Digoxin
58
Q

What is one of the risks with atrial fibrillation

What may be prescribed to alleviate such risk

A

Clots forming on the wall of the atria

Warfarrin

59
Q

What is meant by circus movement and re entry

A

Where the electrical signal doesn’t complete the normal circuit but an alternative one
The refractory muscle which normally prevents re-excitation being reexcited to early
Non refractory by: Unidirectional block or transient bi-directional block

BMS242 CVS Phys (12 decks)

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