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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

25
Normal QT interval
0.4-0.43
26
Normal st interval
Average of about 0.32
27
What is shown by the U wave
Possible repolarisation of the purkinje fibres/papilalry muscles
28
What would a high P wave be indicative of
Atrial hypertrophy | greater muscle mass of the atria so more t depolarise
29
What would a low T wave be indicative of
Ventricular hypoxia (not enough O2)
30
What would a prolonged ST interval be indicative of
Acute myocardial infarction
31
What is electromechanical dissociation
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
What is meant by arrhythmia
Lack of a rhythm
33
What situations may cause natural variations in a hearts rhythm What are these two variations called? Is this normal?
Exercise, sinus arrhythmia Bradycardia and tachycardia Normal
34
What occurs in sinus arrhythmia
Increase in HR by 15% on inspiration | Decrease in HR by 15% on expiration
35
What is non-exercise tachycradia
Where HR is in the region of 150-200 and no exercise is being performed
36
What HRs are achieve when the heart is in a flutter statee
200-300
37
What HRs are seen when the heart is in fibrilation
300
38
What is meant by a heart block
Impairment of the hearts conducting pathways
39
What sort of things could cause a heart block
Heart disease/artery disease/infarction
40
What is a first degree heart block
Block that occurs between the SA and AV nodes | Slowing SA --> AV node conduction
41
What does a first degree heart block lead to on ECG
Increased PR interval
42
What are the two types of second degree heart block
Mobitz I | Mobitz T2
43
Describe a mobitz type 1 second degree heart block
Some SA impulses fail to evoke QRS complex | PROGRESSIVE PROLONGATION of the PR interval leads to a non conducting p-wave
44
In a mobitz 1 when is the PR interval longest
Immediately prior to the dropped beat
45
In a mobitz 1 when is the PR interval shortest
Immediately after the dropped beat
46
Describe a mobitz type 2 second degree heart block
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
What causes a mobitz type 2 heart block
Failure at the level of the purkinje system (below the AV node)
48
What is a mobitz 2 likely to be caused by
Structural damage to the conducting system
49
Why is mobitz 2 described as 'all or nothing'
His-purkinje cells suddenly and unexpectedly stop working | No pattern or fixed relationship
50
What is a type 3 heart block caused by
Complete absence of AV conduction | None of the supraventricular impulses are connected to the ventricles
51
Is perfusing rhythm maintained in a type 3 heart block
Yes at rest | BUT not under stress
52
What are the consequences of 1st degree heart block
Benign | Only usually noticed in athletes
53
What are the consequences of 2nd degree heart block
Mobitz 1 usually benign (beat dropped and then recovery)
54
What is the most common form of arrhythmia
Atrial fibrillation
55
Describe atrial fibrillation
Rapid beating of the atria | Starts with a brief episode that becomes more constant
56
What are the symtpoms of atrial fibrillation
Usually is asymptomatic but some symptoms associated with a high HR are often seen Congestive symptoms
57
Treatments of atrial fibrillation
``` Flecanidide B-blockers Amidrarone Dronedarone Digoxin ```
58
What is one of the risks with atrial fibrillation | What may be prescribed to alleviate such risk
Clots forming on the wall of the atria | Warfarrin
59
What is meant by circus movement and re entry
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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