Electrocardiogram Flashcards

1
Q

What information does an ECG provide? What information does it not provide?

A
Tells you about:
. Timing and direction of depolarisation
. Disturbances in rate and rhythm
. AV conduction time
. Mass of active myocardium and ischaemic areas

. Doesn’t tell you anything about mechanical force
. Can’t see atrial repolarisation because it’s quite a small electrical event and is obscured by ventricular depolarisation, however it happens at the same time as ventricular depolarisation

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2
Q

What does an ECG show you about timing and direction of depolarisation?

A

Shows atrial depolarisation, ventricular depolarisation, and ventricular repolarisation (atrial repolarisation is too small an electrical event to be detected but happens at the same time as ventricular depolarisation)

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3
Q

What can an ECG show about heart rate and rhythm?

A

If there’s tachy/bradycardia, sinus rhythm (normal rhythm), or arrhythmias

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4
Q

What could a downward deflection represent?

A

. Depolarisation moving away from a positive electrode or towards a negative electrode
. Repolarisation towards a positive electrode or away from a negative electrode

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5
Q

What does an upward deflection show?

A

. Depolarisation moving towards a positive electrode or away from a negative electrode
. Repolarisation away from a positive electrode or towards a negative electrode

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6
Q

What does a deflection with minimal amplitude tell us?

A

. Minimal amplitude shows depolarisation is perpendicular to electrode (neither moving towards or away)

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7
Q

What would depolarisation away from a negative electrode show on an ECG trace?

A

Upward deflection

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8
Q

What would depolarisation towards a positive electrode show on an ECG trace?

A

Upward deflection

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9
Q

What would depolarisation away from a positive electrode show?

A

Downward deflection

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10
Q

What would depolarisation towards a negative electrode show?

A

Downward deflection

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11
Q

Negative electrode sees the same thing as …

A

A diametrically opposite positive electrode

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12
Q

Why do deflections always return back to the base line?

A

Because there’s maximal depolarisation resulting in no more movement

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13
Q

When viewing limb lead 2, what does the first upward deflection show?

A

Atrial depolarisation

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14
Q

When viewing limb lead 2, what does the first small downwards deflection show?

A

Septal depolarisation

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15
Q

When viewing limb lead 2, what does the large upward deflection show?

A

Ventricular depolarisation

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16
Q

When viewing limb lead 2, what does the last upward deflection show?

A

Ventricular repolarisation

17
Q

Where are the unipolar leads placed?

A

. Limb leads- Left shoulder, right shoulder, groin area

. Chest leads- V1, V2 (right side of heart), V3 (apex), V4, V5, V6 (left side of heart)

18
Q

What is the first wave called?

A

P wave

19
Q

What is the final wave called?

A

T wave (unless U waves are present)

20
Q

What is any negative wave after a P wave but before an R wave called?

A

Q wave

21
Q

What is the first positive wave after a Q wave called?

A

R wave

22
Q

What is any negative wave after an R wave called?

A

S wave

23
Q

What is any positive wave after an S wave called?

A

R’ wave

24
Q

Draw and label a classical ECG trace.

A

Check slide 21 in ECG lecture!

25
Q

Draw and label an ECG taken from the positive electrode at the right shoulder.

A

Check slide 21 in ECG lecture!

26
Q

What does the P wave show?

A

Atrial depolarisation

27
Q

What does the QRS complex show?

A

Ventricular depolarisation

28
Q

What does the T wave show?

A

Ventricular repolarisation

29
Q

What is axis deviation and what is it caused by?

A

When the cardiac axis is skewed (average direction of depolarisation is skewed), which is caused by extreme hypertension or valvular heart disease