Electrocardiogram Principles Flashcards

1
Q

Role of an ECG

A

Monitoring movement of waves of excitation

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2
Q

What does an ECG provide information on?

A

Timing and direction of cardiac events
(Atrial and Ventricular Depolarisation, Ventricular Repolarisation)

Rate/Rhythm disturbances
(Tahcy/brachy cardia; sinus rhythm; arrythmia)

Conduction abnormalities
(A-V conduction time or abnormalities in spreads across branches)

Mass of active myocardium
(Ischaemic Events)

TRCM
Time - Rhythm Conducted Melodically

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3
Q

Why doesn’t an ECG show Atrial Repolarisation

A

Atrial repolarisation occurs simultaneously with ventricular depolarisation, which is a much more voltage significant event

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4
Q

Does an ECG indicate force of contraction?

A

It does not >:(

bitch

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5
Q

How does an ECG work (basic principles)

A

Imagine a strip of cells placed in a bath filled with conducting solution; positive electrode focally positioned and corners of bath connected to negative electrodes

If a positive impulse (wave of depolarisation) travels across those cells from left to right, an upward deflection is recorded on the trace

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6
Q

What would a unipolar ecg show if depolarisation was moving towards a positive electrode

A

Upwards deflection

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7
Q

What would a unipolar ecg show if depolarisation was moving away from a positive electrode

A

Downward deflection

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8
Q

What would a unipolar ecg show if depolarisation was moving perpendicular to a positive electrode

A

No deflection

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9
Q

What would an ecg show if depolarisation was moving towards a negative electrode

A

Downwards deflection

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10
Q

What would an ecg show if depolarisation was moving away from a negative electrode

A

Upwards deflection

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11
Q

Compare the ecg readings of a focally positioned negative electrode recording the same impulse as a diametrically opposite positive electrode

A

They would yield the same reading

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12
Q

What would a bipolar ecg show

A

It would simply present the composite deflection of what is seen at each electrode (which is the same at both); so is simply a deflection with twice the magnitude

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13
Q

What might a repolarisation event look like as they move to a positive electrode

A

This would cause a downward deflection on the ecg trace; this logic follows for all the other directions and polarities

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14
Q

What does an ECG measure in the actual heart versus in a strip of neatly lined up cells

A

In the heart, electricity flows in various directions, so the ECG measures the mean vector of impulse

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