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Flashcards in ECG Deck (21)
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1

What is the electrocardiograph?

The actual device doing the recording

2

What is the electrocardiogram?

The measurement of potential differences between distant sites on the body surface

3

When is the measured potential difference greatest?

When the lead axis is parallel to the direction of the dipole

4

What does the dipole represent?

An electrical vector

5

What determines the magnitude of the electrical vector?

Magnitude is determined by the mass of cardiac muscle that is involved in the generation of the signal

6

What determines the direction of the electrical vector?

Direction is determined by the overall activity of the heart at any instant in time and varies during the cardiac cycle

7

When is an upward deflection seen on an ECG?

When the wave of depolarisation is moving towards the recording electrode

8

What is the duration of a normal P wave?

0.08-0.1s

9

Which part of the atrial action potential does the P wave correspond with?

The upstroke

10

What is the duration of a normal QRS complex?

<0.1s

11

What does the QRS complex represent?

Ventricular depolarisation masking atrial repolarisation

12

At what parts of the ECG is it completely isoelectric and why?

PR segment: atria completely depolarised ST segment: ventricles completely depolarised TP interval: all regions repolarised

13

What does the T wave represent?

Ventricular repolarisation

14

What does the PR interval represent?

Mostly AV node delay

15

What is the normal duration of the PR interval?

0.12-0.2s

16

Where does the PR interval start and end?

At the beginning of the P wave At the beginning of the QRS complex

17

Which region of the ECG represents systole?

ST segment

18

Why is the recording from the AvR lead inverted?

Wave of depolarisation is moving away from the lead

19

Why might poorly resolved P and T waves be seen in lead 3?

The lead axis is approximately perpendicular to the vector

20

Why is it likely that the P and T waves seen in lead 2 will be well resolved?

The lead axis is approximately parallel to the vector

21

What questions should be answered while determining the rhythm from the rhythm strip?

Is electrical activity present? Is the rhythm regular or irregular? What is the heart rate? P-waves present? What is the PR interval? Is each P-Wave followed by a QRS complex? Is the QRS duration normal?