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1st Year Medicine > ECG > Flashcards

ECG Flashcards

0
Q

What direction is limb lead 2?

A

RA - LL

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1
Q

What direction is limb lead 1?

A

RA - LA.

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2
Q

What direction is limb lead 3?

A

LA - LL

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3
Q

What are the colours of the four limb leads?

A

RA - White
LA - black
RL - green
LL - red

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4
Q

What limb lead is earthed?

A

Right leg.

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5
Q

What causes the PR interval?

A

Largely ventricular node delay.

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6
Q

What is the ST segment?

A

Ventricular systole.

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7
Q

What is the TP interval?

A

Diastole.

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8
Q

What is an ECG actually recording?

A

Potential electrical differences between different sites.

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9
Q

What creates an electrical dipole in the heart?

A

Different parts being depolarised or polarised at the same time.

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10
Q

What does the dipole in the heart create that can be measured by ECG leads?

A

An electrical field called lines of isopotential.

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11
Q

When is the measured potential difference the greatest in relation to the lead axis?

A

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

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12
Q

When is the measured potential difference 0?

A

When the lead axis is perpendicular to the direction of the dipole.

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13
Q

What does the dipole represent and what are the characteristics of this?

A

A vector, it has magnitude and direction.

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14
Q

What determines the magnitude of the ECG vector?

A

The mass of cardiac muscle involved in the generation of the signal.

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15
Q

What determines the direction of the ECG vector?

A

Overall activity of the heart at any given instant.

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16
Q

What does a positive deflection on an ECG mean?

A

Depolarisation towards the electrode.

17
Q

What does a negative deflection on an ECG mean?

A

Depolarisation away from the electrode.

18
Q

What does each large square on an ECG correlate to?

A

5mm amplitude and 0.2 seconds.

19
Q

What does each small square on an ECG correlate to?

A

0.04 seconds and 1mm of amplitude.

20
Q

How do we calculate heart rate from an ECG?

A

300/ the number of large squares between the RR interval.

21
Q

How long should the p wave last?

A

0.08 - 0.10 seconds.

22
Q

How long should the QRS complex last?

A

Less than 0.10 seconds.

23
Q

How long should the pr interval last?

A

0.12 - 0.20 seconds.

24
Q

What is the ST segment?

A

Maintained ventricular depolarisation e.g. Systole.

25
Q

At what points is an ECG isoelectric?

A

During the PR segment, the ST segment and the TP interval.

26
Q

What is the PR segment? How does this differ from the PR interval?

A

Atria are completely depolarised. This is different from the PR interval as it includes the act of atrial depolarisation.

27
Q

What formation do augmented leads have? What do they do?

A

They have a different view from standard limb leads.

They use the einthovens triangle formation, which is the imaginary triangle made of the two shoulders and the pubis.

28
Q

Where do we place 12 lead ECG chest leads?

A

V1 - right sternal edge, 4th intercostal.
V2 - left sternal edge 4th intercostal
V3 - halfway between V2 and V4
V4 - apex beat (may vary with patients).
V5 - horizontal from v4 anterior axillary
V6 - horizontal from v4 mid axillary

29
Q

How do we calculate the HR from an ECG if it is irregular?

A

Count the number of QRS complexes in 30 large squares and then divide it by 10.

30
Q

What are the 11 steps in reading an ECG?

A
  1. Very name and DOB
  2. Check date and time taken
  3. Check calibration
  4. Look at rhythm strip.
  5. Electrical activity present?
  6. Regular or irregular?
  7. What is the HR?
  8. Is there p waves present?
  9. What is the PR interval?
  10. Each p wave followed by a QRS?
  11. Is the QRS duration normal

Then we look at individual leads for changes.

31
Q

What kind of ECG should we do if we suspect intermittent rhythm disturbance?

A

Do an ambulatory recording for 24hrs or 7 days.

32
Q

What type of ECG should we do for suspected stable angina?

A

Exercise ECG. Look for ST changes during or after exercise.

33
Q

What leads are anterolateral? What do these represent?

A

Circumflex and LAD. V4-V6 1 and AVL.

34
Q

What leads are inferior? What arteries/structures do these represent?

A

II, III and AVF. Right coronary artery.

35
Q

What leads are anteroseptal? What arteries/structures do these represent?

A

V1 - V3 LAD/bundle branches.

36
Q

What leads are anterior? What arteries/structures do these represent?

A

V2 -V5 Usually left coronary artery.

37
Q

What leads are posterior?

A

V1 and V2

38
Q

If lead one has a mainly positive deflection and leads II and III are negative mainly what does this mean?

A

Left axis deviation.

39
Q

If lead one has a mainly negative deflection and leads II and III are mainly positive what does this mean?

A

Right axis deviation.

40
Q

What deflection should leads I,II and III normally have?

A

All positive.

1st Year Medicine (64 decks)

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