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CARDIO > Interpreting the ECG > Flashcards

Interpreting the ECG Flashcards

1
Q

what produces HR

A

SAN

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2
Q

what does an ECG measure

A

indirect info of electrical activity of the heart

signals correspond to depolarisation and repolarisation

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3
Q

what is the main test to assess myocardial infarction & ischemia

A

ECG

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4
Q

what does the electrical activity between myocytes produce

A

current flow in heart and surrounding tissue

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5
Q

what is an electrocardiograph

A

potential differences on distant sites on body surfaces detected by electrodes places on the skin coupled to a sensitive recording device
12 Leads

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6
Q

what is a dipole

A

separation of charges

an ECG shows dipoles

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7
Q

what does every electrical vector possess

A

magnitude and direction

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8
Q

how is the magnitude of an electrical vector determined

A

by mass of cardiac muscle in causing the signal this is caused by atria + ventricles

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9
Q

how is the direction of an electrical vector determined

A

by overall activity of the heart at any instant time and varies in cardiac cycle

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10
Q

what is a lead in an ECG

A

imaginary line between 2 or more electrodes

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11
Q

what are the 2 electrodes that form a lead responsible for

A

1 is the -ve lead

the other is the +ve recording lead

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12
Q

what happens when depolarisation moves towards a recording electrode

A

upward stroke on ECG

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13
Q

what happens when depolarisation moves away from the recording electrode

A

downward stroke on ECG

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14
Q

what is the name give to when there is no movement towards or away from the recording electrode

A

ISOPOTENTIAL

no deflection on the ECG

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15
Q

what happens when repolarisation moves towards recording electrode

A

downward stroke

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16
Q

what happens when repolarisation moves away from recording electrode

A

upward stoke

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17
Q

what are the 3 bipolar standard limb leads and where do they connect

A

Lead I: RA (-ve) to LA (+ve)
Lead II: RA (-ve) to LL (+ve)
Lead III: LA (-ve) to LL (+ve)

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18
Q

In lead II what direction is the P wave and why

A

SAN inferiorly to left

depolarisation is moving towards recording electrode producing a normally upward deflection (120ms)

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19
Q

In lead II what direction is the Q wave and why

A

left to right depolarization of the interventricular septum moving slightly away from the recording electrode
< 0.1 sec

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20
Q

what direction is the R wave and why

A

depolarization of the main ventricular mass moving towards the recording electrode so upward stroke

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21
Q

what direction is the S wave and why

A

depolarization of ventricles at the base of the heart moving away from the recording electrode so downwards deflection

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22
Q

is the first positive/upward deflection always called the R wave even if there is no preceding Q wave

A

yes

23
Q

what direction is the T wave

A

ventricular repolarization moving in a direction opposite to that of depolarization accounts for the usually observed upward deflection

24
Q

what does the PR interval show

A

largely AVN delay (0.12 – 0.2 sec)
start of P wave to start of QRS complex
time for SAN to reach the ventricles

25
Q

what does the ST segment represent

A

ventricular systole
end of QRS complex to start of the T wave
usually isoelectric

26
Q

what does the QR interval show and how long is it supposed to last in a person with a HR of 60

A 
depolarisation + repolarization 
start of QRS complex to end of T wave 
whole HR 
440 ms in males
460 ms in females
27
Q

what does the TP segment show

A

ventricular diastole

28
Q

what are the 3 augmented voltage (aV) leads

A

aVR (right)
aVL (left)
aVF (foot)

29
Q

how many electrodes are involved in the augmented voltage leads

A

3

1 recording electrode and the other 2 electrodes are electrically linked together

30
Q

what does the hexacial reference system state

A

3 inferiorly, 2 diagonal, 1 from left to right

31
Q

are aVR waves positive or negative

Explain

A

negative so downstroke
recording electrode is on the right shoulder
depolarisation is moving away from recording electrode

32
Q

are Lead I and aVL positive or negative

A

positive so upstroke

lateral lead has recording electrode on the left arm and views heard from left

33
Q

what are the inferior leads

A

lead II, III and aVF

34
Q

what are the lateral leads

A

Lead I and aVL

35
Q

are leads II, III and aVF positive or negative. Explain

A

positive so upstroke

recording electrode on left foot and views from inferior direction

36
Q

what are the 6 chest leads (precordial leads/Wilsons Leads)

A

V1-V6

electrodes of the standard limbs linked together to provide reference electrode in centre of the heard

37
Q

why is the R wave line in V1 tiny but increases as we go from medial to lateral around the chest wall to V6

A

because vector changes and points towards the electrode

38
Q

what is the position of V1

A
  • 4th intercosstal place on right side beside the border

* Use sternal angle which is at space 2

39
Q

position of V2

A
  • 4th intercostal space

* Immediately left of septum

40
Q

position of V3

A

• Midway between V2 and V4 (place these first)

41
Q

position of V4

A
  • 5th intercostal space
  • Mid clavicular line
  • If apex beat is displaced still put in this position
42
Q

position of V5

A
  • Same horizonatl level as V4

* Anterior axillary line

43
Q

position of V6

A
  • Same horizontal level as V4

* Midaxillary line

44
Q

how many secs is a big square on an ECG

A

0.2 sec

5mm amplitude

45
Q

how many secs is a small square on an ECG

A

0.04 sec

1 amplitude

46
Q

how is heart rate determined by reading an ECG

A

300/number of large squares between beats fro regular rhythm

300/number of large squares between R-R interval

47
Q

what is the purpose of an ECG rhythm strip

A

prolonged recording of lead II to show HR and cardiac rhythm (regular rhythm has same spaces between QRS complex)

48
Q

are limb leads I, II, III, aVF and air upstroke or downstroke

A

upstroke

49
Q

is limb lead aVR upstroke

or downstroke

A

downstroke

50
Q

are chest leads V1, V2 and V3 R wave downstroke or upstroke

A

downstroke

51
Q

are chest leads V4, V5 and V6 R wave downstroke or upstroke

A

upstroke

52
Q

what is sometimes seen in the ECG of a patient with MI

A

ST elevation

53
Q

when should an exercise ECG be carried out

A 
stable angina (form of ischaemic heart disease)
there may be ST changes during exercise that aren't present in rest

CARDIO (14 decks)

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