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cardiovascular lectures > electrocardiograms (ECG) > Flashcards

electrocardiograms (ECG) Flashcards

1
Q

define electrocardiogram (ECG)

A

a measure of the currents
generated in the EXTRACELLULAR FLUID by the changes occurring simultaneously in many cardiac cells

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2
Q

what is on y-axis of an ECG

A

voltage

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3
Q

what is on x-axis of ECG

A

time

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4
Q

define electrode

A

a conductive pad that is attached to the skin and enables recording of electrical currents

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5
Q

define lead

A

a plane in which you are looking at the heart

the resulting measurements of an ECG are referred to as leads

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6
Q

what is the P wave

A

first positive deflection on the ECG

represents atrial depolarisation

occurs when SA node creates an action potential that depolarizes the atria

seen in every lead apart from aVR

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7
Q

what is the QRS complex

A

ventricular depolarisation

still called QRS even if Q and/or S are
missing depending on what lead you are looking at

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8
Q

what is the T wave

A

ventricular repolarisation

occurs after the QRS complex

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9
Q

how many leads in a normal ECG

A

12

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10
Q

define segment

A

a period of isoelectric neutrality

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11
Q

define interval

A

just a region including magnitude

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12
Q

what is the PR segment

A

the flat line between the end of the P-wave and the start of the QRS complex

reflects the time delay between atrial and ventricular activation.

also serves as the baseline

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13
Q

what is the ST segment

A

plateau phase of ventricular repolarization

interval between depolarisation & repolarisation

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14
Q

what is the PR interval

A

atrioventricular conduction time

time taken for atria to depolarise and electrical activation to get
through AV node

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15
Q

what is the QT interval

A

total ventricular contraction during systole.

the time from the start of the Q wave to the end of the T wave, time taken for ventricular depolarisation and repolarisation.

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16
Q

which lead is usually focused on when interpreting an ECG and why

A

lead II (2)

gives a good view of the P wave

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17
Q

what is tachycardia

A

increased heart rate

18
Q

what is bradycardia

A

decreased heart rate

19
Q

what is dextrocardia

A

heart on right side of chest instead of left

20
Q

what is acute anterolateral myocardial infarction

A

ST segments are raised in anterior. (V3- V4) and lateral (V5-V6) leads

21
Q

what is acute inferior MI

A

ST segments are raids in inferior (II, III, aVF) leads

22
Q

is atrial repolarisation usually evident on an ECG

A

no

because it occurs at the
same time as the QRS complex so is hidden

23
Q

describe electrical impulses in the heart

A

they move in 3 dimensions

ECG only measure voltage in 1 dimension

  • If an impulse is towards the electrode it looks big
  • If an impulse is away from the electrode it looks small or even negative
24
Q

compare impulses from atria to impulses from ventricles

A

the impulse from the atria is smaller since the atria are smaller than the ventricles thus less myocytes

25
Q

what are the 12 leads used in an ECG

A

6 limb leads

6 chest leads

26
Q

describe the 6 limb leads used in an ECG

A

3 bipolar - I, II, III

3 unipolar (augmented) - aVR, aVL, aVF

27
Q

describe the 6 chest leads used in an ECG

A

all unipolar - V1, V2, V3, V4, V5, V6

28
Q

what are the bipolar limb leads and where are they

A

I, II, III

form a triangle between electrodes on the wrists and left leg (right leg is a ground electrode)

the negative poles are REFERENCE
electrodes

the positive poles are RECORDING electrodes

29
Q

what are the unipolar (augmented) leads and where are they

A

aVR, aVL & aVF

bisect the angles of the triangle by combining two electrodes as reference

e.g. for lead aVL, the right wrist & foot are combined as the negative pole, thus creating a reference point along the line between them, pointing toward the recording electrode on the left wrist

30
Q

what are the chest leads

A

precordial leads

V1, V2, V3, V4, V5, V6

31
Q

where do you place lead V1

A

4th IC space to right of sternal border

32
Q

where do you place lead V2

A

4th IC space to the left of sternal border

33
Q

where do you place lead V3

A

midway between V2 and V4

34
Q

where do you place lead V4

A

5th IC space, mid-clavicular line

35
Q

where do you place lead V5

A

anterior axillary line at same level as V4

36
Q

where do you place lead V6

A

midaxillary line at same level as V4 and V5

37
Q

what does an ECG graph show

A

the graph shows changes in voltage over time

38
Q

what does each small square on an ECG represent

A

40ms

39
Q

what does each big square on an ECG represent

A

0.2s

40
Q

describe P waves in a normal ECG

A

POSITIVE in EVERY LEAD (apart from the aVR)

41
Q

describe T waves in a normal ECG

A

POSITIVE in EVERY LEAD (apart from the aVR & sometimes the V1
and V2 depending on trace)

cardiovascular lectures (15 decks)

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