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Cardiology > ECG > Flashcards

ECG Flashcards

1
Q

What is an ECG

A

Monitors electrical activity of the heart by recording potential changes on the body surface via electrodes that is simple and non-invasive

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2
Q

How do the potentials at the body surface arise

A

From currents that flow when the membrane potential of only large masses of myocardial tissue changes

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3
Q

What information does an ECG provide and what diseases does it detect (5)

A 
Cardiac rate
Cardiac rhythm
Chamber size
The electrical axis of the heart
Main test to assess myocardial ischaemia and infarction
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4
Q

Electrical activity within and between myocytes causes (2)

A

Current flow within the heart and surrounding tissues

Potential differences between distant sites on the body surface that is recorded by the electrocardiograph

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5
Q

Physics of the ECG (3)

A

The AP propagating in sequence through the conducting system and heart muscle causes separation of charge
Charges that are separated constitute an electrical dipole which is a vector
The net dipole during contraction moves from negative to positive

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6
Q

Why is the electrical vector vital clinically

A

It has a magnitude and direction that allows the electrical axis of the heart to be estimated

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7
Q

Magnitude is determined by

A

The mass of cardiac muscle that generates the signal

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8
Q

Direction is determined by

A

The overall activity of the heart at any instant in time during the cardiac cycle

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9
Q

An ECG lead is the (2)

A

Imaginary line - The lead axis between 2 or more electrodes

It is NOT the wire that connects the electrode to the electrocardiograph

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10
Q

Measured potential is the greatest when

A

The lead axis is parallel to the direction of the dipole and zero when they are perpendicular

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11
Q

In a lead one electrode acts as a _________ while the other is the _________

A

Reference electrode

Recording (positive) electrode

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12
Q

When depolarization moves towards the recording electrode what deflection is produced

A

An upward deflection

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13
Q

When depolarization moves away the recording electrode what deflection is produced

A

A downward deflection

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14
Q

The 12 lead ECG comprises

A

3 standard limb leads (I,II and III) - These are bipolar and vertical (or coronal)
3 augmented voltage leads (aVR - right), (aVL - left) and (aVF - foot) - These are unipolar and vertical (or coronal)
6 chest leads (V1 - V6) - These are percordial and transverse

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15
Q

Standard Limb Lead placements and terminals (3)

A

Lead I : Right Arm negative to Left Arm positive
Lead II : Right Arm negative to Left Leg positive
Lead III : Left Arm negative to Left Leg positive

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16
Q

P wave (3)

A

Duration shows atrial depolarization to be complete
Depolarization moves towards recording electrode in lead II producing an upward direction
Duration is 80 to 100 ms

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17
Q

QRS complex (4)

A

Represents ventricular depolarization
Has a duration of 100 ms or less
A downward (negative) deflection preceding an R wave is called a Q wave
A deflection upwards (positive) irrespective of the Q wave is called an R wave
A downward (negative) deflection following an R wave is called an S wave

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18
Q

QRS complex vectors (3)

A

Q wave is down-right
R is down-left
S is up-right

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19
Q

T wave (2)

A

Represents ventricular repolarization

Its an upwards (positive) deflection due to wave of repolarization spreading away from recording electrode

20
Q

PR interval (3)

A

Reflects the time for the SAN impulse to reach the ventricles
Duration is 120 - 200 ms
It is influenced by the delay of conduction through the AVN

21
Q

ST segment (2)

A

Point of ventricular systole

Normally isoelectric

22
Q

QT interval (3)

A

Reflects the time for ventricular depolarization and repolarization
Duration is 440 ms in males and 460 ms in females
Prolongation predisposes to disturbances of cardiac rhythm

23
Q

Augmented Limb Lead Placements and terminals (3)

A

aVR is Right Arm (+) to Left Arm and Left Foot (-)
aVL is Left Arm (+) to Right Arm and Left Foot (-)
aVF is Left Foot (+) to Right Arm and Left Arm (-)

24
Q

Limb Lead Records (2)

A

Leads I and aVL are lateral leads – each has the recording electrode on the left arm and views the heart from the left
Leads II, III and aVF are inferior leads – each has the recording electrode on the left foot and views the heart from an inferior direction

25
Q

Chest (Precordial) Leads placements (6)

A

V1 – 4th intercostal Right hand side
V2 – 4th intercostal left hand side
V3 - halfway between lead 3 and 4 on the rib and between them
V4 – 5th intercostal space mid clavicular line
V5 – 5 intercostal space anterior axillary line
V6 –5th intercostal mid axillary line.

26
Q

Chest Lead Records (6)

A

V1 and V2 coming from the right are looking at the interventricular septum
V3 and V4 are looking at the anterior of the heart
V5 and V6 are looking at the lateral aspect (left ventricle) of the heart
The first positive deflection in the QRS complex in V1 is an R wave
The negative deflection following immediately is the S wave
The R wave progressively increases while the S wave decreases from V1 to V6

27
Q

TP segment

A

Point of ventricular diastole

28
Q

Calibration of ECG trace (3)

A

Paper speed is 25mm/sec
Reference pulse is 10mm/1mV
One large box represents 200ms of time and 5mm

29
Q

Heart rate calculations via ECG trace (2)

A

= 300/number of large squares between beats (for regular rhythm)
= 300/number of large squares between R-R interval

30
Q

What is the ECG Rhythm Strip (2)

A

Prolonged recording of one lead - Normally lead 2

Allows to determine heart rate and identify cardiac rhythm

31
Q

The importance of 12 leads (3)

A

The 12 leads look at the heart at different directions to:
Determine the heart axis
Look for ST segment or T wave changes - Crucial in diagnosing Ischaemic Heart Disease
Look for any voltage criteria changes - Crucial in diagnosing chamber hypertrophy

32
Q

Practical approach to ECG analyzing (6)

A

Verify patient details: name and date of birth
Check date and time ECG was taken
Check the calibration of the ECG paper
Determine the axis
Workout the rate and rhythm via the rhythm strip
Look at individual leads for voltage criteria changes OR any ST or T-wave changes

33
Q

7 questions to ask when working out the rate and rhythm

A 
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?
34
Q

What significant heart diseases does a normal resting ECG not exclude (3)

A

Myocardial Infarction
Intermittent Rhythm Disturbance
Stable Angina

35
Q

How to find the HR if it is irregular

A

Count the number of QRS complexes in 30 large squares and multiply by 10

36
Q

High QRS complex with chest pain indicates

A

Left ventricular hypertrophy

37
Q

What leads determine axis deviation

A

1 and aVF

38
Q

AF identification

A

P waves are not present in between QRS complexes

39
Q

If AVF is down

A

Axis is deviated to the left

40
Q

M shape in QRS complex in V1 and W in V6 indicates

A

Right Branch Bundle Block

41
Q

Ventricular tachycardia shows

A

Broad QRS complex

42
Q

W shape in V1 and M in V6 of QRS complex indicates

A

Left Branch Bundle Block

43
Q

Someone with LBBB and symptoms of MI indicates

A

Non STEMI

44
Q

Hyperkalaemia patterns (4)

A

Tall tented T waves
Small P waves
Wide QRS
Long PR interval

45
Q

Hypokalaemia patterns (5)

A 
Prolonged PR interval
U waves 
Small/absent T waves
ST depression
Long QT
46
Q

U waves characteristics (3)

A

Small (0.5 mm) deflection immediately following T wave
Usually in same direction as T wave
Seen in leads V2 and V3

Cardiology (11 decks)

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