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Y2 - BRS - CVR > Electrocardiography Revisited > Flashcards

Electrocardiography Revisited Flashcards

1
Q

What is the clinical relevance of the ECG?

A

Conduction abnormalities
Structural abnormalities
Perfusion abnormalities

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2
Q

Are electrodes, cables / wires, and leads all the same thing?

A

No

Electrodes - sticky parts that stick onto the skin e.g. chest

Cables / wires - connect to the electrodes

Leads - views of the heart (i.e. the graph on the ECG)

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3
Q

What is the job of the leads?

What is a vector?

A

Pick up cardiac vectors

A quantity that has both, magnitude and direction

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4
Q

What are the advantages of ECGs?

A

Relatively cheap and easy to undertake
Reproducible between people & centres
Quick turnaround on results/report

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5
Q

What happens if the wave of excitation travels toward the negative electrode?

A

Downward deflections are towards the anode (-)

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6
Q

What happens if the wave of excitation travels toward the positive electrode?

A

Upward deflections are towards the cathode (+)

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7
Q

What does the isoelectric line represent?

A

Represents no net change in voltage. i.e. vectors are perpendicular to the lead

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8
Q

What does the steepness of the line relate to?

What does the width of the line relate to?

A

Steepness of line denotes the ‘velocity’ of action potential

Width of the deflection denotes the ‘duration’ of the event

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9
Q

What is the P wave?

What is the QRS complex?

What is the T wave?

A

The electrical signal that stimulates contraction of the atria (atrial systole)

The electrical signal that stimulates contraction of the ventricles (ventricular systole)

The electrical signal that signifies relaxation of the ventricles

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10
Q

What comprises the SAN?

A

Autorhythmic myocytes

Small amount of muscle that points more positive than negative

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11
Q

What does the action of the SAN show on an ECG?

A

Deflection is wide (slow)
Not very high (thin muscle)
Positive

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12
Q

What does the action of the AVN show on an ECG?

A

AVN depolarisation
Isoelectric ECG
Slow signal transduction
Protective

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13
Q

What does the Bundle of His divide into?

What does the action of the bundle branches show on an ECG?

A

2 bundle branches

Sharp but small downward spike - due to thin wall of muscle

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14
Q

What does the action of the purkinje fibres show on an ECG?

A

Ventricular depolarisation, followed by late ventricular depolarisation

Upward stroke, QRS peak

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15
Q

What does the action of the ventricular repolarisation show on an ECG?

A

Period of isoelectric status

Slow, domed T-wave

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16
Q

Where do you place the leads?

A 
Lead I (one L)
Right Arm to Left Arm
Lead II (two L’s)
Right Arm to Left Leg
Lead III (three L’s)
Left Arm to Left Leg
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17
Q

What is the rule of reading for the leads to figure out which are the anodes / cathodes?

A

English is read left to right and top to bottom.

Polarity does that too.
Drawn as a triangle and reading left to right and top to bottom the first electrode of each pair you reach is the anode (-ve)

Right arm anode
Left Leg cathode
Left arm both

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18
Q

Where are the V1, V2, V3 and V4 electrodes placed?

A

V1 - Right sternal border
In the 4th intercostal space

V2 - Left sternal border
In the 4th intercostal space

V3 - Halfway between V2 and V4

V4 - Mid-clavicular line
In the 5th intercostal space

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19
Q

Where are the V5 and V6 electrodes placed?

A

V5 - Anterior axillary line
at the level of V4

V6 - Mid-axillary line
at the level of V4

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20
Q

An ECG graph paper has big squares, that are further divided up into smaller squares?

What do each of these squares represent?

A

Big square - 0.2s, 0.5mV

Little square - 0.04s, 0.1mV

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21
Q

What else is seen on an ECG graph?

A

Top left = details of the patient e.g. name, sex, age

Bottom = date and printing speed

Left bottom = where the ECG was taken e.g. ICL occupational health service

Top = shows voltage

Names of the 12 leads labelled

Bottom = rhythm strip

Top = HR

Machine can also tell you whether it is a normal sinus rhythm / what the issues may be

22
Q

What view of the heart does V1 and V2 look at?

What view does V5 and V6 look at?

A

V1 and V2 = septum

V5 and V6 = lateral side of the heart

23
Q

What are the three main coronary arteris?

A

Left circumflex (LCx)
Left anterior descending (LAD)
Right coronary artery (RCA)

24
Q

Which leads correspond to which coronary arteries?

A 
LCx = I, aVL, V5, V6
LAD = V1, V2
RCA = II, III, aVF, V3, V4
25
Q

Which single lead is most commonly used to identify sinus rhythm / arrhythmias?

A

Lead II

26
Q

What is the normal duration for:

R-R interval
P wave
P-R interval 
QRS 
QT interval
T wave
A 
R-R interval = 0.6-1.2 s
P wave = 80 ms
P-R interval = 120-200 ms
QRS = <120 ms
QT interval = 420 ms
T wave = 160 ms
27
Q

What are the bipolar leads?

Where are they found?

A

Leads I, II and III - as they all have an electrode that is positive, and an electrode that is negative

I = between right arm (-ve) and left arm (+ve)
II = between right arm (-ve) and left leg (+ve)
III = between left arm (-ve) and left (+ve)
28
Q

What are the augmented leads?

A

aVF, aVL, aVR - they use fixed cathodes but virtual anodes

29
Q

Where are the fixed cathodes and virtual anodes for the leads:

aVF
aVL
aVR

A

aVF = left leg cathode, lead I anode (between right and left arms)

aVL = left arm cathode, lead II anode (between right arm and left leg)

aVR = right arm cathode, lead III anode (between left arm and left leg)

30
Q

Where are the right angles formed between the different leads?

(aVF, aVL, aVR, lead I, lead II, lead III)

A

aVF and lead I

aVL and Lead II

aVR and lead III

31
Q

How can you calculate the net vector / deflection of the QRS?

A

Use the boxes on the graph, find the difference between the positive and negative deflections of the QRS complex

32
Q

Use lead II and aVL to:

Calculate theta in the triangle.

Then calculate the yellow angle as you need to find the angle from 0 degrees.

The yellow angle shows the ventricular axis

A

tan (theta) = 0.444

theta = 24 degrees

Yellow angle =

60 degrees - 24 degrees = 36 degrees

This is the ventricular axis

33
Q

So how do you find the ventricular angle axis?

A

Work out the net vector of 2 leads e.g. of lead II and aVL

Use those 2 net vectors to construct a triangle
Figure out theta in the triangle

Then figure out the angle from 0 degrees to the net vector

34
Q

What is the ECG reporting procedure?

A

Is it the correct recording?

Review the signal quality and leads? - e.g. if they have muscular conditions, may give too much background noise

Verify the voltage and paper speed?

Review the patient background if available

35
Q

What are the 7 steps when looking at an ECG?

A

Step 1 = rate and rhythm - regular?

Step 2 = P wave and PR interval - how long does it last, and does every P wave result in an R wave?

Step 3 = QRS duration

Step 4 = QRS axis - should be between -30 and +90 degrees

Step 5 = ST segment - should be flat and at the isoelectric point

Step 6 = QT interval - duration

Step 7 = T wave - shape

36
Q

Can you defibrillate someone in asystole (i.e. a flatline)?

A

Not a shockable rhythm

Instead good to administer drugs and start CPR (chest compressions)

37
Q

What is a sinus rhythm?

A

Sinus = signal is being generated by the SAN

38
Q

What is a normal sinus rhythm on an ECG?

A

Each P-wave is followed by a QRS wave (1:1)

Rate is regular (even R-R intervals

39
Q

What is sinus bradycardia on an ECG?

A

Each P-wave is followed by a QRS wave (1:1)

Rate is regular (even R-R intervals) and slow (56 bpm)

Can be healthy, caused by medication or vagal stimulation

40
Q

What is sinus tachycardia on an ECG?

A

Each P-wave is followed by a QRS wave (1:1)

Rate is regular (even R-R intervals) and fast (107 bpm)

Often a physiological response (i.e. secondary)

41
Q

What is sinus arrhythmia on an ECG?

A

Each P-wave is followed by a QRS wave

Rate is irregular (variable R-R intervals) and normal-ish (65-100 bpm)

R-R interval varies with breathing cycle

42
Q

What is atrial fibrilation?

A

Oscillating baseline – atria contracting asynchronously

Rhythm can be irregular and rate may be slow

Turbulent flow pattern increases clot risk

Atria not essential for cardiac cycle

43
Q

What is atrial flutter?

A

Regular saw-tooth pattern in baseline (II, III, aVF)

Atrial to ventricular beats at a 2:1 ratio, 3:1 ratio or higher

Saw-tooth not always visible in all leads

44
Q

What are the features of first degree heart block?

A

Prolonged ST segment/interval caused by slower AV conduction

Regular rhythm: 1:1 ratio of P-waves to QRS complexes

Most benign heart block, but a progressive disease of ageing

45
Q

What are the two types of second degree heart block?

A

Mobitz I

Mobitz II

46
Q

What are the features of Mobitz I?

A

Gradual prolongation of the PR interval until beat skipped

Most P-waves followed by QRS; but some P-waves are not

Regularly irregular: caused by a diseased AV node
Also called Wenckebach

47
Q

What are the features of Mobtiz II?

A

P-waves are regular, but only some are followed by QRS

No P-R prolongation

Regularly irregular: successes to failures (e.g. 2:1) or random

Can rapidly deteriorate into third degree heart block

48
Q

What are the features of third degree heart block?

A

P-waves are regular, QRS are regular, but no relationship

P waves can be hidden within bigger vectors

A truly non-sinus rhythm – back-up pacemaker in action

49
Q

What are the features of ventricular tachycardia?

A

P-waves hidden – dissociated atrial rhythm
Rate is regular and fast (100-200 bpm)

At high risk of deteriorating into fibrillation (cardiac arrest)

Shockable rhythm – defibrillators widely available

50
Q

What are the features of ventricular fibrillation?

A

Heart rate irregular and 250 bpm and above
Heart unable to generate an output

Shockable rhythm – defibrillators widely available

51
Q

What are the features of ST elevation?

A

P waves visible and always followed by QRS

Rhythm is regular and rate is normal (85 bpm)

ST-segment is elevated >2mm above the isoelectric line

Caused by infarction (tissue death caused by hypoperfusion)

52
Q

What are the features of ST depression?

A

P waves visible and always followed by QRS

Rhythm is regular and rate is normal (95 bpm)

ST-segment is depressed >2mm below the isoelectric line

Caused by myocardial ischaemia (coronary insufficiency)

Y2 - BRS - CVR (21 decks)

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