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*LSS Cardiovascular Y1* > ECGs > Flashcards

ECGs Flashcards

1
Q

What are the intervals on an ECG?

How long are they?

A

PR Interval: 120-200ms

QRS Interval: 80-120ms

ST Interval: 320ms

QT Interval: 350-450ms

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2
Q

What are the two segments of an ECG and how long are they?

A

PR Segment: 50-120ms

ST Segment: 80-120ms

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3
Q

What are the five waves of an ECG?

How long are they?

A

P Wave: 80ms

Q Wave: \

R Wave: QRS Complex: 80-120ms

S Wave: /

T Wave: 160ms

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4
Q

Label the Waves, Segments and Intervals on this ECG:

A
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5
Q

What do upward and downward deflections represent?

A

Upward deflection: wave of depolarisation towards the cathode (+) or repolarisation away from the cathode (+)

Downward deflection: wave of depolarisation towards the anode (-) or repolarisation away from the anode (-)

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6
Q

What does the gradient on an ECG represent?

A

The velocity of the action potential

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7
Q

What causes the P-wave?

A

P wave: SAN autorhythmic myocytes depolarise, causing the P-wave and atrial depolarisation, with the wave moving across from the right to left atrium via internodal fibres, and slightly towards the cathode

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8
Q

What causes the PR segment?

A

AVN depolarises in the PR segment and isoelectric to delay impulse and allow for ventricular filling

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9
Q

What causes the Q wave?

A

Bundle of His rapidly conducts wave of depolarisation down septum

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10
Q

What causes the R wave?

A

Ventricular depolarisation due to the purkinje fibres, with wave spreading towards the cathode

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11
Q

What causes the S wave?

A

Purkinje fibres carry wave up the myocardium for late ventricular depolarisation, moving away from the cathode

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12
Q

What causes the ST segment?

A

Depolarised ventricles produce an isoelectric ECG

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13
Q

What causes the T wave?

A

Ventricular repolarisation moving towards the cathode

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14
Q

What causes the U wave?

A

Purkinje fibre repolarisation

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15
Q

Where would you place the chest leads?

A
  • V1: 4th intercostal, right sternal margin
  • V2: 4th intercostal, left sternal margin
  • V3: in-between V2 and V4 (on top of 5th rib)
  • V4: 5th intercostal, mid-clavicular line
  • V5: 5th intercostal, anterior axillary line (usually half-way between V4/V6)
  • V6: 5th intercostal, mid-axillary line
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16
Q

Where are the limb leads placed?

A

Red: Right Arm

Yellow: Left Arm

Green: Left Leg

Black: Right Leg

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17
Q

What do the small squares on an ECG represent?

A

0.04s width, 0.1mV height

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18
Q

What do the big squares on an ECG represent?

A

0.2s width, 0.5mV height

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19
Q

What is the run-speed of an ECG?

A

25mm/sec

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20
Q

What is Einthoven’s Triangle?

A

Formed by leads I, II and III running RA-LA, RA-LL, LA-LL; using a coronal plane to measure movement of electricity away from heart

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21
Q

What are the Bipolar leads?

A

I, II, III - measuring potential difference between the limbs; for a given complex the net deflection is equal to the sum of the net deflections in the other two leads;

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22
Q

What are the Unipolar leads?

A

aVR, aVF, aVL - measuring potential difference between null point with relative 0 potential at centre of triangle

Measure flow of electricity from centre of heart towards right arm (aVR), left arm (aVL) and left foot (aVF)

23
Q

What is the difference between Bipolar and Unipolar leads?

A

Bipolar uses two physical leads, unipolar uses one lead and a combination of other leads

24
Q

What is the Rule of L’s?

A

Lead I (1 L):

Right Arm to Left arm

Lead II (2 L’s)

Right arm to Left leg

Lead III (3 L’s)

Left arm to Left leg

Also remembered by reading left to right, up to down

25
Q

Describe the Polarity, Plane, Cath/anode, and View of Leads I-III

A
26
Q

Describe the Polarity, Plane, Cath/anode, and View of Leads aVR, aVF, aVL

A
27
Q

Describe the Polarity, Plane, Cath/anode, and View of Leads V1 and V2

A
28
Q

Describe the Polarity, Plane, Cath/anode, and View of Leads V3 and V4

A
29
Q

Describe the Polarity, Plane, Cath/anode, and View of Leads V5 and V6

A
30
Q

Which leads would you use to look at the Left Circumflex artery?

A
  • 1
  • aVL
  • V5
  • V6
31
Q

What leads would you use to look at the Right Coronary?

A
  • 2
  • 3
  • aVF
  • V3
  • V4
32
Q

What leads would you use to look at the Left Anterior Descending artery?

A
  • V1
  • V2
33
Q

What is the cardiac axis?

A

The axis of a wave/complex is the direction the wave of depolarisation is moving in on the coronal plane (does not use precordial leads)

34
Q

What is the normal range for the Cardiac Axis?

A

-30o to +120o General axis of depolarisation

35
Q

What are the axes of Leads I-III?

A

I: 0o

II: 60o

III: 120o

36
Q

What are the axes of leads aVL, aVF, aVR?

A

aVL: -30o

aVF: 90o

aVR: -150o

37
Q

Which combinations of leads might you select to calculate the axis?

A

I/aVF

II/aVL

III/aVR

38
Q

How do you calculate the cardiac axis?

A
  • Select two leads at 90o
  • Work out net QRS depolarisation on each lead
  • Form a triangle by drawing x mm along the numerical lead e.g. II, and y mm perpendicular from the lead (where x is the numerical lead net depolarisation and y is the augmented lead net depolarisation)
  • Theta = tan-1(aug depol/num depol)
  • Cardiac Axis = Numerical Lead Axis - theta
39
Q

What is the systematic approach to ECG interpretation?

A
  1. Correct recording?
  2. Signal quality and leads? (movement can affect)
  3. Voltage and paper speed?
  4. Patient background? CVS/Resp disease? (axis moves on COPD)
  5. Rate: 300/no. big squares = heart rate
  6. P Wave: should be 80ms; PR: should be 50-120ms
  7. QRS duration: should be 80-100ms
  8. QRS axis: should be -30O to 120O
  9. ST Segment: should be 80-120ms and not isoelectric
  10. QT interval: should be 420ms
  11. T Wave should be 160ms and will change shape in electrolyte disturbances
40
Q

What does this ECG show?

A

Sinus:

Ps followed by QRS 1:1

Regular rate and normal

Otherwise unremarkable

41
Q

What does this ECG show?

A

Sinus Brady:

  • Ps followed by QRS 1:1
  • Regular rate and slow
  • Can be healthy/medication/vagal stimulation
42
Q

What does this ECG show?

A

Sinus Tachy:

  • Ps followed by QRS 1:1
  • Regular rate and fast
  • Often physiological or could be decreased venous return
43
Q

What does this ECG show?

A

Sinus Arrhythmia

  • Ps followed by QRS 1:1
  • Irregular rate and normal-ish rate
  • R-R varies with breathing
44
Q

What does this ECG show?

A

Atrial Fibrillation:

  • Oscillating baseline so asynchronous atria contraction
  • Irregular and slow rhythm
  • Turbulent flow pattern increases clot risk
45
Q

What does this ECG show?

A

Atrial Flutter:

  • Regular saw-tooth pattern in the baseline (II, III, aVF)
  • Atrial:ventricular beats 2:1/3:1 or higher
  • Not visible in all leads; some flutters hidden in QRS complexes
46
Q

What does this ECG show?

A

1st deg heart block

  • Prolonged PR due to slower AV conduction
  • Regular rhythm of P:QRS
  • Mostly benign
47
Q

What does this ECG show?

A

2nd deg heart block (Mobitz 1)

  • Increasing PR until missed QRS
  • Regularly irregular due to diseased AV node
  • AKA Wenkebach
48
Q

What does this ECG show?

A

2nd deg heart block (Mobitz 2)

  • No PR elongation and some QRS complexes are missed
  • Regularly irregular with fixed ratio of successes to failures e.g. 2:1
  • Can rapidly deteriorate to 3rddegree
49
Q

What does this ECG show?

A

3rd deg heart block

  • Regular P waves and QRS complexes but no relationship
  • AVN/myocardium can be auto-rhythmic
  • Non-sinus with backup pacemakers
  • P waves regular and fast, QRS regular and slow
50
Q

What does this ECG show?

A

VTach

  • P waves hidden in dissociated atrial rhythm
  • Ventricles beating rapidly and very hard
  • Rate regular and fast
  • Risk of deterioration to Vfib
  • Shockable rhythm
  • All vectors look same
51
Q

What does this ECG show?

A

VFib:

  • Heart rate irregular and >250bpm
  • No output
  • Shockable
  • Vectors will change and do not all look same
52
Q

What does this ECG show?

A

ST Elevation

  • P waves visible and followed by QRS
  • Regular normal rate
  • ST-segment elevated >2mm above isoelectric
  • Caused by infarction
53
Q

What does this ECG show?

A

ST Depression:

  • P waves visible and followed by QRS
  • Regular normal rate
  • ST-segment depressed >2mm below isoelectric
  • Caused by ischaemia
54
Q

What are the Shockable rhythms?

A

VTach & VFib

*LSS Cardiovascular Y1* (9 decks)

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