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Year 3 Medicine > ECGs > Flashcards

ECGs Flashcards

1
Q

Give the diagnosis:
Sinus rhythm followed by no p wave before a normal QRS, or one immediately before or after the normal QRS; the next p wave is late, followed by sinus rhythm

A

Junctional (nodal) extrasystole

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2
Q

When do you see -ve or +ve deflections of the QRS?

A

-ve in I, and +ve in III is R axis deviation

predominantly -ve in II and III is L axis deviation

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3
Q

What sort of pathology does LBBB indicate?

A 
Heart disease, ~ on the L side
Aortic stenosis
Ischaemic disease
Hypertension
Cardiomyopathy
Acute MI if also chest pain
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4
Q

What do hyperacute T waves indicate?

A

MI

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5
Q

How can you identify atrial flutter on an ECG?

A

Look at leads II, aVR and aVF
Narrow complex tachycardia
P waves at >250 bpm, and multiple p waves per QRS
No flat baseline between p waves (sawtoothed appearance)

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6
Q

If the R-R interval is 5, what is the heart rate?

A

300/5 is 60

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7
Q

Give the diagnosis:
No p waves, only an irregular baseline
Normal shaped QRS complexes, very irregular rate (may be abnormal shape if also a BBB)
V1 may look a bit sawtoothed

A

Atrial fibrillation

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8
Q 
Give the diagnosis:
No relationship between p and QRS
Different rates for p and QRS
Abnormally shaped or broad QRS
Slow QRS rate
A

3rd degree (complete) heart block

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9
Q

What does a thick base line on the ECG reading indicate?

A

Electrical interference eg. from electric lights or electric motors on beds/mattresses

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10
Q

What ECG changes are seen in digoxin Tx?

A

Downward sloping ST segment

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11
Q

Give the diagnosis:
Sinus rhythm followed by an abnormal, early p wave, normal but early QRS; the next p wave is late, followed by sinus rhythm

A

Atrial extrasystole

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12
Q

What ECG changes are seen in R and L atrial hypertrophy? Give 2 causes of each

A

Right:
Peaked p waves
Tricuspid valve stenosis
Pulmonary hypertension

Left:
Broad and bifid p waves (p mitrale)
~ due to mitral stenosis
Also can be due to mitral regurg

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13
Q

What does an RSR1 pattern indicate in V1?

A

RBBB

Normal if <120 ms (partial RBBB)

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14
Q

Give the diagnosis:

Delay after a beat, followed by an abnormal p wave and normal QRS. Returns to sinus arrhythmia

A

Atrial escape

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15
Q

Which direction is the depolarisation wrt the sizes of the R and S waves?

A

R>S (overall upward) means depolarisation is moving towards that lead.
S>R (overall downward) means it’s moving away.
R=S means the depolarisation wave is moving at right angles to the lead.

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16
Q

How do you determine a normal 11 o clock - 5 o clock axis?

A

They will be a predominantly upward deflection in leads I, II and III, with a greater deflection in II

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17
Q

What ECG changes are seen in PE?

A

Can have a normal ECG with sinus tachycardia

RBBB
Peaked p waves
Increased height of the QRS (>35 mm) in V1
Q wave in III but no aVF + R axis deviation
Dominant R waves in V1 (R>S)
Deep S wave in V6
Transition point shifted to V5 or V6 (clockwise rotation)
T waves inversion in III, V1, V2 and possibly V3 and V4

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18
Q

What ECG changes are seen in L anterior hemiblock?

A

Marked L axis deviation

Deep S waves in leads II and III, ~ with a slightly wide QRS complex

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19
Q

When are p waves broad and bifid (p mitrale)?

A

L atrial hypertrophy, which is ~ due to mitral stenosis, or sometimes mitral regurg

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20
Q

How do you work out the position of an MI?

A

Anterior: V3-4 (often V2 and V5)
Inferior: III and aVF
Lateral: I, aVL, V5-6
True posterior: dominant R waves in V1

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21
Q

Give the diagnosis:
Slow QRS rate
No p waves in junctional beats, but normal QRS

A

Nodal (junctional) escape

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22
Q

How do you determine R axis deviation. What sort of conditions is this associated with?

A

I has negative deflection.
III has increased positive deflection of the QRS.

Caused by R ventricular hypertrophy, which is associated with pulmonary conditions that put a strain on the R heart (eg. PE), as well as congenital heart disorders.
Can also be normal in tall, thin people

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23
Q

What are the causes of sinus arrhythmia?

A

Changes in heart rate associated with respiration - ~ seen in young ppl

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24
Q

When are QRS complexes narrow?

A

Supraventricular rhythms (sinus, atrial, nodal)

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25
Q

What can the rhythms arising in the atrial muscle, junctional (nodal) region or ventricular muscle be categorised as?

A

Bradycardic (slow and sustained)
Extrasystoles (occur as early single beats)
Tachycardic (fast and sustained)
Fibrillation (totally disorganised activation of atria / ventricles)

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26
Q

What does a tall R wave to >25 mm indicate?

A

L ventricular hypertrophy if in V5 or V6

R ventricular hypertrophy or normal if in V1

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27
Q

What effect might the pt moving eg. from Parkinson’s or shivering, have on the ECG?

A

A jerky appearance

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28
Q

What are the ECG signs of L ventricular hypertrophy?

A

Deep S in V1/2
Tall R (>25 mm) in V5/6
Inverted T waves in I, II, aVL and V5/6, and sometimes V4
L axis deviation

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29
Q

What does a short PR interval indicate?

A

Wolff-Parkinson-White

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30
Q

How can you identify atrial fibrillation on an ECG?

A

No p waves, only an irregular baseline
Normal shaped QRS complexes, very irregular rate (QRS complexes may be an abnormal shape if also a bundle branch block)
V1 may look a bit like atrial flutter (sawtooth)

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31
Q

How do you work out the position of the ventricular septum? What’s the clinical relevance of this?

A

The QRS goes from predominantly downward in V1 to predominantly upward in V6. The transition point where the R and S waves are equal indicates the position of the ventricular septum.

The more the right ventricle is enlarged, the more this transition point moves from V3/V4 to V4/V5 or V5/V6.

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32
Q

When might the ST segment disappear?

A

High K+

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33
Q

What are the values for one small square laterally, and one large square laterally and vertically?

A

Laterally one small square is 0.04s or 40ms
Laterally one large square is 0.2s or 200ms
Vertically one large square is 0.5mV (0.5cm)

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34
Q

When are p waves peaked?

A

R atrial hypertrophy (eg. from tricuspid valve stenosis or pulmonary hypertension)
R ventricular hypertrophy
PE

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35
Q

Where do you place the leads on the body for the ECG?

A 
LA = L arm
RA = R arm
LL = L leg
RL = R leg

Find the 2nd intercostal space by finding the space below the sternal angle
V1 = R of sternum at 4th intercostal space
V2 = L of sternum at 4th ICS
V3 = Halfway between V2 and V4
V4 = Midclavicular line 5th ICS
V5 = Horizontally inline with V4, anterior axillary line (fold of skin that marks the front of the armpit)
V6 = Horizontally inline with V4/V5, midaxillary line

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36
Q

Give the diagnosis:
After sinus beats, there’s a pause followed by a single wide, abnormal QRS with an abnormal T wave. Sinus rhythm then continues.

A

Ventricular escape

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37
Q

How can you identify ventricular fibrillation on an ECG?

A

No QRS complexes
The ECG is totally disorganised
LOC in pt

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38
Q

If the R-R interval is 2, what is the heart rate?

A

300/2 is 150

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39
Q

How can you identify junctional (nodal) tachycardia on an ECG?

A

No p waves, or very close to the QRS complexes
Normal QRS complexes (might be narrow) (abnormal if also a bundle branch block or ventricular tachycardia)
Fast QRS rate (150-180/min)

40
Q

If the R-R interval is 6, what is the heart rate?

A

300/6 is 50

41
Q

What do the intervals and segments of the ECG represent, and what are their normal time lengths?

A

PR interval is the time taken for excitation to spread from the SA node, through the atrial muscle and AV node, down the bundle of His and into the ventricular muscle. Normally it’s 3-5 small squares (120-200ms).

The duration of the QRS shows how long excitation takes to spread through the ventricles (depolarisation). Normally it’s <3 small squares (120ms).

The ST segment is the time taken for the ventricles to contract.

QT interval is usually <11 small squares (450ms).

42
Q

What are the underlying causes of 3rd degree (complete) heart block?

A

An acute phenomenon in pts with an MI (when it’s ~ transient)
A chronic state, ~ due to fibrosis around the bundle of His
Block of both bundle branches

43
Q

How can you identify extrasystoles on an ECG?

A

Sinus rhythm followed by an:

Atrial: abnormal, early p wave; normal but early QRS; the next p wave is late, followed by sinus rhythm

Junctional (nodal): no p wave before normal QRS, or one immediately before or after the normal QRS; the next p wave is late, followed by sinus rhythm

Ventricular: no p wave, then an abnormal, wide, early QRS; inverted T wave; the next p wave is on time, followed by sinus rhythm

44
Q

What is the normal axis range in degrees?

A

-30° to +90°

45
Q

What ECG changes are seen in R ventricular hypertrophy?

A

R axis deviation
Sometimes RBBB
Peaked p waves
Normally S>R in V1 (and V2), but in R ventricular hypertrophy there’s a tall R wave (>25 mm) so that R>S (but this may be normal)
Deep S wave in V6
T waves inversion in V1, V2 and possibly V3 and V4

46
Q

What does ST elevation indicate?

A

Acute MI or pericarditis

47
Q

What do pathological Q waves indicate?

A

Septal Q waves (>1 mm (1 small square) and 2 mm deep) in MI, or normal in I, II, aVL, V5, V6 and possibly III

in III but not aVF, plus R axis deviation, indicates PE

48
Q

What ECG changes are seen in low K+ and high K+?

A

Low: T waves are flattened and prolonged, and then there’s a hump at the end (u wave)

High: Peaked T waves; ST segment disappears

49
Q

What ECG changes are seen in high Ca+?

A

Shortened QT interval

50
Q

Give the diagnosis:

progressive lengthening of PR intervals, then a p not followed by a QRS, then returns to beginning of cycle

A

2nd degree heart block: Wenckebach

51
Q

What may cause a very jerky appearance to the ECG reading?

A

If the pt isn’t still eg. shivering or moving (eg. Parkinson’s)

52
Q

Heart block refers to interference with which process? Where is this on the ECG reading?
What are the differences between the pathology of the different heart blocks? How do each represent on ECG?

A

The conduction process of depolarisation from the SA node, through the atria, the AV node, the His bundle and then it’s branches, to the ventricular muscle.
This is represented by the PR interval.

1st degree:
Delay somewhere along the conduction pathway.
1 p wave per QRS. PR >200 ms.

2nd degree:
Intermittent failure of the excitation to pass through the AV node or bundle of His.
Mobitz type 2: Mostly constant PR intervals; an occasional p not followed by a QRS.
Wenckebach: Progressive lengthening of PR interval, then a p not followed by a QRS, then returns to beginning of cycle.
2:1: Normal, constant PR interval; 2 p’s per QRS (also can have eg. 3:1) (note p waves can be shown as a distortion of T waves)

3rd degree (complete heart block):
Atrial contraction is normal, but no beats are conducted to the ventricles, so the ventricles are excited by a slow 'escape mechanism'
No relationship between p and QRS; different rates for p and QRS; abnormally shaped or broad QRS; slow QRS rate
53
Q 
Give the diagnosis:
Leads II, aVR and aVF
Narrow complex tachycardia
P waves >250 bpm
Multiple p waves per QRS
No flat baseline between p waves (sawtoothed)
A

Atrial flutter

54
Q

When are QRS complexes wider then 120 ms (3 small squares)?

A

BBB
Wolff-Parkinson-White

When depolarization is initiated in the ventricular muscle, causing ventricular escape beats, extrasystoles or ventricular tachycardia

55
Q

What parts of the heart do the different leads look at?

A

I, II and aVL look at the L lateral surface of the heart.
III and aVF look at the inferior surface.
aVR looks at the R atrium.
V1 and V2 look at the R ventricle.
V3 and V4 look at the septum between the ventricles and the anterior wall of the L ventricle.
V5 and V6 look at the anterior and lateral walls of the L ventricle.

56
Q

What are the underlying causes of 1st +/ 2nd degree heart block?

A 
Can be seen in normal people
Acute MI
Coronary artery or heart disease
Acute rheumatic carditis
Digoxin toxicity
Electrolyte abnormalities
57
Q

What are u waves and what do they indicate?

A

A hump at the end of a T wave

If preceded by a flattened and prolonged T wave, this indicates low K+

58
Q

What is the standard rate for an ECG machine to run at?

A

25mm/s

59
Q

Which direction is the septum normally depolarised?

When might it be depolarised in another direction?

A

Left to right

In LBBB the septum is depolarised from R to L

60
Q

Give the diagnosis:
No QRS complexes
Completely disorganised ECG

A

Ventricular fibrillation

61
Q

How can you identify atrial tachycardia on an ECG?

A

Tachycardia >150 bpm
Normal QRS complexes; regular regularity
P waves may be superimposed on the T waves preceding them, hence a short PR interval; more p wave than QRS complexes

62
Q

Give the diagnosis:
No p waves, or very close to the QRS complexes
Normal QRS complexes (might be narrow) (abnormal if also BBB or ventricular tachycardia)
Fast QRS rate

A

Junctional (nodal) tachycardia

63
Q

What does a shortened QT interval indicate?

A

High Ca+

64
Q

What do deep S waves indicate?

A 
In V6:
PE
Chronic lung disease
R ventricular hypertrophy
RBBB (deep and wide)

V1 or V2:
L ventricular hypertrophy

II and III:
L anterior hemiblock
LBBB

65
Q

If the R-R interval is 4, what is the heart rate?

A

300/4 is 75

66
Q

What do the different waves of the ECG represent?

A

P is contraction of the atria
QRS is the depolarisation of the ventricles
T is repolarisation of the ventricles

67
Q

What are the causes of sinus bradycardia?

A 
Athletic training
Fainting / vasovagal attacks
Hypothermia
Hypothyroidism
Immediately after an MI
68
Q

If there’s a bundle branch block, what implications does this have for looking at the rest of the ECG?

A

LBBB prevents any further interpretation

RBBB can make interpretation difficult

69
Q

What sort of pathology does RBBB indicate?

A

Normal heart
Problems in the R side of the heart
Atrial septal defect or other congenital disease
PE

With L axis deviation: severe conducting tissue disease

70
Q

What are QRS complexes broad with a notched top?

A

In V6 in LBBB

71
Q

What are the signs of cardiomyopathy on ECG?

A

Non-specific ST changes
Conduction defects
Arrhythmias

Hypertrophic:
L axis deviation
L ventricular hypertrophy
Q waves in inferior and lateral leads

Restrictive:
Low voltage complexes

72
Q

What ECG changes are seen during exercise?

A

Tachycardia

ST segment depression (esp. if there’s angina)

73
Q

Explain the changes on an ECG seen in Wolff-Parkinson-White syndrome

A

In addition to the bundle of His, some ppl have an extra or accessory conducting bundle between the atria and ventricles (~ on the L side). This has no AV node to delay conduction, so depolarisation reaches the ventricle early, leading to pre-excitation.

Short PR interval
Early slurred upstroke in QRS complex (delta wave); the rest of the QRS is normal
Sinus rhythm

A paroxysmal tachycardia can occur, causing a re-entry circuit. This shows as a tachycardia with no p waves

74
Q 
Give the diagnosis:
>150bpm
Normal QRS complexes, regular regularity
P waves may be superimposed on the t waves preceding them
More p waves than QRS complexes
A

Atrial tachycardia

75
Q

If the R-R interval is 3, what is the heart rate?

A

300/3 is 100

76
Q

Give the diagnosis:
Normal sinus rhythm followed by an abnormal, ~ wide QRS and inverted T wave; the next p wave is on time, followed by sinus rhythm

A

Ventricular extrasystole

77
Q

Give the diagnosis:

mostly constant PR intervals; occasional p not followed by QRS

A

2nd degree heart block: Mobitz type 2

78
Q

What are the causes of sinus tachycardia?

A 
Exercise
Fear
Pain
Haemorrhage
Thyrotoxicosis
Obesity
Pregnancy
Anaemia
CO2 retention
79
Q

How can cardiac rhythms be classified wrt their origin? What are the ECG changes seen for each and why?

A

Supraventricular
Sinus, atrial, nodal (junctional)
Narrow or normal QRS (depolarisation still passes through His bundle and branches)
Will be wide QRS if also a BBB or Wolff-Parkinson-White
Normal T waves

Ventricular:
Wide, abnormal QRS (depolarisation spreads more slowly through Purkinje fibres)
Abnormal T wave (abnormal repolarisation)

80
Q

What effect might electrical interference eg. from electric lights of electric motors on beds/mattresses have on the ECG?

A

Thick base line

81
Q

What ECG changes are seen in pericarditis?

A

Elevated ST segment

82
Q

What does T wave inversion indicate?

A

Normal in V1, aVR, sometimes III and V2, and V3 and V4 in some black ppl

In V1, V2, and possibly V3-4 indicates R ventricular hypertrophy, PE, RBBB

In aVL, V5 and V6 indicates LBBB or L ventricular hypertrophy

Can also indicate ischaemia, digoxin Tx, MI or Wolff-Parkinson-White

83
Q

What is the order for reporting an ECG?

A 
Rhythm
Abnormalities of the p wave (tall/broad)
Cardiac axis
QRS duration or abnormal Q waves
Elevated or depressed ST segment
T waves normal or inverted
84
Q

What does a shifted transition point indicate?

A

Shifted to V5 or V6 in PE or chronic lung disease (clockwise rotation)

85
Q

How do you determine L axis deviation. What sort of conditions is this associated with?

A

III develops predominantly negative deflection in the QRS.
It only becomes significant once II also becomes predominantly negative as well.

Due to L ventricular hypertrophy / a conduction defect.

86
Q

If the R-R interval is 1, what is the heart rate?

A

300/1 is 300

87
Q

What degree do each of the leads look at the heart from?

A 
I is 0°
II is +60°
aVF +90°
III +120°
aVR -150°
aVL -30°
88
Q

Describe the ECG changes in an MI

A

Over a period of 24-48h:

In a STEMI: first you get an elevated ST segment (1 mm in limb leads, >2 mm in chest leads); Then pathological Q waves appear (>1 mm (1 small square) wide and 2 mm deep); Then the ST segment returns to the baseline; Then T waves become inverted (often permanently).
Also you can get hyperacute T waves

In an NSTEMI: may show T wave inversion or ST depression

In an MI of the posterior of the L ventricle, you get an increased QRS height (>35 mm) in V1

89
Q

Give the diagnosis:
Wide, abnormal QRS complexes in all 12 leads
Difficult to identify p or t waves

A

Ventricular tachycardia

90
Q

Are the deflections in II and aVR mainly positive or negative and why?

A

Positive in II and negative in aVR.

These leads look at the heart from opposite directions.

91
Q

What do peaked T waves indicate?

A

High K+

92
Q

How can you identify ventricular tachycardia on an ECG?

A

Wide, abnormal QRS complexes in all 12 leads
Rate > 160/min
Difficult to identify P or T waves

93
Q

What is a delta wave and when is it seen?

A

An early slurred upstroke of a QRS

Wolff-Parkinson-White

94
Q

What does ST depression indicate?

A

May be seen during exercise (esp. if there’s angina), or in an NSTEMI

Horizontal depression with an upright T wave is ~ ischaemia instead of infarction

Downward-sloping in digoxin Tx

95
Q

What does increased height of the QRS to >35 mm indicate?

A

PE or MI of the posterior of the L ventricle in V1

96
Q

Give the diagnosis:

normal, constant PR interval; 2 p’s per QRS; p waves can be shown as a distortion of T waves

A

A 2:1 2nd degree heart block

97
Q

What’s the effect of a bundle branch block on an ECG and why?

A

Widened QRS (>120ms or 3 small squares) b/c there’s a delay in the depolarisation of the ventricular muscle.

RBBB:
RSR1 pattern in V1 (up, down, up the same amount as the first up).
Inverted T waves in V1 and sometimes V2 and V3.
Deep, wide S waves in V6.
Can be normal in healthy pts if there’s a normal QRS.

LBBB:
Broad QRS in V6 (and sometimes V4-5) with a notched top (small up, small down, big up)
Can have T wave inversion in some or all of I, aVL, V5, V6, and sometimes V4.
Deep S waves in II, III
No septal Q waves

Year 3 Medicine (5 decks)

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