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CC: CVS and Blood vessels > ECGs > Flashcards

ECGs Flashcards

1
Q

What is the correct methodical approach when assessing an ECG?

A

Rate
Rhythm
Axis
P, PR, QRS, QT, ST, T (and J wave?)

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2
Q

How do you calculate the rate from an ECG?

A

The divide 300 by the number of big squares in between each R wave

Or divide 1500 by the number of small squares between each R wave

Or multiply the number of QRS complexes in 10 seconds (ie, the trace at the bottom) by 6

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3
Q

How do you assess a regular rhythm from an ECG?

A

By marking the positions of 3 consecutive R waves on a piece of paper, and moving the piece of paper up and down to different places and leads to see if they match up in rhythm

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4
Q

How can you assess an irregular rhythm from an ECG?

A

Note if the different rates are multiples of each other or 100% irregular (ie AF or VF)

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5
Q

How can you tell if a rhythm is sinus on an ECG?

A

P waves come before each QRS complex

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6
Q

In which leads is the P wave normally upright?

A

II, III, aVF

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7
Q

In which leads of an ECG is the P wave normally inverted?

A

aVR

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8
Q

How can you tell if a patient is in AF based on ECG?

A

No discernible P waves

QRS complexes are irregularly irregular

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9
Q

What does atrial flutter look like on ECG?

A

Sawtooth baseline of atrial depolarisation (300/min) and regular QRS complexes

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10
Q

What does a nodal rhythm look like on ECG?

A

Normal QRS complexes

Absent P waves or they occur just before or within QRS complexes

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11
Q

How do you assess the frontal axis of the heart from an ECG?

A

The sum of all the ventricular forces during ventricular depolarisation

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12
Q

What is the normal frontal axis of the heart?

A

Between -30 and +90

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13
Q

What is a good rule of thumb when it comes to assessing the frontal axis of the heart?

A

If the QRS complex in leads I and II are both +ve, then the axis is very liely to be normal

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14
Q

What is the range of angles of axis for left axis deviation?

A

-30 to -90

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15
Q

What can cause left axis deviation?

A

Inferior MI

VT from LV focus

Wolff-Parkinson-White syndrome

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16
Q

What is the range of angles for right axis deviation?

A

+90 to +180

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17
Q

What can cause right axis deviation?

A

RVH

PE

Anterolateral MI

Some tyes of WPW syndrome

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18
Q

What is a cause of an absent P wave on ECG?

A

AF

Sinoatrial block

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19
Q

What is P mitrale on ECG?

A

A notched P wave

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20
Q

What does P mitrale indicate on ECG?

A

Left atrial hypertrophy

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21
Q

What is P pulonale on ECG?

A

A peaked P wave

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22
Q

What does P pulmonale indicate on ECG?

A

Right atrial hypertrophy

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23
Q

What change to the P wave on ECG can you see in hypokalaemia?

A

Pseudo-P-Pulmonale

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24
Q

What is the normal range for the PR interval?

A

0.12-0.2s

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25
Q

What would a prolonged PR interval on ECG imply?

A

Delayed AV conduction (1st degree heart block)

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26
Q

What would a short PR interval on ECG imply?

A

Fast AV conduction, probably through an accessory pathway (eg WPW syndrome)

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27
Q

What is the normal QRS duration on ECG?

A
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28
Q

What does a QRS complex of longer duration than 0.12 seconds imply?

A

Ventricular conduction defects, such as BBB

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29
Q

What does a large QRS complex on ECG imply?

A

Ventricular hypertrophy

30
Q

What is a normal QT interval on ECG?

A

0.38-0.42s

31
Q

Is the QT interval independant of rate?

A

No

QT(corrected) = QT/(squ-root(RR interval))

32
Q

What are some conditions that can lead to prolonged QT intervals?

A

AMI

Bradycardia

U&E imbalance (lack of K+, Ca2+, Mg2+)

drugs (sotalol, quinidine, antihistamines, macrolides, amiodarone etc)

33
Q

What specifically does the QT interval measure?

A

From the start of the QRS complex to the end of the T wave

34
Q

Where is the T wave normally inverted?

A

aVR, V1 and occasionally V2

35
Q

If the T wave is inverted in I and V5, can that be considered to be normal?

A

No, shouldn’t be elevated in I or V5

36
Q

Does hyperkalaemia peak or flatten the T wave on ECG?

A

Peaks it

37
Q

T/F hypokalaemia doesn’t change the T wave on ECG

A

F

It flattens it

38
Q

When are you likely to see a J wave on ECG?

A

In hypothermia (severe)

39
Q

What is a J wave on ECG?

A

Seen immediately after the QRS complex

Small positive wave, usually peaked

40
Q

Where is a U wave in an ECG?

A

Between the T and P waves

41
Q

What are some causes of tachycardia?

A

Exercise, pain, pregnancy, caffeine, adrenaline

Anaemia, thyrotoxicosis, CO2 retention

Sepsis, hypovolaemia, PE, CHF

Drugs (sympathomimetics)

42
Q

What are some causes of bradycardia?

A

Physical fitness, hypothermia

^ ICP, cholestasis, hypothyroidism

Acute MI, vasovagal attacks, sick sinus syndrome

Drugs (B-blockers, digoxin, amiodarone, verapamil)

43
Q

What are some causes of AF?

A

IHD, HTN

Thyrotoxicosis

44
Q

What is first degree heart block?

A

When conduction is delayed between the atria and the ventricles

Increased PR interval

45
Q

What is second degree Mobitz type 1 heart block?

A

Progressive elongation of the PR interval until a beat is dropped

46
Q

What is a complicating factor when interpreting Mobitz I block?

A

If the atrial rhythm isn’t regular then there could be other interpretations

47
Q

Is Mobitz I block particularly worth treating?

A

No, it’s relatively benign

48
Q

What is second degree Mobitz type II heart block?

A

When there are some non-conducted P waves, but no change in the PR interval otherwise (ie no prolongation before)

49
Q

What is the relationship between P waves and QRS complexes in Mobitz II block?

A

There is normally a fixed number of non-conducted P waves for each conducted P wave (ie, each QRS complex)

This is reported as ‘2:1 Mobitz II’, if there are 2 non-conducted P waves for each conducted one resulting in a QRS

50
Q

Is Mobitz II clinically important and worth treating?

A

Yes

Can rapidly progress to 3rd degree heart block

51
Q

How do you treat Mobitz II heart block?

A

With a pacemaker

52
Q

How does 3rd degree heart block appear on ECG?

A

No concordance between P waves and QRS complexes

53
Q

How do you report the type of Mobitz I that a patient’s ECG shows?

A

Number of P waves for number of QRS complexes per cycle

Eg if there are 4 P waves but only 3 QRS complexes before it resets, then it is 4:3 Mobitz I

54
Q

Is it always necessary to specify which Mobitz block it is?

A

No

Mobitz I is always reported as X:X-1, Mobitz II is always reported as X:1

Thus the only time to specify which the ECG shows is when it is 2:1

55
Q

How do Q waves sometimes change in AMI?

A

Become >0.04s wide and >2mm deep

56
Q

When Q waves change with AMI, how long do they take to go back to normal?

A

Never

Unless PCI was performed quickly they will remain deep and wide indefinitely

57
Q

What can cause a saddle-shaped ST elevation?

A

Acute pericarditis

58
Q

What is a normal variant ST depression?

A

One that slopes upwards

59
Q

What morphology of ST depression does digoxin make on ECG?

A

A downward sloping ST depression

60
Q

What causes a horizontal ST depression?

A

Ischaemia

61
Q

In which leads is T wave inversion normal?

A

V1-V3

62
Q

When do you see T wave depression in V2-V5?

A

Subendocardial MI

Subarachnoid haemorrhage

Lithium

63
Q

When do you see T wave depression in V4-V6 and aVL?

A

Ischaemia

LVH

LBBB sometimes

64
Q

Are ST and T wave changes on ECG specific?

A

No

Should be considered in a clinical context

65
Q

How does a BBB appear on ECG in general?

A

QRS is >0.12s

66
Q

What are some ECG changes associated with RBBB?

A

QRS >0.12s

‘M’ pattern in V1 and V2 (ie, RSR)

Deep and wide S waves esp V6

67
Q

What are some causes of RBBB?

A

Normal variant

PE

Cor pulmonale

68
Q

What are some ECG changes associated with RBBB?

A

QRS >0.12s

‘M’ pattern in V6

Inverted T waves in I, aVL, V5 & V6

69
Q

What is bifascicular block?

A

Combination of RBBB and left bundle hemiblock

70
Q

How does bifascicular block manifest on ECG?

A

Axis deviation

71
Q

What is trifascicular block?

A

Combination of bifascicular block and 1st degree heart block

72
Q

What are some causes of low voltage QRS complexes?

A

Hypothyroidism, COPD, PE, BBB

CC: CVS and Blood vessels (9 decks)

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