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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
What would a prolonged PR interval on ECG imply?
Delayed AV conduction (1st degree heart block)
26
What would a short PR interval on ECG imply?
Fast AV conduction, probably through an accessory pathway (eg WPW syndrome)
27
What is the normal QRS duration on ECG?
28
What does a QRS complex of longer duration than 0.12 seconds imply?
Ventricular conduction defects, such as BBB
29
What does a large QRS complex on ECG imply?
Ventricular hypertrophy
30
What is a normal QT interval on ECG?
0.38-0.42s
31
Is the QT interval independant of rate?
No QT(corrected) = QT/(squ-root(RR interval))
32
What are some conditions that can lead to prolonged QT intervals?
AMI Bradycardia U&E imbalance (lack of K+, Ca2+, Mg2+) drugs (sotalol, quinidine, antihistamines, macrolides, amiodarone etc)
33
What specifically does the QT interval measure?
From the start of the QRS complex to the *end* of the T wave
34
Where is the T wave normally inverted?
aVR, V1 and occasionally V2
35
If the T wave is inverted in I and V5, can that be considered to be normal?
No, shouldn't be elevated in I or V5
36
Does hyperkalaemia peak or flatten the T wave on ECG?
Peaks it
37
T/F hypokalaemia doesn't change the T wave on ECG
F It flattens it
38
When are you likely to see a J wave on ECG?
In hypothermia (severe)
39
What is a J wave on ECG?
Seen immediately after the QRS complex Small positive wave, usually peaked
40
Where is a U wave in an ECG?
Between the T and P waves
41
What are some causes of tachycardia?
Exercise, pain, pregnancy, caffeine, adrenaline Anaemia, thyrotoxicosis, CO2 retention Sepsis, hypovolaemia, PE, CHF Drugs (sympathomimetics)
42
What are some causes of bradycardia?
Physical fitness, hypothermia ^ ICP, cholestasis, hypothyroidism Acute MI, vasovagal attacks, sick sinus syndrome Drugs (B-blockers, digoxin, amiodarone, verapamil)
43
What are some causes of AF?
IHD, HTN Thyrotoxicosis
44
What is first degree heart block?
When conduction is delayed between the atria and the ventricles Increased PR interval
45
What is second degree Mobitz type 1 heart block?
Progressive elongation of the PR interval until a beat is dropped
46
What is a complicating factor when interpreting Mobitz I block?
If the atrial rhythm isn't regular then there could be other interpretations
47
Is Mobitz I block particularly worth treating?
No, it's relatively benign
48
What is second degree Mobitz type II heart block?
When there are some non-conducted P waves, but no change in the PR interval otherwise (ie no prolongation before)
49
What is the relationship between P waves and QRS complexes in Mobitz II block?
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
Is Mobitz II clinically important and worth treating?
Yes Can rapidly progress to 3rd degree heart block
51
How do you treat Mobitz II heart block?
With a pacemaker
52
How does 3rd degree heart block appear on ECG?
No concordance between P waves and QRS complexes
53
How do you report the type of Mobitz I that a patient's ECG shows?
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
Is it always necessary to specify which Mobitz block it is?
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
How do Q waves sometimes change in AMI?
Become >0.04s wide and >2mm deep
56
When Q waves change with AMI, how long do they take to go back to normal?
Never Unless PCI was performed quickly they will remain deep and wide indefinitely
57
What can cause a saddle-shaped ST elevation?
Acute pericarditis
58
What is a normal variant ST depression?
One that slopes upwards
59
What morphology of ST depression does digoxin make on ECG?
A downward sloping ST depression
60
What causes a horizontal ST depression?
Ischaemia
61
In which leads is T wave inversion normal?
V1-V3
62
When do you see T wave depression in V2-V5?
Subendocardial MI Subarachnoid haemorrhage Lithium
63
When do you see T wave depression in V4-V6 and aVL?
Ischaemia LVH LBBB sometimes
64
Are ST and T wave changes on ECG specific?
No Should be considered in a clinical context
65
How does a BBB appear on ECG in general?
QRS is >0.12s
66
What are some ECG changes associated with RBBB?
QRS >0.12s 'M' pattern in V1 and V2 (ie, RSR) Deep and wide S waves esp V6
67
What are some causes of RBBB?
Normal variant PE Cor pulmonale
68
What are some ECG changes associated with RBBB?
QRS >0.12s 'M' pattern in V6 Inverted T waves in I, aVL, V5 & V6
69
What is bifascicular block?
Combination of RBBB and left bundle hemiblock
70
How does bifascicular block manifest on ECG?
Axis deviation
71
What is trifascicular block?
Combination of bifascicular block and 1st degree heart block
72
What are some causes of low voltage QRS complexes?
Hypothyroidism, COPD, PE, BBB

CC: CVS and Blood vessels (9 decks)

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