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Cardiovascular Core Conditions > ECGs > Flashcards

ECGs Flashcards

1
Q

What is the DDx for tachycardia with narrow QRS complexes (<0.12)?

A

REGULAR:
- Sinus tachycardia
- SVTs (AVNRT, Orthodromic AVRT, AFlutter)

IRREGULAR:
- AFib
- AFlutter

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2
Q

What is the DDx for tachycardia with wide QRS complexes (>0.12)?

A

REGULAR:
- Hyperkalaemia
- VT (monomorphic)
- SVT + conduction abnormality

IRREGULAR:
- Hyperkalaemia
- AF + WPW
- Polymorphic VT (incl. torsades)

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3
Q

What are some causes of bradycardia?

A
  • Sinus bradycardoa
  • Second degree AV block
  • Third degree AV block
  • SA Block
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4
Q

How do you determine rate?

A

If irregular: # of QRS complexes x 6

Regular: Divide 300 by the # of boxes between the R waves

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5
Q

What features does an ECG need to be in sinus rhythm?

A

Every QRS is preceded by a p wave and this occurs in a regular rate

And the PR interval is less than 0.22s/some people say 200ms

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6
Q

How do you determine the axis of the ECG?

A

Trick: based on whether the QRS complexes in I, II and aVF are net positive or net negative

Normal= -30 to +90
I+, II+, aVF +

LAD= -30 to -90:
I+
II and aVF -

RAD: 90 to 180:
I-
II and aVF +

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7
Q

What is an extreme axis deviation?

A

-90 to 180

I-, II-, aVF-

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8
Q

What are some of the most common causes of RAD?

A

RVH
Acute cor pulmonale (PE)
Chronic cor pulmonale (COPD, pulmonary HTN)
LV infarction

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9
Q

What are some of the commonest causes of LAD?

A

LBBB
LVH
Inferior infarction

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10
Q

What does the p wave represent?

A

Depolarisation of the atria

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11
Q

What are the normal characteristics of p waves?

A

Duration <0.12 seconds
Amplitude <2.5mm (remember 1 lil square is 1 mm) in limb leads, <1.5mm in chest leads

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12
Q

What does a sawtooth p wave baseline indicate?

A

Atrial flutter

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13
Q

What does a chaotic p wave baseline indicate?

A

Atrial fibrillation

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14
Q

What does a flat line where the p wave should be indicate?

A

No atrial activity

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15
Q

What is p pulmonale?

A

P wave with an abnormally high amplitude in II

Caused by right atrial hypertrophy

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16
Q

What is p mitrale?

A

Biphasic p wave in II (second hump) and a deep negative deflection in V1

Caused by left atrial hypertrophy

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17
Q

What is the PR interval?

A

Time interval from the start of atrial depolarisation to start of ventricular depolarisation

Start of p wave to start of QRS

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18
Q

What is the PR segment?

A

From the end of the p wave to the start of the QRS

Reflects the slow impulse conduction through the AV node (baseline/isoelectric line of the ECG)

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19
Q

What is a normal PR interval?

A

0.12-0.22s (people kinda just say less than 200ms)

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20
Q

What does a PR interval of greater than 0.22s mean?

A

First degree AV block

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21
Q

What are some common causes of first degree AV block?

A

Degenerative fibrosis
Ischaemia
Beta blockers

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22
Q

What does a PR interval of less than 0.12 mean?

A

Pre-excitation –> WPW Syndrome

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23
Q

What is second degree AV block mobitz type 1?

A

Wenckebach

Gradually increasing PR interval until the atrial impulse (p wave) is blocked at the AV node and you don’t have a QRS

24
Q

What is second degree AV block mobitz type 2?

A

The PR interval stays the same but you have intermittently blocked atrial impulses (a block infra-nodal, usually His bundle) so not every p wave causes a QRS

25
Q

What is 3rd degree AV block?

A

Complete Heart Block

The p wave and the QRS have no relation BUT both the atrial and escape rhythm are typically regular (the atrial rhythm is just usually faster)

All atrial impulses/p waves are blocked by the AV node. The perfusing rhythm is maintained by a spontaneous escape rhythm

26
Q

What are some common causes of 3rd degree AV block?

A
  • Ischaemia heart disease (acute MI, ICM)
  • Non-ischaemic heart disease: aortic stenosis, dilated cardiomyopathy, infiltrations (sarcoid, amyloidosis)
  • Idiopathic fibrosis
  • Infections: endocarditis, chagas, SLE, RA
  • AV blocking drugs: CCBs, Bblocks, digoxin
27
Q

What are the two types of escape rhythms?

A

Junctional (narrow QRS and 40-60bpm, originates in the His bundle) and Ventricular (wide QRS and 20-40bpm, originates below the His bundle)

28
Q

What is the QRS complex?

A

The depolarisation of the ventricles

Q wave= first negative deflection (won’t be present in all leads). Represents the depolarisation of the septum (which travels in the opposite direction to the main conduction so it’s negative)

R wave= the positive deflection. Represents the depolarisation of the ventricles (but you don’t see the right ventricle because the LV produces too big of a vector)

S wave= the depolarisation in the purkinje fibres as they go back up through the walls of the ventricles (opposite to the main electrical vector so it’s negative)

29
Q

What is a normal QRS complex duration?

A

<0.12s

30
Q

What pathological thing should you check for when you look at the QRS complexes?

A

Pathological Q waves: >0.3s and/or an amplitude of >25% of the R wave in the same lead

31
Q

What are some causes of broad QRS? >0.12s

A

It means slower than normal ventricular depolarisation
- Bundle branch block
- Hyperkalaemia
- Drugs (TCA, class 1 anti-arrhythmics)
- WPW syndrome

32
Q

What are some causes of narrow QRS? <0.12s

A

Supra-ventricular complexes

33
Q

What are the 3 main places that supraventricular complexes arise from?

A

SA node (normal p wave)
Atria (abnormal p wave- fibrillation or flutter)
AV node/junction= either no p wave or an abnormal p wave with an increased PR interval

34
Q

What is the ST segment?

A

From the end of the QRS to the start of the T wave (relatively brief period)

Corresponds to the plateau phase in the cardiac conduction cycle. The membrane potential is relatively unchanged and most ventricular cells are in this phase simultaneously so nil electricular potential differences

35
Q

What level of ST segment depression can you accept in the chest leads?

A

<0.5mm (half a lil square)

36
Q

What are some causes of ST elevation?

A

STEMI!!!!!

Can be LBBB, LVH, Brugada syndrome, takotsubo, hyperkalaemia, PE

37
Q

What are some causes of ST depression?

A

Ischaemia! NSTEMI!

Hypokalaemia, digoxin, LBBB/RBBB, LVH, RVH

38
Q

What is the t wave?

A

Ventricular repolarization. Takes longer than depolarisation so typically longer

39
Q

What are the characteristics of normal t waves?

A

Should be concordant with the QRS complex and positive in most leads

40
Q

In what leads can an isolated t wave inversion be accepted?

A

V1 and III

41
Q

What does t wave inversion with ST deviation indicate?

A

Acute myocardial ischaemia

42
Q

What does t wave inversion in the absence of ST deviation indicate?

A

Not a sign of ongoing ischaemia but can occur post-ischaemia.

Cerebrovascular haemorrhage, PE, perimyocarditis

43
Q

What can cause high t waves?

A

Hyperkalaemia
LVH
LBBB

44
Q

What does the QT interval represent?

A

The total time for de and repolarisation. It is the time from beginning of the QRS to the end of the t wave

45
Q

Why do we worry when someone has a prolonged QTc?

A

A high risk of ventricular arrhythmias- especially Torsades de Pointes

46
Q

What is the normal QTc for men?

A

<0.45s

47
Q

What is the normal QTc for women?

A

<0.46s

48
Q

What are some causes of acquired QT prolongation?

A

Anti-arrhythmics
TCAs
SSRIs
Lithium
Hypokalaemia
Hypocalcaemia
Hypomagnesia
MI
Hypothyroidism

49
Q

What causes congenital QT prolongation?

A

Genetic disease –> 15 variations

50
Q

What is short QTc syndrome?

A

A QTc <0.32ms

Caused by hypercalcaemia and digoxin

51
Q

What is a U wave?

A

The U wave sometimes occurs when the ECG picks up the repolarisation of the purkinje fibres. It isn’t very common.

52
Q

What ECG changes happen in RBBB?

A
  1. QRS duration >0.12s (broad complex)

MaRRoW

  1. V1/V2: the QRS complex appears as an M
  2. V6: appears to have a W due to the broad S wave and S wave duration which is longer than the R wave duration
  3. ST changes that occur secondary to the other changes (because if depolarisation is whacky repolarisation will also be whacky): V1-V2 have down-sloping ST and TWI
53
Q

What ECG changes happen in LBBB?

A
  1. QRS duration >0.12s (broad complex)

WiLLiaM

  1. V1/V2: the R wave is missing or smaller (R wave is normally the depolarisation of the LV wall as the electrical signals pass through the L+R bundle branches), so you have a broad and deep S wave which can be notched like a W
  2. V6: broad, clumsy, often notched R wave (looks like an M)
  3. ST changes: V1-3 = ST elevation and positive t waves. V5/6= TWI and ST depression
54
Q

What are some overall characteristics of SVTs?

A

Narrow QRS complexes
Because the block is AV node or above, the conduction through the His-Bundle-Purkinje system is usually normal (unless an aberrant conduction issue like BB) so the QRS during the tachycardia is usually similar to that seen in the same patient at their baseline

55
Q

What are the features of Slow-Fast AVNRT? (the most common)

A

Slow-Fast AVNRT =
- Slow AV nodal pathway for anterograde and fast AV nodal path retrograde

Rate is 140-280 bpm and it’s regular

P waves= either hidden behind the QRS complexes (because they’re retrograde) or appear as a pseudo R wave at the end of the QRS in V1

SO the typical SVT appearance of absent P waves and tachycardia!!

56
Q

What are the features of Pre-Excitation on ECG?

A

Pre-excitation (e.g. WPW)

  • Short PR interval <0.12s (because the QRS starts earlier than expected)
  • Delta wave at the start of the QRS from the early depolarisation of the ventricles by the accessory path (broad QRS) which can cause a broad QRS
57
Q

What is Torsades de Pointes?

A

A specific type of polymorphic ventricular tachycardia (PVT) that occurs in the context of QT prolongated

It has a characteristic morphology in which the QRS complexes twist around the isoelectric line

Can degenerate in VF but does usually self-terminate relatively quick

Cardiovascular Core Conditions (10 decks)

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