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IM Internal Med > ECG 2: Beyond the Basics > Flashcards

ECG 2: Beyond the Basics Flashcards

1
Q

What is the axis?

A

the “average” vector direction

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2
Q

Which leads are in the coronal plane?

A

I, II, III

aVR, aVL, aVF

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3
Q

If all the coronal-plane leads are arranged together coming from one 0 point, how are they arranged?

A

Roughly in a circle, with 30 degrees between each lead

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4
Q

Which lead is defined as 0 degrees?

A

Lead I

points straight to pt’s left

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5
Q

Are the leads defined in a clockwise or counterclockwise way?

A

Clockwise
eg aVF is +90 degrees
aVL is -30 degrees

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6
Q

What is the isoelectric lead?

A

Lead that is not positive or negative, but has equal amt of upward and downward deflection

important

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7
Q

What is a shortcut for left axis deviation?

A

Up in I and down in II

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8
Q

What is a shortcut for right axis deviation?

A

Down in I and up in aVF

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9
Q

What does the normal axis look like?

A

Upgoing QRS in both I and II

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10
Q

How is the extreme axis defined?

A

Down in I and down in aVF

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11
Q

How can you use an isoelectric lead to define axis?

A
  • find which lead is the most isoelectric
  • the axis is along that lead’s line
  • use the other activity (eg upgoing in I and II) to define which “quadrant” it’s in (eg the +60 vs the -120 end of the line)

[This is lesson 4 of Axis module if you want to review!]

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12
Q

How do you determine which direction is greater, in a lead that is both + and - ?

A

Area under the curve: more area under + or - side

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13
Q

Which 3 leads are used to define axis?

A

I, II, and aVF

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14
Q

How do you use leads to define axis?

A
  • draw the 3 leads as arrows
  • look at each lead to see if it is positive or negative
  • shade in the relevant (+ or -) semicircle for that lead (at right angle to direction of the lead)
  • see where they overlap!
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15
Q

What are the main axis categories? Define their range (in degrees)

A

Normal: -30 to + 90 degrees
Right axis deviation: +90 to +180 degrees
Left axis deviation: -30 to -90 degrees
Extreme axis deviation: -90 to -180 degrees

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16
Q

Which bundle depolarizes the septum?

A

Left bundle

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17
Q

Which is depolarized first, endocardium or epicardium?

A

Endocardium: fibres are near the endocardium, and the wave travels out from there

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18
Q

If a bundle branch is blocked, what happens?

A

Opposite ventricle depolarizes first

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19
Q

What do abnormalities of repolarization cause on ECG?

A

Changes in the ST segment

20
Q

If you see ST changes, what should you think of?

A

MI or ischemia

But before diagnosing, always consider other things that can cause ST changes! Always do your full 12 lead interpretation.

21
Q

What leads are particularly important for assessing LBBB?

A

V1 and V6 (anterior and lateral)

22
Q

What happens in the heart with LBBB?

A

Fast RV depolarization followed by slow late LV depolarization

23
Q

If a small upgoing deflection is seen in V1, what does that reflect?

A

RV depolarization

24
Q

What does slow late LV depolarization show as in V1?

A

Large wide negative deflection

25
Q

What does slow late LV depolarization show as in V6?

A

Large wide positive deflection

26
Q

What is the intrinsicoid deflection?

A

Time from start of QRS to peak of R wave

Also called the R peak time

27
Q

What is the LBBB criterion for intrinsicoid deflection?

A

> 60 ms ( = 1.5 little boxes)

28
Q

What happens to the wave of repolarization in BBB?

A

Normal pattern is lost: repolarization goes from inside to outside (instead of outside to inside)

Thus, T wave is in the opposite direction of the QRS

29
Q

What is discordance?

A

When the T wave is in the opposite direction of the QRS

30
Q

What are the diagnostic criteria for LBBB?

A

Summary of Diagnostic criteria for LBBB:

  • QRS > 120 ms
  • V6: broad (wide) R wave (upgoing wave) (also in leads I, aVL and V5)
  • V1: small R wave, big S wave (also called rS)
  • QRS and T waves are in opposite directions (discordance) in most/all of the precordial leads
  • (optional but not required) V6: intrinsicoid deflection > 60 ms
  • (notice there are no Q waves in precordial leads)
31
Q

Name 2 exceptions to LBBB Dx criteria

A

sometimes the QRS and T waves can both be upgoing (“positive” concordance). However, they cannot both be downgoing (“negative” concordance)
sometimes there is an R + S wave in V6 instead of just an R wave. Late LV depolarization AWAY from V6 causes the S wave (see image).

32
Q

What are the QRS width criteria for LBBB in children

A

> 100 ms in ages 4-16

> 90 ms in ages < 4 yrs

33
Q

Name 3 important ways RBBB is different from LBBB

A
  • common in normal healthy adults
  • does not cause big changes in ST or T wave (bc LV is functioning normally)
  • thus does not cause Dx interference with MI, ischemia, or LVH
34
Q

What are the diagnostic criteria for RBBB?

A

QRS > 120 ms
RSR’ configuration in V1/2
slurred (wide) S wave in V5/6

35
Q

What happens in the heart with RBBB?

A
  • septum depolarizes early and quickly
  • LV depolarizes quickly
  • RV depolarizes slowly
36
Q

How does septum depolarization show on ECG in RBBB?

A

Early upgoing R wave in V1/V2

Might produce a small downgoing (Q wave) in V6

37
Q

How does LV depolarization show on ECG in RBBB?

A

downward deflection (S wave) in V1/V2 and an upward deflection (R wave) in V6

38
Q

How does RV depolarization show on ECG in RBBB?

A

Produces a second upward deflection in V1/V2
We call this waveform R prime (R’)

V6: wide downgoing waveform, called a “slurred” S wave

39
Q

What is the shape of the QRS complex in V1/2 in RBBB?

A

RSR’ configuration

RaBBBit ears

40
Q

What is a slurred S wave?

A

Result of slow late RV depolarization

wider that the R wave or > 40 ms (1 little square)
Wide with rounded, not pointy, bottom

41
Q

Is the intrinsicoid deflection narrow or wide in RBBB?

A

Narrow (normal): reflects normal LV depolarization

42
Q

What do lower case letters in QRS indicate?

A

Relative wave size

eg rSR’: the second R wave is larger than the first R wave

43
Q

When might the first R wave be missing in RBBB?

A

if the patient has had an old anterior infarct with Q waves

First R wave in V1/2 might be missing because the R wave is replaced by a Q wave

44
Q

What are the diagnostic criteria for incomplete BBB?

A

essentially share the same diagnostic criteria as complete bundle branch blocks with one difference: the QRS duration is shorter with incomplete blocks

QRS duration diagnostic criteria for incomplete bundle branch blocks is 100 - 120 ms (which is 2.5 - 3 little squares)

45
Q

What it intraventricular delay?

A 
wide QRS (QRS > 120 ms)
Does not meet the criteria for LBBB or RBBB

not diagnosed if the rhythm has a ventricular origin, such as VT

46
Q

What is Brugada syndrome?

A

can mimic or be associated with RBBB; caused by Na+ or Ca++ channel mutation

Diagnostic criteria:

  • J point elevation with ST elevation in V1-V3
  • the ST is described as coved or saddlebacked
coved = downsloping and convex upward
saddlebacked = flat ST elevation with initial and final parts of ST segment slightly higher
47
Q

What is ventriculophasic sinus arrythmia?

A

non-respiratory sinus arrhythmia seen in complete AV block.

The PP interval enclosing a QRS complex is shorter than a PP interval not enclosing a QRS.

IM Internal Med (11 decks)

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