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EKG Final > Intraventricular Conduction Defects > Flashcards

Intraventricular Conduction Defects Flashcards

1
Q

_______ occurs as a result of volume overload where chamber(s) stretches to accommodate increased blood volume

A

Dilation (Enlargement)

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2
Q

Condition in which muscular wall of the ventricle(s) becomes thicker than normal

A

Hypertrophy

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3
Q

_______ changes are used to identify Atrial Enlargement

A

P wave

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4
Q

______ changes are used to identify ventricular hypertrophy

A

QRS complex changes

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5
Q

Morphology of normal P waves

A

Upright and rounded in Lead II

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6
Q

Normal amplitude for P waves

A

0.5 - 2.5 mm (up to 2.5 small boxes)

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7
Q

Normal duration for P waves

A

0.06 - 0.10 s (60-100 ms, or up to 2.5 small boxes)

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8
Q

Initial portion of the p wave represents…

A

Right atrial depolarization

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9
Q

Terminal portion of the p wave represents…

A

Left atrial depolarization

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10
Q

When might you see right atrial dilation?

A

From greater filling pressures in chronic pulmonary disease (P pulmonale)

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11
Q

When might you see left atrial dilation?

A

Mitral valve pathology

Reduced ventricular compliance such as in LVH

(P mitrale)

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12
Q

The ideal leads for assessing atrial enlargement are…

A

Lead II and V1

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13
Q

Criteria for Right Atrial Enlargment

A

P wave > 2.5 mm tall

OR

The initial component of the P wave in V1 is larger than the terminal component if the P is biphasic (upward deflection > downward deflection)

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14
Q

Criteria for Left Atrial Enlargement

A

P wave > 0.10s (100ms)

OR

The terminal portion of the P wave in V1 is negative with a duration of ≥0.04s AND a depth of ≥1mm

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15
Q

Ventricular hypertrophy is commonly caused by …

A

Chronic, poorly treated hypertension

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16
Q

Most common characteristic of RVH in limb leads is…

A

Right axis deviation

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17
Q

In cases of RVH, what will you observe in the precordial leads?

A

R waves that are increased in amplitude over RV (leads V1-2) and decrease moving towards V6

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18
Q

What are the characteristic EKG changes in LVH?

A

In precordial leads, R waves are increased in amplitude over LV (leads V5 and V6)

S waves are deeper in leads V1 and V2

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19
Q

Criteria for LVH

A

Deepest S wave in V1/V2 + Tallest R wave in V5/V6 > 35mm

Or

R wave in Lead I + S wave in Lead III > 25mm

Or

R wave in aVL > 11mm

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20
Q

Criteria for RVH

A

Right axis deviation

Or

R wave > S wave in V1

Or

S wave > R wave in V6

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21
Q

What are the different divisions of the bundle branches?

A

Bundle of His divides into the Right and Left bundle branches

Left bundle branch further divides into septal, anterior, and posterior fascicles

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22
Q

Morphology of normal QRS complexes

A

Narrow

Duration ≤ 0.12s (120ms)

Electrical axis 0˚ to +90˚

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23
Q

One or both bundle branches failing to conduct impulses is referred to as…

A

A Bundle Branch Block (BBB)

Produces a delay in depolarization of the ventricles it supplies

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24
Q

Generalized criteria for a BBB

A

QRS > 0.12 s (120ms)

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25
Q

RR’ configuration with normal QRS interval

A

Incomplete BBB

26
Q

What do we mean by “rabbit ear” QRS complex?

A

Double peaked or RR’

Due to bundle branch block (the delayed ventricle is represented by R’)

27
Q

What are the possible sites of bundle branch blocks?

A

Right bundle branch block (RBBB)

Left bundle branch block (LBBB)

Fascicular blocks
• Left anterior fascicle (LAFB) or left anterior hemiblock (LAHB)
•Left posterior fascicle (LPFB) or left posterior hemiblock (LPHB)

Or any combo of the above

28
Q

Criteria for a RBBB

A

QRS > 0.12s

M-shaped RR’ in V1***

Wide S wave in Lead I and V6***

(ST-T waves opposite of terminal portion of QRS)

29
Q

Why do we see a RR’ (“rabbit ears”) QRS complex in V1 with RBBBs?

A

LV depolarizers normally but RV is delayed, represented by the R’ in the leads over the RV

30
Q

When might you see a RBBB?

A

Coronary artery disease

Pulmonary embolism

31
Q

What will you see on the EKG in RBBB with abnormal ST-T changes?

A

T wave oriented in SAME direction as terminal QRS forces in limb leads

(Normal ST-T are opposite terminal portion of QRS)

32
Q

Criteria for LBBB

A

QRS > 0.12s

Wide R wave in Leads I and V6

QRS complexes shave tall R waves, with prolonged duration and either notched or flattened tops (not true “rabbit ears” like with RBBB)

Leads over RB show reciprocal, broad, deep S waves

33
Q

Can you diagnose LVH in the setting of a complete LBBB?

A

Technically no, although some texts cite suggestive criteria

34
Q

Can you diagnose RVH in the setting of RBBB?

A

Technically no, although some texts indicate the RVH is likely if the R’ in V1 is >15mm

35
Q

How do you distinguish a hypertrophied ventricle from a BBB?

A

If a monophasic R wave is used to diagnose hypertrophy, it can mimic BBB but usually QRS < 0.12s (aka “incomplete BBB pattern”)

When a hypertrophied ventricle takes very long to depolarize, it can mimic a BBB - look for other criteria and clinical correlation

Add “cannot R/O” to your list (but with discretion)

36
Q

Left or Right BBB:

QRS > 0.12s

A

Either

37
Q

Left or Right BBB:

Tall, prolonged R waves that may be notched or flattened on top

A

LBBB

38
Q

Left or Right BBB:

RR’ (M-shaped) in V1 or V2

A

RBBB

39
Q

Left or Right BBB:

Wide R waves in Lead I and V6

A

LBBB

40
Q

Left or Right BBB:

Wide S waves in Lead I and V6

A

RBBB

41
Q

Left or Right BBB:

ST-T waves oriented opposite direction to terminal QRS forces

A

RBBB

42
Q

What are hemiblocks?

A

Occur when one of the fascicles of the LBB is blocked
• Anterior fascicle
• Posterior fascicle
• (Septal fascicle)

43
Q

Can you get a hemiblock off of the RBB?

A

No - RBB does not divide into separate fascicles

44
Q

What is the key to detecting a hemiblock?

A

A change in the QRS axis, but the QRS duration is NOT prolonged (unless there is a concomitant RBBB)

45
Q

A left anterior hemiblock (LAFB) will result in what axis?

A

LAD

46
Q

A left posterior hemiblock (LPFB) will result in what axis?

A

RAD

47
Q

Left anterior hemiblocks are characterized by…

A

Conduction blockage down the left anterior fascicle —> mean axis directed up and to the left

Result is a STRONG LAD (pathological: -45˚ to -90˚)

48
Q

How do you recognize Left Anterior Hemiblock on EKG?

A

STRONG LAD

Tall R waves in Lead I

Deep S waves in Lead III

Usually normal QRS duration (< 0.12s)

49
Q

Characteristics of a left posterior hemiblock

A

Blocked conduction down the posterior fascicle

Mean axis is directed down and to the right

50
Q

How to recognize a left posterior hemiblock on EKG

A

STRONG RAD (≥ +120˚ to +180˚)

Tall R waves in Lead III

Deep S waves in Lead I

Usually normal QRS duration (<0.12s)

51
Q

What do you need to r/o when considering a diagnosis of left posterior hemiblock?

A

Cor pulmonale

Pulmonary HTN

52
Q

Which is more common - LAHB or LPHB?

A

LAHB

53
Q

LPHB may be difficult to diagnose without …

A

Prior ECGs

Must r/o RVH or anterior infarction

54
Q

What is a Bi-fascicular block?

A

RBBB plus either LAHB OR LPHB

Will see features of RBBB plus frontal plan features of the fascicular block (axis deviation)
• RBBB + LAHB —> LAD
•RBBB + LPHB —> RAD

55
Q

When the QRS is prolonged without features of either RBBB or LBBB, this is called…

A

Nonspecific intraventricular conduction delay (or defect)

QRS > 0.12 s indicates slowed conduction but criteria for specific BBB or fascicular blocks not met

56
Q

Causes of nonspecific IVCDs

A

Ventricular hypertrophy (esp LVH)

Myocardial infarction (peri-infarction blocks)

Certain antiarrhythmic drugs (ie quinidine, flecainide)

Hyperkalemia

Paced complexes

57
Q

What is a Pre-excitation syndrome?

A

Accessory conduction pathways that sometimes exist between atria and ventricles
• WPW: Bundle of Kent
• LGL: James fibers

These bypass AV node and bundle of His and allow early depolarization of ventricles

Results in a SHORT PR interval

58
Q

What is Wolff-Parkinson-White (WPW) Syndrome?

A

AV pathway - Bundle of Kent

Short PR interval (<0.12s) and wide QRS, with Delta wave seen in some leads

59
Q

Patients with WPW syndrome are vulnerable to …

A

PSVT

60
Q

Short PR interval

Wide QRS

Delta wave in some leads

A

Wolff-Parkinson-White (WPW) Syndrome

AV pathway = Bundle of Kent

61
Q

What is Lown-Ganong-Levine (LGL) Syndrome?

A

Intranodal accessory pathway (James fibers)

PR interval short (<0.12s) and normal QRS complex

Absence of delta waves

62
Q

Short PR interval

Normal QRS with no delta waves

Intranodal accessory pathway

A

Lown-Ganong-Levine (LGL) Syndrome

EKG Final (4 decks)

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