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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
RR’ configuration with normal QRS interval
Incomplete BBB
26
What do we mean by “rabbit ear” QRS complex?
Double peaked or RR’ Due to bundle branch block (the delayed ventricle is represented by R’)
27
What are the possible sites of bundle branch blocks?
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
Criteria for a RBBB
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
Why do we see a RR’ (“rabbit ears”) QRS complex in V1 with RBBBs?
LV depolarizers normally but RV is delayed, represented by the R’ in the leads over the RV
30
When might you see a RBBB?
Coronary artery disease Pulmonary embolism
31
What will you see on the EKG in RBBB with abnormal ST-T changes?
T wave oriented in SAME direction as terminal QRS forces in limb leads (Normal ST-T are opposite terminal portion of QRS)
32
Criteria for LBBB
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
Can you diagnose LVH in the setting of a complete LBBB?
Technically no, although some texts cite suggestive criteria
34
Can you diagnose RVH in the setting of RBBB?
Technically no, although some texts indicate the RVH is likely if the R’ in V1 is >15mm
35
How do you distinguish a hypertrophied ventricle from a BBB?
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
Left or Right BBB: QRS > 0.12s
Either
37
Left or Right BBB: Tall, prolonged R waves that may be notched or flattened on top
LBBB
38
Left or Right BBB: RR’ (M-shaped) in V1 or V2
RBBB
39
Left or Right BBB: Wide R waves in Lead I and V6
LBBB
40
Left or Right BBB: Wide S waves in Lead I and V6
RBBB
41
Left or Right BBB: ST-T waves oriented opposite direction to terminal QRS forces
RBBB
42
What are hemiblocks?
Occur when one of the fascicles of the LBB is blocked • Anterior fascicle • Posterior fascicle • (Septal fascicle)
43
Can you get a hemiblock off of the RBB?
No - RBB does not divide into separate fascicles
44
What is the key to detecting a hemiblock?
A change in the QRS axis, but the QRS duration is NOT prolonged (unless there is a concomitant RBBB)
45
A left anterior hemiblock (LAFB) will result in what axis?
LAD
46
A left posterior hemiblock (LPFB) will result in what axis?
RAD
47
Left anterior hemiblocks are characterized by...
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
How do you recognize Left Anterior Hemiblock on EKG?
STRONG LAD Tall R waves in Lead I Deep S waves in Lead III Usually normal QRS duration (< 0.12s)
49
Characteristics of a left posterior hemiblock
Blocked conduction down the posterior fascicle Mean axis is directed down and to the right
50
How to recognize a left posterior hemiblock on EKG
STRONG RAD (≥ +120˚ to +180˚) Tall R waves in Lead III Deep S waves in Lead I Usually normal QRS duration (<0.12s)
51
What do you need to r/o when considering a diagnosis of left posterior hemiblock?
Cor pulmonale | Pulmonary HTN
52
Which is more common - LAHB or LPHB?
LAHB
53
LPHB may be difficult to diagnose without ...
Prior ECGs Must r/o RVH or anterior infarction
54
What is a Bi-fascicular block?
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
When the QRS is prolonged without features of either RBBB or LBBB, this is called...
Nonspecific intraventricular conduction delay (or defect) QRS > 0.12 s indicates slowed conduction but criteria for specific BBB or fascicular blocks not met
56
Causes of nonspecific IVCDs
Ventricular hypertrophy (esp LVH) Myocardial infarction (peri-infarction blocks) Certain antiarrhythmic drugs (ie quinidine, flecainide) Hyperkalemia Paced complexes
57
What is a Pre-excitation syndrome?
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
What is Wolff-Parkinson-White (WPW) Syndrome?
AV pathway - Bundle of Kent Short PR interval (<0.12s) and wide QRS, with Delta wave seen in some leads
59
Patients with WPW syndrome are vulnerable to ...
PSVT
60
Short PR interval Wide QRS Delta wave in some leads
Wolff-Parkinson-White (WPW) Syndrome | AV pathway = Bundle of Kent
61
What is Lown-Ganong-Levine (LGL) Syndrome?
Intranodal accessory pathway (James fibers) PR interval short (<0.12s) and normal QRS complex Absence of delta waves
62
Short PR interval Normal QRS with no delta waves Intranodal accessory pathway
Lown-Ganong-Levine (LGL) Syndrome

EKG Final (4 decks)

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