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Axis and BBB Flashcards

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1
Q

The QRS complex is indicative of what within the heart?

A

deolarization of the ventricles

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2
Q

What is the normal order of depolarization within the heart?

A

septum (L to R)
Main portion of ventricle (largest vector)
Basilar/bottom portion of ventricle

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3
Q

What leads are in the frontal plane?

A

limb leads

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4
Q

What leads are in the transverse (coronal) plane?

A

precordial leads

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5
Q

What is amplitude affected by?

A

the size and direction of vectors in relation to lead

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6
Q

What happens to amplitude with hypertrophy?

A

There is more heart, thus more vector, thus more amp

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7
Q

What happens to amplitude with infarct?

A

Dead hear cells, thus less heart, less of a vector and thus decreased amp

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8
Q

What are the criteria for low voltage?

A

<10mm in all precordial leads

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9
Q

What is a big determinant in voltage?

A

the amount and location of fluid and fat

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10
Q

How is voltage affected with a pericardial effusion?

A

decreased

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11
Q

What is the normal duration of QRS?

A

<.12 sec, 3 small boxes

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12
Q

How do we measure QRS?

A

measure it in several different leads and use the widest one

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13
Q

What are some causes of wide QRS?

A 
hyperkalemia (wide and peaked T waves)
medications
ventricular tachy
idioventricular rhythms
WPW
BBB and IVCD
ventricular premature contractions
aberrrantly conducted complexes
pacemaker
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14
Q

Where is QRS notching most common?

A

precodial leads

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15
Q

What is QRS notching usually indicative of?

A

generally a/w benign causes of ST elevation
early repol
pericarditis

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16
Q

What is an Osborn Wave?

A

large deflection at the end of QRS complex (much larger than benign notching)

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17
Q

Where do we see Osborn waves?

A

Severe hypothermia

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18
Q

How do we determine if a Q wave is benign or pathologic?

A

based on size

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19
Q

What can cause a slight variation in the depth of a Q wave with respiration

A

obeses, pregnant or ascites

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20
Q

What are the characteristics of a pathological Q wave?

A

> 1/3 total height of QRS
0.04 seconds wide (one small box)
Look at regional pattern (inferior, anterior, lateral)

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21
Q

What is normal transitional pattern?

A

mostly neg to mostly pos in precordial leads

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22
Q

Where is the transition zone?

A

V3-V4

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23
Q

What happens if the transition zone is before V3?

A

axis is rotated counterclockwise = early rotation

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24
Q

What happens if the transition zone is after V4?

A

axis is rotated clockwise = late rotation

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25
How do we measure the QT interval?
beginning of QRS to the end of T wave
26
What is a normal QT interval?
less than 1/2 R-R interval
27
What are multiple variables that affect QT interval?
age, HR, meds, etc
28
What is indicative of a prolonged QT?
Torsades
29
What is the definition of the electrical axis?
sum of all vectors of individual ventricular myocytes
30
What is the normal average direction of the hearts electrical axis?
down and to the left
31
What can axis be helpful in diagnosing?
``` L or R ventricularhypertrophy Hemiblock pulmonary embolism dextrocardia lead misplacement ```
32
What is the most common mistake with lead misplacement? What happens?
interchanging R and L arm leads; will see negative P and QRS in lead II and positive P and QRS in aVR (opposite of normal)
33
What else can cause a negative P and QRS in lead II and positive P and QRS in aVR (opposite of normal)?
dextrocardia
34
What is the hexiaxial system?
represented by circle with limb leads enclosed, each limb having a positive and negative pole
35
What is each "spoke" seperated by in the hexiaxial system?
30 deg
36
What are the degree markers for each of the leads?
``` I 0 II 60 III 120 aVL -30 aVF 90 aVR -150 ```
37
What is an isoelectric lead?
each lead has a corresponding isoelectric lead, found at 90 deg from lead; or at line dividing +/- halves of lead
38
What leads are used to calculate axis?
I and aVF (isoelectric)
39
What is normal axis?
0-90 deg
40
What is the axis for LAD?
(-1)-(-90) deg
41
What is the axis for RAD?
91-180
42
What is the axis for Indeterminate?
extreme LAD or RAD (-91)-(180)
43
What are the characteristics of I and aVF in a normal axis?
both pos
44
T/F: if one lead is isoelectric, then the axis is parallel to that lead.
false perpendicular
45
What are causes of RAD?
``` normal variant in adolescents and children RV hypertrophy L posterior hemiblock dextrocardia pulmonary pathology ```
46
What are causes of LAD?
normal variant with agin | left anterior hemiblock
47
When is LAD pathologic?
if lead II is negative, this makes axis more neg than -30
48
What is a LAF?
left anterior fasicle; thin bundle of fibers that innervate anterior and lateral walls of LV
49
What is a LPF?
left posterior fasicle; bundle that fans out and innervates inferior and posterior walls of LV
50
Which fascicle is easier to block?
LAF
51
What is LAH?
Left anterior hemiblock; creates a late unopposed vector point UP and LEFT Between -30 and -90 (= pathologic LAD)
52
What are other characteristics of LAH?
if QR complex or tall R wave in lead I; rS complex in lead III
53
What is LPH?
Left posterior hemiblock; creates a late and unopposed verctor DOWN and RIGHT Axis 90 and 180
54
What are other characteristics of LPH?
rS in lead I and qR in lead III diagnosis of exclusion
55
What are bifascicular blocks
RBBB with LAH or LPH
56
What is the impulse in a BBB?
impulse is conducted until it is blocked at either R or L BB (cell to cell transmission is slow and chaotic)
57
What are characteristics of a BBB?
wide QRS and flipped T wave (opposite of QRS) = discordance
58
Characteristics of RBBB?
wide QRS RSR' pattern in lead V1 - rabbit ears Deep S wave in leads 1 and V6
59
What else can be seen in a RBBB in replace of RSR'?
QR' - found with old anteroseptal infarct in lead V1
60
Characteristics of LBBB?
wide QRS broad R waves in lead 1 and V6 - all positive broad S waves in V1 - all negative
61
What is the clinical significance of LBBB?
very difficult to diagnose infarction in presence of LBB
62
What is LBBB until proven otherwise?
NEW LBBB IS CAD UNTIL PROVEN OTHERWISE
63
What leads do we use to diagnose BBB?
I, V1, V6
64
What are the characteristics of IVCD?
intraventricular conduction delay; wide QRS but not BBB- "mixed"
65
What is commonly associated with IVCD?
hyperkalemia
66
What is discordance?
T wave in opp direction of last wave of QRS
67
What is concordance?
T wave in same direction of last wave of QRS

EKG (2 decks)

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