Lecture 7: EKG Flashcards by Claire Mann

Standard 12-lead ECG. Where do you put leads I, II, and III?

6 precordial (V1 - 6), 6 limb leads (I, II, III, aVR, aVL, aVF); I = right arm, II = left arm, III = left leg

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Right 4th intercostal space

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Left 4th intercostal space

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Halfway between V2 and V4

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Left 5th intercostal space, mid clavicular line

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Horizontal to V4, anterior axillary line

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Horizontal to V5, mid-axillary line

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Lead I lies at __ degrees and represents…

0; right arm –> left arm

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Lead II lies at __ degrees and represents…

+60; right arm –> left leg

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Lead III lies at __ degrees and represents…

+120, left arm –> left leg

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Heart lies between…

0 and 90 degrees

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aVR is at ___ degrees

-150

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aVF is at ___ degrees

+90

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aVL is at ___ degrees

-30

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In a normal heart, what leads should be upright?

Lead I, II, III, aVF, aVL

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What should be upside down?

aVR

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II, III, aVF…

Inferior wall of L ventricle

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I, aVL…

Lateral wall of L ventricle

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What else tells us about the lateral wall?

V5, V6

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Each small box is…(horizontally)

40 ms

Each small box is…(vertically)

0.1 mV

P wave is depolarization of the…

SA node (time it takes for wave to spread through atria)

Time it takes depolarization to get from SA node to the AV node

PR interval

Time it takes ventricles to depolarize after AV node. How long?

QRS interval; 100 ms

What is the "Q"

First negative deflection

What is the "S"

Second negative deflection

T wave is...

Repolarization

Normal EKG requires looking for...

Normal waves (P, QRS, T) and intervals (PR, QRS, QT); normal rate, rhythm, axis

Abnormal P wave (left/right)

Height > 2.5 mm in lead II = R atrial enlargement; two humps in lead II = L atrial enlargement

Where is the best place to view P wave?

Lead II because SA node is ~60 degrees axis

Normal PR interval; what lead?

120 - 200 ms (3-5 small squares); no particular lead (all should have same interval)

Normal QRS complex; what lead? What if it's broad?

bundle branch block; V1

Normal QT interval requires you to know what two terms...How long?

QT and QTc (corrected for HR);

How to "cheat" calculate QTc

HR > 60, add 20 ms for each 10 increase in HR; if HR

EKG indication Normal Sinus Rhythm (3)

P wave upright in I, upright in II, inverted in aVR; each P wave followed by QRS, P wave rate = 60-100 bpm (

Premature atrial contraction. How do you know it's atrial?

"Extra/Premature beat" coming from another (non-SA node) atrial foci...it's atrial because you have a P wave.

Premature ventricular contraction. How do you know it's ventricular?

"Extra/Premature beat" coming from a ventricular foci...it's ventricular because the morphology of the QRS is BROAD (non-Purkinje fiber depolarization is slow)

How can we see dextrocardia?

P wave present but not in sinus node morphology (inverted in I, upright in II, inverted in aVR) w/ reverse R-wave progression along chest leads

How can we tell if we've switched the leads?

P wave present but not in sinus node morphology (inverted in I, upright in II, inverted in aVR) w/ normal R-wave progression along chest leads

How do you calculate rate?

1500/n (n = number of smalls squares between R-R)

How many boxes = 60 bpm. What are the other "Cheat" times?

5 big squares; 1 big square = 300, 150, 100, 75, 60...

-90 to 0

Left deviation

0 - 90

Normal

90 - 0

Right deviation

0 - -90

Indeterminant

If both I and aVF are upright...Normal/Abnormal?

Normal (normal people are always upright)

For axis, we look at which two leads?

Lead I and aVF

If Lead I is negative but aVF is positive, what happened?

Lead I is pointing 180 degrees (to the right), so right deviation (right people meet)

If Lead I is positie, but aVF is negative, what happened?

aVF is now negative, so you have left deviation (left don't see eye to eye)