EKG Basics Part 1 Flashcards by Enoch Koo

How long does a standard EKG last?

10s. Speed: (25mm/s)

Each view will be 2.5s

Running lead will be 10s.

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What is the standard gain on an EKG?

10mV

Higher gain = higher magnification

Ex: a 30mV chest gain would make much larger chest leads.

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What are primary errors associated with EKGs?

Interpretation Error
Performance Error
Artifact

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What does the P wave correspond to in terms of electrical activity?

The first half is the RA.
The second half is the LA.

Bachmann’s bundle depolarizes the LA.

Impulse begins at the SA node.

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How long does a large box on an EKG strip correspond to? Small Box?

Large: 0.2s
Small: 0.04s

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What does the P wave, QRS complex, and T wave correspond to in terms of electrical pathway?

P Wave: Atrial depolarization
QRS: Ventricular depolarization + (covered atrial repolarization)
T Wave: Ventricular depolarization

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What is the difference between a Q and an R and a S on EKG?

Q is always the first NEGATIVE deflection.
R is always POSITIVE.
S is the negative deflection after R always (if it is present)

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What is the difference between a segment and an interval?

Segment is between a wave and complex.
Intervals include a wave and a segment.

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Where is the electrical signal in the heart during a PR segment?

AV Node

Traveling from the SA node.

It is paused because the ventricles are currently filling.

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What interval includes both ventricular depolarization and repolarization?

QT interval

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What are the 3 types of cells that make up the electrical system of the heart?

Pacemaker cells
Conduction fibers
Cardiac myocytes

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For depolarization, what direction generates a positive deflection? Negative?

Towards an electrode: positive
Away from an electrode: negative

The primary indicator of deflection

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For repolarization, what direction generates a positive deflection? Negative?

Towards an electrode: negative
Away from an electrode: positive

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What are the limb leads and the precordial leads?

Limb (frontal plane): I, II, III, aVF, aVR, aVL
Precordial/Chest (horizontal plane) : V1, V2, V3, V4, V5, V6

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What intercostal space are V1 and V2 usually placed?

4th intercostal space

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Einthoven’s triangle for I, II, III

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Einthoven’s triangle for aVL, aVR, aVF

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What are the inferior limb leads? Lateral? Right-sided?

Inferior: II, III, aVF
Lateral: I, aVL
Right-sided: aVR

Based on the direction they point to.

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What are the anterior chest leads? Lateral? Right-sided? Septal?

Anterior: V2, V3, V4
Lateral: V5, V6
Right-sided: V1
Septal: V2, V3

V2 and V3 are just lateral to the interventricular septum.

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What is unique about septal depolarization?

It goes from left to right, which is opposite of ventricular.

What leads can typically show a small Q wave due to septal depolarization?

I, aVL, V5, V6 (Lateral leads)

Sometimes can appear in II, III, aVF, V3, and V4

What is R wave progression?

The R wave should get larger beginning from V1 to V6.

Slowly getting bigger as it gets towards V6.

R wave is representative of ventricular depolarization.
Usually peaks around V4 or V5.

What two leads are used to determine EKG axis and why?

We only require frontal plane leads.

Specifically, we use lead I and aVF.

aVF and I should both be positive in their QRS deflection, which corresponds to the bottom left quadrant of the heart, which is normal.

What lead abnormality would suggest right axis deviation?

aVF normal with positive deflection.
Lead I with negative deflection.

What lead abnormality would suggest left axis deviation?

* aVF with negative deflection. * Lead I with positive deflection.

What lead abnormalities would suggest extreme right axis deviation?

* aVF with negative deflection. * Lead I with negative deflection.

What does the AP of a cardiac pacemaker cell look like?

## Footnote No true resting potential.

What is the term given to the ability of every cell in the heart to behave like a pacemaker cell?

Automaticity. ## Footnote It is suppressed by the SA node cells, but can appear problematic when there is SA node dysfunction.

How many large boxes is 1mV equivalent to on a normal EKG?

2 large boxes.

What are the 3 divisions of the left bundle branch?

* Septal fascicle: IV septum in a left-to-right direction. * Anterior fascicle: anterior LV * Posterior fascicle: posterior LV

6 QRS complexes

What does the PR segment correspond to?

Conduction pause at the AV node

What limb leads generate the frontal plane of a 12-lead?

* Lead I: 0 deg * Lead II: 60 deg * Lead III: 120 deg * Lead aVL: -30 deg * Lead aVR: -150 deg * Lead aVF: +90 deg

What are the inferior leads?

* Leads II * Lead III * Lead aVF

What are the left lateral leads?

* Lead I * Lead aVL * V5 * V6

What are the right sided leads?

* Lead aVR * V1

What are the anterior leads?

* V2 * V3 * V4

Which frontal lead should present with a negative P-wave?

aVR, because the depolarization is moving AWAY from the electrode.

What frontal lead should present with a biphasic wave?

Lead III, which begins positive then becomes negative.

What is a normal PR interval duration?

0.12s-0.2s

Describe R wave progression.

As we going from V1 to V5, the R wave amplitude is expected to increase. ## Footnote R refers to the first positive deflection after the PR segment.

How long is a typical QRS complex?

.08s to .12s | AKA 2-3 small boxes

In a lead that has a tall R wave, what kind of T wave should I expect?

Positive T wave. ## Footnote Ex: V1 has a very small R wave, and its T wave is negative. V6 has a tall R wave, and its T wave is positive. Generally, a T wave is 1/3-2/3 the amplitude of its preceding R wave.

On average, how much of an R-R interval does a Q-T interval take up?

40%, as the T wave is generally wider than the QRS.

What leads do we look at to determine normal axis?

* I (Positive QRS) * aVF (Positive QRS) | 0-90 deg ## Footnote This generates the bottom left quadrant of the heart (towards the apex)

How would right axis deviation present on I and aVF?

* Lead I should have a NEGATIVE QRS. * Lead aVF should have a POSITIVE QRS. ## Footnote AKA, going away from Lead I causes it to be negative. aVF is still positive because it is pointing right but down.

How would left axis deviation present on I and aVF?

* Lead I should have a POSITIVE QRS. * Lead aVF should have a NEGATIVE QRS. ## Footnote AKA, going towards the left = positive in I. Going up towards the head = negative in aVF.

How would extreme right axis deviation present on I and aVF?

* Lead I should have a NEGATIVE QRS. * Lead aVF should have a NEGATIVE QRS. ## Footnote Going towards the right = negative in I. Going up towards the head = negative in aVF.

What do you look for to define axis angle more precisely and why?

* You look for a biphasic QRS (positive and negative deflection approximately equal on both sides) * The axis must be perpendicular to whatever lead has the biphasic wave. * The biphasic wave tells you that there are only two axis orientations possible (90 deg perpendicular to the lead) * Based on whether you have normal axis, left, or right, you can determine which one makes the most sense. * This requires 3 leads: I and aVF to determine normal axis, and the lead with a biphasic QRS to determine the axis degree specifically. ## Footnote Example: Lead III shows a biphasic QRS. A normal III has an orientation of 120 deg. Perpendicular to that is either 30 or -150 deg. If the axis is normal (aka I and aVF are positive), then it must be 30 deg.