Cardiac Exam Lecture 4 (EKG) Flashcards

1
Q

What does the EKG measure?

A

EKG records differences in voltages (wave of depolarization)

Measures direction and amplitude of VECTORS within the heart

EKG only measures electrical activity of atria and ventricles

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2
Q

What do the upward and downward reflections of an EKG recording mean?

A

Up and down deflections result in vector moving towards or away from an electrode

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3
Q

What does the EKG tell us about contractile activity or strength?

A

NOTHING, the EKG tells us nothing about contractile activity or strength

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4
Q

Explain the twelve leads of an EKG

A

3 Bipolar Limb Leads: I, II, III

3 unipolar limb leads: aVF, aVR, and aVL

6 unipolar/pericardial leads: V1-V6

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5
Q

In most people with normal cardiac function, which lead has the largest QRS complex?

A

Lead II, which is why it is used as emergency standard

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6
Q

Where does the normal frontal plane vector of the heart point?

A

The normal frontal plane vector of the heart points down and to the anatomical left because the LV is the largest chamber of the heart and therefore it generates the most electrical current

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7
Q

Think about the diagram where the APs are shown above the EKG so you can see when things depolarize

A
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8
Q

Draw the EKG that shows the activation of different cardiac tissues within the EKG

A
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9
Q

Explain the rule of 300 and how you calculate HR on an EKG

A

For the Rule of 300: you count how many big boxes are between each R spike.

300/# of boxes btwn QRS complex

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10
Q

How fast is a normal QRS segment?

A

100 ms

that is 0.10 seconds

(for reference the blink of an eye is 0.30 s or 300 ms)

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11
Q

Draw Eintoven’s Triangle

A
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12
Q

Explain the placement of the positive and negative electrodes for the following leads:

Lead I

Lead II

Lead III

A

Lead I : RA is negative electrode, Left arm is positive electrode

Lead II: RA is negative electrode, left leg is positive electrode

Lead III: LA is negatie electrode, LL is positive electrode

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13
Q

Draw the snowflake diagram

A

remember, start by putting ZERO degrees on the anatomical LA (positive end of Lead I).

As you go up from there the angles are negative

As you go down the angles are positive and just go around until you get to 180

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14
Q

Explain what the following vectors lead to on the EKG:

Atrial Depolarization Vector

Septal Depolarization vector

Ventricular Depolarization Vector

Ventricular Repolarization

A

Atrial Depolarization: P wave

Septal Depolarization: Q wave (downwards)

Ventricular Depolarization: R wave

Ventricular Repolarization: T wave

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