CPR 21 - ECG Basics 2 - ECG Leads and Mean Electrical Axis/Vectors Flashcards by Joshua Bora | Brainscape

Q

Describe the two planes through which an ECG views the heart.

A

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Q

Which lead numbers are the bipolar limb leads? How are they positioned and which leads are considered positive and negative?

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Q

What are the augmented limb leads? How are they positioned and which leads are considered positive and negative?

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Q

Where are each of the precordial chest leads placed?

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Q

Aside from the mass of tissue that is depolarizing/repolarizing, what would cause the amplitude of a wave to increase or decrease?

A

If a wave of depolarization/repolarization is moving directly towards or away from an electrode then its deflection will be maximal (for that given mass of tissue). If that wave is moving perpendicular to a lead then there will be no deflection (biphasic). Refer to image.

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Q

Draw out the circle of axis. Be sure to label the degrees and the leads associated with them. Is the circle of axis in the horizontal or vertical plane?

A

Vertical

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Q

Will the QRS wave have a positive or negative deflection for Lead 1? Why?

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Q

Will the QRS wave have a positive or negative deflection for lead 2? Why?

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Q

Will the QRS wave have a positive or negative deflection for lead 3? Why?

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Q

Will the QRS wave have a positive or negative deflection for lead aVR? Why?

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Q

Will the QRS wave a positive or negative deflection for lead aVL? Why?

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Q

Will the QRS wave have a positive or negative deflection for lead aVF? Why?

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Q

In what plane do the precordial chest leads view the heart?

A

Horizontal

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Q

In which direction does a QRS wave typically deflect for leads v1-v6?

A

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Q

What are the precordial chest leads used to detect?

A

Changes to mass of left ventricle (hypertrophy, infarcts, etc)

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Q

What is the mean electrical axis?

A

The average of all the instantaneous mean electrical vectors occurring sequentially during depolarization of the ventricles

Q

What is used to calculate the mean electrical axis (MEA)? What plane is it calculated in?

A

Calculated in frontal plane only, using QRS deflections and amplitudes in limb leads (Leads 1, 2, 3, aVF, aVR, and aVF).

Q

Draw out the MEA quadrants and label whether each quadrant represents a deviating or normal MEA.

A

Q

What is a quick way to tell if the MEA is within the normal axis?

A

The QRS deflection is positive for Leads 1, 2, and aVF.

Q

In which quadrant is this patient’s MEA? Explain.

A

Left axis deviation quadrant

Lead 1 is positive, lead 2 is biphasic, lead 3 is negative

Q

How do you calculate overall QRS amplitude?

A

Q

How can calculating QRS amplitude help to find the MEA angle?

A

Q

How can you eyeball an MEA?

A

MEA will be closest to the lead with the largest QRS amplitude

MEA will be perpendicular to the lead with a biphasic QRS