Basic ECG Concepts & Lead Monitoring

Question 1

Why is lead II used most commonly for a rhythm strip?

Answer 1

Of all the leads, lead II represents “normal” activity through the heart (R—>L)

Question 2

What leads view the anterior surfaces of the heart?

Answer 2

V2

V3

V4

Question 3

What leads view the Lateral surfaces of the heart

Answer 3

V5

V6

I

aVL

Question 4

What leads view the Inferior (diaphragmatic) surfaces of the heart?

Answer 4

II

III

aVF

Question 5

Explain what the electrocardiogram (ECG) represents

Answer 5

• Recording of the electrical activity of the heart
• machine that reads the change in polarity or electrical activity of the heart

Question 6

List the 2 major waveforms from an ECG used to determine proper AV conduction.

Answer 6

P wave and QRS

Question 7

List the steps to determine a proper PR interval length.

Answer 7

Locate a P wave that immediately preceeds a QRS.

Locate the start of the P wave

Locate the start of the QRS

Determine the length from beginning of P wave to start of QRS

Length should be between 3-5 small boxes or 0.12-0.20s

Question 8

Discuss AV conduction in terms of P wave:QRS ratios

Answer 8

Sinus rhythms should conduct from the SA node —> AV node —> Bundle of HIS —-> Purkinje fibers.

If conduction is regular, every P wave should have a QRS and every QRS, a P wave in a 1:1 ratio.

Question 9

What does the PR interval represent and how much time should it take?

Answer 9

Atrial depolarization to the start of ventricular depolarization

or the time it takes the electricity to travel from SA node to AV node

It should take 0.12-0.20 seconds, or 3-5 little boxes

Question 10

What measurement can be done from one ventricular depolarization to the next ventricular depolarization?

Answer 10

R-R interval

Question 11

What does the ST segment represent?

Answer 11

time between ventricular depolarization and ventricular repolarization, it is also important to see its relationship to the baseline

Question 12

2 ways to determine the rate of an ECG

Answer 12

1. Count the number of R peaks; figure out how many seconds the strip is; multiply the peaks by the number that equals the seconds to 60
2. Use the 300, 150, 100, 75, 60, 52 method

Question 13

Normal P Wave

Answer 13

The amplitude of a P wave does not normally exceed 0.25 mV (2.5mm or 2.5 small squares)

Amplitude is usually most + in lead II and most - in lead aVR

Question 14

Abnormal P Wave

Answer 14

If amplitude exceeds 0.25 mV (2.5mm or 2.5 small squares)

Question 15

Normal T wave

Answer 15

Typically find + T waves in the same leads that have tall R waves,

The amplitude of a normal T wave is one-third to two-thirds that of the corresponding R wave.