EKG Fundamentals

What does the standardized EKG grid system allow?

Comparison and measurement of amplitude (voltage) and duration (seconds)

Each small box on EKG paper equals how many millimeters?

1 mm

Each small box on EKG paper equals how many seconds?

0.04 seconds

Each large box on EKG paper equals how many seconds?

0.20 seconds

Each large box on EKG paper contains how many small boxes?

5 small boxes

EKG paper moves at what standard speed?

25 mm/second

An upward deflection indicates what?

Electrical activity moving toward a lead/electrode

A downward deflection indicates what?

Electrical activity moving away from a lead/electrode

What do bipolar limb leads include?

Leads I, II, and III

What do Leads I, II, and III form?

Einthoven’s Triangle

Lead I axis

0 degrees

Lead II axis

60 degrees

Lead III axis

120 degrees

What augmented leads are used on an EKG?

aVR, aVL, aVF

aVR electrode location

Right arm

aVL electrode location

Left arm

aVF electrode location

Left foot

What precordial leads are used on a 12-lead EKG?

V1-V6

What does the P-wave represent?

Depolarization of the atria

What part of the EKG represents atrial contraction/systole?

P-wave

What is the normal appearance of a P-wave?

Rounded waveform

What does the PR interval represent?

Time for electrical impulse to travel from SA node to ventricles

PR interval is measured from where to where?

Beginning of P-wave to beginning of QRS complex

Normal PR interval

0.12-0.20 seconds

What does the QRS complex represent?

Depolarization of the ventricles

What part of the EKG represents ventricular contraction/systole?

QRS complex

Normal QRS duration

0.04-0.12 seconds

What does the T-wave represent?

Repolarization of the ventricles

What part of the EKG represents ventricular filling/diastole?

T-wave

What is the normal appearance of a T-wave?

Rounded waveform

What does the QT interval represent?

Time for ventricles to depolarize then repolarize

Normal QT interval

0.33-0.42 seconds

Why were the letters PQRST chosen?

Randomly chosen by Dr. Einthoven to prevent confusion

Positive impulses are represented by what?

Upward deflections

Negative impulses are represented by what?

Downward deflections

No electrical impulse creates what?

Isoelectric line

What does a single lead EKG monitor?

Heart rate and rhythm

Where is single lead monitoring commonly used?

24-hour telemetry in CMU and ICU settings

What can a 12-lead EKG determine?

Presence of ischemia, hypertrophy, or infarction

What EKG changes are clues to injury?

T-wave inversion or ST segment changes

What is the first step of EKG interpretation?

Look at the rate

What is the second step of EKG interpretation?

Look at the rhythm

What is the third step of EKG interpretation?

Look at the P-waves

What is the fourth step of EKG interpretation?

Look at the PRI

What is the fifth step of EKG interpretation?

Look at the QRS

After the five-step process, what should be done?

Name the rhythm, interpret ectopic beats, and determine clinical significance

How is heart rate calculated using the six-second strip method?

Count R-waves in a 6-second strip and multiply by 10

6 large blocks between R waves equals what heart rate?

50 bpm

5 large blocks between R waves equals what heart rate?

60 bpm

4 large blocks between R waves equals what heart rate?

75 bpm

3 large blocks between R waves equals what heart rate?

100 bpm

2 large blocks between R waves equals what heart rate?

150 bpm

1 large block between R waves equals what heart rate?

300 bpm

What should be assessed when evaluating regularity?

Whether the rhythm is regular or irregular

What is a regularly irregular rhythm?

Predictable irregularity

What is an irregularly irregular rhythm?

Unpredictable irregularity

What should be assessed when evaluating P-waves?

Presence, normal upright appearance in Lead II, similar appearance, regularity, relationship to QRS, and association with ectopic beats

What should be assessed when evaluating QRS complexes?

Duration within normal limits, equal duration, and similar appearance

Normal QRS duration for interpretation

0.04-0.12 seconds

How should ectopic beats be counted when determining rate?

Include them in the rate count unless known not to produce a pulse