Chapter 6 - Interpretation of an EKG Strip

Incorrect Interpretation

A quick glance at a strip will often lead to an:

Step 1: Heart rate

Step 2: Heart rhythm

Step 3: P wave

Step 4: PR interval

Step 5: QRS complex

Five-Step Approach

Heart Rate

Five-Step Approach: Step 1

Heart Rhythm

Five-Step Approach: Step 2

P wave

Five-Step Approach: Step 3

PR interval

Five-Step Approach: Step 4

QRS complex

Five-Step Approach: Step 5

Five-Step Approach: Step 6

Counting the PQRST complexes conducted through the myocardium in 60 seconds

Heart Rate as the first step in the Five-Step approach is counting the number of electrical impulses by:

Counting the P waves

Counting the Atrial Rate on the EKG

Counting the number of QRS complexes noted

Counting the Ventricular rate on the EKG

Count the number of QRS complexes that occur within a 6-sec interval, and multiply by 10.

The Six Second Method:

Look at Q R S complex that falls on a heavy line on the strip, count number of large boxes between this R wave and the next R wave and divide this number by 300

The R-R interval Method:

Rhythm

Sequential beating of the heart as a result of the generation of electrical impulses:

Regular pattern

Intervals between R waves are regular

Irregular pattern

Intervals between R waves are not regular

0.06 sec or 1.5 small boxes

If the intervals vary by less than ___ seconds or ___ small boxes, we can consider the rhythm to be regular

Regularly irregular

Irregular rhythms that occur in a pattern

Occasionally irregular

Intervals of only one or two R to R are uneven

Irregularly irregular

R to R intervals exhibit no similarity

the atria depolarize

P wave is produced when:

Rounded and upright

The P wave should be:

S A node pacing or firing

P wave is the:

Sinus Rhythm

The P Wave pattern is referred to as a:

Step 1: Are P waves present?

Step 2: Are P waves occurring regularly?

Step 3: Is there one P wave present for each Q R S complex present and/or is there a Q R S for each P wave present?

Step 4: Are the P waves smooth, rounded, and upright in appearance, or are they inverted?

Step 5: Do all P waves look similar?

Five Questions to ask with the P Wave:

time interval from the onset of atrial contraction to onset of ventricular contraction

The PR interval measures:

from onset of P wave to the onset of the Q R S complex

The PR interval on the EKG appears from:

0.12-0.20 sec (3-5 small squares)

Normal PR interval:

1. Are P R intervals greater than 0.20 sec?

2. Are P R intervals less than 0.12 sec?

3. Are the P R intervals constant across the E K G strip?

P R Interval: Three Questions to Ask

Depolarization and contraction of the ventricles

The QRS complex represents:

Q wave

First negative or downward deflection of this large complex

R wave (tallest waveform)

First upward or positive deflection following the P wave

S Wave

The sharp, negative, or downward deflection that follows the R wave

1. Are Q R S intervals greater than 0.12 sec (wide)?

2. Are Q R S intervals less than 0.12 sec (narrow)?

3. Are the Q R S complexes similar in appearance across the E K G strip?

Q R S Complex: Three Questions to Ask

ST Segment

Begins with the end of the Q R S complex and ends with the onset of the T wave (consistent with isoelectric line)

J-Point

Point at which the Q R S complex meets the S T segment

myocardial ischemia or injury may be indicated

If S T segment is elevated or depressed:

T Wave

the first upward or positive deflection following the Q R S complex

ventricular repolarization or relaxation

T Wave represents:

U wave

May appear after the T wave, usually not easily visible on EKG strips, appearing as a rounded or positive deflection, smaller than the T Wave

Hypokalemia or hyperthyroidism

A prominent U wave may represent:

Artifact

E K G waveforms from sources outside the heart

- Patient movement

- Loose or defective electrodes (fuzzy baseline)

- Improper grounding (60-cycle interference)

- Faulty E K G apparatus

Four causes of EKG artifact: