Download File

Understanding EKGs
A Practical Approach
For the Dental Hygienist
CHAPTER
6
Interpretation of an
EKG Strip
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Anatomy of the Heart
• Objectives
– Describe the basic approach to interpretation
of EKG strips
– Explain the five steps used in interpretation of
EKG strips
– Explain how to calculate heart rate, given a 6second strip
– Name four causes of artifact
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
General Rules
• First and most important, look at your
patient
• Read EVERY strip from left to right,
starting at the beginning of the strip
• Apply the five-step systematic
approach that you will learn in this
chapter
• Avoid shortcuts and assumptions
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
General Rules
• A quick glance at a strip will often lead to
an incorrect interpretation
• Ask and answer each question in the
five-step approach in the order that is
presented here… this is important for
consistency
• Master the accepted parameters for each
dysrhythmia and apply them to each of the
five steps when analyzing the strip
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
The Five-Step Approach
• This five-step approach, in order of
application, includes analysis of the
following
Step 1:
Step 2:
Step 3:
Step 4:
Step 5:
Heart rate
Heart rhythm
P wave
PR interval
QRS complex
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Step 1: Heart Rate
• Number of electrical impulses as
represented by PQRST complexes
conducted through the myocardium in 60
seconds (1 min)
• Atrial rate
– Counting the number of P waves noted
• Ventricular rate
– Counting the number of QRS complexes
noted
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Heart Rate
• SA node discharges impulses at a rate of
60-100 times per minute
• Bradycardia
– Heart rate less than 60 bpm
• Tachycardia
– Heart rate greater than 100
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Heart Rate Determination
• Two methods of determination of the heart
rate
– 1. The 6-second method
 Denotes a 6-second interval on EKG strip
 Strip is marked by 3-or 6-second tick marks on
the top or bottom of graph paper
 Count the number of QRS complexes occurring
within the 6-second interval and then multiply that
number by 10
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Sample of 6-Second Method
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Two Methods to Determine Heart Rate
• Two methods of determination of the
heart rate
– 2. Second method is the R-R interval
method
 Most accurate if heart rate is regular
 An estimation of the heart rate
 Look at QRS complex that falls on a heavy line on
the strip, count number of large boxes between
this R wave and the next R wave
 Divide this number into 300
• Or use small boxes and divide by 1500
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Sample Strip for R - R Method
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
STEP 2: Heart Rhythm
• Rhythm
– Sequential beating of the heart as a result of
the generation of electrical impulses
• Classified as
– Regular pattern
 Interval between R waves are regular
– Irregular pattern
 Interval between R waves are not regular
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Regular Rhythm
• Measure the intervals between P to P waves or
R to R waves
• If the intervals vary by less than 0.06
seconds or 1.5 small boxes, we can consider
the rhythm to be regular
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Irregular Rhythm
• If the intervals between the P to P waves
or R to R waves are variable by greater
than 0.06 seconds (1 ½ boxes), rhythm is
considered irregular
– Regularly irregular
 Irregular rhythms that occur in a pattern
– Occasionally irregular
 Intervals of only one or two R to R are uneven
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Irregular Rhythm
• If the intervals between the P to P waves
or R to R waves are variable by greater
than 0.06 seconds, rhythm is considered
irregular
– Irregularly irregular
 R to R intervals exhibit no similarity
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Practice Strip for Rate and Rhythm
Analysis
Pg 63 top
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Practice Strip for Rate and Rhythm
Analysis
Pg 63 bottom
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
STEP 3: The P Wave
• P wave is produced when the right and left
atria depolarize
• First deviation from the isoelectric line
• Should be rounded and upright
• P wave is SA node pacing or firing at
regular intervals
• This pattern is referred
to as a sinus rhythm
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
P Wave: Five Questions to Ask
Step 1: Are P waves present?
Step 2: Are P waves occurring regularly?
Step 3: Is there one P wave present for
each QRS complex present and/or is
there a QRS 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
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
P Wave Practice Strip
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
STEP 4: The PR Interval
• Measures the time interval from the onset
of atrial contraction to onset of ventricular
contraction
• Measured from onset of P wave to the
onset of the QRS complex
• Normal interval is
0.12-0.20 seconds
(3-5 small squares)
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
PR Interval: 3 Questions to Ask
1. Are PR intervals greater than 0.20
seconds?
2. Are PR intervals less than 0.12
seconds?
3. Are the PR intervals constant across the
EKG strip?
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
PR Interval Practice Strip
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
STEP 5: The QRS Complex
• Represents depolarization
or contraction of the
ventricles
– Q wave
 First negative or downward
deflection of this large complex
– R wave
 First upward or positive
deflection following the P wave
(tallest waveform)
– S wave
 The sharp, negative, or
downward deflection that
follows the R wave
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
QRS Complex: 3 Questions to Ask
1. Are QRS intervals greater than 0.12
seconds (wide) or are they less than 0.12
secs (Narrow)?
2. Are the QRS complexes similar in
appearance across the EKG strip?
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Sample QRS Rhythm Strip
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
The ST Segment
• Begins with the end of the QRS complex
and ends with the onset of the T wave
(consistent with isoelectric line)
• J-point
– Point at which the QRS complex
meets the ST segment
• If ST segment is elevated
or depressed, myocardial
ischemia or injury may be indicated
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
The T Wave
• Produced by ventricular repolarization
or relaxation
• Commonly seen as the first upward or
positive deflection following the QRS
complex
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
The U Wave
• Usually not visible on EKG strips
• Cause or origin not completely
understood
• Typically follows the T wave
• Appears much smaller than T wave,
rounded, upright, or positive deflection
if they are present
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Artifact
• EKG waveforms from sources outside the
heart
• Interference seen on a monitor or EKG
strip
– 4 causes
 Patient movement
 Loose or defective electrodes (fuzzy baseline)
• Clean your pt……
 Improper grounding (60 cycle interference)
 Faulty EKG apparatus
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Sample Rhythm Strip of Artifact
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.