1. Analyzing the Electrocardiogram3
Analyzing the Electrocardiogram
Fast & Easy ECGs, 2nd E – A Self-Paced Learning Program

2. Heart’s Electrical Activity
Depolarization and repolarization of the atria and ventricles are electrical events
The ECG detects this electrical activity and displays it on the oscilloscope or prints it

3. ECG Characteristics
The electrical activity of the heart produces waveforms with specific shapes and duration that occur at a certain rate and regularity
These are referred to as ECG characteristics
Each dysrhythmia and cardiac condition produces certain characteristics that can be identified through analysis of the ECG tracing

4. Nine-Step Process
A systematic process such as the Nine-Step Process can be used to identify the characteristics of each ECG tracing

5. Analysis and Interpretation
Once the ECG characteristics in each tracing are identified they are compared against what is considered the normal ECG
commonly referred to as sinus rhythm

6. Characteristics of NSR
Waveforms and intervals that appear at regular intervals at a rate of 60 to 100 beats per minute (in the adult)
Upright and slightly asymmetrical P waves, each followed by a QRS complex of normal upright contour, duration, and configuration
A PR interval (PRI) of normal duration that precedes each QRS complex
A flat ST segment followed by an upright and slightly asymmetrical T wave
A normal QT interval
Sometimes the presence of a U wave

7. Heart Rate
The average heart rate in the adult is 60 to 100 beats per minute
A heart rate that is slower or faster is considered abnormal and may indicate significant problems requiring prompt intervention
For this reason, it should be checked as soon as possible

8. Regularity
Normally the heart beats in a regular, rhythmic fashion. The cycle repeats itself over and over again

9. Regularity Regular rhythm: Irregular rhythm:
Distance between the consecutive P waves is the same, just as the distance between the consecutive QRS complexes is the same throughout the tracing
Irregular rhythm:
Distances between the consecutive P waves and/or consecutive QRS complexes differ

10. Morphology
When assessing the waveforms seen on an ECG tracing, we look at the appearance or morphology of the complexes
Instructional Points:
The morphology may be normal, wide, short, tall, flat, spiked, jagged, or bizarre (meaning its shape is far from normal). It often yields a great deal of information and can help us identify both dysrhythmias as well as cardiac conditions I

11. P Wave Produced by: Waveform is upright and slightly asymmetrical
initiation of impulse in SA node
depolarization of RA and LA
impulse passing through AV junction
Waveform is upright and slightly asymmetrical

12. QRS Complex
Represents movement of electrical impulse through ventricles causing their contraction
Consists of:
Q wave
first negative deflection following PR segment
R wave
first positive deflection following Q wave or PR segment
S wave
next negative deflection after the R wave
Instructional points:
The S wave begins at the point where the negative deflection of the R wave reaches the baseline. I

13. PR Interval
Represents depolarization of the heart from the SA node through the atria, AV node and His-Purkinje system
Is the distance from the beginning of the P wave to the beginning of the Q wave
First portion is the P wave while the second portion is the PR segment
Instructional Points:
Flat (isoelectric) line seen as impulse travels through His-Purkinje system I

14. ST Segment and T Wave ST segment is flat line that follows QRS complex
T wave is larger, slightly asymmetrical waveform that follows ST segment
Instructional point:
The J point is the site where the S wave connects to the ST segment. I

15. QT Interval Distance from onset of QRS complex until end of T wave
Measures time of ventricular depolarization and repolarization
Has normal duration of 0.36 to 0.44 seconds
Instructional points:
The QT interval shouldn’t be greater than half the distance between consecutive R waves when the rhythm is regular.
It varies according to age, sex, and heart rate, the faster the heart rate the shorter the QT interval. I

16. U Wave
Small upright seen following the T wave, but before the next P wave
Its voltage is so low, however, that the U wave often goes unnoticed

17. Analyzing the ECG Using the monitor Follow tracing from left to right
Observe the rate, regularity, and presence of P waves and get a general view of the PR interval, QRS complexes and T waves
If you identify anything abnormal print a tracing for further analysis

18. Analyzing the ECG Using the rhythm strip
Look at the waveforms, intervals, and durations of each from left to right
Compare the findings against normal sinus rhythm

19. Analyzing the ECG Using the 12-lead tracing
Look at each lead (from left to right), starting at the top and moving to the bottom in the first column
Then in the second column, next in the third column, and then lastly, in the fourth column

20. Summary
The key to making sense of what is seen on any ECG tracing is to approach it in a logical and systematic manner
The Nine-Step Process assesses the main elements of the ECG tracing

21. Summary
The average heart rate in the adult is 60 to 100 beats per minute.
A heart rate that is slower or faster is considered abnormal
The heart beats in a regular, rhythmic, cyclical fashion, producing specific waveforms and intervals with each heartbeat.
An irregular rhythm is abnormal

22. Summary
Throughout the ECG tracing, there should be one normal upright P wave preceding each narrow upright QRS complex
The PR interval that precedes each QRS complex should be of the same duration and within 0.12 and 0.20 seconds

23. Summary
After each QRS complex of the ECG tracing, there should be a flat ST segment, followed by an upright and slightly asymmetrical T wave
The QT intervals should be between 0.30 and 0.44 seconds in duration
U waves may or may not be present

24. Summary
What is identified in the step-by-step analysis of an ECG tracing is compared against the characteristics of normal sinus rhythm
Each dysrhythmia and cardiac condition has characteristics that are unique to it, making it identifiable
An ECG can be analyzed on the monitor screen, on a rhythm strip, or on a 12-lead ECG tracing