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Dx Wisely
ECG
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ECG
Level 1
Tutorial: Analyze the Waveforms
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Tutorial: Analyze the Waveforms
This module will teach the basic waveforms on ECG and a stepwise approach of how to analyze them. Practice each step and get feedback on your performance.
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Tutorial: Analyze the Waveforms
Determine the heart rate
Lessons
42
Times Practiced
1284
Cases Completed
1h 24m
Total Time spent
1m 24s
Average Time
Progress
Accuracy
Efficiency
Accuracy
Efficiency
1
Anatomy
Anatomy
2
Waveform Identification
Waveform Identification
3
Waveform Identification #2
Waveform Identification #2
4
Determine the heart rate
Determine the heart rate
5
Do you have Rhythm?
Do you have Rhythm?
6
P waves! Where are you?
P waves! Where are you?
7
How many P waves?
How many P waves?
8
P wave Size and Shape
P wave Size and Shape
9
PR Interval
PR Interval
10
P conducted to QRS?
P conducted to QRS?
11
QRS Width
QRS Width
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Determine the heart rate
In this lesson, we will learn how to determine the heart rate.
(Not so interesting) Math Facts:
ECG paper is measured in mm. A
little square
is 1 mm wide (and tall)
A
big square
is 5 little squares = 5 mm
ECG's are recorded at 25 mm/sec, which means:
1 sec = 25 mm = 5 big squares
1 min = 5 big squares x 60 = 300 big squares
Now that was exciting. However, it is the logic behind the method below:
If we had
one heartbeat with every big square
, then there would be
300
beats per minute (bpm). If we had one heartbeat every
2
big squares, then the heart rate would be
150
bpm. If we had one heartbeat every
3
big squares, then the heartrate would be
100
bpm.
Starting to see a pattern?
Simply put,
Heart rate = 300 / (# of big squares between 2 QRS's)
You can use this method with the
ventricular rate
(# of big squares between QRS complexes) and also
atrial rate
(# of big squares between P waves). Make sure however, that you identify 2
consecutive
P waves. Sometimes P waves are sneaky and 1 might be hiding, so you could end up measuring the distance between the 1st and 3rd P wave, giving double the correct distance.
Sometimes, the
rhythm of the ECG is not regular
(there will be faster and slower sections). If that is the case, then do your best to take an AVERAGE value for the heart rate. In truth, sometimes the heart rate is variable and changing from minute to minute and there is no single correct heart rate value.
The spacing here is 3 big squares, so 300/3 = 100 bpm
The spacing here is about 1.2 big squares, so the rate is 300/1.2 = 250 bpm (crazy fast!)
The spacing here is about 11 squares, so the rate is 300/11 = 27 bpm
You can ignore this, but:
a slightly different way of doing the math is to use small squares instead of big squares. There are 5 small squares in a big square, so the equation becomes (300 x 5) / (small squares) = 1500 / (small squares).
One challenge you will encounter is how to calculate the rate when the rate seems to be changing. For example, if the rhythm is not regular, the rate will apear to be always changing. There are 2 ways to deal with this. First, you can measure a few different QRS complexes and average it out.
The
second method
is to use a full page 12 lead ECG. A full page 12 lead ECG is 10 second long. If you multiply by 6, then you can calculate the rate in one minute. Beware of this method: if the strip is not a full length strip, you can't use this method.
Summary:
rate = 300 / (big squares)
rate = 6 x (# of QRS) on a full one page ECG
Now go practice your awesome heart rate skills!
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