How To Determine Heart Rate
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The calculation of the heart rate of an electrocardiogram is of great diagnostic importance, because determining a tachycardia or bradycardia may make us suspect certain pathologies and their severity.
The easiest way to calculate the heart rate isâ¦ to look for the value given by automated analysis of most electrocardiograms.
Are we kidding? No, many times this heart rate value is an actual one and speeds up the diagnostic process.
Anyway, every professional must know the different methods to calculate the heart rate, because not always the automatic analysis is real or there are electrocardiogram equipment that do not provide the value of the heart rate.
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Help With Calculating A Rate With Pvcs
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VirginiaEMT said:When calculating the rate for a rhythm strip, do PACs,PJCs,and PVCs get used as well as the normal QRS complexes? Let’s say it’s a irregular rate of 4 normal QRS complexes and 2 PVC’s, would the rate be 60 bpm? To be clear, I am not assessing a patient, I am looking at the strip itself.Here’s another example, let’s say I’m looking at a strip that has 5 nice R waves and 2 PVCs, is the rate 50, or is it 70. Is the patient bradycardic or not?
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Here’s a scenario:Asystole is a symptom or syndrome. It will not be corrected by CPR if it is due to infarct, trauma, or poison. CPR buys your patient time to defintive care.
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How To Measure Heart Rate From Ecg:
Before going to calculate heart rate from an ecg strip. Lets me give a short introduction to ECG and its leads.
Electrocardiogram
Graphic recording of electrical potential generated due to transmission of depolarization wave through the heart, and due to its spread into surrounding tissue and body surface. Is called electrocardiogram .
Father of ECG
Site of pacemaker is recorded
Heart. Rate can be calculated
Rhythm of heart can be recognised
The voltage produced due to potential changes in the heart can be calculated.
Helps to diagnose heart diseases.
Calculate Heart Rate With The Number 300
This is one of the simplest methods to calculate the heart rate on an ECG. However, this method can only be applied if the heart rhythm is regular.
To calculate the heart rate with the number 300 the RR interval is used. What you need to do is look for an R wave that matches a thick line on the ECG paper. Next, the large squares that are up to the next R wave are counted. 300 is then divided by the number of squares.
It is important to remember that every five of these large squares represents one second on the EKG.
The example in Figure 1 shows an Electrocardiogram with a regular rhythm in which, in the DII lead, there are 5 large squares between two R waves.
So the process to calculate the heart rate in this EKG would be to divide 300 by 5. Resulting in a Rate of 60 beats per minute .
If in the previous example the number of large squares had been 4 then the rate would have been 75 bpm. .
Another example of the 300 method for calculating Heart Rate on an ECG is shown in Figure 1B. In this example there are 3 large squares between both R Waves so the Rate is 100 bpm .
The problem with this method is that in most cases the second R wave does not coincide with one of the thick lines and sometimes none of the R waves coincide with these lines.
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Analyzing P Waves On A Ekg Strip
First, make sure that there are actually P waves on the EKG strip because there are certain dysrthythmias where P waves are missing.
Once youâve determined that a strip includes P waves, youâll want to make sure the P waves are occurring regularly and have a consistent appearance across the strip. P waves should be upright, smooth and rounded with an amplitude, or height, of up to 2.5 millimeters high.
Then we want to make sure there is one P wave for each QRS complex on the strip. There are certain dysrhythmias that cause abnormalities, which we will cover in later articles, that can cause the P wave to be inverted. These types of abnormalities are definitely things youâll want to take note of while analyzing P waves on an EKG strip.
Normal Heart Rate Values
The normal range of the heart rate is between 60 to 100 beats per minute.
Any value above 100 beats per minute is considered Tachycardia. And any value that is below 60 beats per minute is Bradycardia.
It is important to mention that Bradycardia and Tachycardia may not be a sign of a disease. Certain drugs like beta blockers can lower your heart rate. In addition, certain substances such as caffeine can cause tachycardia.
References consulted
 Dubin, D. . La Frecuencia. En D. Dubin, Interpretacion de ECG . COVER Publishing Company.
 Uribe, W., Duque, M., Medina, L. E., Marín, J., Velásquez, J. E., & Aristizábal, J. . ELECTROCARDIOGRAFÍA BÁSICA. Sociedad Interamericana de Cardiología, 4454.
 YouBiot. . Qué es un electrocardiograma. Obtenido de YouBiot.com:
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If The Second R Wave Does Not Match
It is important to remember that each large square on the EKG paper equals 0.20 seconds and is made up of 5 small squares that equals 0.04 seconds. You can read more about this in ECG Paper Characteristics.
To calculate the heart rate in the event that the second R wave does not coincide with a thick line on the EKG paper, the small squares must be counted up to the R wave and multiplied by 0.2. The result is then added to the number of large squares and 300 is divided by that number.
In figure 2 you can see an electrocardiogram in which the second R wave does not coincide with the thick line.
In this example there is a distance of 5 large squares between both R waves. But there are also 2 small squares until the next R wave .
As explained before, the small squares must be multiplied by 0.2, and the result must be added to the number of large squares. In this case 2 x 0.2 = 0.4, this value is added to the 5 large squares that lie between both R waves, resulting in 5.4. This value is then divided by the 300. Giving a rate of 55 bpm.
How To Calculate The Heart Rate On An Ekg Strip With The Six Second Rule
When you are interpreting an EKG, you must know how to count the heart rate. When you count the heart rate you are counting the ventricular and atrial rate. In this article, I am going to tell you how to count a heart rate using the six second rule.
There are many ways you can count a heart rate on an EKG, but I find the six second rule to be the easiest and fastest way. In addition, the six second rule is great for counting heart rhythms that arent regular like, atrial fibrillation, atrial flutter, sinus arrhythmia, sinus rhythm with PVCs etc.
Before you can understand how to count the heart rate using the 6 second rule, you must first be familiar with the squares found on the EKG paper. These squares are found on the background, behind the rhythm. These squares can be hard to see at time, so if you dont have the best vision, you may need a small magnifying glass. Each square and block represents a fraction of time.
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Ecg Heart Rate Calculation
There are just a few steps ahead of you to get your patients heart rate using our calculator:

With the ruler: measure the distance between two R wave peaks. R wave, part of QRS complex , is defined as the first upward deflection after the P wave . While measuring, try to put your ruler parallelly to the horizontal lines on the ECG paper.

With the caliper: place each of measuring tips of your caliper on peaks of subsequent R waves. Then, without changing the angle between the arms of the caliper, put one of the tips on an intersection of ECG paper lines and the other tip on the same horizontal line. Count the number of ECG boxes between the tips of your caliper. A small box represents 1 millimeter while the big box measures 5 millimeters.
Check the lengths of some other RR intervals. If there are differences, your patient might have an arrhythmia! This calculator is not suitable for calculating the heart rate of patients with irregular heart rhythm. For more information, check out the 6 second ECG paragraph!
Put the result of your measurement to the corresponding field: RR interval for length in millimeters, number of boxes for length in boxes.
If you chose to measure RR interval in boxes, select the type of boxes.
Choose the ECG paper speed. The standard is 25 mm/s, but sometimes a 50 mm/s option is preferred.
Read the ECG heart rate in beats per minute!
Three Methods To Calculate The Heart Rate
When we talk about the heart rate, we often mean the ventricular rate.
There are several methods for determining the ventricular rate or heart rate. Below, I share three of them.
Method #1: Identify an Rwave that is on a line. Use that as the start Rwave and then count success big boxes from the start as 300, 150, 100, 75, 60, 50. Below 50, use the formula given in method #2. This method is good for regular rhythms.
Method #2: 300 divided by the number of large squares between the QRS complexes. When the rhythm is regular, the heart rate is 300 divided by the number of large squares between the QRS complexes.
Because there are 5 small boxes in one large box, an alternative, more tedious way is to count the number of small boxes for a typical RR interval and divide 1500 by this number to determine heart rate.
Method #3: The number of QRS complexes per 6second strip multiplied by 10. Count the number of QRS complexes over a 6second interval. Multiply by 10 to determine heart rate. This method works well for both regular and irregular rhythms and for bradycardias. Its recommended for irregular rhythms and for bradycardias.
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Determining Heart Rate From The Electrocardiogram
The term heart rate normally refers to the rate of ventricular contractions. However, because there are circumstances in which the atrial and ventricular rates differ , it is important to be able to determine both atrial and ventricular rates. This is easily done by examining an ECG rhythm strip, which is usually taken from a single lead . In the example below, there are four numbered R waves, each of which is preceded by a P wave. Therefore, the atrial and ventricular rates will be the same because there is a onetoone correspondence. Atrial rate can be determined by measuring the time intervals between P waves . Ventricular rate can be determined by measuring the time intervals between the QRS complexes, which is done by looking at the RR intervals.
In the above examples, the ventricular rate was determined based on the interval between the first two beats. However, it is obvious that the rate would have been faster had it been calculated using beats 2 and 3 because of a premature atrial beat, and slower if it had been calculated between beats 3 and 4 . This illustrates an important point when calculating rate between any given pair of beats. If the rhythm is not regular, it is important to determine a timeaveraged rate over a longer interval . For example, because the recording time scale is 25 mm/sec, if there are 12.5 beats in 10 seconds, the rate will be 75 beats/min.
Revised 3/11/16
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The 300 And 1500 Rule
What if there is no Internet and you are not able to use our fantastic ECG heart rate calculator? How to calculate heart rate facing such conditions? Don’t worry. We have a solution! You can use the 300 or 1500 rule:
With your caliper, count the number of big or small boxes between two R wave peaks.
Divide 300 by the number of big boxes or 1500 by the number of small boxes.
You have your patient’s heart rate!
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Ecg Heart Rate Calculator
With this calculator, you will be able to acquire your patient’s heart rate from an ECG. You will only need to measure the distance between two R wave peaks the RR interval. You can use either a ruler or a caliper and type in the result in millimeters or quantity of ECG boxes, you choose! But remember! If RR intervals between at least two ECG complexes are different, your patient might have an arrhythmia, and our calculator may give you a false result. Don’t forget to check it! In the following text you will learn:

how to calculate heart rate with our calculator or by yourself using some easytoremember methods

a method to estimate heart rate in a patient with an arrhythmia using the 6 second ECG method

a way to use our calculator differently in order to get your patient’s expected RR interval based on his or her heartbeat.
Please note that using this calculator is by no means equivalent to a consultation with a specialist. If the result you obtained is troubling you, make sure to visit your physician! If you are interested in cardiology, don’t forget to check out our cardiac output and stroke volume calculators!
Arrhythmias On The Ecg Rhythm Strip
An arrhythmia is any abnormal rhythm other than normal sinus rhythm the baseline rhythm of the heart. This can be a benign variant , or it could be deadly .
In order to know how to read an EKG rhythm strip, you need to first be able to understand what normal sinus rhythm looks like.
You should be comparing every rhythm strip to NSR. Recognizing where the rhythm differs from NSR will help you identify the rhythm.
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Regular Or Irregular Heart Rhythm
Determining if the Heart Rhythm is regular or irregular is the first step in analyzing the Heart Rhythm on the ECG.
To define it, the RR interval is used. Remember that the RR interval is the distance between two consecutive R waves. The most commonly used Lead to analyze the Rhythm is the DII.
A Regular Rhythm is one in which the distance is similar between each RR interval or QRS complex. Whereas when this interval is not similar between each R wave, the Rhythm is considered to be Irregular.
In Figure 1 an Electrocardiogram can be seen in which the QRS complexes, more specifically the R waves of these, are separated by 13 small squares . If you look closely, this separation is similar between the different RR intervals. So it is confirmed that this ECG has a Regular Rhythm.
It is important to remember that each small square on the ECG has a value of 0.04 seconds. So in the previous example, each QRS complex is separated by 0.52 seconds or 520 milliseconds . This value is constant between each R wave, so the Rhythm is Regular.
In Figure 2 we can see an Electrocardiogram with an irregular rhythm. In the first QRS complexes we can observe a distance of 5 large squares or 1 second. While in the last RR interval it can be seen that the distance is only 4 large squares and 1 small square, that is, 840 milliseconds. This difference between the different RR intervals results in an Irregular Heart Rhythm.
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Heart Rate In Irregular Rhythms
The above options are only valid if the rhythm is regular. Soâ¦
How do we calculate HR is the rhythm is not regular, such as in atrial fibrillation? It may be even easier, like finger counting
Heart rate: 20 QRS complexes x 6 = 120 bpm
Usually electrocardiograms record 10 seconds, so all you have to do is count all QRS and multiply by 6.
If the EKG is not a 10 seconds one, or you are not aware of its duration, count 30 large squares , and multiply the number of QRS complexes on them by 10. The result is an approximate heart rate.
For example: Count the number of QRS complexes in 30 large squares and multiply by 10. If there are 11 QRS complexes, the heart rate is 110 bpm .
We hope we have been able to help you. For further details on heart rhythm analysis, click Next.
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Count The Number Of R
The first step in analyzing an EKG or ECG strip is to calculate the heart rate. There are different ways to calculate ECG heart rate on a 6 second strip. One of the easiest ways to calculate heart rate on a 6 second strip is to count the amount of R waves on a 6 second strip and and multiply it by 10. This can be done if a heart rhythm is regular or irregular.
To determine if a rhythm is regular, measure the R to R intervals. If the intervals between each R wave is equal, then you can say this is a regular rhythm. If there is an abnormality within the R to R interval, then the rhythm will be considered irregular. In the above EKG strip, you see the R to R intervals are equal so we can say that this is a regular rhythm. If RR intervals vary by less than 1.5 boxes, the rhythm is still considered a regular rhythm. We see that there are 7 Rwaves. We multiply 7 x 10 and that equals 70 bpm . So the ECG heart rate in the above is 70 bpm. This technique also works well for slow heart rates as well.
There are other ways to calculate heart rate on a 6 second ECG strip, but the rhythm must be regular to do so. There is also the 300 method, the 1500 method, and the sequence method.