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How To Calculate Heart Rate From Ecg With Irregular Rhythm

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If The Second R Wave Does Not Match

EKG Rhythm | How to Count the Heart Rate on EKG strip 6 (six) Second Rule

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.

Is It Sinus Rhythm

To ascertain whether a rhythm is sinus or not you need to be able to identify key features.

  • There must always be a p wave.
  • The P wave should be a rounded shape
  • Each P wave should be the same shape
  • Each P wave should be followed by a QRS
  • The P-R interval should be 3-5 small squares and constant
  • The rhythm should be regular.

You do not need to be able to recognise a “T wave” for it to be sinus rhythm. Many abnormalities obscure the t wave. Suffice to say, if the patient is alive then the ventricles are definitely repolarising.

School of Health SciencesB Floor Queen’s Medical Centre

How To Determine Heart Rate


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 is⦠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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Video On How To Count Heart Rate With 6 Second Rule

Here is a diagram to illustrate what Im talking about:

Important things to note about the squares:

  • Each large block contains 25 squares
  • Each small square represents 0.04 seconds of time
  • 5 small squares equal 0.20 seconds of time
  • When you are trying to calculate the heart rate with the six second rule, you must count out enough LARGE squares to equal 6 seconds. Therefore, 30 large squares would equal 6 seconds.

The Ecg Heart Rate Formula

How to Calculate Heart Rate from ECG: 8 Steps (with Pictures)

ECG paper has a speed of 25 mm/s . It means that a distance on the horizontal axis between two points on ECG paper corresponds to a certain duration. RR_distance / 25 mm/s = duration_of_RRThanks to the last equation, you can get the duration of the RR interval. The only thing left to do is to check how many times we can fit this period in a minute. This is the ECG rate formula: 60 s / duration_of_RR = Heart Rate

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How To Calculate Heart Rate From Ecg

This article was medically reviewed by Shari Forschen, NP, MA. Shari Forschen is a Registered Nurse at Sanford Health in North Dakota. She received her Family Nurse Practitioner Master’s from the University of North Dakota and has been a nurse since 2003.There are 9 references cited in this article, which can be found at the bottom of the page. This article has been viewed 218,368 times.

Although heart rate can be calculated easily by taking a pulse, studies show that an ECG may be necessary to determine if there is any damage to the heart, how well a device or drug is working, whether the heart is beating normally, or to determine the location and size of the heart chambers.XTrustworthy SourceAmerican Heart AssociationLeading nonprofit that funds medical research and public educationGo to source This test detects the electrical activity of the heartbeat through electrodes attached to the surface of the skin. Experts agree that calculating your heart rate from an ECG can help catch heart disease, heart problems, or determine your heart health.XTrustworthy SourceMedlinePlusCollection of medical information sourced from the US National Library of MedicineGo to source

Using The Distance Between Qrs Complexes

  • 1Be aware of how a normal “wave form” looks on an ECG trace.XTrustworthy SourcePubMed CentralJournal archive from the U.S. National Institutes of HealthGo to source This will allow you to determine what area of the ECG represents one heart beat. From the length of a heart beat on the ECG trace, you will be able to calculate the heart rate. A normal heart beat contains a P wave, a QRS complex, and an ST segment. The one you will want to pay particular attention to is the QRS complex, as this is the easiest one to use to calculate heart rate.
  • The P wave is a small semi-circular shape located right before the tall QRS complex. It represents the electrical activity of the atria , which are the two small chambers located at the top of the heart.
  • The QRS complex is the tallest most visible aspect of the ECG trace. It is usually pointy, like a tall, thin triangle and very easy to recognize. It represents the electrical activity of the ventricles , which are the two large chambers located at the bottom of the heart that forcefully pump blood throughout the body.
  • The ST segment directly follows the tall QRS complex. It is actually the flat area prior to the next semi-circular shape on the ECG . The importance of this flat segment , located right after the QRS complex, is that it provides important information to physicians about things such as potential heart attacks.
  • Speak to a physician if the person you are calculating heart rate for appears to have an abnormal value.
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    The Heart Rate Magic Number

    On a normal electrocardiogram, there are five large squares per second and 300 per minute. Knowing this, we can calculate the heart rate measuring the R-R interval, providing the rhythm is regular.

    Heart rate: 4 large square = 75;bpm

    On the EKG, locate a R;wave that matches a thick line, count the number of large squares to the next R;wave. Heart rate is 300 divided by the number of large squares, and thatâs it!

    For example: if there is 1 large square between R waves, the heart rate is 300;bpm; two large squares, 150;bpm, three large squares, 100;bpm, four⦠75;bpm.

    Three Methods To Calculate The Heart Rate

    How to Calculate Heart rate from ECG for beginners made Easy

    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 R-wave that is on a line. Use that as the start R-wave 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 R-R interval and divide 1500 by this number to determine heart rate.

    Method #3: The number of QRS complexes per 6-second strip multiplied by 10. Count the number of QRS complexes over a 6-second 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 one-to-one 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 R-R 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 time-averaged 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

    Using The 6 Second Method

  • 1Draw two lines on the ECG trace. The first line should be near the left-hand side of the paper containing the ECG trace; the second line should be exactly 30 large squares subsequent to the first line. 30 large squares on an ECG trace represents exactly 6 seconds.XResearch source
  • 2Count the number of QRS complexes between the two lines.XResearch source As a reminder, the QRS complex is the tallest peak of each wave form that represents one heart beat. Tally up the total number of QRS complexes between your two lines and write down this number.
  • 3Multiply your answer by 10.XResearch source Because 6 seconds x 10 = 60 seconds, multiplying your answer by 10 will give you the number of heart beats that have occurred in one minute . For example, if you count 8 beats in the 6 second period, then your heart rate calculation gives you 8 x 10 = 80 beats per minute.
  • 4Understand that this method is particularly effective for irregular heart rhythms. If the heart rate is regular, the first method of simply determining the distance between one QRS and the next can be very effective, because the distance between all the QRS complexes is presumably the same with a regular heart rate. On the other hand, with an irregular heart rate , the 6 second method works better because it averages the distance between heart beats, giving a more accurate overall number.XResearch sourceAdvertisement
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    Of Calculating Heart Rate

    The 1500 method is very similar to the 300 method for calculating heart rate on ECG. However, this is exceptionally useful when none of the R waves coincide with a vertical line on the ECG. This is the most accurate method to calculate heart rate.

    Unlike the previous method, this one counts the number of small squares that are in the RR interval. Then this amount is divided by the number 1500 to get the heart rate. It is important to mention that this method, like the previous one, only works if the rhythm is regular.

    In figure 3 you can see an ECG in which none of the R waves coincide with a vertical line.

    If you look closely, you can count 2 small squares after the first R wave. Next there are a total of 2 large squares, remember that each large frame has a total of 5 small squares.

    Before the next R wave there are 3 more small squares giving a total of 15 small squares between both R waves.

    To calculate the heart rate then 1500 is divided between the 15 small squares. In this example the heart rate is 100 beats per minute.

    How To Calculate The Heart Rate On An Ekg Strip With The Six Second Rule

    1.3 Calculating Heart Rate

    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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    What If The Second R Wave Does Not Match

    Do you think I have cheated and given you the most simple example?

    We know that usually on an electrocardiogram strip the second R wave does not match a thick line. The solution is a little bit tricky, but simple: We divide 300 by the number of large squares + 0.2 per small square.

    Heart rate: 4 large squares + 3 small square = 65;bpm

    For example: If there are 4 large squares and 3 small squares between R waves, the heart rate is 65;bpm .

    If you want to avoid the hassle, you can find a heart rate calculator in our calculations section to make it easy for you.

    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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    Normal Duration Times For The 3 Waves

    As well as being able to recognise the 3 different parts of the cardiac cycle, each stage should be completed within a specific time period to be considered normal. Although these measurements are in fractions of a second, the ECG paper allows you to count the time in small squares. Measurement in small squares is more universally used than tenths and hundredths of seconds.

    A Simplified Method For 12

    EKG Count of Heart Rate (Regular & Irregular)

    As you look at the rhythm, locate the QRS segment which represents the depolarization within the ventricles, the two lower chambers of the heart that gather and expel blood towards the body and lungs. Within the QRS, identify the R wave, the positive wave above the isoelectric line . Using a six second strip, measure the R to R intervals between QRS segments and determine if the rhythm is regular or irregular.

    If you discover an abnormality or irregularity here or in any of your subsequent findings on the ECG ask your patient if this is normal for them and look for any associated symptoms such as C.H.A.P.S. chest pain, hypotension, altered mental status, poor perfusion, or shortness of breath. ;

    2. Calculate the heart rate

    Take a radial pulse at the patients wrist, confirm it with the number displayed on the cardiac monitor or print a six-second strip of ECG paper and count the number of QRS complexes and multiply by 10 to arrive to a minute heart rate. From there, decide if the patient’s heart rate is bradycardic ; within a normal range ; tachycardic or a potentially dangerous rhythm above 150 bpm such as supraventricular tachycardia or ventricular tachycardia with a pulse.

    At this stage of ECG interpretation, be careful not to jump to a quick interpretation. Instead, note the information you find and continue with the subsequent steps.

    3. Find the P waves

    4. Measure the PR interval

    5. Measure the QRS segment

    6. Observe the T wave

    7. Note any ectopic beats

    Thank You!

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