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 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.;
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.
How To Read An Ecg
If you’d like to support us and get something great in return, check out ourOSCE Checklist Booklet containing over 120 OSCE checklists in PDF format. We’ve also just launched an OSCE Flashcard Collection which contains over 1500 cards.
This guide demonstrates how to read an ECG using a systematic approach. If you want to put your ECG interpretation knowledge to the test, check out our;ECG quiz on the Geeky Medics quiz platform.
ECG flashcard deck
Don’t Miss: Reflux And Palpitations
Large Block Method To Calculate Heart Rate
Understand and learn to use the large block method to estimate heart rate on the electrocardiogram
Large Block Method
The fastest and easiest method to calculate the heart rate on the ECG;is the large block method. It can tell you at a glance whether or not youre dealing with a bradycardia or a tachycardia;but only;a minority of clinicians have incorporated this skill into their daily practice!
Granted, its more useful for rhythm strips, but when it comes to computers you should trust but verify!
This method can be used when:
- The heart rhythm is regular
- The paper speed is 25 mm/s
All you do is find an R-wave that is lined up with a large block on the ECG paper and count the number of large blocks between that cardiac cycle and the next. In other words, you measure the R-R interval in large blocks.
- 6 large blocks: 50
- 2 large blocks: 150
- 1 large block: 300
We know the normal heart rate is 60-100 . Using 60-100 the normal heart rate should have 3-5 large blocks between R-waves. More than 5 large blocks is a bradycardia and fewer than 3 blocks is a tachycardia.
Lets say it doesnt work out perfect. For example, lets say there are 3 1/2;large blocks between R-waves. Well, then you know the heart rate is somewhere between 75 and 100!
Lets look at some examples!
Heart rate: 50
6 large blocks: 50
Here there are 6 large blocks in between R-waves for an estimated heart rate of 50 BPM.
Heart rate: 60
5 large blocks: 60
Heart rate: 75
4 large blocks: 75
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.
Don’t Miss: How To Calculate Resting Heart Rate
Representation Of The Electrical Activity Of The Heart On The Ecg
The electrical conduction of the heart is represented in the Electrocardiogram by the different waves, intervals and segments.
In Figure 3 you can see an image that represents the electrical activity of the heart. Let us remember that the activity begins in the Sinus Node at the level of the Atria, which depolarize and contract to allow the passage of blood to the Ventricles. This first point is represented in the Electrocardiogram as the P Wave.
The electrical impulse then passes to the Atrioventricular node. This step generates a small delay in electrical conduction that is represented as the PR Segment.
The AV node then sends the electrical impulse through the Bundle of His for Ventricular Depolarization to occur. The one that is represented in the Electrocardiogram as the QRS Complex.
Lastly, Ventricular Repolarization occurs, which is represented by the T Wave in the Electrocardiogram. In this other article you can read more about the electrical conduction of the heart.
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.
Read Also: How Much Blood Does The Heart Pump
How To Count Atrial And Ventricular Rate Using The 6 Second Rule
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.
Don’t Miss: Does Acid Reflux Cause Heart Palpitations
Ecg Heart Rate Calculation
There are just a few steps ahead of you to get your patient’s 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!
Data Processing And Validation
The application software used to program the loggers and download the data from the loggers was Mercury V4.23 . Heart-rate calculations were first validated by feeding frequencies from 0.5 to 5;Hz from a built-in cardiac signal generated with an Agilent 33500B signal generator to the electrodes of the tag. Then the RR interval of the QRS pulses was manually calculated and compared to the values calculated by the algorithm of the DST milli-HRT.
Don’t Miss: How Do You Calculate Max Heart Rate
How To Calculate Heart Rate On An Ekg
Electrocardiography ECG or EKG is a non-invasive diagnostic tool. EKG measures the electrical activity of the heart using electrodes attached to the surface of the body. It can be used for a number of applications including providing a baseline reading for the activity of the heart, detection of heart rhythm disturbances or detection of a number of heart conditions. EKG readings can also be used to determine the heart rate of the patient.
Things Youll Need
- Conducting media
Recording the EKG
Calculating Heart Rate
Identify the R waves of two consecutive heart beats. The R wave is the highest peak on the trace, and should look fairly narrow and sharp.
Count the number of large 5mm boxes between the two R waves. EKG machines are programmed such that each 5mm box represents a time of .2 seconds. The time in seconds between consecutive heart beats can therefore be calculated by multiplying the number of boxes by 5.
Calculate the heart rate by dividing 300 by the number of large 5mm boxes between the two consecutive R waves. This calculation will determine the heart rate in beats per minute.
Tips & Warnings
- Choose a portion of the trace where there are several waves which are close to identical, and select two consecutive R waves from the middle of this portion to perform your calculation.
- For a more accurate estimate of heart rate, repeat this process for several different waves and take an average.
How To Perform The Ecg
Patients should be placed in right lateral recumbency. If using a metallic table top a blanket or cushion should be used to prevent artifact. There are generally 4 leads to attach to the patient. There are several techniques for attaching leads but the easiest for recording is to use alligator clip leads. These can be used in conjunction with alcohol or water soluble gel to help conduction. The leads should be placed behind the elbows on the forelimbs and over the stifles on the hindlimbs.
The leads of the electrocardiograph are color coded, red, green, black and white. These colors correspond to placement on the patient.
There are several pneumonics that can be used to remember which colors go to which limbs. One is if you think of yourself driving your car on a sunny day, your left arm is out the window and getting tan while your right arm remains in the car . Your right foot uses the brake to stop and the gas to go is on the left .
Your patient should be as calm as possible when recording the ECG, as motion such as struggling and tremors will cause artifact.
When ready to record the ECG the settings on the electrocardiograph should be checked. It is considered standard to record leads I, II, III, AVR, AVL and AVF at a sensitivity of 1.0 cm = 1.0 mv and a paper speed of 50 mm/sec. An additional lead II recording can be made at 25 mm/sec and is referred to as a rhythm strip. Each lead should be recorded for a couple of seconds and the rhythm strip for longer.
Don’t Miss: How To Calculate Target Heart Rate Zone
What Can Heart Rate Variability Tell You
While the medical uses of HRV are widely used, there are also aspects of thoughts, emotions, and behaviors that can be derived from HRV data.
Read Blog: Heart Rate Variability What This Measure Means for Emotions
From psychology studies, we know that HRV is associated with many factors. Researchers have found that an increase in HRV is related to increased self-control abilities, greater social skills, and better abilities to cope with stress, among other findings. The applications are therefore clearly more broad than directly medical situations.
Overall HRV can be said to be an indicator of physiological stress or arousal, with increased arousal associated with a low HRV, and a decreased arousal associated with high HRV. Using ECG alongside other measurements therefore provides another way to investigate how people respond to different settings or stimuli.
How Do You Calculate Atrial And Ventricular Rate
Atrial rateVentricular rate
The normal heart rate is 60 to 100 beats per minute. In atrial fibrillation or flutter, the heart rate may be 100 to 175 beats per minute. Blood pressure may be normal or low.
Subsequently, question is, how do you calculate rate on ECG? Heart rate can be easily calculated from the ECG strip: When the rhythm is regular, the heart rate is 300 divided by the number of large squares between the QRS complexes. For example, if there are 4 large squares between regular QRS complexes, the heart rate is 75 .
Just so, what is ventricular rate on ECG?
The normal ventricular rate is 60-100 beats per minute . Bradycardias are usually caused by diseases affecting the sinoatrial or atrioventricular nodes or the conducting tissues of the heart .
How do you calculate an irregular rhythm?
If the heart rate is irregular, count the number of QRS complexes on the ECG and multiply by 6 to obtain the average heart rate in bpm .
Recommended Reading: Can Too Much Vitamin D Cause Heart Palpitations
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
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.
Don’t Miss: Acid Reflux Heart Fluttering