The electrocardiogram, or ECG, measures the electrical activity of the heart over a specified period of time. The measurement takes place through electrodes applied to the skin that transmit the signal to an external device. Although the heart rate is easily detected through the wrist, an ECG may be needed to evaluate possible damage to the heart, the effectiveness of a drug or implant, to understand if the muscle is beating normally, or to identify its location and size. of the heart chambers. This test is also done to monitor heart conditions, to diagnose them, or to know if an individual is healthy enough to undergo surgery.
Steps
Method 1 of 2: Exploiting the Distance Between QRS Complexes
Step 1. Be aware of the normal appearance of the echocardiograph
This way, you can figure out which area a heartbeat represents. You can derive the frequency starting from the duration of a beat shown on the graph; this contains a P wave, the QRS complex and the ST segment. You need to pay special attention to the QRS complex, as it is one of the simplest ways to calculate heart rate.
- The P wave has a semicircular appearance and is located to the right just before the QRS complex which is high. It represents the electrical activity of the depolarization of the atria, the two small chambers found in the upper part of the heart.
- The QRS complex is the highest and most visible wave on a trace; it typically has a pointed shape, almost like a very thin triangle and is easy to recognize. It indicates the electrical activity of the ventricles ("depolarization of the ventricles"), the two large chambers located in the lower part of the heart muscle that pump blood around the body.
- The ST segment comes immediately after the QRS complex and is the flat part of the trace that precedes the next semicircular wave (the T wave). Its importance lies in the fact that it provides valuable information regarding a potential heart attack.
Step 2. Identify the QRS complex
It generally represents the highest "peak" of the graph and which repeats cyclically along the ECG trace. It is a tall, thin tip (in a healthy individual) and occurs evenly, equidistant in the graph. For this reason, you can use the distance between two consecutive QRS complexes to calculate your heart rate.
Step 3. Measure the space between the QRS complexes
The next step is to establish the number of squares present between two consecutive peaks. The paper on which the ECG trace is represented generally shows large and small squares; in this case, you have to use the large ones as a reference and count how many there are between the peak of one QRS complex and the next.
- A fractional number is often obtained because the complexes do not fall exactly on the line that separates the squares; for example, you may find that there are 2, 4 or 3, 6 squares between two consecutive QRS complexes.
- In each large square there are generally 5 small ones which allow an approximate calculation of the distance between two QRS peaks with an accuracy of 0.2 units (since 1 large square is divided into 5 sections, each section represents 0.2 units).
Step 4. Divide the number 300 by the number of the squares you counted earlier
Once you have found the distance between two QRS complexes (eg 3, 2 squares), perform this calculation to find the heart rate: 300/3, 2 = 93, 75. Round the result to the nearest whole number, in this case the frequency corresponds to 94 beats per minute.
- Note that a normal value is between 60 and 100 beats; knowing this detail helps you to understand if you are doing the calculations correctly.
- However, this reference is only indicative. Many athletes who are in excellent physical condition can have a much lower heart rate.
- There are also pathologies that can cause an unhealthy reduction in frequency (pathological bradycardia) and others that can accelerate it in an equally unnatural way (pathological tachycardia).
- Talk to your doctor if the person you're measuring heart rate is experiencing abnormal values.
Method 2 of 2: Using the Six Seconds Technique
Step 1. Draw two lines on the ECG strip
The first should be on the left of the sheet and the second precisely after 30 large squares; this distance is exactly 6 seconds.
Step 2. Count the number of QRS complexes present in the graph section between the two lines
Remember that the QRS complex is the highest peak of each wave representing a heartbeat. Add the number of complexes between the two lines and note the result.
Step 3. Multiply that value by 10
Since 10x6 seconds corresponds to 60 seconds (1 minute), this operation lets you know how many beats there are in a minute (the time interval used to measure heart rate). For example, if you count 8 beats in 6 seconds, you get a rate of 8x10 = 80 beats per minute.
Step 4. Know that this method is particularly effective in the case of arrhythmias
If the heart rhythm is regular, the first method described in this article is very accurate because the distance between two consecutive QRS peaks presumably remains constant throughout the ECG graph. In the presence of arrhythmia, however, the QRS complexes are not equidistant from each other, the 6-second method is therefore more suitable because it allows you to calculate the average of the distances between one beat and another, providing a more accurate value.
