function calculateECGRate() {
var complexesInput = document.getElementById("numComplexes");
var durationInput = document.getElementById("stripDuration");
var resultBox = document.getElementById("resultDisplay");
var bpmText = document.getElementById("bpmResult");
var interpText = document.getElementById("interpretation");
var complexes = parseFloat(complexesInput.value);
var duration = parseFloat(durationInput.value);
// Validation
if (isNaN(complexes) || complexes < 0) {
alert("Please enter a valid number of R waves.");
return;
}
if (isNaN(duration) || duration <= 0) {
alert("Please select a valid strip duration.");
return;
}
// Calculation: (Count / Duration) * 60
// For a 6 second strip, this effectively equals Count * 10
var heartRate = (complexes / duration) * 60;
// Round to nearest whole number
heartRate = Math.round(heartRate);
// Interpretation
var classification = "";
var classificationColor = "";
if (heartRate = 60 && heartRate 100) {
classification = "Tachycardia (Fast Heart Rate)";
}
// Display results
resultBox.style.display = "block";
bpmText.innerHTML = heartRate + " BPM";
interpText.innerHTML = "Interpretation: " + classification + "Based on a " + duration + "-second strip analysis.";
}
Calculating Heart Rate for Irregular Rhythms
Accurately determining heart rate from an electrocardiogram (ECG/EKG) is a fundamental skill in cardiology and emergency medicine. However, standard calculation methods used for regular rhythms—such as the "300 Method" (counting large boxes) or the "1500 Method" (counting small boxes)—often yield inaccurate results when the patient has an irregular heart rhythm.
Irregular rhythms, such as Atrial Fibrillation (AFib), Multifocal Atrial Tachycardia (MAT), or frequent ectopy, require a different approach. The distance between R-waves (the R-R interval) changes from beat to beat, making it impossible to use a single interval to determine the rate for the entire minute.
The 6-Second Method
The gold standard for calculating the ventricular rate of an irregular rhythm is the **6-Second Method**. This technique is simple, quick, and provides the mean heart rate over a specific period, smoothing out the irregularities.
How to Use the 6-Second Method
Obtain the Strip: Identify a 6-second interval on the ECG paper. Most ECG paper has markers (often small vertical lines or hashes) at the top or bottom indicating 3-second intervals. Two of these 3-second sections equal 6 seconds. Alternatively, counting 30 large boxes (0.20 seconds each) horizontally equals exactly 6 seconds.
Count the R Waves: Count the number of complete QRS complexes (R waves) falling within that 6-second window. Do not count p-waves or t-waves.
Multiply by 10: Since 6 seconds is one-tenth of a minute, multiply your count by 10 to get the beats per minute (BPM).
Example: If you count 8 R waves in a 6-second strip, the calculation is 8 × 10 = 80 BPM.
Alternative: The 10-Second Method
For even greater accuracy, especially with highly erratic rhythms, a 10-second strip may be used. In this case, you count the R waves and multiply by 6 (since 10 × 6 = 60 seconds). This calculator allows you to select either duration.
Clinical Interpretations
Heart Rate Range
Classification
Clinical Notes
< 60 BPM
Bradycardia
May cause dizziness or fainting if cardiac output is compromised. Common in athletes or during sleep, but may indicate heart block or medication effects in others.
60 – 100 BPM
Normal
Standard resting rate for adults. Confirms adequate perfusion in most hemodynamically stable patients.
> 100 BPM
Tachycardia
May result from stress, fever, dehydration, or arrhythmias like rapid Atrial Fibrillation. Requires investigation of the underlying cause.
Why the 300 Method Fails for Irregular Rhythms
The 300 method involves dividing 300 by the number of large boxes between two consecutive R waves. In an irregular rhythm, the distance between the first two R waves might be 3 boxes (Rate = 100), while the distance between the next two might be 5 boxes (Rate = 60). Calculating the rate based on just one interval would give a wildly incorrect picture of the patient's actual cardiac output per minute. The 6-second method averages these variations effectively.