This calculator helps determine a patient's heart rate using an electrocardiogram (ECG) rhythm strip. Two common methods are presented: the "6-second strip method" and the "large box method" (for regular rhythms).
Typically 6 seconds for standard ECGs.
Count all the QRS complexes within the specified strip duration.
Only use this for perfectly regular rhythms. Measure the number of large boxes between two consecutive R waves.
Results:
Understanding the Calculations
Heart Rate Calculation Methods:
6-Second Strip Method: This is the most common and versatile method, especially for irregular rhythms. Count the number of QRS complexes within a 6-second strip and multiply that number by 10. This gives an approximate heart rate in beats per minute (bpm). Most ECG machines will print a 6-second strip.
Large Box Method: This method is quicker but only accurate for perfectly regular heart rhythms. Each large box on an ECG grid represents 0.20 seconds (5 mm wide). The heart rate can be calculated by dividing 300 by the number of large boxes between consecutive R-R intervals. For example, if there are 4 large boxes between R waves, the heart rate is 300 / 4 = 75 bpm.
Important Notes:
Ensure accurate counting of QRS complexes.
The 6-second strip method provides a more reliable estimate for irregular rhythms.
For very fast or very slow rhythms, or when precision is critical, other methods (like using the paper speed or the R-R interval in milliseconds) might be employed.
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function calculateHeartRate() {
var stripDuration = parseFloat(document.getElementById("stripDuration").value);
var qrsCount = parseFloat(document.getElementById("qrsCount").value);
var largeBoxCount = parseFloat(document.getElementById("largeBoxCount").value);
var resultDiv = document.getElementById("result");
var regularRhythmResultDiv = document.getElementById("regularRhythmResult");
resultDiv.innerHTML = "";
regularRhythmResultDiv.innerHTML = "";
// Method 1: 6-Second Strip Method
if (!isNaN(stripDuration) && stripDuration > 0 && !isNaN(qrsCount) && qrsCount >= 0) {
var heartRateFromStrip = qrsCount * (60 / stripDuration);
resultDiv.innerHTML = "Heart Rate (6-sec strip method): " + heartRateFromStrip.toFixed(0) + " bpm";
} else if (!isNaN(qrsCount) && qrsCount >= 0) {
// Allow calculation if stripDuration is not provided but qrsCount is valid, assuming standard 6 sec
var heartRateFromStrip = qrsCount * (60 / 6);
resultDiv.innerHTML = "Heart Rate (assuming 6-sec strip): " + heartRateFromStrip.toFixed(0) + " bpm";
} else {
resultDiv.innerHTML = "Please enter a valid number of QRS complexes and a strip duration (e.g., 6 seconds).";
}
// Method 2: Large Box Method (for regular rhythms)
if (!isNaN(largeBoxCount) && largeBoxCount > 0) {
var heartRateRegular = 300 / largeBoxCount;
regularRhythmResultDiv.innerHTML = "Heart Rate (large box method for regular rhythm): " + heartRateRegular.toFixed(0) + " bpm";
} else if (largeBoxCount === 0) {
regularRhythmResultDiv.innerHTML = "Large box count cannot be zero for this method.";
}
}