Count every R-wave spike visible in the selected timeframe.
6 Seconds (30 Large Boxes)
3 Seconds (15 Large Boxes)
10 Seconds (Full Standard Strip)
Estimated Ventricular Rate:
— BPM
How to Calculate Heart Rate in Irregular Rhythms
Standard ECG calculation methods like the "300 Rule" or "1500 Rule" rely on constant intervals between beats. When a rhythm is irregular (such as in Atrial Fibrillation), these methods fail because the distance between R-waves varies constantly.
The 6-Second Method: This is the gold standard for irregular heart rates. You count the number of QRS complexes within a 6-second window on the ECG paper and multiply that number by 10. This provides the average number of beats per minute (BPM).
Visual Identification on Paper:
1 Large Box: 0.2 seconds
5 Large Boxes: 1 second
15 Large Boxes: 3 seconds
30 Large Boxes: 6 seconds
Example Calculation
If you identify an "irregularly irregular" rhythm on an ECG strip and count 9 QRS complexes within 30 large boxes (6 seconds):
9 complexes × 10 = 90 BPM (Average Rate)
Why it Matters
Accurate rate calculation for irregular rhythms is vital for diagnosing tachycardia or bradycardia in patients with arrhythmias. For instance, in Atrial Fibrillation, the ventricular response rate determines whether a patient needs rate-control medication or urgent intervention.
function calculateIrregularRate() {
var qrs = document.getElementById("qrsCount").value;
var duration = document.getElementById("stripDuration").value;
var resultDiv = document.getElementById("ecg-result-area");
var bpmValue = document.getElementById("bpmValue");
var interpretationText = document.getElementById("interpretationText");
if (qrs === "" || qrs <= 0) {
alert("Please enter a valid number of QRS complexes.");
return;
}
var qrsNum = parseFloat(qrs);
var durationNum = parseFloat(duration);
// Formula: (Count / Duration in seconds) * 60 seconds
var bpm = (qrsNum / durationNum) * 60;
var finalBpm = Math.round(bpm);
bpmValue.innerHTML = finalBpm + " BPM";
resultDiv.style.display = "block";
var message = "";
if (finalBpm = 60 && finalBpm 100) {
message = "Interpretation: Tachycardia (Fast heart rate).";
}
interpretationText.innerHTML = message;
}