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function calculateBPM() {
// Get input values using var
var durationElement = document.getElementById("stripDuration");
var countElement = document.getElementById("rWaveCount");
var resultContainer = document.getElementById("resultContainer");
var resultValue = document.getElementById("bpmResult");
var resultInterp = document.getElementById("bpmInterp");
var duration = parseFloat(durationElement.value);
var rWaves = parseFloat(countElement.value);
// Validation
if (isNaN(rWaves) || rWaves < 0) {
alert("Please enter a valid number of R-Waves.");
return;
}
if (isNaN(duration) || duration <= 0) {
alert("Invalid duration selected.");
return;
}
// Calculation: (Count / Seconds) * 60 Seconds = BPM
// For a 6 second strip, this effectively multiplies the count by 10.
var bpm = Math.round((rWaves / duration) * 60);
// Interpretation logic
var classification = "";
var color = "";
if (bpm = 60 && bpm 100) {
classification = "Tachycardia (Fast Heart Rate)";
}
// Display Results
resultContainer.style.display = "block";
resultValue.innerHTML = bpm + "
How to Calculate Heart Rate in Irregular ECG
Calculating the heart rate from an Electrocardiogram (ECG) is a fundamental skill for healthcare professionals. When the heart rhythm is regular, methods like the 300 Rule (counting large boxes) or the 1500 Rule (counting small boxes) offer high precision. However, these methods fail when the rhythm is irregular, such as in cases of Atrial Fibrillation (AFib), frequent premature beats, or sinus arrhythmia.
In these scenarios, the distance between R-waves (the R-R interval) varies constantly, making single-interval calculations inaccurate. The standard approach for irregular rhythms is the 6-Second Method.
The 6-Second Method Explained
The 6-second method is a statistical approximation that provides the mean heart rate over a specific period. It is less precise than the 1500 rule but is the only reliable manual method for irregular rhythms.
The Formula
The logic is simple: If you count how many times the heart beats in 6 seconds and multiply that by 10, you get the number of beats in 60 seconds (1 minute).
Heart Rate (BPM) = (Number of R Waves in 6 seconds) × 10
Step-by-Step Calculation Guide
- Identify a 6-Second Strip: Most ECG paper has hash marks at the top or bottom indicating 1-second or 3-second intervals. A 6-second strip consists of 30 large boxes (since 1 large box = 0.20 seconds).
- Count the QRS Complexes: Count the number of R-waves (the tall spikes) that fall strictly within the 6-second marker lines.
- Note: If a QRS complex falls exactly on the starting line, it is typically not counted. If it falls on the ending line, it is counted. Consistency is key.
- Multiply by 10: Take the count and multiply it by 10 to get the Beats Per Minute (BPM).
Example Calculation
Let's look at a realistic example for a patient with Atrial Fibrillation:
- You select a 6-second strip on the ECG tracing.
- You count 11 R-waves within that timeframe.
- Calculation: 11 × 10 = 110 BPM.
- Result: This indicates Tachycardia (Rapid Ventricular Response).
Alternative: The 10-Second Method
Sometimes, a 12-lead ECG provides a 10-second rhythm strip at the bottom of the page. The math adapts accordingly:
Heart Rate = (Number of R Waves in 10 seconds) × 6
This method is slightly more accurate than the 6-second method because it averages the rate over a longer duration, smoothing out the irregularities further.
Interpreting the Results
Once you have calculated the rate, categorize it clinically:
- Bradycardia: Less than 60 BPM.
- Normal: 60 to 100 BPM.
- Tachycardia: Greater than 100 BPM.
Medical Disclaimer: This calculator and article are for educational and informational purposes only. It does not constitute medical advice, diagnosis, or treatment. Always consult with a qualified healthcare provider for interpretation of ECG results and patient care.