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Understanding ECG Heart Rate Calculation
The electrocardiogram (ECG or EKG) is a vital diagnostic tool that records the electrical activity of the heart. One of the most crucial pieces of information derived from an ECG is the heart rate, which tells us how fast the heart is beating per minute.
The heart rate can be calculated from an ECG trace using the R-R interval, which is the time between two consecutive R waves on the QRS complex. The R wave represents the depolarization of the ventricles, a key event in the heart's electrical cycle.
How the Calculator Works:
- R-R Interval (seconds): This is the measured time in seconds between two successive R-R peaks on the ECG waveform. A shorter R-R interval indicates a faster heart rate, and a longer interval indicates a slower rate.
- ECG Sampling Rate (Hz): This is the number of data points collected by the ECG machine per second. It's essential for accurately measuring intervals in digital ECGs. Higher sampling rates generally lead to more precise measurements.
The formula used in this calculator is derived from the relationship between the R-R interval and the total number of beats in a minute.
The Calculation Formula:
Heart Rate (beats per minute) = (60 seconds/minute) / (R-R Interval in seconds)
Alternatively, if you have the number of small boxes between R-R peaks and the duration of each small box (often 0.04 seconds), you can calculate the R-R interval first:
R-R Interval (seconds) = Number of Small Boxes * Duration of Small Box (seconds)
This calculator simplifies this by directly taking the R-R interval in seconds. The sampling rate is often implicitly used in the device that provides the R-R interval, but is included here for completeness in understanding digital ECG data processing. The primary calculation relies on the R-R interval.
Interpreting the Results:
A normal resting heart rate for adults typically ranges from 60 to 100 beats per minute (bpm). Rates below 60 bpm are considered bradycardia, and rates above 100 bpm are considered tachycardia. However, these ranges can vary based on factors like age, fitness level, and medical conditions.
function calculateHeartRate() {
var rRIntervalInput = document.getElementById("rRInterval");
var samplingRateInput = document.getElementById("samplingRate");
var resultDiv = document.getElementById("result");
var rRInterval = parseFloat(rRIntervalInput.value);
var samplingRate = parseFloat(samplingRateInput.value);
if (isNaN(rRInterval) || isNaN(samplingRate) || rRInterval <= 0 || samplingRate <= 0) {
resultDiv.innerHTML = "Please enter valid positive numbers for R-R Interval and Sampling Rate.";
return;
}
// The primary calculation for heart rate from R-R interval in seconds.
// The sampling rate is crucial for obtaining an accurate R-R interval measurement
// from raw ECG data, but the direct calculation of bpm uses the interval itself.
var heartRateBPM = 60 / rRInterval;
// Round to two decimal places for a cleaner display
heartRateBPM = heartRateBPM.toFixed(2);
resultDiv.innerHTML = "Calculated Heart Rate: