Heart Rate: — bpm
Understanding Heart Rate Calculation from an ECG
An electrocardiogram (ECG or EKG) is a vital diagnostic tool that records the electrical activity of the heart. One of the key pieces of information an ECG provides is the heart rate, which is the number of times the heart beats per minute. While ECGs display complex waveforms, calculating the heart rate from it is a straightforward process, especially when you focus on the R-R interval.
The R-R Interval
The R-R interval is the time duration between two consecutive R waves on an ECG tracing. The R wave is typically the tallest and most prominent peak in the QRS complex, representing the ventricular depolarization – the contraction of the ventricles. Measuring the time between these R waves gives us a direct indication of the heart's rhythm.
How to Calculate Heart Rate from ECG
The fundamental principle is that if you know the time between two heartbeats (the R-R interval), you can determine how many beats would occur in a minute. The standard formula used is:
Heart Rate (bpm) = 60 / R-R Interval (seconds)
This formula works because there are 60 seconds in one minute. By dividing 60 by the duration of one cardiac cycle (represented by the R-R interval), we get the number of cycles, or heartbeats, that occur within that minute.
Example Calculation
Let's say you measure the R-R interval on an ECG tracing and find it to be 0.75 seconds. Using the formula:
Heart Rate = 60 / 0.75 = 80 bpm.
This means the heart is beating at a rate of 80 times per minute.
Accuracy and Considerations
For the most accurate calculation, it's best to measure the R-R interval over several beats and calculate an average. This helps to account for normal variations in heart rhythm. The calculator above uses a single R-R interval input for simplicity. In clinical settings, specialized ECG machines often perform these calculations automatically and continuously.