Calculate Heart Rate from Irregular ECG
This calculator helps estimate your heart rate from an electrocardiogram (ECG) tracing, especially useful when the rhythm is irregular.
Estimated Heart Rate Range:
Understanding Heart Rate Calculation from ECG
An electrocardiogram (ECG or EKG) is a non-invasive test that records the electrical activity of the heart. This activity is displayed as a series of waves and complexes on a grid, typically printed on specialized graph paper. The paper moves at a standard speed, and has grid lines to help measure intervals and durations.
Standard ECG Paper
Standard ECG paper has small squares that are 1 mm wide and 1 mm high. Several small squares form larger squares that are 5 mm wide and 5 mm high.
- Paper Speed: The most common paper speed is 25 mm/s. This means that for every second of cardiac activity, 25 mm of paper is used.
- Small Squares: Each small square (1 mm) represents 0.04 seconds (40 milliseconds) at a speed of 25 mm/s.
- Large Squares: Each large square (5 mm) represents 0.20 seconds (200 milliseconds) at a speed of 25 mm/s.
Calculating Heart Rate
For regular rhythms, you can use simpler methods like counting large squares between R-waves or the "300 method." However, for irregular rhythms, it's more accurate to measure the shortest and longest RR intervals (the time between consecutive R-waves of the QRS complex) and calculate a heart rate range.
The Formula for Irregular Rhythms:
The core principle is to determine the heart rate based on the time duration of the shortest and longest RR intervals. Since heart rate is measured in beats per minute (BPM), we need to convert the measured intervals (in millimeters on the ECG paper) into time and then into beats per minute.
- Calculate RR Interval Duration (in seconds):
RR Interval Duration (seconds) = RR Interval (mm) / ECG Paper Speed (mm/s) - Calculate Heart Rate (in BPM):
Heart Rate (BPM) = 60 seconds / RR Interval Duration (seconds)
By applying this to both the shortest and longest RR intervals, we get a range representing the heart's rate variation.
Example Calculation
Let's assume:
- ECG Paper Speed = 25 mm/s
- Longest RR Interval Measured = 30 mm
- Shortest RR Interval Measured = 15 mm
Calculating for the Longest RR Interval:
- Longest RR Interval Duration = 30 mm / 25 mm/s = 1.2 seconds
- Estimated Heart Rate (Low End) = 60 seconds / 1.2 seconds = 50 BPM
Calculating for the Shortest RR Interval:
- Shortest RR Interval Duration = 15 mm / 25 mm/s = 0.6 seconds
- Estimated Heart Rate (High End) = 60 seconds / 0.6 seconds = 100 BPM
Therefore, the estimated heart rate range for this irregular rhythm is 50-100 BPM.
Disclaimer: This calculator is for informational purposes only and should not be used for medical diagnosis. Always consult a qualified healthcare professional for any health concerns.