How to Calculate Heart Rate from an ECG
Understanding your heart rate is crucial for monitoring your cardiovascular health. An electrocardiogram (ECG or EKG) is a common diagnostic tool that records the electrical activity of the heart. One of the key pieces of information derived from an ECG is the heart rate, which indicates how many times your heart beats per minute (bpm). Calculating this accurately from an ECG strip can be done using a few simple methods.
Methods for Calculating ECG Heart Rate
1. The 6-Second Strip Method (Most Common for Irregular Rhythms)
This method is generally preferred for irregular rhythms as it provides an average heart rate over a 6-second interval. Most ECG machines print a 6-second strip as standard.
- Locate the 6-second interval on the ECG strip. This is usually marked at the top or bottom of the tracing.
- Count the number of QRS complexes (the large, spiky waves that represent ventricular depolarization) within that 6-second interval.
- Multiply the number of QRS complexes by 10. The result is your average heart rate in beats per minute (bpm).
Formula: Heart Rate (bpm) = Number of QRS complexes in 6 seconds × 10
2. The R-R Interval Method (Most Accurate for Regular Rhythms)
This method is highly accurate for regular heart rhythms. It involves measuring the time between two consecutive R waves (the peak of the QRS complex).
- Using Large Boxes: If the rhythm is regular, count the number of large boxes (each representing 0.20 seconds) between two consecutive R waves. Divide 300 by this number.
- Using Small Boxes: If the rhythm is regular, count the number of small boxes (each representing 0.04 seconds) between two consecutive R waves. Divide 1500 by this number.
Formulas:
- Heart Rate (bpm) = 300 / Number of large boxes between R-R intervals
- Heart Rate (bpm) = 1500 / Number of small boxes between R-R intervals
These methods provide reliable ways to assess your heart rate from an ECG. For inconsistent rhythms, the 6-second method offers a practical average, while the R-R interval method is precise for steady rhythms.