6-Second Strip HR Calculator
Note: This method is used primarily for irregular rhythms on an EKG/ECG strip.
Understanding the 6-Second Strip Method
Calculating the heart rate from an electrocardiogram (ECG or EKG) strip is a fundamental skill for healthcare providers. While there are several methods available—such as the 300, 150, 100 method or the Sequence method—the 6-second strip method is the most versatile, especially when dealing with irregular heart rhythms.
How the Calculation Works
On standard ECG paper, time is measured along the horizontal axis. Each "large block" represents 0.20 seconds. Therefore, 30 large blocks equal exactly 6 seconds (30 x 0.20 = 6). To calculate the beats per minute (BPM) using this timeframe:
- Step 1: Identify a 6-second section of the ECG rhythm strip (look for the 3-second marks at the top of the paper or count 30 large boxes).
- Step 2: Count the number of QRS complexes (the "spikes" or R-waves) within that 6-second window.
- Step 3: Multiply that number by 10.
Since there are 60 seconds in a minute, multiplying the number of beats found in 6 seconds by 10 gives you the estimated heart rate for one full minute.
Example Calculation
| Scenario | QRS Count in 6 Seconds | Formula | Resulting Heart Rate |
|---|---|---|---|
| Regular Rhythm | 7 beats | 7 x 10 | 70 BPM |
| Tachycardia | 12 beats | 12 x 10 | 120 BPM |
| Bradycardia | 4 beats | 4 x 10 | 40 BPM |
When to Use the 6-Second Method
While the 1500 method (1500 divided by the number of small boxes between R-waves) is more precise for regular rhythms, it fails when the heart rate is inconsistent. The 6-second strip method is the gold standard for irregular rhythms, such as Atrial Fibrillation (A-fib), because it averages the heart rate over a longer period, providing a more clinically relevant estimation of the patient's hemodynamic status.
Key Tips for Accuracy
- Identify the R-Wave: Always count the R-wave (the highest point of the QRS complex). If a QRS complex falls exactly on the line at the beginning or end of the 6-second window, follow your facility's specific protocol for inclusion.
- Check the Calibration: Ensure the ECG paper speed is set to the standard 25 mm/sec. If the speed is different, the 30-box rule for 6 seconds will not apply.
- Look for Markers: Most ECG paper has small vertical ticks at the top. The distance between three ticks usually represents 6 seconds.
Summary of EKG Math
The beauty of the 6-second rule lies in its simplicity. It requires no complex division and can be performed at the bedside in seconds. Whether the rhythm is regular or irregular, simply count the spikes and add a zero to the end of your count to find the beats per minute.