Final answer:
You can determine the heart rate on an ECG by measuring the time intervals between the QRS complexes and using a standard calculation based on the number of large squares counted.
Step-by-step explanation:
To determine the heart rate using an electrocardiogram (ECG), you will analyze the time intervals between the QRS complexes, which represent the depolarization of the ventricles. Each small square on the ECG paper represents 0.04 seconds, and each large square, composed of 5 small squares, represents 0.20 seconds. To calculate the heart rate in beats per minute (bpm), find the number of large squares between successive QRS complexes and divide that number into 300 (since there are 300 large squares in a minute). If the time between beats is constant, this method will give you a reliable heart rate.
For example, if there are 4 large squares between each QRS complex, the heart rate is 300 divided by 4, which equals 75 bpm. Remember that an abnormal electrical pattern prior to the QRS complexes or an increased frequency between them may indicate changes in pulse or heart rate.