Certified Cardiographic Technician (CCT) Practice Exam 2025 – Your All-in-One Guide to Exam Success!

The calculation of heart rate from an ECG strip is based on the relationship between time and the number of R-R intervals—these intervals represent the time between successive R wave peaks in the QRS complex. One common method for calculating heart rate involves counting the number of large squares between R-R intervals on the ECG. Each large square on the ECG paper represents 0.2 seconds (200 milliseconds). Consequently, the heart rate can be roughly calculated by dividing the number of large squares into 300, since there are 300 large squares in one minute (60 seconds divided by 0.2 seconds per square equals 300). This method provides a quick estimation of the heart rate based on the pattern of the ECG and is widely used by healthcare professionals.

In contrast, methods such as counting the number of small squares or measuring the distance between P waves do not reliably yield the heart rate and do not consider the full rhythm of the heart as represented by the R-R intervals. Counting R-R intervals and dividing by 60 may incorrectly simplify the assessment, as it doesn't take into account the specific structure of the intervals represented on the ECG. Thus, the correct answer aligns with the accepted method used in clinical practice for calculating heart rate from ECG data.