How are the heavy black lines following an R wave numbered?

How are the heavy black lines following an R wave numbered?

• A. 100, 75, 60
• B. 300, 150, 100
• C. 75, 60, 50
• D. 300, 150, 100, 75, 60, 50

Answer: (D)

The heavy black lines that follow an R wave on an EKG represent the large boxes on the graph paper, each corresponding to a duration of 0.2 seconds (or 200 milliseconds). For interpreting heart rate using the EKG, the numbering of these heavy black lines is crucial as it provides a visual cue for calculating the heart rate based on the number of large boxes between R waves.

The correct series of numbers begins with 300 for the first heavy black line after the R wave, followed by 150 for the second line, 100 for the third, 75 for the fourth, 60 for the fifth, and finally 50 for the sixth line. This progression reflects a method of estimating heart rate based on the number of large boxes: 300 divided by the number of boxes between R waves gives the heart rate in beats per minute (bpm). Therefore, the option that lists all these numbers in the correct sequence is the most complete and accurate.

Understanding this numbering system is essential for effective EKG interpretation and helps clinicians quickly assess the heart rate during rhythm analysis.