Question

If the distance between P waves is 9 boxes, then the atrial rate is approximately:

Group of answer choices

A. can't tell from the information provided

B. 187

C. 90

D.167

E. 99

180

Answer 1

Correct answer is option (A) can't tell from the information provided

In an ECG strip, atrial rate is determined by looking into P-P interval (time interval between P waves)

Equation to calculate rate is :

- Atrial Rate = 1500/Number of small boxes

ECG strip has large boxes and small boxes. In question, it is given that distance between P waves are 9 boxes.

ECG strip shows large boxes and small boxes.

One large box has width of 5 mm and one small box is 1 mm.

If there are 9 small boxes, rate would be 1500/9=166.66 ~ 167

If there are 9 large boxes, it means 9x5=45 small boxes.
Then rate = 1500/45 = 33.33 ~ 33

So, from the details given in the question, we cannot say the actual atrial rate.