How to properly measure intervals in an EKG

Specialties Cardiac

Published

Hi guys,

Is there a proper way of measuring PR, QRS and QT intervals in an EKG strip? I swear I'm always 0.02 or 0.04 off (when practicing in my EKG book).

Thanks!

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Just remember the small boxes are .04sec and the large are .20sec when measuring use a good set of calipers. In a pinch I use a post it note and mark for measurements. In the ICU where I used to work as a Tele Tech I had software that measured. Its important to look for ST changes and QT elongation. If your other measurements are not coming out exact as either software or another RN reading it is probably not a big deal as long as you're looking for those changes stated above. I always had the charge nurse look at any I had questions or concerns or I spoke to one of our cardiologists. It's more of the nurses responsibilities to look at the whole picture for changes.

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Do you average out the intervals or do you take just one PR interval (for instance) when calculating an accurate measurement? Unless it's appropriate to document a range (ie. 0.12-0.14). Thanks!

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As far as measuring out PR intervals I measure the first clear one and then marched them out to check for regularity. Any changes then I started looking for other signs.

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Specializes in RETIRED Cath Lab/Cardiology/Radiology.

Do you use calipers or just eyeball it (or use "poor man's calipers" = a piece of paper slid under the rhythm, marked to measure)?

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Specializes in Critical Care, ED, Cath lab, CTPAC,Trauma.

Be sure to use calipers.....ECG Primer: Calculations

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Do you use calipers or just eyeball it (or use "poor man's calipers" = a piece of paper slid under the rhythm, marked to measure)?

Yes. Guilty as charged. I use poor man's calipers. Haha.

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Specializes in ER, progressive care.

Yup, use some calipers, measure whatever you are measuring and then march it out on the rest of the strip to look for consistency.

If I am (for example) measuring the QT interval, it helps to find the beginning of that Q directly on the line on a little box (remember = 0.04 sec) instead of in the middle of the little box, if that makes any sense at all, lol.

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Yup, use some calipers, measure whatever you are measuring and then march it out on the rest of the strip to look for consistency.

If I am (for example) measuring the QT interval, it helps to find the beginning of that Q directly on the line on a little box (remember = 0.04 sec) instead of in the middle of the little box, if that makes any sense at all, lol.

Yes it does make sense. You mean to say that you look for a beat with the Q directly on the vertical line, right? Lol

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I was taught that 0.02 or 0.04 or whatever is no big deal as long as it is WNL. It may never be what someone else says they measured.

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Specializes in ER, progressive care.
Yes it does make sense. You mean to say that you look for a beat with the Q directly on the vertical line, right? Lol

Lol yes. I don't know why I made that sound so complicated.

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Specializes in cardiac.

I don't think 0.02 or 0.04 is a big deal as long as there is not a noticeable change in the PR interval or QRS or QT during your shift. Always make sure to measure that QT (a lot of nurses don't) to make sure the medications you're giving don't elongate or change it in any way. Best of luck!!

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