calipers 2

Admittedly, complex electrophysiology is much easier with paper in hand, especially if you have calipers. The difference in how easy it is to figure out a tough rhythm is so marked that most mortals without calipers just give up (or miss critical findings).

Unfortunately, there is no one perfect way to get that with the site as it currently exists. There are three decent options I can think of (each explained below, and demonstrated in the 2 minute video):

  1. Quick and dirty: use a scrap of paper.
  2. Clean and more ergonomic (if you have a PC): the ‘Cardio Caliper’ free version.
  3. Be a nerdball: make a pair of screen calipers.

The quick way to check intervals and see if rhythms march out across the strip is to click on a zoomable image to bring up the full-screen zoom. Then put a piece of paper on the screen and mark off your desired interval with a pencil or a felt-tip pen so you don’t need to press hard. If you want to divide an interval in half, fold the paper and you’ve got it.

It ain’t pretty, but it works.


Obviously, the same paper-caliper hack works in the real world. This is nice because without calipers some of this stuff will break your head, but who carries calipers to codes?

Another good option, especially if you work on your own computer and have a PC, is the free version of the “Cardio Caliper” program, which superimposes an easily adjustable caliper over your screen, including an easily calibrated measurement. It’s actually quite ergonomic, and the free trial I installed is noninvasive and does everything I need for arrhythmia interpretation and I don’t think there is a time limit after which it stops working. I put a quick demo in the video above. Check it out or download here.

Neither of these options is as good as the real thing, though. So its worth mentioning that you can also just hold the calipers up against the screen, but be careful you don’t damage it- the common soft flatscreens would probably be easily damaged with the sharp point. Personally, if you are a regular and dedicated online ECG reader, I’d say it probably makes sense to make yourself a modified caliper– one with protected or dull or plastic points- so that you can enjoy the sheer ease of using calipers online without any fear of punching holes in your co-worker’s 36″ flatscreen when you’re showing off your mAd ArRhythMiA Skillz. The easiest way is just to slip a bit of something over the pointy bits and cut it down to size (butterfly tubing works nicely).

Some (but not all) of the inexpensive calipers have removable points, and all architectural calipers do so you could replace them with pointed plastic or pencil lead. Or you could sand down the sharp metal points of a four-dollar caliper to a smooth rounded point with a file, sandpaper, or a knife sharpener. Or a rock…  A DIY project for a rainy afternoon, perhaps.


1,391 total views, 1 views today

2 thoughts on “calipers

  1. Reply Ken Grauer, MD Apr 26,2013 08:48

    Your brief video works as an excellent illustration of the “poor man’s calipers” – and this is: i) always available (as long as you have a pen/pencil and paper); ii) usually works; and iii) is the next best thing. That said – it is not as good as a real pair of calipers, that works so much faster and better when you have a subtle change and/or exact measurement you need to check out and carry through a tracing … And yes – I did carry calipers to codes for 35 years. I did NOT use them during codes (saving the patient comes before admiring the rhythm) – but in a case, they are easy to carry – and it takes just seconds when there is a pause in the action to pull them out.

  2. Reply JF Portales Sep 7,2014 09:05

    Try camera ECG from the app store. You have all you need for a complete analysis of your ECG photos . Including screen shots. English and spanish available

Leave a Reply