Online QTc Calculator for normal and wide QRS (LBBB, RBBB, etc.)

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Online QTc Calculator for Normal and Wide QRS (LBBB, RBBB)

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There are 2 parts to this QTc Calculator. You should immediately see Part-1. You may need to scroll over to see Part-2 of this embedded Excel table.

• Part-1: Calculation of the QTc by the 5 most commonly used methods. Enter the Heart Rate and the QT interval that you measure (in msec.) — and after you click Return, you should see the 5 values!
• Part-2: Calculation of the modified QTc if the QRS is wide (ie, because of LBBB, RBBB, IVCD). Enter the Heart Rate — the QRS duration (in msec.) — and the QT interval that you measure (in msec.) — and the Rautaharju QTc (modified to account for QRS widening) should come up.
• The Bogossian value that comes up if for the QT has now been "modified" to account for the widened QRS. After getting this Bogossian QT value — Plug this QT value in to Part-1 to get the modified QTc.

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NOTE: This QT calculator has been created by Arron Pearce. 

• The calculator is a work in progress — as we aim to continue optimizing making it. In the meantime — we welcome your feedback (Send to Ken Grauer, MD — ekgpress@mac.com).
• The calculator was created on an Excel file, that we have embedded in this blog post in Dr. Smith’s ECG Blog (Easy access available by clicking in the Menu Bar at the TOP of every page in Dr. Smith’s ECG Blog.)
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• ATTENTION: Some users have reported that the Calculator is not working for them ... For some — this appears to be browser specific (ie, whether using Safari - Foxglove - Chrome, etc.) — but for me, the Calculator is working on Mac computer, ipad & iphone in all 3 of the above browsers.
• KEY: Sometimes the Calculator needs to be "woken up". For example, on smart phone or tablet — You may need to tap twice, quickly and firmly over the box where you enter data — and then it works! Similarly, on computer — You may need to tap more than once — and then it works.
• Please — Let me know if you are unable to get the application to work (and if so — what kind of device and which browsers is it not working on. Thank you! ).

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Grauer: The fact that you will see slightly different values in the above QTc calculator conveys the lack of universal agreement on QTc calculation at different heart rates. That said — 4 of the 5 methods are generally quite close to each other (You might mentally take an average of those readings for the value you select — or pick your "favorite" among the methods).

• In our experience — We find the Bazett method potentially problematic, in that it tends to overestimate the QTc for faster heart rates — and underestimate the QTc for slower heart rates.
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• For QTc estimation when the QRS is wide — I find the Bogossian method to be problematic because the simplified formula that is used by the Bogossian method to calculate the modified QT = QT minus ~50% of QRS duration. But since all this entails is to subtract ~50% of QRS width (ie, for a widened QRS = 0.16 msec — 0.08 msec would be subtracted from the QT you measured) — there is no compensation for any change in heart rate (and since we know the QTc is altered by faster or slower heart rates — I believe the Bogossian method is fatally flawed).

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ADDENDUM (1/13/2025):

Our goal for this QTc Calculator is to facilitate QTc estimation (for any tracing — regardless of whether the QRS is normal or wide).

• We've added a quick link to the QTc calculator in the Menu at the top of every page in Dr. Smith's ECG Blog (Figure-1).

Figure-1: Quick link to the QTc Calculator in the Meno on every Blog page.

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Add a quick link on your smart phone!

• Figures-2 and -3 below show how to easily do this on iphone.
• To find out how to do this for other brand smart phone — Simply do a Google Search for, "Can you add link to home screen of Android? (or other brand).

Figure-2: To add a quick link on iphone — GO TO the QTc Calculator page in Dr. Smith's ECG Blog. Once there — Click in the bottom Menu on the icon within the BLUE rectangle (LEFT panel).
This takes you to the page shown in the RIGHT panel — Scroll down that page until you get to, "Add to Home Screen". 

Figure-3: After the actions in Figure-2 — You'll be taken to the page shown in the LEFT panel. You need to choose a short title in order to "fit" on your iphone screen. We suggest, "QTc Calculator". Then click on "Add" — and you are done! You'll find your quick link to the QTc Calculator on the home screen of your iphone (within the YELLOW rectangle, as shown in the RIGHT panel).

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  — Please give us your feedback! (Ken Grauer, MD — ekgpress@mac.com )

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