Skip to main content
. 2019 Jul;8(3):161–165. doi: 10.15420/aer.2019.8.3.G1

Figure 1. Tangent Method of QTc Measurement.

Figure 1.

Leads II or V5 may be measured. The tangent of the downslope of the T wave is taken to the baseline of the ECG and the QT interval measured in seconds between the Q wave and point where the tangent hits the baseline. It is important to use seconds as the measurement rather than milliseconds in the calculation if using a calculator or the QTc value will be incorrect. An average of 3–5 beats should be measured. A number of online or mobile apps can be employed to simplify the calculation of QTc, including https://www.mdcalc.com/corrected-qt-interval-qtc and https://www.omnicalculator.com/health/qtc.