Fast, accurate and easy-to-teach QT interval assessment: The triplicate concatenation method

Abstract

Background The gold standard method for assessing the QTcF (QT corrected for heart rate by Fridericia's cube root formula) interval is the “QTcF semiautomated triplicate averaging method” (TAM), which consists of measuring three QTcF values semiautomatically, for each 10-second sequence of a triplicate electrocardiogram set, and averaging them to get a global and unique QTcF value. Thus, TAM is time consuming. We have developed a new method, namely the “QTcF semiautomated triplicate concatenation method” (TCM), which consists of concatenating the three 10-second sequences of the triplicate electrocardiogram set as if they were a single 30-second electrocardiogram, and measuring QTcF only once for the triplicate electrocardiogram set. Aim To compare the TCM method with the TAM method. Methods Fifty triplicate electrocardiograms were read twice by an expert and a student using both methods (TAM and TCM). We plotted Bland–Altman plots to assess agreement between the two methods, and to compare the student and expert results. The time needed to read a set of 20 consecutive triplicate electrocardiograms was measured. Results Limits of agreement between TAM and TCM ranged from −8.25 to 6.75 ms with the expert reader. TCM was twice as fast as TAM (17.38 versus 34.28 min for 20 consecutive triplicate electrocardiograms). Bland–Altman plots comparing student and expert results showed limits of agreement ranging from −4.34 to 11.75 ms for TAM, and −1.2 to 8.0 ms for TCM. Conclusions TAM and TCM show good agreement for QT measurement. TCM is less time consuming than TAM. After a learning session, an inexperienced reader can measure the QT interval accurately with both methods.