Short-term repeatability of electrocardiographic Tpeak–Tend and QT intervals

BackgroundThe electrocardiographic (ECG) Tpeak–Tend interval (TpTe) is associated with arrhythmias and sudden cardiac death. TpTe offers a supplementary measure for the QT interval (QT), yet its repeatability has not been established.PurposeEvaluate short-term repeatability of TpTe and QT.MethodsFour ECGs were obtained on sixty participants. The sources of variation, intra-class correlation coefficient (ICC) – an index of reproducibility – and minimal detectable change (MDC) were estimated for TpTe and QT. The impact of repeated measurements on repeatability was estimated for a hypothetical clinical trial designed to detect drug-induced prolongation of TpTe and QT.ResultsWe used heart rate-adjusted QT [(QT)a] but TpTe in the study group was rate-invariant. The ICC [95% confidence interval (CI)] was 0.77 (0.69, 0.85) for TpTe, 0.75 (0.65, 0.85) for QT and 0.60 (0.47, 0.73) for (QT)a. The MDC (ms) was 21, 32 and 26 for TpTe, QT and (QT)a respectively.ConclusionTpTe has excellent repeatability supporting its use as a supplement to QT in observational and clinical studies.