Number of ECG Replicates and QT Correction Formula Influences the Estimated QT Prolonging Effect of a Drug

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Introduction:The present analysis addressed the effect of the number of ECG replicates extracted from a continuous ECG on estimated QT interval prolongation for different QT correction formulas.Methods:For 100 healthy volunteers, who received a compound prolonging the QT interval, 18 ECG replicates within a 3-minute window were extracted from 12-lead Holter ECGs. Ten QT correction formulas were deployed, and the QTc interval was controlled for baseline and placebo and averaged per dose level.Results:The mean prolongation difference was >4 ms for single and >2 ms for triplicate ECG measurements compared with the 18 ECG replicate mean values. The difference was <0.5 ms after 14 replicates. By contrast, concentration–effect analysis was independent of replicate count and also of the QT correction formula.Conclusion:The number of ECG replicates impacted the estimated QT interval prolongation for all deployed QT correction formulas. However, concentration–effect analysis was independent of both the replicate number and correction formula.

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