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Man Versus Machine: Is There an Optimal Method for QT Measurements in Thorough QT Studies?

From Daiichi Medical Research, New Jersey, and the Department of Cardiology, Karolinska University Hospital, Stockholm, Sweden (Dr Darpo); and Clinical Development, Pfizer Inc, United Kingdom and United States (Dr Agin, Dr Kazierad, Mr Layton, Mr Muirhead, Dr Gray, Dr Jorkasky).

Electrocardiographic (ECG) recordings from 3 placebo-controlled thorough QT healthy volunteer studies were used to compare QT intervals obtained by manual measurement with those generated by ECG machines. The effect of the positive control was compared to placebo at each time point for data obtained from both sources. Both manual and automated techniques consistently demonstrated statistically significant prolongation of QTcF with the positive controls. The proportion of outlier values was small for both methods. The pairwise comparison between manual and automated uncorrected QT intervals demonstrated clear differences, with intervals derived from one machine on average 16 to 19 milliseconds shorter and from the other 7 milliseconds longer than the manually measured QT intervals, but these differences disappeared when analyzing QT change from baseline. Both manual and automated, commercially available QT algorithms demonstrated small statistically significant effects on the QTc interval induced by positive controls.

Key Words: QT prolongation • ECG methodology • manual methods • automated methods

Address for reprints: Gary Layton, MSc, Clinical Statistics, Clinical R & D, Pfizer Global Research and Development, Ramsgate Road, Sandwich, Kent, CT13 9NJ, United Kingdom; e-mail: gary.layton{at}pfizer.com

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