Performance of an electrocardiographic analysis system: implications for pharmacodynamic studies

The performance of a digital data-acquisition and -analysis system in measuring cardiac complex intervals was compared with manual measurements in 10 healthy subjects. A data set of 500 cardiac complexes was created from lead II electrocardiographic samples from each subject. Intervals were measured to the nearest 5 msec by hand and to the nearest 1 msec by the analysis system. Automated measurements of the RR interval and QRS duration exhibited no bias and median absolute errors of 3 msec. Measurements of the PR interval exhibited a significant bias (18 msec) that accounted for the majority of the imprecision (19 msec). A small but significant bias (4 msec) was found in the measurement of the QT duration with a median absolute error of 12 msec. The traditional method of averaging the values of 10 consecutive complexes provided results similar to individual complex measurements. The automated analysis of cardiac intervals can produce data that are suitable for pharmacodynamic studies.