Using digital versus analog ECG data in clinical trials.

In 54 patients, we measured 3 different electrocardiogram (ECG) parameters required in the Symphony 1 trial and compared various combinations of pairs of measurements from 4 different sets of analog data and 1 set of digital data. Particularly for measurements of the durations of R waves in lead aVF, we found poor intraobserver and interobserver reliability and poor agreement between analog and digital data. There was much better agreement in measurements of the amplitudes of S waves in lead V3. The poorer agreement involving durations appears to be due to difficulties in accurately identifying the offsets of portions of the QRS complex, especially in lead AVF. We conclude that, particularly in measurements of duration, digital and analog data are not equivalent.