Derivation of orthogonal leads from the 12-lead electrocardiogram. Performance of an atrial-based transform for the derivation of P loops

The objective of this study was the evaluation of the accuracy of Dower inverse transform for the derivation of the P wave in orthogonal leads.We tested the accuracy of Dower transform on the P wave and compared it with a P-wave–optimized transform in a database of 123 simultaneous recordings of electrocardiograms and vectorcardiograms. This new transform achieved a lower error when we compared derived vs true measured P waves (mean ± SD, 12.2 ± 8.0 VRMS) than Dower transform (14.4 ± 9.5 Root mean squared voltage) and higher correlation values (Rx, 0.93 ± 0.12; Ry, 0.90 ± 0.27; Rz, 0.91 ± 0.18; vs Dower: Rx, 0.88 ± 0.15; Ry, 0.91 ± 0.26; Rz, 0.85 ± 0.23).We conclude that derivation of orthogonal leads for the P wave can be improved by using an atrial-based transform matrix.