Derivation of orthogonal leads from the 12-lead ECG. accuracy of a single transform for the derivation of atrial and ventricular waves

Vectorcardiograms are not usually recorded in clinical practice and must be derived from the conventional 12- lead ECG, for example by making use of Dower´s transform. However, its accuracy for the derivation of the P wave is questionable. We tested the accuracy of Dower´s transform on the P-wave and compared with a P-wave optimized transform in a database of 123 simultaneous recordings of ECGs and VCGs. This new transform achieved a lower error when we compared derived vs. true measured P-waves (12.2 plusmn 7.96 muVRMS) than Dower´s transform (14.4 plusmn 9.5 muVRMS) and higher correlation values (Rx = 0.93 plusmn 0.12, Ry = 0.90 plusmn 0.27, Rz = 0.91 plusmn0.18 vs. Dower´s: Rx = 0.88 plusmn 0.15, Ry = 0.91 plusmn 0.26 , Rz = 0.85 plusmn 0.23). We concluded that derivation of P-waves and QRS complexes VCGs were optimized by the use of different transform matrices for each wave in this database.