Delineation of Premature P Waves on Four-Dimensional Electrocardiography, a New Display of Electrical Forces by Computer Techniques

Abstract

This study investigated the feasibility of four-dimensional electrocardiography (4-D ECG), a new display in which the vector loop was rotated and scanned along a timed axis to overcome the shortcomings of vectorcardiography (VCG). The subjects consisted of 38 patients with premature atrial complexes and 30 controls. The orthogonal Frank elec trocardiograms were rotated three-dimensionally according to the right-hand rectangular coordinate system and scanned along a timed axis. The P wave delineation score, signi fying good agreement with the intraobserver and interobserver variability, was signifi cantly higher in 4-D ECG than those in the orthogonal leads or those on the transverse and frontal projections (P < 0.001). The authors measured the premature P loop areas as viewed from 361 directions. P loop areas were best delineated when viewed from cranial directions of 42.6 ±34.0 degrees and from rightward directions of 11.3 ±30.7 degrees. Adequate cranial rotation followed by scanning along a timed axis will maximally delineate premature atrial signals and provide comprehensive visualization of electrical forces.