A spatial study of the ST segment

A new method for real-time spatial ST segment evaluation was developed and preliminarily tested with three stress electrocardiograms and five long-term rest electrocardiograms. The classic function of spatial velocity was modified in order to improve the performance of the QRS complexes onset and offset identification; this function was computed for three groups of leads and identification thresholds were set up for each group. QRS complexes were classified as non-premature and premature according to the complex width and the RR interval duration. To avoid wrong ST measurements on the first branch of the T wave, an inverse relationship was set between the average RR interval duration and the distance since the J-point to the ST segment middle point. Vectors associated to leads II, V1 and V5 were considered like the axes of an orthogonal system and the ST deviation for each lead like the projections of the ST vector. The vector module was computed for non-premature complexes according to the classic expression and its value showed an earlier sensitivity to ST pathological changes than the traditional lead by lead study. The proposed method was tested with 10758 beats, all of them were detected and never a premature beat was misclassified. ST measurements never were made in the first branch of the T wave.