Techniques include determining a first vector of temporal changes inelectrical datameasured at multiple electrical sensors positioned at corresponding locationson a surfaceof a living body due to a natural electrical pulse. A different vector oftemporal changes inelectrical data measured at the same electrical sensors is determined due toeach stimulatedsignal of multiple stimulated signals within the living body. Stimulatedposition data isreceived, which indicates a different corresponding position within the livingbody where eachof the stimulated signals originates. The site of origin of the naturalelectrical pulse isdetermined based on the first vector and the multiple different vectors andthe stimulatedposition data. Among other applications, these techniques allow the rapid,automaticdetermination of the site of origin of ventricular tachycardia arrhythmia(VT).
