1. An apparatus comprising a non-volatile computer readable medium storing instructions for causing a computing system to perform operations comprising: receiving, from two or more ECG leads, an ECG signal of a patient; generating at least two orthogonal ECG vectors based on the ECG signal; processing the at least two orthogonal ECG vectors to determine a vectorcardiogram loop trajectory of at least a portion of the ECG signal; identifying a trajectory bifurcation by comparing the vectorcardiogram loop trajectory to a control vectorcardiogram loop trajectory for at least three consecutive cardiac cycles of a plurality of cardiac cycles; determining a variation of the trajectory bifurcation over time, the determination based on an analysis of the trajectory bifurcation of the at least three consecutive cardiac cycles; determining an indicator of a cardiac event based on the variation of the trajectory bifurcation; and delivering a treatment to the patient based on the determined indicator of the cardiac event.