1. A system, comprising: three or more ECG leads configured to receive an ECG signal; and a first computing device comprising a processor coupled to a memory, the processor and the memory configured to perform operations comprising: generating at least two orthogonal ECG vectors based on the ECG signal of a patient, processing the at least two orthogonal ECG vectors to determine a loop trajectory of at least a portion of the ECG signal, identifying a trajectory bifurcation by comparing the loop trajectory to a control loop trajectory for a plurality of cardiac cycles, and determining an indicator of a cardiac event based on the trajectory bifurcation.