A system for managing care of a person receiving emergency cardiac assistance includes one or more capacitors arranged to deliver a defibrillating shock to a person; one or more electronic ports for receiving a plurality of signals from sensors for obtaining indications of an electrocardiogram (ECG) for the person; and a patient treatment module executable on one or more computer processors using code stored in non-transitory media and to provide a determination of a likelihood of success from delivering a future defibrillating shock to the person with the one or more capacitors, using a mathematical computation applied to a vector value defined by signals from at least two of the plurality of signals.