An injectable device for use in a subcutaneous physiological monitoring of a patient includes a body, a plurality of sensors, and a monitoring unit. The plurality of sensors provide an indication of at least one physiological event of a patient, wherein the plurality of sensors includes two or more electrodes in contact with tissue of the patient. The monitoring unit is located within the body and is coupled to the plurality of sensors and configured to monitor a physiologic signal of the patient using the electrodes, wherein the physiologic signal includes an impedance signal related to hydration of tissue of the patient and wherein the monitoring unit is further configured to, based at least in part on the impedance signal measured from the patient, detect an impending cardiac decompensation of the patient.
