An improved method and apparatus for non-invasively assessing one or more physiologic parameters, such as for example those associated with the circulatory system of a living organism. In one exemplary embodiment, the invention evaluates cardiac events (e.g., beats) present within an ECG waveform to determine which beats should be retained and which rejected. This evaluation is conducted based on a hierarchical method, wherein the ECG noise and morphology, as well as various aspects of the Delta Z (change in thoracic impedance), are utilized to evaluate beats for retention/rejection. In one variant, fuzzy models are used in conducting the foregoing evaluations. Parameter median filtering is also optionally applied. The foregoing techniques increase the accuracy, stability and robustness of any systems (e.g., impedance cardiographic or otherwise) which make use of the events. Improved impedance cardiographic apparatus and methods of treatment are also disclosed.