Detection of worsening heart failure

A system for detecting a target physiological event, the system comprising:

• a physiological sensor circuit including a sense amplifier circuit to sense a first physiological signal;
• a signal processor circuit coupled to the physiological sensor circuit, the signal processor circuit including:
• a predictor circuit configured to generate a first predictor trend using the first physiological signal, the first predictor trend indicating a change of the first physiological signal over time;
• and
• a signal transformation circuit configured to transform the first predictor trend into transformed indices using a first plurality of threshold pairs each including an onset threshold and a reset threshold;
• and
• a detector circuit coupled to the signal processor circuit, the detector circuit configured to detect the target physiological event using the transformed indices;
• and
• an output circuit configured to generate a human-perceptible alert in response to the transformed indices satisfying a detection criterion.