A system, comprising: a signal input circuit, including a sense amplifier circuit to receive at least one physiological signal sensed from a patient; a memory circuit; a baseline value generator circuit coupled to the signal input circuit and the memory circuit, the baseline value generator circuit configured to generate one or more baseline values using one or more first signal portions of the received at least one physiological signal during one or more first time durations, and to store the one or more baseline values in the memory circuit; a short-term value generator circuit coupled to the signal input circuit and the memory circuit, the short-term value generator circuit configured to generate one or more short-term values using one or more second signal portions of the received at least one physiological signal during one or more second time durations, and to store the one or more short-term values in the memory circuit; a comparator circuit coupled to the memory circuit or coupled to both the baseline value generator circuit and the short-term value generator circuit, the comparator circuit configured to determine a difference between the one or more short-term values and the one or more baseline values; and a cardiac condition detector circuit (230, 330) including an accumulator circuit, the cardiac condition detector circuit (230, 330) coupled to the comparator circuit, the cardiac condition detector circuit (230, 330) configured to determine a cardiac condition indicator using a weighted combination of the difference between the one or more short-term values and the one or more baseline values, wherein the weighting includes one or more weight factors determined according to timings of the one or more first signal portions or the one or more second signal portions, wherein the accumulator circuit is configured to compute said cardiac condition indicator as a detection index, the DI being a weighted sum of deviations of the short-term values from the baseline values scaled respectively by the weight factors, characterised in that the weighted sum of the deviations is computed such that all the deviations are accumulated at the accumulator circuit regardless of short-term value relative to the corresponding baseline value. a signal input circuit, including a sense amplifier circuit to receive at least one physiological signal sensed from a patient; a memory circuit; a baseline value generator circuit coupled to the signal input circuit and the memory circuit, the baseline value generator circuit configured to generate one or more baseline values using one or more first signal portions of the received at least one physiological signal during one or more first time durations, and to store the one or more baseline values in the memory circuit; a short-term value generator circuit coupled to the signal input circuit and the memory circuit, the short-term value generator circuit configured to generate one or more short-term values using one or more second signal portions of the received at least one physiological signal during one or more second time durations, and to store the one or more short-term values in the memory circuit; a comparator circuit coupled to the memory circuit or coupled to both the baseline value generator circuit and the short-term value generator circuit, the comparator circuit configured to determine a difference between the one or more short-term values and the one or more baseline values; and a cardiac condition detector circuit (230, 330) including an accumulator circuit, the cardiac condition detector circuit (230, 330) coupled to the comparator circuit, the cardiac condition detector circuit (230, 330) configured to determine a cardiac condition indicator using a weighted combination of the difference between the one or more short-term values and the one or more baseline values, wherein the weighting includes one or more weight factors determined according to timings of the one or more first signal portions or the one or more second signal portions, wherein the accumulator circuit is configured to compute said cardiac condition indicator as a detection index, the DI being a weighted sum of deviations of the short-term values from the baseline values scaled respectively by the weight factors, characterised in that the weighted sum of the deviations is computed such that all the deviations are accumulated at the accumulator circuit regardless of short-term value relative to the corresponding baseline value.