A cardiac stimulation system and associated capture management method are provided in which capture and device longevity are improved. The device determines a series of capture thresholds. Capture threshold is the minimum pulse level (pulse energy or pulse amplitude or pulse width) that captures the heart. Each determination requires delivery of pacing pulses at several (at least two) known levels (pulse energy, pulse amplitude and/or pulse width) over time. The individual determined capture thresholds are combined into a set and the variability of the set is used to set the safety margin. The greater the variability in the capture thresholds, the bigger the safety margin.
