Systems and methods for filtering artifacts from composite signals

A nonlinear filter for processing a signal derived from a biological event comprising sample values arranged with respect to time, the derived biological signal having an artifact signal portion and a useful signal portion, the filter comprising

• a derived biological signal input,
• means for establishing a sample window that encompasses a predetermined number of sample values X(k), where k=1 to WL, and WL varies according to the number of sample values that the artifact signal portion contains,
• means for advancing the sample window sequentially along the biological signal in increments of one sample value, while, upon each advance:
• sorting the sample values X(k) within the sample window into a permutation from the smallest to the largest sample values X(p[k]), where p[k] comprises a sort position of the permutation,
• selecting a sort position p[f] expressed as ##EQU14## where z is the sort position of WL positions and generating an interim output comprising the value of X(p[f]), and
• means for generating a filter output comprising the interim outputs arranged with respect to time in sequence with the composite signal.

A method for processing a composite signal comprising sample values arranged with respect to time, the composite signal having an artifact signal portion and a useful signal portion, the method comprising the steps of

• selecting sets of WL sample values in time-sequence along the composite signal,
• arranging the WL sample values of each set into ordered positions following a predetermined permutation,
• determining the duration AL of the artifact signal position in terms of the number of sample values the artifact signal position contains,
• selecting one of the ordered positions, z, within each permutation taking into account AL, and
• generating a filter output comprising the sample values occupying the ordered position, z, of each permutation in time-sequence with the composite signal.

An element that filters a pacing artifact from an electrogram comprising

• means for selecting sets of WL sample values in time-sequence along the electrogram,
• means for arranging the WL sample values of each set into ordered positions following a predetermined permutation,
• means for determining the duration AL of the artifact in terms of the number of sample values that the artifact contains
• means for selecting one of the ordered positions, z, within each permutation taking into account AL, and
• means for generating a filtered electrogram comprising the sample values occupying the ordered position, z, of each permutation in time-sequence with the electrogram, the filtered electrogram being essentially free of the pacing artifact.

A method for analyzing an electrogram comprising the steps of

• emitting a pacing signal and sensing an electrogram as a result of the pacing signal, the electrogram including a pacing artifact,
• selecting sets of WL sample values in time-sequence along the electrogram,
• arranging the WL sample values of each set into ordered positions following a predetermined permutation,
• determining the duration AL of the pacing artifact in terms of the number of sample values that the artifact signal position contains,
• selecting one of the ordered positions, z, within each permutation taking into account AL, and
• generating a filtered electrogram comprising the sample values occupying the ordered position, z, of each permutation in time-sequence with the electrogram, the filtered electrogram being essentially free of the pacing artifact.