EP0526973

A method and apparatus for aligning periodic cardiac signal waveforms for the purpose of signal averaging over a number of cardiac cycles. The aligning method and apparatus sense cardiac electrical signals over a number of cardiac cycles, store a template characterizing these signals, reduce the data rate of the same sensed signals by temporal data compression, and store a compressed template sequence. Subsequently, the method and apparatus perform signal averaging by monitoring cardiac electrical signals, storing samples of these signals, temporally compressing these samples and scan correlating the compressed samples with the previously stored compressed template sequence to derive correlation coefficients. Thereafter, the method and apparatus utilize the maximum correlation coefficient to roughly align the monitored waveform with the averaged signal, and then they scan correlate a portion of the noncompressed monitored waveform adjacent to the maximum correlation coefficient with a corresponding portion of the noncompressed template to provide precise alignment of the monitored waveform with the averaged signal.