Abstract: A patient-implantable cardiac stimulation apparatus adapted to measure body impedance, derive at least one physiological parameter from the impedance measurement, sample a time sequence of the physiological parameter and transmit the sequence to an external monitoring device for display and analysis. The apparatus may also sense intracardiac electrograms while it is measuring body impedance and deriving the physiological parameter, in which case it formats and transmits a combined intracardiac electrogram and physiological signal to the monitoring device.

Abstract: 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.

Abstract: A method and apparatus for detecting cardiac arrhythmias in a patient's heart is disclosed. The monitoring method and apparatus sense cardiac electrical signals when the heart is functioning in a known cardiac state, then characterize this known cardiac state by storing a temporally compressed template of time sequence samples. The method and apparatus allow testing during multiple different cardiac states and provide for storage of templates associated with each state. Subsequently, when the heart is functioning in an unknown cardiac state, the method and apparatus monitor cardiac electrical signals by temporally compressing samples and scan correlating these samples with the previously stored template sequences to derive correlation coefficients. The method and apparatus then use these correlation coefficients to characterize cardiac function.

Abstract: A method and apparatus for storing a representation of a cardiac signal by compressing the data using scan correlation and temporal data compression techniques. The method and apparatus sense cardiac signals when the heart is functioning in a known cardiac state, then characterize this known state by storing a temporally compressed template of time sequence samples. The method and apparatus may perform testing for multiple different cardiac states and store templates associated with each state. Subsequently when the heart is functioning in an unknown cardiac state, the method and apparatus monitor cardiac signals by temporally compressing samples and scan correlating these samples with the previously stored templates to derive correlation coefficients. These correlation coefficients are a basis for identifying and classifying cardiac signal waveforms.