Abstract: First cardiac signal data generated from measured heart beats of a subject is received. Characteristics of alternans occurring in the received first cardiac signal data are determined. Second cardiac signal data generated from measured heart beats of the subject after a change relating to an administration of a pharmacological agent is received. Characteristics of alternans occurring in the received second cardiac signal data are determined. The characteristics of alternans occurring in the received first cardiac signal data are compared with the characteristics of alternans occurring in the received second cardiac signal data.

Abstract: Cardiac signal data of heart beats measured with an ambulatory electrocardiography device is accessed. The cardiac signal data is segmented into cardiac signal data segments such that each cardiac signal data segment includes cardiac signal data of sequential heart beats. Whether alternans is present in the cardiac signal data segment is determined for each of multiple cardiac signal data segments. Characteristics of the alternans is determined by analyzing cardiac signal data segments for which alternans is determined to be present or by analyzing characteristics of cardiac signal data segments for which alternans is determined to be present.

Abstract: One or more electrocardiographic signals are detected from a subject. The occurrence of alternans in the electrocardiographic signals are detected using one or more processors. One or more characteristics of detected alternans are determined. The determined characteristics of the detected alternans are analyzed to determine whether cardiac ischemia is present.

Abstract: A method for identifying infants at risk for SIDS includes applying electrodes to an infant, receiving electrical signals from the electrodes, analyzing the received electrical signals to measure alternans of a heart of the infant, and identifying whether the infant is at risk for SIDS. A system for identifying infants at risk for SIDS includes an input unit configured to receive electrical signals from electrodes applied to an infant, a processor connected to the input unit and configured to process the received electrical signals to measure alternans of a heart of the infant, and a comparator configured to compare the measured alternans with alternans in a population of infants.

Abstract: A method for identifying infants at risk for SIDS includes applying electrodes to an infant, receiving electrical signals from the electrodes, analyzing the received electrical signals to measure alternans of a heart of the infant, and identifying whether the infant is at risk for SIDS. A system for identifying infants at risk for SIDS includes an input unit configured to receive electrical signals from electrodes applied to an infant, a processor connected to the input unit and configured to process the received electrical signals to measure alternans of a heart of the infant, and a comparator configured to compare the measured alternans with alternans in a population of infants.

Abstract: Identifying infants at risk for SIDS includes applying electrodes to an infant, receiving electrical signals from the electrodes, analyzing the received electrical signals to measure alternans of a heart of the infant, and identifying whether the infant is at risk for SIDS. A system for identifying infants at risk for SIDS includes an input unit configured to receive electrical signals from electrodes applied to an infant, a processor connected to the input unit and configured to process the received electrical signals to measure alternans of a heart of the infant, and a comparator configured to compare the measured alternans with alternans in a population of infants.

Abstract: Alternans is measured in a physiological signal, such as an electrocardiogram, by processing the physiological signal to create a processed signal having an asymmetric spectrum, and processing the processed signal to measure alternans in the physiologic signal. The physiological signal may be processed to produce an analytical signal by converting the signal to the frequency domain, removing components corresponding to negative frequencies, and converting back to the time domain.

Abstract: Interpreting alternans data includes accessing alternans data and automatically evaluating the alternans data to produce one or more interpretation parameters based on the alternans data. The interpretation parameters are used to generate interpretation results related to the alternans data. Finally the interpretation results are made accessible for examination.

Abstract: Heart function is improved by inducing heart rate variability through cardiac pacing. Electrical pacing signals are generated and applyied to a heart to improve heart function. The pacing signals are controlled to vary a heart rate during periods of less than five minutes in duration to induce beneficial heart rate variability.

Abstract: A subject suspected of experiencing a myocardial infarction is monitored by applying sensors to the subject, where the sensors are configured to produce electrical signals representative of cardiac activity of the subject. Electrical signals are received from at least two of the sensors. The received signals then are processed to obtain a localized cardiac measure that is analyzed to determine whether the subject is experiencing a myocardial infarction.

Abstract: Cardiac electrical stability is assessed by generating a measure of cardiac electrical stability (e.g., an alternans measure) using a physiologic signal representative of activity of a patient's heart, generating a reference signal that provides information regarding whether the measure is representative of cardiac electrical stability, and visually presenting the measure and the reference signal in a way that permits visual evaluation of whether the measure is representative of cardiac electrical stability in view of characteristics of the reference signal.

Abstract: A method of reducing noise in a biological signal, such as an ECG signal, includes acquiring a biological signal, comparing the biological signal to a representative signal, and generating a predicted signal corresponding to the representative signal when the biological signal sufficiently matches the representative signal. The predicted signal is subtracted from the biological signal to produce a second signal, and a filter is applied to the second signal to produce a filtered signal. The predicted signal and the filtered signal then are combined to produce a noise-reduced signal.

Abstract: Abnormal cardiac activity in a patient may be detected by acquiring an electrocardiogram waveform associated with a first level of physiologic activity of the patient and an electrocardiogram waveform associated with a second, different level of physiologic activity of the patient. QRS complexes of the electrocardiogram waveforms are compared to identify an abnormal portion of the QRS complex of the electrocardiogram waveform associated with the second level of physiologic activity. The abnormal portion of the QRS complex is processed to detect abnormal physiologic activity.

Abstract: A localized cardiac measure, such as a localized measure of myocardial ischemia, is obtained by applying sensors to a subject, where the sensors are configured to produce electrical signals representative of cardiac activity of the subject. The subject's heart is then physiologically stressed by, for example, exercise stress testing, and electrical signals are received from at least two of the sensors. The received signals then are processed to obtain a localized cardiac measure.

Abstract: Noise is reduced from a received ECG signal representative of activity of the heart of a patient. A collection of beats from the ECG signal is selected and transformed into a multi-dimensional representation. A multi-dimensional filter function is applied to the multi-dimensional representation to enhance a signal-to-noise ratio of the collection of beats.

Abstract: A connector that connects an electrode to a lead includes a connector housing. A conductive contact is positioned in the connector housing and has a tapered end, and a seating surface is positioned in the connector housing opposite the tapered end of the conductive contact. The seating surface and the tapered end are configured to positively retain an electrode when a connection hole of the electrode is positioned around the tapered end. The connector also includes a mechanism for pressing the seating surface against the tapered end of the conductive contact.

Abstract: A multi-segment ECG electrode includes a flexible basepad, a central segment defined on a surface of the basepad, and exterior segments defined on the surface of the basepad. The exterior segments may be sized, shaped and positioned relative to the central segment so that an average position of the exterior segments approximates a position of the central segment.

Abstract: The alternans pattern of cycle-to-cycle variability in physiologic waveforms is assessed by applying transducers to a subject, recording physiologic signals, and analyzing the alternans pattern of variation in waveform morphology.

Abstract: A method of reducing noise in a signal that represents a physiologic process includes obtaining multiple input signals, measuring a relationship between noise content of the input signals, and combining the input signals in consideration of the measured relationship to produce an output signal having low noise content. The multiple input signals may include, for example, two or more primary physiologic input signals or one or more primary physiologic input signals and two or more secondary input signals that represent noise. The method may further include dividing one or more ECG input signals and secondary input signals into set of segments, where each set of segments represents a beat of the ECG signal, measuring a relationship between noise content of corresponding points from successive sets of segments, and combining the input signals based on the measured relationship.

Abstract: Method and apparatus for improved electronic display and interpretation of physiologic waveforms. The apparatus generates a two-dimensional grid on the video screen simulating the appearance of electrocardiographic recording paper or other physiologic signal recording paper. At least one physiologic signal is superimposed upon the grid for a display of the combined signal and grid. In a preferred embodiment of the invention the grid includes lines some of which are separated by no more than 2.6 millimeters. In another embodiment of the invention the grid includes horizontal or vertical lines of at least two types.