Abstract: An R-wave detection system includes an electrode for placement in close proximity to or in contact with a heart to sense electrical activity of the heart. A signal processor is in communication with the electrode, and is responsive to receipt of the analog signal from the electrode to condition the signal to account for noise and far-field effects. The system is operative to determine whether the conditioned signal exceeds a dynamic threshold value and, if so, the system generates a synchronization pulse to indicate the rising edge of an R-wave.

Abstract: Methods and apparatus for providing a single, accurate indicator of a patient's autonomic nervous system function are described. The indicator is a combination of results of a plurality of different autonomic nervous system tests performed on the patient and referenced to a cross-sectional population. In one embodiment, the results of the different autonomic nervous system tests are referenced to a limited age group of the cross-sectional population. A method according to the invention includes generating a mathematical expression for each of the autonomic nervous system tests as a function of physiological data of the cross-sectional population, inserting measured physiological data of the patient into the mathematical expressions to compute output values for each of the tests, and combining the output values to provide the autonomic function indicator.

Abstract: A method of generating a template in an implantable medical device for implantation within a patient, and a processor readable medium for performing the method, that includes generating a template corresponding to a supraventricular rhythm of the patient, determining whether the template is valid, and monitoring the template to determine whether the template is an accurate representation of the supraventricular rhythm. The template is created from non-paced R waves that are below a predetermined heart rate, and a statistical validation of the template is performed by evaluating the template based on matches against ongoing slow heart rhythm. The quality of the template is continuously monitored, similar to the statistical validation, with the exception that one thousand beats are evaluated and once more than thirty out of the last one hundred beats do not match the template within the threshold, an attempt is made to create a new template.

Abstract: A system and method are disclosed to acquire high temporal resolution free-breathing cardiac MR images. The technique includes monitoring heart rate of a patient just prior to image acquisition to acquire a time period of an R-R interval, and using this time period from the heart rate monitoring to prospectively estimate future R-R intervals. The acquisition of MR data can then commence at any point in an R-R interval and extend for the time period recorded. The data acquisition can be segmented and acquired in successive R-R intervals, then combined to create high temporal resolution images.

Abstract: We show how to determine whether there has been an axis shift in an electrocardiogram waveform and how to use this for filtering out bad electrocardiogram information and to modify an adaptive filter that can be used to adapt the filtering of such electrocardiogram information to make it available for determining physiologic conditions even after an axis shift.

Abstract: A signal evaluation method for detecting QRS complexes in electrocardiogram signals incorporates the following process steps:

Abstract: Method and apparatus for measuring the heart rate in a human body. A first and second derivative of an electrical signal from the heart known as the QRS complex or R-wave is measured, and the values of the peak of the R-wave, the peak of the first derivative of the R-wave, and the peak of the second derivative of the R-wave are determined. The three peak values are then multiplied together to provide an output responsive to the occurrence of the R-wave which is greater than either the value of the peak of the R-wave, the value of the peak of the first derivative of the R-wave, or the value of the peak of the second derivative of the R-wave.

Abstract: Method of analyzing biological signals representative of voltage changes, including obtaining an analog biological signal representative of voltage changes, using digital processing software to digitize the biological signal, displaying the processed biological signal in analog form on a display in a time compressed format, wherein an amount of compression for the time compressed formal is selected such that graphical patterns are made perceivable on the display that signify an abnormality in the biological signal, and visually analyzing the biological signal on the display to characterize the abnormality.

Abstract: An implantable pacemaker delivers a stimulation pulse in the ventricular chamber of patient's heart and automatically verifies ventricular capture. A control system of the pacemaker sets a far-field interval window after a predetermined delay period from the delivery of the stimulation pulse, for verifying ventricular capture. The far-field interval window is approximately 100 msec, and provides an opportunity for the control system to sense the far-field signal that occurs in response to the stimulation pulse. The delivery of the stimulation pulse also initiates a post ventricular atrial blanking period on an atrial channel, and the far-field interval window is initiated during the post ventricular atrial blanking period.

Abstract: We show how to determine whether there has been an axis shift in an electrocardiogram waveform and how to use this for filtering out bad electrocardiogram information and to modify an adaptive filter that can be used to adapt the filtering of such electrocardiogram information to make it available for determining physiologic conditions even after an axis shift.

Abstract: Based upon patient studies indices a high degree of correlation was found between HRV and VO2max, i.e., the patient's exercise capacity. Based on this finding, a pacing therapy optimization protocol for treating patients with CHF has been devised. The protocol involves first pacing the patient's heart with a pacemaker programmed to operate in a first mode for a predetermined time period and then collecting electrogram data from which a HRV index is derived. The mode is then changed and the steps repeated until all possible modes have been utilized. At that time, a determination is made as to which of the modes is associated with the largest HRV index and the pacemaker is then programmed to function in that mode. Alternatively, the method of the present invention can be applied to changes in drug therapy instead of or in combination with pacing therapy. By the plotting the HRV index computed in the manner described, the efficacy of a change in therapy on patient exercise capacity can be assessed.

Abstract: In a computed tomography apparatus, and a method for operating same, for obtaining cardiac images, a spiral scan of a measurement volume containing a patient's heart is conducted, the production of the scanning data during the spiral scanning being synchronized with an ECG signal from the patient, in order to produce a graphic representation of the examination volume, and thus an image of the patient's heart. The ECG signal is employed to control the generation of the data during the spiral scanning at phase of the cardiac cycle wherein minimum movement of the heart takes place. The chronological correlation between the recording of the scanning data and the ECG signal is fixed, so that within each number of successive time intervals, a dataset is obtained completely within that time interval. The datasets from the successive time intervals are then combined to produce an image of the heart.

Abstract: An implantable medical device which preferably has a segmented looping memory for storing triggered physiologic events also has autotriggers to record the ECGs and any other relevant physiologic signals occurring during triggering events. The problem is that in the far field R-wave sensing is difficult because of noise. Denial and extensible accommodation periods are introduced into the R-wave sensing registration for triggering data storage. If the event is sensed during an accommodation period the sense will not add an R-wave sense to the trigger's count of R-waves. It may cause resetting of the trigger count in some circumstnaces. Typical triggering events may include arrhythmia's and syncopal events. Preferably the device can function without a microprocessor. An outside device or other patient activated manual trigger may be included. Auto triggers and manually set triggers may be of different sizes. Electrode spacing can be critical. Additional sensors may be provided to the device.

Abstract: A method is disclosed for inflating an inflatable vest to assist the heart in patients suffering from heart failure. The inflation of the vest is synchronized with on-set of the systole phase of the heart, when the left ventricular compresses to force blood out of the heart and through the aorta. The inflated vest compresses the patient's chest and increases the intrathoracic pressure. This increase in pressure assists the heart in moving blood out of the heart and through the aorta. In addition, the vest is arranged to leave the patient's abdomen free of restraint so that the increase in intrathoracic pressure due to the vest moves blood into the abdomen, and to allow the abdomen to dynamically recoil in response to the vest inflation. In addition, ECG signals from electrodes applied to the patient are processed to trigger the vest inflation in real time with the current heartbeat cycle, such that the vest inflation is triggered when the heart begins to contract.

Abstract: A compression algorithm for the compression of ECG recordings uses the Karhunen-Loeve Transform (KLT) to transform a set of N sampled ECG beats from a matrix of N.times.M samples into a new form, from which a selected subset can be retained for storage, transmission, or analysis. In order to reduce computation time and storage space, a multirate downsampling operation may be applied, which retains the appropriate spectral information in each block. The downsampled beats are then padded to make them of uniform size, and a Karhunen-Loeve Transform is applied to the sample set. Coefficients from the Karhunen-Loeve Transform of the sample set are retained for reconstruction according to one of two criteria. The average variance of the reconstructed sample set may be controlled, or different numbers of coefficients may be retained for each beat. The KLT compressed data may be reconstituted by reverse KLT transforming the data.

Abstract: As particularly useful for implantable medical devices we teach a method and apparatus for orienting electrocardiogram input from electrodes of unknown vector orientation. This can be used for locating a fiducial point in the electrocardiogram signal by which other parameterization of measurements taken of the electrocardiogram signal can be made. It is of particular relevance in any cardio electrogram reading where the orientation of the electrogram signal is unknown, and knowledge of the orientation and a fiducial point can form the basis for useful analysis of electrogram signals for detection of physiologic conditions.

Abstract: The present invention relates to a method and an apparatus for determining exertion levels in fitness or athletic training and for determining the stress caused by training. According to the invention, the ECG signal of a person and the timing moment of at least one waveform of the ECG signal, for instance the QRS complex, are measured by means of a heartbeat rate monitor during a training period. The heartbeat rate is calculated on the basis of corresponding ECG signal waveform distances, and a value proportional to the magnitude of the heartbeat rate variation or to that of a total or partial power of a spectrum derived from the heartbeat rate is provided by means of a mathematical function. Those exertion levels of the person which are essential as regards to training period or the stress caused by the training in relation to the exertion levels are determined on the basis of the heartbeat rate variation.

Abstract: An MRI system includes a detector system which receives an ECG signal from a patient being scanned and produces a gating signal. The gating signal is produced when a detected peak in the ECG signal meets a set of R-wave criteria which includes a specified positive slope on the leading segment of the detected peak, a minimum duration of the leading segment, specified negative slope on the segment trailing the detected peak and a minimum peak amplitude.

Abstract: An adaptive line noise detection and cancellation system having a baseline wander filter, high and low pass filters, an adaptive line noise canceler and various noise detectors is provided to identify, signal and remove contamination from an ECG signal wherein the ECG signal is conditioned to remove various portions of the ECG signal prior to processing in various noise detectors while minimizing the signal conditioning effect of the filters on the ECG signal and while further providing the operator with the ability to manually or automatically activate the filters and to indicate the status of the filters on a printout or display.

Abstract: Refractory delay circuitry ensures that induced currents do not falsely rigger the acquisition phase of magnetic-resonance instrumentation. Immediately after the triggering of the acquisition sequence, for example, by the R-wave of a subject's cardiac cycle, the adjustable delay circuit is used to inhibit further trigger signals for a predetermined duration of the acquisition gradient activity. The acquisition sequence will thus not be triggered by extra peaks in the biological signal, which may take the form of non-R-wave signals in the cardiac cycle. In this embodiment of the invention triggering will occur only at most once per heartbeat. As cardiac signals may be divided into two major groups, electrical (ECG) and non-electrical (e.g.

Abstract: Based upon patient studies indices a high degree of correlation was found between HRV and VO2.sub.max, i.e., the patient's exercise capacity. Based on this finding, a pacing therapy optimization protocol for treating patients with CHF has been devised. The protocol involves first pacing the patient's heart with a pacemaker programmed to operate in a first mode for a predetermined time period and then collecting electrogram data from which a HRV index is derived. The mode is then changed and the steps repeated until all possible modes have been utilized. At that time, a determination is made as to which of the modes is associated with the largest HRV index and the pacemaker is then programmed to function in that mode. Alternatively, the method of the present invention can be applied to changes in drug therapy instead of or in combination with pacing therapy.

Abstract: Delays in event detection in time-varying data can be reduced by predicting the time-varying data and then detecting the event in the predicted data. This finds application in the triggering of medical imaging devices, where physiological events can be detected in the time-varying data. An artificial neural network can be trained to predict data such as ECG signals from which a detection algorithm can accurately predict the occurrence of an event that will serve as a reference point for triggering.

Abstract: An automatic sensing system for an implantable cardiac rhythm management device comprises a variable gain amplifier and associated filters where the gain of the amplifier is adjusted as a function of the peak amplitude of a cardiac depolarization signal (either a P-wave or an R-wave) and especially the relationship of the peak value to a maximum value dictated by the circuit's power supply rail. The trip point comparator has its trip point adjusted as a function of the difference between the detected peak value of the signal of interest and the peak value of noise not eliminated by the filtering employed.

Abstract: A large universe of signals can be rapidly examined for a specific phenomenon by searching for a morphology representative of a subgroup of the universe. A detector for each such representative morphology is arranged in parallel to examine a signal input and provide an indication of positive identification a specific morphology.

Abstract: A signal detector for detecting a biosignal with approximately known morpogy in a complex input signal (ECG), in particular for the detection of QRS complexes in an electrocardiogram. The detector has circuitry for detecting the maximum amplitude (PEAK) of the detected signal complex within a predetermined time window, with a threshold value discriminator, a detector parameter preselection circuit for determining an initial value for the detector parameter characterizing the detector sensitivity, which parameter determines the detector threshold value when responding to a detection signal in dependence on the maximum amplitude and a detector parameter timing circuit for adjusting a predetermined time dependence of the detector parameter and thus the detection threshold value.

Abstract: The present invention relates to a method and apparatus in connection with measuring the heartbeat rate of a person. In the method, the ECG signal of the person and the timing moment of at least one ECG signal waveform, such as the QRS complex, are measured with a heartbeat rate monitor. The average heartbeat rate frequency of the heartbeat rate is calculated from the ECG signal. Heartbeat rate variation information proportional to the magnitude of the heartbeat rate variation or to that of the total or partial power of a spectrum derived from the heartbeat rate is provided by means of a mathematical function. The heartbeat rate variation information is displayed on the display of the heartbeat rate monitor together with the average heartbeat rate frequency.

Abstract: A ventricular tachycardia (VT) complex is distinguished from a sinus tachycardia or a supraventricular tachycardia. A template based on morphology of a normal sinus rhythm is collected. A test signal is compared against the template to determine how closely the test and template signals correspond based on morphology. The comparison is done based on peak information in the template and the test signal. A score is generated to indicate the degree of similarity between the template and the test signal. The peak information is extracted as follows. First, a group of three consecutive peaks having a largest cumulative peak amplitude is located in the template and in the test signal. The polarity, position and area of each peak within the group is then determined. The area of each peak is normalized. The polarities, positions and normalized areas represent the peak information that is used for comparison.

Abstract: A method and system for discriminating atrial and ventricular signal components from a single heart lead, and for using this information for identifying an arrhythmia condition as being atrial or ventricular in origin. The invention is effective in identifying P waves occurring in complex signal which includes relatively stronger R waves or other ventricular artifacts which mask the P waves. The contribution of the R wave signal to the complex signal is obtained by filtering, time windowing and transfer function estimation, then the R wave estimate is subtracted from the combined signal to leave the P wave. The ratio of P waves to R waves, P--P and R--R intervals, and their ratios to one another and to fixed values can be estimated, and used in a comparison to discriminate between atrial and ventricular arrhythmia, to thereby enable appropriate treatment.