Abstract: A minimally invasive, implantable monitor and associated method for chronically monitoring a patient's hemodynamic function based on signals sensed by one or more acoustical sensors. The monitor may be implanted subcutaneously or submuscularly in relation to the heart to allow acoustic signals generated by heart or blood motion to be received by a passive or active acoustical sensor. Circuitry for filtering and amplifying and digitizing acoustical data is included, and sampled data may be continuously or intermittently written to a looping memory buffer. ECG electrodes and associated circuitry may be included to simultaneously record ECG data. Upon a manual or automatic trigger event acoustical and ECG data may be stored in long-term memory for future uploading to an external device. The external device may present acoustical data visually and acoustically with associated ECG data to allow interpretation of both electrical and mechanical heart function.

Abstract: A minimally invasive, implantable heart sound and ECG monitor and associated method for deriving blood pressure from heart sound data. The device is equipped with an acoustical sensor for detecting first and second heart sounds which are sampled and stored during sensing windows following R-wave and T-wave detections, respectively. ECG and heart sound data are stored in a continuous, looping memory, and segments of data are stored in long-term memory upon an automatic or manual data storage triggering event. Estimated blood pressure is calculated based on custom spectral analysis and processing of the first and second heart sounds. A calibration method includes measuring a patient's blood pressure using a standard clinical method and performing regression analysis on multiple spectral variables to identify a set of best fit weighted equations for predicting blood pressure. Concurrent ECG and estimated blood pressure may be displayed for review by a physician.

Abstract: A medical device for multi-vector sensing of cardiac depolarization signals is disclosed. Specialized algorithm is implemented to enhance multi-vector electrode sensing. Further a geometric shape is optimized to enable space-volume efficiencies for deployment and navigation of the medical device for implant in a patient.

Abstract: An improved turning point system and method for performing data compression is disclosed. The system improves the conventional turning point compression method by selecting a predetermined number of the “best” turning points in the sample window including data samples X0 and XN. From this sample-window, ones of the data samples X1 through X(N−1) will be identified as turning points using a selected one of a disclosed set of turning point detection methods. In one embodiment, a turning point is identified by determining that the slopes in the lines interconnecting adjacent data points have different polarities. In an alternative embodiment, a data sample XM is considered a turning point if the slope of the line between the data samples XM and X(M+1) has a different polarity as compared to the slope of the last waveform segment that was encountered that did not have a slope of zero.

Abstract: A system and method for obtaining a virtual physiologic voltage signal between a first predetermined point in a second selected point in the body is disclosed. At least three electrodes are used to measure two voltage signals S1 and S2 in a body. In one embodiment, the signal S1 is measured between a first electrode and a common electrode, and the signal S2 is measured between a second electrode and the common electrode. A selected point within the body may be chosen to define a pair of virtual electrodes existing between this selected point and the common electrode. An approximation of the voltage signal S as could be measured between electrodes positioned at these virtual electrode locations may be derived as a function of S1, S2, and &thgr;, wherein &thgr; is the angle between the directional vector U1 for the signal S1 and the directional vector U for the signal S.

Abstract: A system and method for determining the optimal positioning of an implantable system for sensing physiologic signals within a body. According to a one embodiment of the system, electrodes are positioned on an external surface of a body, and an ECG monitoring device is used to measure cardiac signals between various pairs of the electrodes. One or more of the electrodes may be re-positioned until an electrode pair position and orientation is located that provides a maximum signal reading. This position and orientation may then be used as the position and orientation in which to implant a corresponding device.

Abstract: A minimally invasive implant, means for insertion, and description of how to most efficiently use it are described n several embodiments. This implant preferably has a segmented looping memory for storing triggered physiologic events. Preferred events for setting autotriggers to record physiologic signals occurring during events include arrhythmias and syncopal events. Preferably the device can function without a microprocessor. An outside device or other patient activated manual trigger is included. Auto triggers and manually set triggers may be of different sizes. The preferred physiologic events are ECG signals. Electrode spacing can be critical. Additional sensors may be provided to the device. Preferred communications with the device is through telemetry such as is used for pacemakers and other implanted devices.

Abstract: Triggers and noise should be available as information in recorded electrograms in memories of implantable medical devices. Particularly where the recording of electrogram data is done in the far field, there will be considerable noise and the interpretation of ECG's reproduced from such recorded data will benefit from the storing of information regarding contemporaneous noise. By storing contemporaneous trigger data and noise data directly in the ECG data, recordings of the ECG data become more useful for physician use when played back through an external display system with minimal loss of ECG data, since out of range values are employed for the noise and trigger information and this non-ECG data is limited in size to no longer than individual point values of the ECG signal.

Abstract: A system for recording trigger events and noise in conjunction with the recording of physiological signals is provided for use in an implantable medical device. In one embodiment, recorded trigger and noise data is provided for display to a physician along with reconstructed ECG data to facilitate interpretation of the ECG signal. In one embodiment, digitized ECG samples that are outside of a predetermined range are discarded during the sampling process so that one or more ranges of encoded values are available for use in encoding noise and trigger information. This non-physiologic data may be limited in size to individual point values of the ECG signal.

Abstract: A medical device for multi-vector sensing of cardiac depolarization signals is disclosed. Specialized algorithm is implemented to enhance multi-vector electrode sensing. Further a geometric shape is optimized to enable space-volume efficiencies for deployment and navigation of the medical device for implant in a patient.

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: An implantable dual transducer apparatus for use with an implantable medical device and control method are disclosed. The dual transducer assembly includes two physiologic sensors coupled to the medical device via a pair of lead conductors. Switching circuitry is controlled by the medical device to selectively activate and deactivate the two physiologic sensors by application of a supply voltage of an appropriate polarity. Each sensor of the dual transducer assembly is connected to the pair of lead conductors through a respective power switch. In response to the polarity of the supply voltage applied to the lead conductors, the power switches activate or deactivate their respective sensor in an alternating manner. Selective activation of one of the sensor while concurrently deactivating the other sensor of the dual transducer assembly provides for reduced power consumption and reliable communication of sensor data and other information transmitted over the pair of lead conductors.

Abstract: A minimally invasive implant, means for insertion, and description of how to most efficiently use it are described n several embodiments. This implant preferably has a segmented looping memory for storing triggered physiologic events. Preferred events for setting autotriggers to record physiologic signals occurring during events include arrhythmias and syncopal events. Preferably the device can function without a microprocessor. An outside device or other patient activated manual trigger is included. Auto triggers and manually set triggers may be of different sizes. The preferred physiologic events are ECG signals. Electrode spacing can be critical. Additional sensors may be provided to the device. Preferred communications with the device is through telemetry such as is used for pacemakers and other implanted devices.

Abstract: A capacitive pressure and temperature sensing system for providing signals representative of the magnitude of body fluid absolute pressure at a selected site and ambient operating conditions, including body temperature, at the site. An implantable lead having a sensor module formed in its distal end is coupled to a monitor that powers a sensor circuit in the sensor module and demodulates and stores absolute pressure and temperature data derived from signals generated by the sensor circuit. The sensor module is formed with a pickoff capacitor that changes capacitance with pressure changes and a reference capacitor that is relatively insensitive to pressure changes. The sensor circuit provides charge current that changes with temperature variation at the implant site, alternately charges and discharges the two capacitors, and provides timing pulses having distinguishable parameters at the end of each charge cycle that are transmitted to the demodulator.

Abstract: A method and apparatus for providing an enhanced capability of detecting and gathering electrical cardiac signals via an array of relatively closely spaced subcutaneous electrodes (located on the body of an implanted device) which may be employed with suitable switching circuits, signal processors, and memory to process the electrical cardiac signals between any selected pair or pairs of the electrode array in order to provide a leadless, orientation insensitive means for receiving the electrical signal from the heart.

Abstract: A method of and apparatus for controlling one or more parameters of an electrical stimulation generator in response to measured results of the stimulation. In the preferred mode, this technique is employed in a system for the treatment of obstructive sleep apnea. Sensors are used to determine the effectiveness of the stimulation. Amplitude and pulse width are modified in response to the measurements from the sensors.

Abstract: A method of and apparatus for controlling one or more parameters of an electrical stimulation generator in response to measured results of the stimulation. In the preferred mode, this technique is employed in a system for the treatment of obstructive sleep apnea. Sensors are used to determine the effectiveness of the stimulation. Amplitude and pulse width are modified in response to the measurements from the sensors.