Abstract: There is provided an implantable device system such as a battery-powered pacemaker system, with an improved capability of measuring battery internal impedance, thereby providing the means to determine anticipated device End of Life. Within one pacemaker cycle following a sensed beat or a delivered stimulus, and before delivery of a next stimulus, three battery measurements are taken at equally spaced time intervals. Due to the RC nature of the battery internal impedance, the first two battery voltage measurements can be used to calculate what the voltage would be at the third time, assuming no change in current load. At the third time, a predetermined incremental current load is added, and the battery voltage at the time of the added current load is measured. The voltage differential between the calculated battery voltage and the measured battery voltage at the third time, together with the predetermined incremental current load, is used to calculate the battery impedance.

Abstract: There is provided a dual site pacing system, either bi-ventricular or bi-atrial, wherein the pacemaker looks for a signal sense during the refractory period following delivery of the pulse pair. If the threshold of either heart chamber has risen above the level of the delivered pulses, that chamber will not be captured, and will not have an inherent refractory period following delivery of the pulse pair. Under these circumstances, and where the patient has conduction delay from one chamber to the other, e.g., LBBB or RBBB, the excitation signal from the other chamber will be sensed in the non-captured chamber during the pacemaker refractory period. Such a sensing during the pacemaker refractory period is recognized to result from loss of capture, and is utilized to automatically increase pulse output back up to a safe level above threshold.

Abstract: The present invention relates to multi-layer ceramic packaging of hybrid micro-electronic devices, including those for implantable medical devices. The invention permits size reduction and design simplification in such packaging by eliminating the need for electrolytic or electroless plating, and by eliminating or substantially eliminating the shrinkage variation typically associated with surface metallization techniques.

Abstract: An implantable sensor assembly for use with an implantable medical device are disclosed. The sensor assembly preferably includes two or more physiologic sensors coupled to the medical device via a pair of lead conductors, or alternatively an oxygen sensor having certain features. The oxygen sensor permits more accurate and reliable measurement of oxygen saturation in blood masses flowing within the human body.

Abstract: An ambulatory recorder having an enhanced ergonomic case is described. The case has a smooth curved semi-circular surface within a first plane along the top surface while further having an at least partially curved surface along a second end. These curved surfaces render the recorder less likely to be caught on objects or on the patient's arms or hands while worn. The recorder is thus more comfortable to wear and operate.

Abstract: A method of modifying the surface characteristics of a substrate, particularly a polymeric material. The method involves grafting ethylenically unsaturated monomers and attaching biomolecules, such as heparin, to the surface of the substrate, such as a polymeric material, in one step using an oxidizing metal, such as ceric ions.

Abstract: A method and apparatus for discriminating between evoked response signals and post-pace polarization signals sensed by a sense amplifier of an implantable medical device. The polarity of the positive or negative change in voltage in respect of time (or dv/dt) of the waveform incident on the lead electrodes is monitored during a short period of time immediately following a paced event. The post-pace polarization signal exhibits a relatively constant polarity during the capture detect window, and the evoked response signal may cause the polarity of post-pace polarization signal to reverse during the capture detect window. The sign of the post-pace polarization polarity, either positive or negative, is determined. The evoked response signal may reverse the polarity of the sensed signal from positive to negative or from negative to positive, during the time window of interest.

Abstract: A system and method of providing for cardiac pacing which incorporates modulation of the pacing rate in order to minimize variations in ventricular power output, e.g., variation related to patient respiratory phases. In a preferred embodiment, pacing rate is increased during inspiration relative to expiration, to restore a measure of the normal rate modulation which occurs in a normal person. Patient respiration is monitored and a respiration signal is processed to determine the timing of rate modulation. Parameters representative of respiratory changes, such as right ventricular volume and right ventricular blood pressure are also monitored and, together with respiration amplitudes changes, are used to determine an incremental rate signal for controlling the extent of rate variation.

Abstract: An ambulatory data recorder having a slidable patient activity period switch. The slidable patient activity period switch permits the patient to slide the switch from a first position to a second position upon the start of a pre-defined activity, e.g. eating. Upon completion of the pre-defined activity, the switch is slide from the second position back to the first position. While in either the first or second position the switch position corresponds to a marking on the recorder enclosure such that the patient can readily understand which activity the switch is indicating. The slidable patient activity period switch is further configured to have minimal power consumption. In one embodiment the switch is provided through a standard keyboard interrupt service routine.

Abstract: An implantable medical device such as a defibrillator is described. The device includes an hermetically sealed housing containing a flat electrolytic capacitor and an energy source such as a battery. The battery is connected to the capacitor and provides charge thereto. The capacitor stores the charge at a relatively high voltage. The charge stored in the capacitor is discharged through a defibrillation lead to a site on or in the heart when fibrillation of the heart is detected by the implantable medical device. Methods of making and using the implantable medical device, the capacitor, and their various components are disclosed.

Abstract: There is provided an implantable system and method for monitoring pancreatic beta cell electrical activity in a patient in order to obtain a measure of a patient's insulin demand and blood glucose level. A stimulus generator is controlled to deliver stimulus pulses so as to synchronize pancreatic beta cell depolarization, thereby producing an enhanced electrical signal which is sensed and processed. In a specific embodiment, the signal is processed to determine the start and end of beta cell depolarization, from which the depolarization duration is obtained. In order to reduce cardiac interference, each stimulus pulse is timed to be offset from the QRS signal which can interfere with the pancreas sensing. Additionally, the beta cell signals are processed by a correction circuit, e.g., an adaptive filter, to remove QRS artifacts, as well as artifacts from other sources, such as respiration.

Abstract: An electrochemical cell has a silver vanadium oxide cathode material formed into a pellet shape which expands as the cell is discharged. A cathode current collector circumferentially surrounds the cathode pellet and is in contact with the peripheral edge of the cathode pellet to prevent peripheral cathode expansion. The peripheral cathode current collector maintains a stable cell impedance during cell discharge. The cell has a D-shaped housing in which the cathode is disposed adjacent to a first interior surface, and a lithium anode is disposed adjacent to a second interior surface.

Abstract: An implantable sensor assembly for use with an implantable medical device are disclosed. The sensor assembly preferably includes two or more physiologic sensors coupled to the medical device via a pair of lead conductors, or alternatively an oxygen sensor having certain features. The oxygen sensor permits more accurate and reliable measurement of oxygen saturation in blood masses flowing within the human body.

Abstract: A pacing system and method for determining a heart failure condition such as left ventricular dysfunction in a patient are provided, based upon obtaining information from cardiac signals, which information is processed and examined for an indication of the onset or progression of LVD. Since LVD is generally characterized by conduction disorders and other body responses calling for different heart rates during exercise, an examination of sensed cardiac signals is utilized to obtain data reflective of an LVD condition. In one embodiment, a QT rate responsive pacemaker is utilized, wherein variations in QT interval corresponding to heart rate are detected and stored, and then periodically analyzed to detect changes of sufficient magnitude to indicate onset of LVD. In another embodiment, changes in lower natural rate at nighttime or rest are monitored and analyzed for detection for a trend indicating LVD.

Abstract: The invention provides heat-treated silver vanadium oxide for use in the cathodes of electrochemical cells, particularly in implantable medical devices. The heat-treated silver vanadium oxide is capable of being pressed into a pellet having a pressed pellet density of about 3.10 g/cm.sup.3 to about 3.45 g/cm.sup.3 when about 2 grams of the heat-treated silver vanadium oxide are uniaxially pressed into a pellet using a 1.6 cm diameter cylindrical die with a 7500 pound force applied for 5 seconds.

Abstract: A method for forming a thin film resistor includes providing a sputter target having one or more silicon containing components and chromium diboride. For example, the one or more silicon containing components may include silicon and/or silicon carbide. The resistor film is then sputter deposited on a surface using a nitrogen containing sputter gas. The resistor material generally is sputtered to a thickness in the range of about 125 .ANG. to about 500 .ANG. while maintaining a desirable sheet resistance. The resistor film may be used in one or more electrical circuits, such as in an implantable medical device.

Abstract: There is provided a pacemaker system having the feature of delivering a ventricular safety pulse (VSP) following an early ventricular sense (VS), wherein the pacemaker automatically determines whether VSPs are to be delivered following early VSs, and if yes, with what timing. The pacemaker gathers data following delivered VSPs, which data contains information indicative of whether each early VS was indeed the result of a spontaneous R wave, or was due to crosstalk from a prior delivered atrial pace pulse. This data is processed and, when it presents a high statistical confidence, is used to make a determination of whether to respond with the assumption of a true R wave, or of crosstalk. If the data is not statistically significant, the pacemaker delivers VSPs in a normal fashion, e.g., at the end of a programmable VSP interval timed out following delivery of an atrial pace pulse.

Abstract: A device for treating sleep apnea comprising means for detecting an apnea event and means responsive to detection of an apnea event for stimulating the heart at a higher rate than the heart's natural rate.

Abstract: An ambulatory recorder having a volatile and a non-volatile memory is described. The recorder actively manages the transfer of the data in the volatile to the non-volatile memory. In particular, the sampling frequency and number of channels to be sampled are monitored. These parameters, along with the total buffer size available, are used to determine the final complete data set which can be stored in the buffer. Thereafter, the contents of the buffer are transferred to the non-volatile memory. In such a manner the recorder avoids filling the buffer in the middle of a sampling tick, in which case the remaining data to be sampled would be lost.

Abstract: An implantable sensor assembly for use with an implantable medical device are disclosed. The sensor assembly preferably includes two or more physiologic sensors coupled to the medical device via a pair of lead conductors, or alternatively an oxygen sensor having certain features. The oxygen sensor permits more accurate and reliable measurement of oxygen saturation in blood masses flowing within the human body.