Abstract: A device for recording and playing back a selected episode from an input analog audio-visual signal. A "deferred recording" feature allows the user to briefly delay his/her decision to record a live signal episode until after the signal episode has at least partially transpired. Thus, the user can first evaluate the episode prior to deciding whether to record it. The recorded signal episode contains both preamble and postamble segments, i.e. the signal segments preceding and following activation of a record switch. The analog playback signal is directed to an A/V output device so it can be heard/viewed by the user. Some embodiments provide for recording multiple signal episodes, multi-signal channel episodes, variable length episodes, simultaneous record and playback, episode deletion, variation of sampling rate, skip forward, reverse, and squelch.

Abstract: Improved methods and apparatus are provided for applying atrial and ventricular therapies to the heart of a patient using an implanted cardiac stimulating device. Atrial and ventricular heart rates are monitored and analyzed to determine whether the patient is suffering from an atrial or ventricular arrhythmia and to determine what type of therapy is appropriate to apply to the heart. Atrial and ventricular heart rates are compared to determine if the ventricular heart rate exceeds the atrial heart rate and to determine whether the ventricular heart Fate is stable. An early atrial stimulation pulse can also be applied to determine whether the ventricular heart rate follows the atrial heart rate. Atrial and ventricular therapies are applied to the heart based on these determinations.

Abstract: An apparatus for annotating physiological waveforms is provided. The apparatus comprises an implantable medical device, which may be a pacemaker or a cardioverter/defibrillator, and a programmer for use with the implantable medical device. The implantable medical device may be modeled as a finite state machine. Whenever the implantable medical device enters a new state, a state transition vector or a current state vector is transmitted to the programmer. The programmer implements a state machine model of the implantable medical device to determine the current state of the device based on the received state vectors. Because the exact state of the implantable medical device is known, the programmer can annotate the physiological waveform more completely than has previously been possible. For example, when the behavior of the implantable medical device is unclear, the programmer can place an explanatory label adjacent to the displayed physiological waveform.

Abstract: Methods and apparatus are provided for generating multiphasic charge-balanced cardioversion and defibrillation shocks to apply to a patient's heart to terminate episodes of arrhythmia such as tachycardia and fibrillation. The time-integrated positive shock phase current equals the time-integrated negative shock phase current. The use of charge-balanced shocks has been determined to significantly reduce the effects of post shock block that result when conventional shocks are applied to the heart.

Abstract: An implantable blood flow sensor for measuring a blood flow rate through a blood vessel within a person's body. The flow sensor includes a rigid cylindrical tube, sized to fit within the blood vessel, a heater attached to the tube, and a pyroelectric detector located within the tube. A predetermined amount of heat energy is produced by the heater and the pyroelectric detector monitors the resultant temperature change and generates a temperature signal based on the temperature change. A processor generates a data signal, based on the temperature change, that indicates the blood flow rate through the blood vessel or artery. The rigid tube protects the pyroelectric detector from external forces that may produce unwanted signals due to piezoelectric effects. Additionally, the heater may be incorporated into one of the electrodes of the pyroelectric detector as a serpentine path in the electrode that forms a resistive heating element.

Abstract: A two-conductor bus system is provided to electrically interconnect a plurality of physiologic sensors to a pacemaker, each sensor being adapted for placement along a pacing lead. The conductors of the bus extend longitudinally through the insulating material of the lead, connecting to each sensor. The pacemaker provides a supply voltage on the bus to provide power to the sensors. The sensors modulate the supply voltage on the bus to transmit information to the pacemaker. This information may be used by the pacemaker to adaptively pace the heart. In one embodiment, the sensors include bus monitoring circuitry for receiving control signals from the pacemaker.

Abstract: A combination lead for use with an implanted pulse generator which may be a pacemaker or defibrillator or combination thereof. The lead can deliver an electrical charge to pace, cardiovert or defibrillate the ventricles of the heart, and can sense cardiac activity in the heart. The lead includes atrial ring sensors capable of sensing electrical activity in the atrial cavity. The lead allows cardioversion and/or defibrillation stimuli to be provided by a large surface area electrode which is passively implanted in the ventricle, and allows the pulse generator to provide ventricular pacing appropriately synchronized to atrial depolarizations, cardioversion or defibrillation.

Abstract: An endocardial lead assembly, adapted to transmit electrical signals between a proximal end portion of the lead assembly and a distal end portion of the assembly and to thereby stimulate selected body tissue, includes at least two coiled, insulatively coated conductors extending between the proximal and distal end portions for transmitting the electrical signals. The coils of the at least two insulated conductors are contiguous and have substantially the same first outer diameter, one of the coiled conductors having a portion extending through said distal end portion of the lead and being electrically connected to said tip electrode. The remaining conductor(s) terminate at a proximal extremity of the distal end portion, the portion of the one coiled conductor within the distal end portion including contiguous, uninsulated coils having a second outer diameter that is less than the first diameter.

Abstract: A flow sensor adapted for placement along a pacing lead or other catheter comprises a thermopile formed on the outer surface of a tubular substrate. The thermopile comprises a plurality of interconnected conductors of an alternating metal type. Junctions between conductors of the thermopile are alternately located near the longitudinal ends of the flow sensor, so that a voltage generated by the thermopile indicates the difference in temperature between the ends of the flow sensor. To measure blood flow with the flow sensor, an alternating current is induced through the thermopile to heat the flow sensor in a generally symmetrical manner. A voltage generated by the thermopile is then measured to obtain a sample of the magnitude and direction of the velocity of blood flow.

Abstract: The electrochemical cell includes an electrode structure having an aluminum current collector in combination with an active cathode material containing polycarbon monofluoride. The electrode structure also includes a polymeric separator and a lithium anode. The electrode structure is spiral wound and mounted within a cylindrical housing formed of conventional stainless steel. Care is taken to ensure that the aluminum foil isolates the polycarbon monoflouride of the cathode material from the stainless steel of the housing. The cylindrical housing is flooded with a non-aqueous electrolyte solution. The resulting cell is employed within an implantable medical device. In an alternative embodiment, electrode structures employing the aluminum current collector and the polycarbon monoflouride active cathode material are formed as rectangular plates and are mounted in parallel within a rectangular housing. In another alternative embodiment, the aluminum current collector is employed within a button cell.

Abstract: An improved input protection circuit for use in a circuit for processing sensor signals from a piezoelectric patient activity sensor is provided. The input protection circuit includes a field-effect transistor to prevent the voltage at an input terminal of the processing circuit from rising beyond a first predetermined voltage or falling below a second predetermined voltage. The gate and drain terminals of the transistor are connected to a first of two input terminals of the processing circuit and the source and body terminals are connected to the second terminal. When the voltage at the first terminal rises or falls sufficiently, the transistor conducts current, thereby preventing the voltage from rising or falling further.

Abstract: An expanded screen current collector is provided with side edges coined inwardly to prevent sharp tines formed along the side edges from damaging adjacent components within the electrochemical cell. The expanded screen current collector is formed by cutting a thin flat sheet of current collector material, such as titanium or stainless steel, to have a height somewhat greater than a height required for use within the electrochemical cell. The current collector material is cut and expanded, then the side edges are coined inwardly by an amount sufficient to reduce the height of the resulting expanded screen current collector to a height appropriate for use within the electrochemical cell. An active cathode material, such as polycarbonmonoflouride, is coated onto side surfaces of the expanded screen current collector. An electrode structure employing the expanded screen current collector having the coined edges is also described.

Abstract: A periodic electrical lead integrity testing system is provided which periodically tests electrical leads used with an implantable cardiac stimulating device. The system is especially advantageous in multi-functional implantable cardiac stimulating devices. Lead integrity is evaluated by periodically comparing the impedance of the electrical leads to a reference impedance. A pass/fail algorithm is used to determine if electrical lead integrity has been compromised. The system improves the efficacy and safety of implantable cardiac stimulating devices by detecting electrical failures independent of the delivery of therapeutic shocks. The required circuitry adds only minimal complexity and cost to the implantable cardiac stimulating device.

Abstract: An implantable pacing lead having a flexible insulative material injected into the passageway accommodating the electrical conductor(s) to encapsulate the conductor(s) for at least the portion of the lead body most subject to physical damage to in the lead body.

Abstract: An implantable bipolar pacing lead having a bipolar active fixation electrode for use with a cardiac pacemaker. The bipolar active fixation electrode may include a pair of coaxial electrodes, separated by an intermediate insulator, formed into the shape of a helix. The bipolar electrode helix is preferably advanceable from a distal end of the bipolar pacing lead.

Abstract: A pacing lead having a stylet introduced anti-inflammatory drug delivery element advanceable from the distal tip electrode. The element is preferably formed as a moldable biocompatible composite material. The element has a biocompatible matrix material which may be combined with drugs and therapeutic agents to deliver the drugs and agents by co-dissolution or diffusion to the point of either passive or active fixation. The drug delivery element may be rigid and serve to center the means, preferably a helix, for active fixation of the lead in the myocardium.

Abstract: A cardiac device that stores physiological sensor data from multiple sensors is provided. A patient may use a portable triggering device to cause the cardiac device to store the data when the patient experiences symptoms that appear to be due to an abnormal heart condition. Alternatively, the data may be stored when the cardiac device identifies an abnormal physiological condition. A physician may select which sensors are used to store the data and may also adjust the number of memory buffers in which the data is to be stored.

Abstract: A cathode material is fabricated using two binder compounds, polyethylene oxide and acrylic resin, which react during processing to achieve enhanced bonding. The cathode material is formed by dissolving acrylonitril resin within the acetonitrile solvent. Polyethylene oxide powder is added yielding a homogenous solution. A powder mix containing a carbon material, such as high surface area carbon powder, and an active cathode compound, such as polycarbon monoflouride, is added to the binder mixture to produce a slurry. In one embodiment, the slurry is heated to evaporate the solvents, yielding a thin flexible cathode material for mounting to an expanded screen current collector. In an alternative embodiment, the slurry is spread directly onto a foil current collector. The solvents thereafter evaporate from the slurry yielding excellent mechanical and electrical coupling between the active cathode compound and the current collector.

Abstract: An implantable pacemaker operates in a DDD mode and reverts to a modified DDI mode in response to sensing atrial depolarization early in the pacing cycle. The modified DDI mode, when invoked, provides additional atrial kick by generating an atrial stimulation pulse (A-pulse) when there is sufficient time left in the current pacing cycle for the atrial kick resulting from such A-pulse to be of hemodynamic and electrophysiologic benefit. A time window, T.sub.A, is defined that follows the post-ventricular atrial refractory period (PVARP) of the normal DDD pacing cycle. If a P-wave is sensed during T.sub.A, then the modified DDI mode is invoked. In such modified DDI mode, the time between the last ventricular event and the next scheduled V-pulse, absent the detection of an inhibiting R-wave, is preserved. Further, in such modified DDI mode, if there is sufficient time to supply an A-pulse before the next V-pulse is scheduled, such A-pulse will be generated to provide the additional atrial kick.

Abstract: A programming system is provided that allows a physician or medical personnel to optimize the settings of various arrhythmia detection criteria and/or parameters related to hemodynamic performance to be programmed into the implanted cardiac stimulating device. The cardiac stimulating device may be a pacemaker or cardioverter/defibrillator that detects heart arrhythmias by using various arrhythmia detection criteria. The cardiac stimulating device is capable of recording the patient's cardiac signals and/or sensor data. The programming system may play back the recorded signals to test the detection criteria and hemodynamic performance and may simulate the response of the device to the cardiac signal. Alternatively, the programming system may play back an artificially created or previously stored cardiac signal for test purposes. As a result, the recorded signal may be played back repeatedly without unnecessarily stressing the patient's heart.