Abstract: A method and apparatus for evaluating heart rate variability of the heart of a person in order to forecast a cardiac event. A cardiac stimulator receives heart beat signals from the heart and determines a measurement of heart rate variability based on statistical data derived from the heart beat signals and sensing data derived from a sensor. This measurement of heart rate variability is compared with previously stored heart rate variability zones defining normal and abnormal heart rate variability. These zones are modifiable after the occurrence of a cardiac event. Once a cardiac event is detected, a pathway is computed which extends from a generally normal heart rate variability condition to an abnormal heart rate variability condition. Subsequent measurements of heart rate variability are compared with this pathway. Selective therapy regimes are initiated depending on the measurement of heart rate variability.

Abstract: A cardiac stimulator capable of measuring pacing impedance includes a tank capacitor for delivering charge to the heart via device leads, a shunt resistor, and high-impedance buffers for measuring pacing current through the shunt resistor. Soon after the leading edge of the stimulation pulse, the voltage across the shunt resistor, as sampled by a high-impedance buffer, indicates lead and cardiac tissue resistance. Just prior to opening the pacing switch to terminate the stimulation pulse, the voltage across the shunt resistor is sampled by a high-impedance buffer and held once again to allow the capacitance of the lead/heart tissue to be calculated. In alternative embodiments, a high-impedance buffer measures the voltage between the tank capacitor and ground immediately following the stimulation pulse to allow estimation of the lead/heart tissue capacitance.

Abstract: It has been determined that certain dual-chambered cardiac stimulators may operate in a region in which an atrial pacing event may obscure the detection of a ventricular tachyarrhythmia. Various exemplary techniques may be used to improve the ability of dual-chamber cardiac stimulators to detect such ventricular events. In accordance with one technique, it is determined whether a ventricular event should be classified as a ventricular tachyarrhythmia. If not, the VA interval is restarted as usual. However, if the ventricular event may be classified as a ventricular tachyarrhythmia, it is determined whether the ventricular event falls within the region in which an atrial pacing event may obscure its detection. If not, then the VA interval is restarted as usual. However, if the ventricular event falls within this region, the VA interval is restarted with the VT rate detection boundary.

Abstract: A cardiac stimulator lead is provided that includes a connector for connecting to a cardiac stimulator and a tubular insulating sleeve that has a first end coupled to the connector and a second end. An electrode is coupled to the second end and has a longitudinal bore. An extendable/retractable corkscrew is positioned in the bore. In one aspect, the lead includes a radiopaque member moveable with the corkscrew to verify axial movement. In another aspect, the bore is configured so that the corkscrew will not extend fully unless tissue is present to engage the corkscrew. In another aspect, a shape-memory polymeric washer is included to restrict fluid influx after corkscrew deployment.

Abstract: A technique for acquiring and accessing information from a medical implantable device is provided. Analog waveforms of interest are sensed and processed by signal acquisition circuitry. Analog parameters of interest are applied to selector switches which are controlled by a logic circuit. The logic circuit is also coupled an A/D converter for converting the analog signals to digital values. The digital values are stored in dedicated registers and are available for telemetry to an external device upon receipt of a request or prompt signal. When a digitized value is accessed and telemetered, the control logic circuit changes the conductive state of the selector switches to apply the corresponding analog signal to the A/D converter. The resulting digital value is applied to the corresponding register to refresh the accessed and telemetered value. The technique permits the external device to request and configure the implanted device to send only digitized values of interest.

Abstract: A method of forming trimmable resistors, resistor ray be embedded into a substrate. A portion of the resistor may be exposed, by segmenting the substrate, so that the resistor may be trimmed to a desired resistance level. Alternatively, a portion of a resistor may be embedded into a substrate, with another portion of the resistor being disposed on the outer surface of the substrate. The portion of the resistor on the outer surface may be trimmed to adjust the resistance of the resistor to a desired level.

Abstract: An electrode for a cardiac lead and method of making the same are provided. The electrode includes an electrode member and a coating applied to the electrode member. A method of fabricating a high impedance cardiac lead electrode is provided. The method includes the steps of providing an electrode member and coating a first portion of the electrode member with an electrically insulating material and placing a tubular mask or shield over the electrode. Portions of the insulating material are removed to expose selected areas of the electrode. The second or exposed portion enhances the impedance of the electrode, resulting in power savings and extended life spans for implantable stimulation and sensing devices. Exemplary materials for the coating includes diamond-like carbon and sapphire.

Abstract: A memory device particularly useful in size-constrained electronic products, such as cardiac stimulators. To provide additional memory for such size-constrained products, memory chips are stacked one on top of another. The memory chips are configured to facilitate bonding without crossed contacts, using aligned bonding pads, vias, or castellations. Each memory chip also includes an address selection circuit that receives signals from one or more address lines to selectively enable and disable the memory chips in the stack.

Abstract: A thin film capacitor for use in an implantable defibrillator. A first dielectric polymer film layer has a metallized film on one side thereof. A second dielectric polymer film layer has a metallized film on one side thereof. The first and second layers are overlain on each other and wound spirally with the metallized film of one layer adjacent the dielectric polymer of the other layer. The beginnings and ends of the first and second metallized films are offset from the respective beginnings and ends of the first and second polymer film layers. The dielectric layers can be tapered in increasing thickness toward the respective beginnings and ends of the layers. The dielectric layers can themselves comprise at least two layers of differing polymer materials, the preferred materials being polyvinylidene fluoride and polyester for improved energy density and self-healing properties.

Abstract: A multiprogrammer system for monitoring and optimizing implantable device performance. In one embodiment, the system includes at least two programming devices and an implantable device. Each of the programming devices may be used to perform inquiry and programming operations on the implantable device. In an inquiry operation, the programming device retrieves some or all of the configuration parameters from the implantable device. In a programming operation, the programming device provides one or more modified parameters to the implantable device. As part of the programming operation, the programming device is configured to verify that it is aware of the implantable device's current parameters before sending the modified parameters. In other words, the current programming device verifies that the implantable device's parameters have not been altered by another programming device since the current programming device's last interaction with the implantable device.

Abstract: It has been determined that certain dual-chambered cardiac stimulators may operate in a region in which an atrial pacing event may obscure the detection of a ventricular tachyarrhythmia Various exemplary techniques may be used to improve the ability of dual-chamber cardiac stimulators to detect such ventricular events. In accordance with one technique, it is determined whether a ventricular event should be classified as a ventricular tachyarrhythmia. If not, the VA interval is restarted as usual. However, if the ventricular event may be classified as a ventricular tachyarrhythmia, it is determined whether the ventricular event falls within the region in which an atrial pacing event may obscure its detection. If not, then the VA interval is restarted as usual. However, if the ventricular event falls within this region, the VA interval is restarted with the VT rate detection boundary.

Abstract: A first fixture holds a plurality of circuit components backside up in a substantially coplanar relationship. An adhesive applying device, such as screen printer, applies adhesive to the backside of each circuit component. A second fixture is aligned with and placed on the first fixture. The fixtures are then flipped so that the circuit components are supported in a right side up position by the second fixture. A device such as a pick and place machine, may then be used to transfer the circuit components from the second fixture to a substrate.

Abstract: A technique for acquiring and accessing information from a medical implantable device is provided. Analog waveforms of interest are sensed and processed by signal acquisition circuitry. Analog parameters of interest are applied to selector switches which are controlled by a logic circuit. The logic circuit is also coupled an A/D converter for converting the analog signals to digital values. The digital values are stored in dedicated registers and are available for telemetry to an external device upon receipt of a request or prompt signal. When a digitized value is accessed and telemetered, the control logic circuit changes the conductive state of the selector switches to apply the corresponding analog signal to the A/D converter. The resulting digital value is applied to the corresponding register to refresh the accessed and telemetered value. The technique permits the external device to request and configure the implanted device to send only digitized values of interest.

Abstract: A cardiac stimulator lead is provided. The cardiac stimulator lead includes a connector for connecting to a cardiac stimulator and a flexible tubular sleeve that has a first end coupled to the connector and a second end. An electrode has a proximal end that is inserted into the second end of the sleeve. An annular member is disposed around the proximal end and the second end and is deformed to clamp the second end to the proximal end. A conductor wire is coupled between the connector and the electrode. The deformed annular member eliminates reliance on an adhesive-to-metal molecular bond as the sole or primary mechanism for securing the distal end of a lead sleeve to the tip electrode. Manufacturing and assembly time may be significantly reduced.

Abstract: An implantable endocardial defibrillation lead having a looped cable conductor for conducting at least high voltage defibrillation shocks. A coil electrode is connected to an elongated, flexible, electrically non-conductive lead body and is supplied with electrical power for delivering electrical shocks to the heart through a looped cable conductor that extends through the lead body and is associated with a power source.

Abstract: A cardiac stimulator capable of measuring pacing impedance includes a tank capacitor for delivering charge to the heart via device leads, a shunt resistor, and high-impedance buffers for measuring pacing current through the shunt resistor. Soon after the leading edge of the stimulation pulse, the voltage across the shunt resistor, as sampled by a high-impedance buffer, indicates lead and cardiac tissue resistance. Just prior to opening the pacing switch to terminate the stimulation pulse, the voltage across the shunt resistor is sampled by a high-impedance buffer and held once again to allow the capacitance of the lead/heart tissue to be calculated. In alternative embodiments, a high-impedance buffer measures the voltage between the tank capacitor and ground immediately following the stimulation pulse to allow estimation of the lead/heart tissue capacitance.

Abstract: A tubular sleeve is provided for enabling a physician to impart a preselected shape in an implantable tubular device, such as a cardiac lead, a catheter or some other tubular structure. The sleeve may be deformed by the surgeon before or at the time of implantation to customize the shape of the tubular device to the particular anatomical structures to be encountered by the device. To retain the deformation imparted by the physician, the sleeve may be composed of a heat-sensitive shape-memory material or an elastomeric material provided with a plastically deformable rib.

Abstract: An implantable defibrillation lead with steerable characteristics, allowing the lead to be more easily placed within the coronary sinus. The lead comprises an elongated lead body having a proximal end and a distal end. Adjacent the distal end, there is an electrode, preferably a coiled defibrillation electrode placed on the exterior of the elongated lead body. The distal end of the lead body has a permanent set or bend. A torque tube, extending through a lumen in the lead body from the proximal end of the lead to an anchor block adjacent the distal end of the lead, can be rotated by a physician to orient the bend in the lead. A cable passes through the torque tube from the proximal end of the lead through the anchor block to the distal end of the lead. This cable is affixed to a wall of the lumen, preferably in the direction of the bend. Pulling on the cable temporarily changes the bend in the distal end of the lead.

Abstract: An implantable medical interventional device is disclosed for treating any of multiple cardiac dysrhythmias that may be suffered by a patient in whom the device is to be implanted, by automatic selection of an appropriate therapeutic regimen from among a plurality of such regimens the device is capable of delivering according to the particular dysrhythmia being experienced by the patient at the time, through enhanced recognition and discrimination of the dysrhythmia and its probable origin. Upon recognition and discrimination of the dysrhythmia, the device applies the selected regimen to the patient's heart to treat the dysrhythmia at its source.

Abstract: Surface mount device packages with increased mounting strength and a method therefor. In one embodiment, an, electronic device is made up of a device package and one or more electrically conductive terminals. For surface mounting, the device terminals are each provided with a mounting surface which is bonded using a conductive adhesive to a corresponding contact pad on a circuit board. The terminals are further provided with at least one groove across the mounting surface. When conductive adhesive is used to mount the device on a circuit board, this groove serves to form the conductive adhesive into a ridge or “dam” over the contact pad. This provides increased mounting strength which may eliminate the need for additional adhesive material to provide side reinforcement of the device, and thereby allow an increase in the packing density of devices on the circuit board.