Abstract: Implantable leads incorporating accelerometer-based cardiac wall motion sensors, and a method of fabricating such leads, are provided. The cardiac wall motion sensors transduce accelerations of cardiac tissue to provide electrical signals indicative of cardiac wall motion to an implantable cardiac stimulating device. The implantable cardiac stimulating device may use the electrical signals indicative of cardiac wall motion to detect and discriminate among potentially malignant cardiac arrhythmias. In response to a detected abnormal cardiac rhythm, the cardiac stimulating device may deliver therapeutic electrical stimulation to selected regions of cardiac tissue.

Abstract: A single-pass atrio-ventricular (A-V) pacing lead includes an elongated main lead body having an atrial electrode at the distal end thereof, and includes a ventricular branch which departs from the main lead body just proximal to the tip of the atrial electrode. The ventricular branch has a ventricular electrode at its distal tip. The main lead body includes a preformed "J"-shaped portion which, following proper implantation, projects the atrial electrode against a wall of the atrial appendage. The ventricular branch includes a preformed bend which curves in the opposite direction of the J-shaped portion so as to maintain the ventricular branch generally away from the wall of the atrial appendage. The lead includes a single lumen which extends through both the main lead body and the ventricular branch, allowing the lead to be implanted using a single stylet.

Abstract: An improved "VF immune" cardiac event detector for an implantable medical device consists of high-frequency and a low-frequency delta converters coupled to an intracardiac signal. The high-frequency delta converter is tuned to be responsive to R-waves and VF waveforms. However, the low-frequency delta converter is tuned to be responsive only to VF waveforms. By monitoring the difference between the outputs of the high-frequency and the low-frequency delta converters, the system can effectively discriminate between "true" R-waves and VF waveforms.

Abstract: A wireless feedthrough assembly, for coupling leads received in the receptacles of a connector assembly to the electronic circuit within a cardiac pacemaker, includes a weld ring mounted in hermetically sealed fashion within a housing wall of the pacemaker and itself hermetically sealed to an intermediate portion of an elongated, multilayered structure. The multilayered structure includes layers of electrically insulating ceramic material on opposite sides of a planar array of printed conductors extending between a first portion of the structure within the connector assembly and an opposite second portion of the structure within the pacemaker. Connector pads at the ends of the printed conductors within the first portion are coupled to the receptacles of the connector assembly, while contact pads at the exterior of the second portion and coupled by vias to connector pads at the ends of the printed conductors are coupled to the electronic circuits within the pacemaker.

Abstract: A monitoring and/or programming device communicates with a cardiac stimulation device, such as a pacemaker, which is operatively implanted within a patient. Communication between the programmer and cardiac device occurs over a radio frequency (RF) telemetry link. During a monitoring and/or programming procedure, data is transmitted over the RF telemetry link between the programming device and the cardiac device. Parameters indicating the quality of the RF telemetry link are continuously measured, evaluated and formatted for display to an operator of the programming device.

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: A calibration system for use with an implantable pacemaker allows the intracardiac electrogram (IEGM) generated by the pacemaker to be calibrated when the pacemaker is coupled to an external programmer. The calibration system includes telemetry circuits within both the pacemaker and programmer that allow data signals to be sent from the pacemaker to the programmer, and that allow command signals to be sent from the programmer to the pacemaker, in conventional manner. The system further includes circuitry within the pacemaker that generates a precision reference voltage as well as a zero reference voltage, and that selectively switches the precision reference voltage and/or the zero reference voltage into the IEGM data signals being telemetered to the external programmer from the pacemaker. The switching of the precision reference voltage and/or zero reference voltage into the IEGM data occurs within the pacemaker upon receipt of a special calibration command signal from the programmer.

Abstract: A device for transmitting binary information, in the form of two information-carrying symbols, between two or a number of units, in which transmission is by optical means in free medium, includes an optical transmitter module with a transmitter unit for transmitting an optical transmission signal and an optical receiver module with a receiver unit for receiving the optical transmission signal, and the device is arranged for high speed communications without a carrier wave. The transmitter module is equipped with a formatting unit devised to activate the transmitter unit to emit the transmission signal only during part of a complete symbol interval corresponding to one of the symbols, and the receiver module is equipped with a normalizing unit devised to recreate, from the transmission signal received by the receiver unit, both the symbol corresponding to the transmission signal throughout its entire symbol interval and the residual information-carrying symbol in the digital information.

Abstract: A device for detecting hemodynamic conditions in a heart, in particular conditions corresponding to dangerous arrhythmias contains a sensing unit for a physiological variable, such as blood pressure, the unit emitting a signal on the basis of the variable having an average value, a signal conditioning unit connected to the sensing unit, a calculation unit connected to the signal conditioning unit and a comparator after the calculation unit. The calculation unit is devised to calculate a variability measure relative to the signal's average value, the variability measure being correlated to average blood pressure, and the variability measure is compared in the comparator to an adjustable threshold value corresponding to a specific hemodynamic condition, whereupon the comparator emits an indication signal when the variability measure falls below the threshold value.

Abstract: In a method for manufacturing a working electrode for an implantable, electrochemical oxygen sensor a thin layer of a uniform mixture composed of an epoxy-based resin, a hardener and powdered vitreous carbon is applied onto a ring or hollow cylinder of biocompatible, inert, electrically conductive material, and the resin is hardened.

Abstract: An electrode device, for intracardiac stimulation of heart tissue and/or sensing heart signals in a patient, has an electrode cable containing at least two elongate, flexible conductors, insulated from each other, and with an electrode head, arranged at the distal end of the electrode cable and at least two conductive surfaces, each connected to a separate conductor. In order to permit the distance between the conductive surfaces to be varied over a continuous range, simply and easily, the electrode head has at least two parts, moveable in relation to each other, each part being provided with at least one conductive surface, and the a control element is movably arranged at the distal end of the electrode cable immediately behind the electrode head, so any change in the position of the control element causes the control element to act on the parts of the electrode head such that the distance between the conductive surfaces is varied.

Abstract: A microprocessor-controlled implantable cardiac stimulating device having a normal mode, an intermediate mode, and a backup pacing mode is provided. The device switches from one mode to another in response to the detection of any one of an address error, parity error, opcode error, or watchdog timer error. The microprocessor is shut down during the delivery of a cardioversion or defibrillation shock in order to prevent signals produced by the microprocessor from being subjected to transient electrical signals. The interrupt registers of the microprocessor are also disabled during the delivery of a cardioversion or defibrillation shock. In an alternative embodiment, an implantable cardiac stimulating device is provided with redundant microprocessors in order to detect malfunctions of the microprocessors.

Abstract: A micropower analog-to-digital converter (ADC) for use in an implantable medical device is disclosed. The ADC achieves a high conversion speed at micropower levels through a number of timing and circuit improvements over the conventional implementation of the successive approximation ADC architecture. The ADC includes a digital-to-analog converter (DAC) that preferably is implemented as a binary-weighted, switched capacitor array that employs top plate charging and performs bipolar conversion. The DAC provides an analog output signal representing array charge to a comparator. During a comparator latch phase, the DAC asynchronously determines a bit of the ADC digital output signal in response to the comparator output, and initiates a test of the next least significant bit during the same latch phase. Further, the DAC analog output signal is timed to settle during the latch phase in response to both the bit update and the next bit test.

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: The electrode structure includes a cathode, anode and polymeric separator, wound into an oval configuration having a length and width equal to interior dimensions of the rectangular housing. The oval shape is achieved by winding a long, flat electrode structure around a mandrel. The length of the electrode structure is chosen based upon the size of the mandrel, the interior dimensions of the housing, and the width of the electrode structure, such that, after winding, the resulting oval structure snugly fits within the rectangular housing leaving no remaining spaces, other than in corners of the housing. A leaf spring is provided between a free end of the electrode structure and an interior wall of the housing for ensuring that the electrode structure remains tightly wound. Appropriate electrical contacts are provided to the anode and cathode of the electrode structure.

Abstract: In a method for measuring the flow of an electrolytic fluid, the voltage or current is measured between two stationary electrodes immersed in the electrolytic fluid. A device for measuring the flow has at least two electrodes intended for immersion in the electrolyte. The electrodes are stationary, and a measurement unit is arranged to measure the voltage or current between the electrodes.

Abstract: In a method and apparatus for determining whether electrical signals in a heart are caused by atrial depolarizations or ventricular depolarizations, heart signals are sensed in the upper part of the ventricular heart tissue, preferably the upper part of the ventricular septum. The detection of heart signals from both the atrium and ventricle and the identification of depolarization is facilitated if the course of the signals is monitored, with monophasic heart signals being caused by an atrial depolarization and biphasic signals being caused by a ventricular depolarization.

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 cardioversion shock therapy system is provided which delays delivery of a cardioversion shock until late in the cardiac cycle to optimize the chance for the vast majority of ventricular myocardial tissue to be non-refractory. The system in intended to increase efficacy and safety by properly synchronizing the cardioversion shock to the appropriate portion of the cardiac cycle to successfully terminate a tachycardia episode. The timing of the cardioversion shock is programmable as either a percentage of measured tachycardia cycle length or fixed delay in milliseconds.

Abstract: An implantable dual-chamber pacemaker programmed to operate primarily in an atrial tracking mode is provided, where the pacemaker maintains a consistent atrial rate of entry into, and exit from, a 2:1 block response mode by setting rate-responsive AV delay values in accordance with a continually monitored intrinsic atrial rate incorporating atrial events occurring during atrial refractory periods. The atrial rate of entry into, and exit from the 2:1 block response mode is determined by the length of a total atrial refractory period, which is the sum of the rate-responsive AV delay and a programmable refractory period.