Abstract: A balloon catheter having an outer shaft and an inner shaft in which the inner shaft is constructed to protect itself over its entire length and especially in its most vulnerable areas without adversely effecting its flexibility, trackability, or pushability or the catheter's deflation time. The inner shaft can be reinforced to prevent it from collapsing or breaking throughout its length and also improving the deflation time of the balloon.

Abstract: A pressure device for use with a balloon angioplasty catheter includes a housing, a syringe body, rubber stopper and a pressure gauge. The rubber stopper is connected to a threaded plunger leading to a handle. The threaded plunger is engaged by a half nut. The half nut may also be disengaged. A forward located thumb button controls the engagement of the half nut with the threaded plunger. The initial operation of the thumb button also irreversibly illuminates the pressure gauge.

Abstract: A method and apparatus for stimulating the right or left vagus nerve with continuous and/or phasic electrical pulses, the latter in a specific relationship with the R-wave of the patient's electrogram. The automatic detection of the need for vagal stimulation is responsive to increases in the heart rate greater than a predetermined threshold, the occurrence of frequent or complex ventricular arrhythmias, and/or a change in the ST segment elevation greater than a predetermined or programmed threshold. The system is described with a microprocessor driven, brady therapy device with programming and telemetry capabilities for recording in memory the aforementioned stimulation triggering indicia, including electrogram segments for periods of time preceding and following each instance of vagal stimulation for telemetry out on command.

Abstract: In a coiled wire medical lead structure, such as a transvenous, endocardial cardiac pacemaker and/or cardioverter/defibrillator lead, an improved mechanical structure for strengthening the lead to enable its intact removal by traction after a period of chronic implant, one or more normally relaxed, nonextensible filaments loosely contained within the insulating sheath and having proximal and distal ends mechanically coupled to the connector and electrode shank, respectively, of the lead operate as means for restraining the stretching of the lead body to a stretched length exceeding the relaxed, predetermined length by an amount sufficient to allow the lead to be stretched without breaking in its normal usage and during removal by traction. In certain embodiments, the filament may take the form of a loosely woven fabric sheath formed in a tubular shape and fitted in the space between the lead body outer sheath and one or more coiled wire conductors.

Abstract: An implantable heart-assist device including extra-aortic balloon pump (EAB pump) for use in cooperation with a fluid pump is disclosed. The extra-aortic balloon pump includes a rigid, generally cylindrical housing and a flexible, generally cylindrical diaphragm residing generally within a longitudinal passageway in the rigid housing and secured to the rigid housing so as to create a plurality of separate expansion chambers. A plurality of fluid communication ports are provided for passing fluid into and out of the respective expansion chambers. The rigid housing includes interior and exterior surfaces, proximal and distal ends, and a longitudinal passageway. The diaphragm has an inner surface which defines a longitudinal lumen within the longitudinal passageway. The longitudinal lumen has a longitudinal axis and the respective expansion chambers and corresponding fluid communication ports are oriented axisymmetrically in respect to the longitudinal axis.

Abstract: A method and apparatus for stimulating the right and/or left carotid sinus nerves or the right stellate ganglion or the epidural space at about T.sub.2 with continuous and/or phasic electrical pulses in response to detected myocardial ischemia to decrease cardiac workload as a method to protect the myocardium. The automatic detection of the need for such stimulation is responsive to a change in ST segment variation different from a predetermined or programmed threshold suggesting acute myocardial ischemia and/or other criteria or indicators of myocardial ischemia, including changes if pH and/or oxygen saturation (SO.sub.2) detected from a sensor located in the heart, preferably the coronary sinus.

Abstract: A software-controlled, external programmer for transcutaneously programming and receiving data from an implanted medical device providing enhanced discrimination and detection of pulse-interval-coded signals of interest telemetered out of the implanted medical device from undesirable transient and steady-state noise. The programmer incorporates a detector including an active mixer and a precision tuned active phase shifting network providing low level signal rectification, precise narrow bandpass filtering, and 30 decibels of amplification. At the detector, the received signal is mixed with a phase shifted version of itself to produce a detected DC component which is a function of frequency. The DC response emulates a system with a narrow 25 kHz bandpass filter operating at 175 kHz, but does not share its undesirable transient response. For signals in the reject band, the output produces a signal of the opposite polarity of the signals within the pass bands.

Abstract: A rate responsive cardiac pacemaker for providing an optimized pacing rate of stimulation pulses as a function of at least one selected rate control parameter. Each rate control parameter has a value which varies as a function of changes in a patient's physiologic demand an includes a sensor system for sensing the rate control parameter value and for providing a sensor output representative thereof. The cardiac pacemaker also includes control circuitry which includes a rate response defining means for deriving desired pacing rates as a function of the sensor output and an achievement monitoring means that has a predetermined achievement criterion, for monitoring the relationship between the derived pacing rates and the achievement criterion over an achievement output. An output circuitry provides optimized pacing rates as a function of the desired pacing rates; and a rate response control means adjusts the rate response defining means accordingly.

Abstract: A rate responsive cardiac pacemaker for providing an optimized pacing rate of stimulation pulses as a function of at least one selected rate control parameter. Each rate control parameter has a value which varies as a function of changes in a patient's physiologic demand and includes a sensor system for sensing the rate control parameter value and for providing a sensor output representative thereof. The cardiac pacemaker also includes control circuitry which includes a rate response defining means for deriving desired pacing rates as a function of the sensor output and an achievement monitoring means that has a predetermined achievement criterion, for monitoring the relationship between the derived pacing rates and the achievement criterion over an optimization period.

Abstract: A new and improved all monolithic transceiver manufactured on a single semiconductor die and operative from a 5 volt DC power supply. The transceiver meets all of the pulse width and timing requirements of the MIL-STD-1553 transceiver and is operative at high switching speeds and high output current levels to generate bi-phase TX OUT and TX OUT signals used to drive, respectively, two center tapped primary windings of an output transformer. The transmitter includes two dynamically driven data channels which are driven out of phase and in a controlled manner that ensures that one data channel has been completely turned off before the other data channel turns on, thereby maximizing power transfer and operating efficiency while minimizing unnecessary current drain and eliminating current spiking in the output of the transmitter.

Abstract: A dual chamber rate responsive pacemaker with automatic mode switching between the DDD mode, the VVIR mode, and the DDIR mode, based on the difference between the average sensor rate and the average atrial rate. The primary pacing mode of operation is DDD, unless that mode is contraindicated by too great a difference between the average sensor rate and the average atrial rate. When the average sensor rate and average atrial rates are not too different, the DDD mode prevails. During bouts of sustained atrial tachyarrhythmia or atrial oversensing, the average atrial rate is greater than the average sensor rate. When that difference exceeds a programmable function of the two rates, the mode is switched to VVIR to avoid tracking high atrial rates. Conversely, if there is atrial chronotropic incompetence or atrial undersensing, then the average sensor rate is greater than the average atrial rate.

Abstract: A battery impedance measurement apparatus for battery powered implantable medical apparatus in which current source means and reference impedance means are selectively connected across the battery after it has been isolated from the medical apparatus, and the resulting currents of interest are digitized to provide a factor directly related to the value of the internal impedance of the battery. The digitized value may be telemetered out of the implanted medical apparatus to enable critical decisions to be made based on the remaining life of the implanted battery. The same measurement apparatus can be used to form an accurate end-of-life signal.

Abstract: An apparatus for and method of measuring the current which flows through a cardiac pacing lead to artificially stimulate contractions of the myocardium. This current measurement is useful for estimating battery life and monitoring proper operation of the pacing lead and the implantable pulse generator.The measurement is accomplished by carefully controlling the gain of the output amplifier and timing the rate of charge and discharge of the output capacitor. The average pacing current can be determined from the relative charge and discharge times given that the other circuit component values are known and controlled.

Abstract: A rate responsive pacemaker and a pacing method for optimizing the pacing decay curve after a period of increased activity. The pacing method includes the steps of selecting a set of predetermined achievement criteria such as an achievement rate and an achievement time interval. The achievement rate is selected between an upper pacing rate and a first pacing switch rate threshold. The pacing method then determines whether the achievement criterion has been met. If the achievement criterion has been met, then the decay time constant of the decay curve changes from a first value to a second value, as the pacing rate drops below the first pacing switch rate threshold. A second pacing switch rate threshold lower than the first pacing switch rate threshold is then selected, and, if the achievement criteria have been met, then the decay time constant of the decay curve is modified from the second value to a third value, as the pacing rate drops below the second pacing switch rate threshold.

Abstract: A monolitic rise and fall time generator system utilizing a trimmable bias resistor connected to a current generator. The trimmable resistor permits the rise and fall time to be trimmed to any value. A switch is connected between a current source and a current sink. A level shifter connects to the switch and receives a data input signal. A ramped voltage output signal is generated at the common node of the current source and the switch through a capacitive load and a voltage clamp.

Abstract: A method and apparatus are disclosed for telemetering both analog and digital data from an implantable medical device to an external receiver, such as between an implanted cardiac pacer and its external programming equipment. Analog data is first converted to digital format by an analog-to-digital converter, such that the transmission is digital data. A damped carrier at 175 kilohertz is pulse position modulated by the data. The modulation scheme defines a frame of slightly less than 2 milliseconds. The frame is divided into 64 individual time periods using a crystal clock. The data, along with synchronization and identification codes, are positioned into predefined ranges within each frame as measured by the individual time periods. The data is uniquely identified by the position of a burst of the carrier within the predetermined range.

Abstract: A technique for improving detection of the pacing artifact in patients having artificially paced myocardial contractions. The improved detection is accomplished by sensing all three commonly monitored EKG leads. Each lead is differentially amplified and rectified to produce a signal of absolute value. The resulting three signals are algebraically summed and differentiated. Because the pacing artifact consists of higher frequency components than the naturally occurring QRS complex, it can easily be detected by its much larger first derivative.Reliable detection of the artificial pacing artifact is extremely important in monitoring and programming implantable pacers. It is necessary to accurately determine whether a pacing pulse has been delivered and precisely measure the time of its occurrence.

Abstract: A technique for improving the radio frequency coupling between an external programming device and a medical device implanted within a patient. The radio frequency coupling is typically used to non-invasively change the operating parameters of the implanted device, such as a cardiac pacer. A common frequency for transmission is 175 khz. At this frequency, in view of the low power and the short distances involved, positioning of the external antenna with respect to the implanted antenna becomes critical. This criticality is heightened because of the great change in transmitter antenna loading and tuning with small changes in relative position.To assist the attending medical personnel, the transmitter antenna is ordinarily mounted within a paddle-like structure. A feedback coil is placed within the same physical package. The signal induced within the feedback coil is amplified, filtered, and integrated to produce a signal which controls the output amplifier of the transmitter.

Abstract: A system intended for being at least partly implanted into a living body and comprising at least two modules or devices which are interconnected by a communication transmission channel, at least one of said modules being provided with transmitting and receiving means for a bidirectional exchange of information with at least one further module and at least one other module of which being provided at least with receiving means or transmitting means for receiving information from at least one further module or for transmitting information to at least one further module, respectively. Within the intracorporeal region, said communication transmission channel by data modulated ultrasound. The body mass provides for an ultrasonic coupling between two or more implantable modules and/or between at least one implantable module and an external skin transducer intended for connection to an external module.

Abstract: A software-controlled, external programmer for transcutaneously programming and receiving data from an implanted medical device providing a real-time indication of the implanted medical device RF telemetry signal strength to the user of the device programmer while automatically optimizing gain level to minimize interference in the presence of noise. The method and apparatus involves monitoring the validity of received intervals or frames uplinked from the implanted medical device to adjust the gain of the RF amplifier in a pre-determined range. When noise is detected, indicating a relatively small signal-to-noise ratio, the automatic gain control (AGC) level is decreased, effectively tracking this condition. Similarly, lack of any signal of loss of individual RF pulses causes the AGC level to be increased.