Abstract: An apparatus and method for brachytherapy. One method includes locating a region of cardiac tissue having a relatively large probability of originating or transmitting electrical signals which result in arrhythmic activity and irradiating the region of cardiac tissue to reduce the amount of arrhythmic activity. Irradiating can include regulating protein expression of myocardial cells, killing myocardial cells, ablating myocardial cells, irradiating sleeves of atrial muscle that extend from a left atrial wall around the pulmonary veins, and/or creating lesions that block electrical conduction through myocardial tissue. Locating the region can include locating a foci of an atrial arrhythmia or locating the foci adjacent a pulmonary vein.

Abstract: An apparatus and method for brachytherapy. One method includes locating a region of cardiac tissue having a relatively large probability of originating or transmitting electrical signals which result in arrhythmic activity and irradiating the region of cardiac tissue to reduce the amount of arrhythmic activity. Irradiating can include regulating protein expression of myocardial cells, killing myocardial cells, ablating myocardial cells, irradiating sleeves of atrial muscle that extend from a left atrial wall around the pulmonary veins, and/or creating lesions that block electrical conduction through myocardial tissue. Locating the region can include locating a foci of an atrial arrhythmia or locating the foci adjacent a pulmonary vein.

Abstract: The present invention provides a method, and an apparatus, for forming a prescribed concentration of a substance in a mixture with a fluid, from a comparatively dilute mixture. The mixture is most preferably a solution of a solute in a solvent. The following summary and description generally discuss the invention in terms of a particularly preferred solution and a preferred use for that solution; however, in its broadest embodiments, the invention encompasses both the use for other solutions, and the use for a suspension of a solid substance in a fluid to form a mixture (which can also be referred to as a slurry). The invention provides for significant economic, safety and quality benefits over conventional evaporative systems.

Abstract: The present invention provides a method, and an apparatus, for forming a prescribed concentration of a substance in a mixture with a fluid, from a comparatively dilute mixture. The mixture is most preferably a solution of a solute in a solvent. The following summary and description generally discuss the invention in terms of a particularly preferred solution and a preferred use for that solution; however, in its broadest embodiments, the invention encompasses both the use for other solutions, and the use for a suspension of a solid substance in a fluid to form a mixture (which can also be referred to as a slurry). The invention provides for significant economic, safety and qualify benefits over conventional evaporative systems.

Abstract: A compact cartridge for an afterloader includes a housing containing a radioactive sourcewire and a dummy test wire, each accommodated in a helical groove on the periphery of a wire storage drum. The wires are contained in the grooves by low friction bearings, such as rollers, so that advancement of the wire from the drum is under very low friction conditions. The cartridge is removably inserted in the head of an afterloader apparatus and engages a primary drive system and an emergency retract mechanism mounted in the head. The cartridge also contains an electronics board with software for updating the software in the control electronics for the afterloader.

Abstract: A method is disclosed for treating a blood vessel which has been subjected to interventional dilatation, to inhibit restenosis that would otherwise occur from cellular proliferation attributable to traumatic response at the site of the vessel interior wall where the dilatation was performed. The method includes introducing a radioactive source into the blood vessel so that the source is positioned adjacent to the site, and exposing targeted tissue of the vessel interior wall at the site to said radioactive source for a period of time sufficient to deliver a prescribed dose of radiation to the tissue. The rate at which the prescribed dose is delivered to the targeted tissue is adjusted to positively assure that the rate is held in a range with an upper limit of about 60 rads per second.

Abstract: A transvenous lead for defibrillation and pacing of the heart includes a single defibrillating coil electrode adapted to be introduced into the right ventricle of the heart. The coil constitutes a relatively long flexible large surface area electrode conformable to the shape of the ventricle and thereby readily disposed along the entire length of the vertricle for use in delivering defibrillating shocks. A pacing electrode at the tip of the lead is used both in stimulating the heart with pacing pulses and in sensing the response of the heart to the pulses and to shocks. The coil electrode is multi-filar, composed of a plurality of wires tightly wound side by side, each wire composed of copper-zirconium alloy wrapped with tantalum, and is flared from the diameter at its ends to a lager diameter intermediate its ends to increase the exposed surface area thereof in the ventricle.

Abstract: An implantable cardiac stimulator for detecting and treating cardiac arrhythmias includes a sense amplifier responsive to sensed cardiac signals for detecting and distinguishing normal and abnormal cardiac activity within the sensed signals. The sense amplifier includes an automatic gain control amplifier, a filter and quad comparator having a pair of signal channels for processing the sensed signals according to different frequency bandpass characteristics to establish sensing thresholds, margins and signal gain. The sense amplifier has a feedback loop containing a microprocessor which implements preselected algorithms in conjunction with the outputs of the quad comparator to variably adjust the amplifier gain and to programmably control the sensing margin.

Abstract: An implantable cardiac stimulator integrates the functions of bradycardia and anti-tachycardia pacing-type therapies, and cardioversion and defibrillation shock-type therapies. The stimulator is programmable to provide a multiplicity of hierarchical detection algorithms and therapeutic modalities to detect and treat classes of ventricular tachycardia according to position within rate range classes into which the heart rate continuum is partitioned, and thus according to hemodynamic tolerance, with backup capabilities of defibrillation and bradycardia pacing at the higher and lower regions of the rate continuum outside the range of the ventricular tachycardia classes. Aggressiveness of the therapy is increased with elapsed time and increasing heart rate, and detection criteria are relaxed with increasing heart rate and thus with increasing hemodynamic intolerance of the tachycardia.

Abstract: A pair of defibrillation patch electrodes is adapted for close fitting placement over the ventricles of the heart, either epicardially or pericardially. One of the patches is contoured to fit over the right ventricle, and the other is contoured to fit over the left ventricle in spaced relationship to the first patch to form a substantially uniform gap between confronting borders of the two. The gap is sufficiently wide to avoid the shunting of current between edges of the patches upon delivery of defibrillation shocks, as well as to accommodate the ventricular septum and the major coronary arteries therein. The size and shape of the patches is such that they encompass most of the ventricular myocardium within and between their borders, to establish a nearly uniform potential gradient field throughout the entire ventricular mass when a defibrillation shock is delivered to the electrodes. Flat versions of the two electrodes provide ease of manufacture.

Abstract: In a method and apparatus for defibrillating a heart in fibrillation, the onset of fibrillation of the heart is detected, and a biphasic waveform having only a first phase and a second phase is applied to the fibrillating heart. Each phase of the waveform is characterized by a predetermined time duration and by a predetermined polarity and magnitude of voltage, the duration of the first phase being greater than the duration of the second phase, and the initial voltage magnitude of the first phase being greater than that of the second phase. The biphasic waveform is applied by delivering it to a pair of patch electrodes affixed over and contoured to conform substantially to the surface of the right and left ventricles, respectively. The patch electrodes are affixed to either the epicardium or the pericardium. The left ventricular patch electrode is used as the cathode for the first phase of the applied biphasic waveform, and as the anode for the second phase.

Abstract: A controller for variably controlling the pacing rate of a cardiac pacer responsive to temperature which includes a logic and control unit, a parameter communication unit, an analog to digital converter and a temperature sensor. The temperature sensor in the right ventricle or atrium communicates a value related to blood temperature through the analog to digital converter to the logic and control unit. The logic and control unit operates under control of the rate algorithm to calculate a pacing rate value related to variations in the blood temperature. The pacing rate value is calculated as the sum of a reference rate, a natural rate response term, and a dynamic rate response term which contributes rate only in response to physical activity. A step rate response is also added to the calculated pacing rate when predetermined criteria related to the blood temperature and calculated pacing rate indicate the onset of physical activity.

Abstract: A temperature driven rate responsive cardiac pacemaker adapted to distinguish between physiologically determined changes of the patient's blood temperature under conditions of exercise and non-exercise, and to adaptively vary the rate at which stimuli are generated accordingly, is also capable of recognizing the blood temperature dip which is characteristic of the commencement of exercise. In response to such a temperature dip, the pacemaker initiates a rapid and physiologically beneficial increase in the stimulation rate. To assure the proper selective initiation of a rate increase, the pacemaker discriminates between a blood temperature drop indicative of the onset of exercise and those temperature drops which occur for other reasons, such as upon cessation of exercise or as normal phasic variations, including respiration and circadian fluctuations.

Abstract: An implantable microprocessor-controlled dual chamber heart pacemaker is programmed to control the timing of the pacing of the ventricle in response to high rate atrial signals. The microprocessor operates in conjunction with an atrial timer to detect atrial signals which occur at a rate in excess of a predefined atrial rate limit. The microprocessor paces the ventricle at a predefined desirable demand rate and inhibits pacing of the atrium in response to the high rate atrial activity. The microprocessor also controls the timing of an atrial refractory interval which includes an absolute refractory portion during which atrial signals are not detected and a relative refractory portion during which atrial signals are detected but are not tracked. The combined absolute and relative atrial refractory portions insure that relatively high rate atrial signals are detected and spurious signals conducted from the ventricle are ignored.

Abstract: A microprocessor-controlled pacemaker is programmed to extend an atrial refractory interval in response to the detection of events which could initiate a pacer sustained tachycardia. The extended atrial refractory interval ensures that a spurious atrial event resulting from retrograde conduction of a ventricle event will not cause a pace of the ventricle.

Abstract: An external command device and an internal decoding and verification device are used to non-invasively alter the operating parameters of a programmable device implanted in an animal body. Thus, physiological changes can be easily accommodated by the implanted device. In a preferred embodiment, pulse position modulation is used to externally encode the command information. A resulting string of current pulses generates voltage spikes (in the internal decoding device) through inductively coupled coils. Each incoming data bit is verified and the entire command word is verified. After verification, the decoded command is transferred to a command register for simultaneously altering the selected operating parameters. The internal receiver circuitry may conveniently utilize energy from the induced voltage spike, using passive components for forming an output suitable for processing.

Abstract: An improved body function assistance device is provided wherein a microprocessor controls the response of the device to various external physiological events and internal timer events. The microprocessor is adapted for use with the limited energy supply available from a battery by activating internal logic components of the processor only in response to selected events and to perform an operating routine corresponding to the "wakeup" event. At the end of the operating routine, a new set of wakeup events is selected and the internal logic components are deactivated. A further reduction in the average operating current is obtained by providing a plurality of counting rates to minimize the number of state changes during counting cycles. The microprocessor may be provided with a fixed operating routine or may be provided with the capability of actually introducing program changes in the implanted device.

Abstract: An improved body function assistance device is provided wherein a microprocessor controls the response of the device to various external physiological events and internal timer events. The microprocessor is adapted for use with the limited energy supply available from a battery by activating internal logic components of the processor only in response to selected events and to perform an operating routine corresponding to the "wakeup" event. At the end of the operating routine, a new set of wakeup events is selected and the internal logic components are deactivated. A further reduction in the average operating current is obtained by providing a plurality of counting rates to minimize the number of state changes during counting cycles. The microprocessor may be provided with a fixed operating routine or may be provided with the capability of actually introducing program changes in the implanted device.

Abstract: Apparatus and methods are provided for manually altering the function of the distal electrodes of a body implantable tissue stimulator assembly. In one exemplary embodiment, the polarity of distal electrodes may be reversed by axially repositioning the proximal connectors within the female connector assembly of a tissue stimulator.

Abstract: Apparatus and methods are provided for manually altering the function of the distal electrodes of a body implantable tissue stimulator assembly. In one exemplary embodiment, the polarity of distal electrodes may be reversed by axially repositioning the proximal connectors within the female connector assembly of a tissue stimulator.