Abstract: The present invention provides an implantable drug infusion device which features a reliable and leak proof weld joint. The implantable drug infusion device features a hermetic enclosure; a drug reservoir positioned within the hermetic enclosure, a drug handling component, the drug handling component joined with a top surface of a docking station, the drug reservoir joined with a bottom surface of the docking station by a welded joint. The drug handling component typically being a MEMS-type device and fashioned from a silicon-glass or silicon--silicon sandwich. The docking station functions to isolate the thermal stresses created during the formation of the welded joint from the other joints and particularly from the joint between top surface of the docking station and the drug handling component.

Abstract: There is provided a pacemaker system with an SRD detection and intervention feature, which enables a simple way of initiating confirmation of SRD, i.e., looking for an AS/AP transition in a DDD or DDI pacemaker, or a transition from a VS to a VP in a DDI pacemaker. This simple initiation of SRD confirmation is made possible by use of a relatively wide hysteresis band which is normally operative when a spontaneous rate is present, and which tracks physiological changes in the patient's natural rate, across the pacemaker rate range. Transitions which result from a gradual decrease in natural rate and thus represent physiological bradycardia are not interpreted as suggesting SRD. The detection is confirmed only after a predetermined number of pace pulses are delivered at the hysteresis rate, i.e., 1-5 pulses.

Abstract: A medical electrical lead having a drug which is no more than sparingly soluble in water applied to the electrode surface. In the preferred embodiment the lead of the present invention possesses an electrode treated with a very slightly soluble in water steroid, such as beclomethasone dipropionate anhydrous. Preferably the steroid is applied to the surface of the electrode which contacts tissue when implanted. A method of manufacturing such a lead is also disclosed. Through such a design, a high impedance, low threshold lead which is simple and easy to manufacture is disclosed.

Abstract: A pacing lead, and system for pacing, where the lead has an improved distal tip designed to provide reliable chronic fixation of the electrode-heart interface, while also providing low pacing threshold. The distal end of the lead has a standard surface, of roughly hemispherical shape, made of a porous material. In one embodiment, the tip surface is suitably about 6-8 square mm, and there is a smaller surface of about 1.5-2.0 square mm which is electrically isolated from the remainder of the porous surface; the smaller surface acts as a high impedance electrode, providing low threshold, while the larger porous surface provides the stable fixation. A steroid source is housed in the distal end of the lead, so as to provide an eluted steroid to the electrode surface area, as well as at least part of the remaining porous surface, whereby the overall porous surface and the eluted steroid minimizes the resulting capsule of non-excitable tissue around the electrode, providing for a stable reduced threshold.

Abstract: Apparatus and method are provided for obtaining a measure of blood flow, and more specifically cardiac output, by analyzing blood temperature variations in the arterial tract. In a first embodiment, a lead carrying two closely spaced temperature sensors is positioned so that the sensors are in the atrial tract and produce temperature signals representative of small cyclical temperature variations of the blood outputted from the heart. The two signals have substantially similar patterns for each cardiac cycle, but the signals are separated by a short time (.increment.T) representative of the distance between the two sensors. The patterns are correlated to find .increment.T, from which cardiac output is calculated. In an alternate embodiment, a single blood temperature sensor is employed along with a sensor for determining cardiac contractions, and a measure of cardiac output is obtained by comparing the time difference between a feature of the blood temperature signal with the time of cardiac contraction.

Abstract: A transvenous lead specifically designed for coronary sinus implantation. In the preferred embodiment the lead features an electrode which is eccentricity placed along the lead body. Disposed on the opposite side of the lead body is a tine-like member to push or maintain the electrode into contact with the vessel wall. Because the electrode and tine-like member do not entirely block the cross sectional area of the vessel, blood flow through the vessel is not impeded. Through such a configuration electrical stimulation with the tissue comprising the left side of the heart may be accomplished. In alternative embodiments other mechanisms besides tine-like member are used to maintain the contact of the electrode with the vessel wall. In a still further alternative embodiment the eccentricity disposed electrode is positioned instead upon the tip of the tine.

Abstract: A system and method are provided for catheter location mapping, and related procedures. Three substantially orthogonal alternating signals are applied through the patient, directed substantially toward the area of interest to be mapped, such as patient's heart. The currents are preferably constant current pulses, of a frequency and magnitude to avoid disruption with ECG recordings. A catheter is equipped with at least a measuring electrode, which for cardiac procedures is positioned at various locations either against the patient's heart wall, or within a coronary vein or artery. A voltage is sensed between the catheter tip and a reference electrode, preferably a surface electrode on the patient, which voltage signal has components corresponding to the three orthogonal applied current signals. Three processing channels are used to separate out the three components as x, y and z signals, from which calculations are made for determination of the three-dimensional location of the catheter tip within the body.

Abstract: There is provided a pacing system having special functions for treating the patient's atrium with atrial pacing so as to reduce the probability of occurrence of dangerous atrial arrhythmias. The pacemaker of the system provides for atrial Pace.sub.-- Conditioning, whereby the patient's normal intrinsic atrial rate is overridden by higher rate pacing whenever a predetermined sequence of intrinsic heartbeats is sensed. The pacemaker also provides for special pacing routines following the detection of one or more PACs. The PAC response routines include pacing at an elevated rate for a predetermined time or number of beats, and smoothing out pacing intervals for one or several cycles following the occurrence of a PAC.

Abstract: There is provided a system and method for treating cardiac arrhythmias such as atrial defibrillation, and in particular a method for providing temporary atrial defibrillation which involves insertion of only one defibrillation lead. A lead introducer is provided having a sheath with an electrode configured around the outside of the sheath and a lumen for receiving therethrough a standard defibrillation lead. After insertion of the introducer into a patient's vein and positioning it so that the introducer electrode is placed within the vein, a defibrillation lead is passed through the introducer lumen. The defibrillation lead carries at least one electrode, suitably an electrode spaced from its distal end so that it can be positioned in the patient's coronary sinus.

Abstract: There is provided an output stage for a battery powered implantable device, such as a cardiac pacemaker, for generating biphasic or triphasic pulses, each pulse having at least a prestimulus or poststimulus pulse of a first polarity, and a stimulus pulse of opposite polarity. The output stage provides for charging of a small sized pacing capacitor from the battery through a high rate charge pump only during delivery of a prestim or poststim pulse, and for discharging the pacing capacitor during the stimulus portion of the overall pulse. A fast or high rate capacitive charge pump is used with a controllable high rate clock signal, adjustment of the clock signal being used for controlling the charging rate during the prestim or poststim pulses, thereby allowing for tuning of the parameters of the prestim or poststim pulse portions.

Abstract: There is provided an air core antenna, and method of production of same, suitable for use in implantable device, the antenna being used for telemetric communication with an outside programmer unit. The air core antenna is fabricated upon a hybrid substrate, which substrate is subsequently processed to contain electronic circuits for use in the implantable device. A groove is milled into the perimeter side walls of the antenna, and the coil wire is wound within the groove, the two ends of the coil then being attached to connector pads on the substrate. There is thus provided an antenna which is integrally incorporated into the substrate so that space requirements of the antenna are minimized, providing an antenna which has a sufficient loop area to provide the receiving and transmission characteristics required of a modern programmable implanted device.

Abstract: An output pulse generator is provided which is particularly suitable for implantable medical simulators, such as cardiac pacemakers, where there is a high premium on efficient energy transfer from the battery source to the output load. A plurality of relatively small size output capacitor are utilized in combination with a switching circuit for alternately charging respective capacitors and then discharging them through the load in such a manner that there is always one capacitor providing a substantially constant output voltage while at least one other capacitors is being recharged. Different combinations of switching networks are used to provide programmable output voltage levels. The use of relatively small capacitors, e.g., in the range of 0.1-0.5 F, along with a relatively high drive frequency, e.g.

Abstract: There is provided a pacemaker system and method for enabling special rate control for patients who have specially recognized conditions, e.g., patients who are post-ablation and thus are susceptible to bradycardia-dependent ventricular fibrillation or other arrhythmias. In a preferred embodiment, the pacemaker has a special function rate control algorithm which, for the post-ablation patient, commences pacing with a lower rate limit at a high start value of around 80-100 bpm, and decays the lower rate limit down to an end value of about 60-70 bpm over a duration of about a month. Additionally, the pacemaker is provided with one or more selectable special function rate response algorithms, for enabling higher rate response to patient exercise and demand for increase cardiac output. The combination of the gradual decay of lower rate limit over the programmable duration as well as the specially programmable rate response enables optimization of pacing so as to prevent arrhythmias.

Abstract: A medical electrical lead for establishing an electrical connection with a tissue of the body, the lead having a lead body and a semi-cylindrical cuff. In the preferred embodiment the semi-cylindrical cuff features one or more electrodes. The semi-cylindrical cuff having a long flap which wraps about the cuff and a short flap which wraps about the long flap. The semi-cylindrical cuff is relatively stiff as compared to the short flap. The short flap, in turn, is relatively the same stiffness as the long flap. The stiffness of each flap may be varied, however, so that one is more or less than the other, and in turn, than the cuff. Through such a multi-flap construction the electrodes may be positioned proximal to a nerve in such a manner that the mechanically induced damage may be minimized or even entirely eliminated. Finally, a method of implanting such an electrode is also disclosed.

Abstract: There is provided a system for automatically responding to insulin demand without any need for external monitoring or injecting of insulin into the diabetic patient. The system provides for sensing glucose levels internally, and responding by stimulating either the pancreas or a transplant of pancreatic islets in order to enhance insulin production. The enhancing stimulation is delivered at a rate greater than the burst rate, or is otherwise controlled so that the depolarization burst constitutes a greater portion of each islet electrical cycle, thereby resulting in increased insulin production. The system also provides for continuous glucose monitoring, and reacts to sensed hypoglycemia by delivering stimulus pulses timed to reduce the burst durations, and thus to inhibit insulin production.

Abstract: There is provided a system and method for high rate pacing of patients for training, or revalidation of heart muscle. The system and method of this invention provide a therapy particularly directed for patients with CHF, to enable effective exercise of the cardiac muscle without requiring the patient to exercise. In another embodiment, an alternate high rate routine, or algorithm is provided for assisting a patient to exercise during at least some part of the high rate pacing routine. The high rate pacing therapy may be initiated either automatically, based upon the patient's circadian rhythm; automatically by patient data sensed by a system of sensors; or may be initiated directly by the patient by use of a simple external programmer device. The pacemaker of the invention suitably stores a plurality of algorithms which can be selected, or which can be modified or replaced by an external programmer.

Abstract: A system and method are provided for inducing ventricular tachycardia in a patient to enable testing to determine the optimum parameters for anti-tachycardia stimulation. The implantable device provides for overdrive pacing of the heart for a short sequence, followed by delivery of a series of pulse pairs. Each pulse pair has a first stimulus pulse delivered at the same or similar overdrive rate, and an inducing pulse which is delivered in timed relation to the evoked T-wave, preferably during the falling edge portion of the T-wave. In this way, each cycle the inducing pulse is timed for efficaciously inducing tachycardia. The timing of the inducing pulse is enhanced by near field sensing of the T-wave at about the location where the pulses are delivered, preferably using bipolar sensing and/or sense circuitry designed to recover the signal with an optimum time response. In one preferred embodiment, near field sensing is enabled by use of an FDC circuit.

Abstract: A transvenous lead specifically designed for coronary sinus implantation. The lead of the present invention features an electrode/anchoring portion at its distal end. The electrode/anchoring portion features a dual tapered self-propelling spiral electrode. Through this design the electrode supplies excellent direct electrical contact to the inside of the vessel. The dual tapered spiral permits the electrode to either be propelled forward within the vessel and toward the more distal locations by turning in a first direction and also permits the electrode to be propelled backwards within the vessel toward the more proximal locations by turning in a second, opposite direction. The spiral shape does not obstruct blood flow. The taper to the spiral also permits the electrode portion to be placed through any valves which may be within the vessel without causing damage.

Abstract: A connector system and method for anchoring a tubular lead or catheter member within a cranial burr hole in a patient, providing for direct in-line positioning and reliable fixation of the member with respect to the patient's skull after the distal end portion has been accurately positioned within the patient's brain. The system includes a baseplate, with or without adaptor to adapt for the burr hole size, and a two element fixation subassembly positioned within the baseplate for enabling fixing of the member to the baseplate after the member has been accurately positioned with a stereotactic instrument. The fixation subassembly suitably includes a compression seal made of a compressible material and a compression screw which, when screwed down into the baseplate, exerts an inwardly radial force on the compression seal, causing the seal to fixedly engage the lead or catheter member within the axial lumen of the baseplate.

Abstract: Method and apparatus for providing on-demand stimulation of the gastrointestinal tract. The apparatus features an implantable pulse generator which may be coupled to the gastric system through one or more medical electrical leads. In the preferred embodiment the leads couple to the circular layer of the stomach. The pulse generator preferably features sensor for sensing abnormalities in gastric electrical activity. The pulse generator further features means for recognizing the type of gastric abnormality sensed. That is means for detecting whether gastric arrhythmia, bradygastria, dysrhythmia, tachygastria or retrograde propagation or uncoupling are present. If any of these gastric rhythm abnormalities are detected, then the pulse generator features means for emitting stimulation pulse trains to the gastric system to treat the detected gastric rhythm abnormalities. The stimulation pulse trains may take many forms and may be emitted for various periods of time.