Abstract: A deterministic and jitter-free dual chamber brady pacemaker utilizes both a programmed microprocessor and a hardware state machine, both of which are coupled to a real time clock (RTC), random access memory (RAM) and a common escape interval timer. Time of occurrence (TOC) data representative of the time and nature of atrial and ventricular sensed events and pacing events is stored in the RAM. Escape interval periods are timed by the escape interval timer. The microprocessor is operable in both an active mode and an inactive mode without interrupts. In response to the receipt of wakeup commands, the microprocessor operates in the active mode and uses the TOC data from the RAM to reset the escape interval timer to a desired next event interval. The hardware state machine uses the common escape interval timer for timing timeout events and atrial and ventricular sensed events such that pacing pulses are delivered in a determinate manner.

Abstract: A system and method for reducing the perceived pain by a patient occurring during cardioversion/defibrillation countershocks to the heart. The system comprises an electrode subsystem for positioning at least one electrode in contact with a patient, a pain reducing stimulation subsystem for providing pain reducing electromagnetic stimulation to the electrode subsystem, a cardioversion/defibrillation countershock subsystem so that delivery of pain reducing stimulation to the patient begins prior to a cardioversion/defibrillation countershock.

Abstract: An implantable defibrillator for treating cardiac dysrhythmias in a human patient in which the delivery of electrical defibrillation countershocks to a plurality of implanted electrodes is synchronized to predetermined aspect of an atrial portion of the cardiac signals sensed by the device. The defibrillator includes a sealed housing structure constructed of a biocompatible material containing a battery source of electrical energy and a capacitor system to store electrical energy provided by the battery source to generate high voltage electrical countershocks. A control system within the implantable defibrillator includes sensing circuitry that senses cardiac signals representative of a heart rate and detection circuitry that evaluates the cardiac signals to detect a ventricular fibrillation.

Abstract: A multi-conductor fluted channel construction catheter lead is comprised of an elongated flexible tubular inner body member having a peripheral surface on which a plurality of longitudinally-oriented fluted channels are defined. A plurality of elongated conductors are provided with at least one conductor being disposed within one of the fluted channels and operably connected at a distal portion to an electrode and at a proximal portion to a connector. An outer insulative sheath member surrounds the inner body member and the conductors. A method of constructing a fluted channel catheter lead is also disclosed.

Abstract: The invention relates to an ablation catheter which controls the temperature and reduces the coagulation of biological fluids on a tip of a catheter, prevents the impedance rise of tissue in contact with the catheter tip, and maximizes the potential energy transfer to the tissue, thereby allowing an increase in the lesion size produced by the ablation. The ablation catheter includes a catheter body. The ablation catheter also includes a tip for monitoring electrical potentials, and applying electrical energy to a biological tissue. A fluid source is positioned at one end of the catheter for supplying a fluid flow through the catheter to the tip means. Passages are positioned within the tip in a variety of manners for directing the fluid flow through the tip means to the exterior surface of the tip to control the temperature and form a protective fluid layer around the tip. Monitoring structure is also positioned within the tip structure for measurement of the electrical potentials in a biological tissue.

Abstract: A magnetic sensing circuit is arranged in cooperative relation to a flyback transformer in a capacitor charging circuit for directly sensing the state of the transformer magnetic field for controlling the switching of power to the primary winding of the flyback transformer. A first threshold is sensed when the flyback transformer is nearly saturated with magnetic energy storage. A second threshold is sensed when all of the magnetic energy stored in the flyback transformer has been transferred to the capacitor. The sensed thresholds are used to optimally control the switching of power to the primary winding to maximize the efficiency and minimize the charging time of the capacitor charging circuit. A capacitor charging circuit which utilizes the present invention can be part of an implantable cardioverter defibrillator.

Abstract: A tiered therapy cardiac detection system is provided for a medical device that senses cardiac signals representative of beat-to-beat intervals and delivers at least one therapy in response to a detected cardiac dysrhythmia corresponding to one of a plurality of programmed zones of heart rates. The detection system includes a global counter that counts at least all beat-to-beat intervals indicating a rate greater than a programmed threshold value representative of a minimum heart rate for delivering any therapy once an initial threshold condition is met. A plurality of window memories and parameter memories are provided in the device. Each window memory corresponds to a given one of the zones and stores an indication of whether each of a last N cardiac signals are within that zone. Each parameter memory corresponds to a given one of the zones and stores a programmed trigger value of the global counter required in order for a therapy in that zone to be delivered.

Abstract: A device and method for performing automatic battery maintenance as particularly applied in an implantable cardioverter defibrillator (ICD). The battery is maintained at a predetermined state-of-charge to enable charging a capacitor in the ICD to discharge high voltage pulse into a human patient via electrodes implanted in the patient.

Abstract: An automatic capacitor maintenance system for an implantable cardioverter defibrillator (ICD) reforms the capacitor system of the ICD based on measurements relating a current leakage and a charge time of the capacitor system as determined at a stable low voltage state. Preferably, differential changes in current leakage across the capacitor system are monitored and the capacitor system is reformed based on a pre-set estimated charge time. The automatic capacitor maintenance system produces significant savings in the amount of battery energy consumed to reform the capacitor system of an ICD, while maintaining the capacitor system at an optimum charging efficiency so as to insure high reliability of both the capacitor system and the ICD.

Abstract: An implantable cardioverter defibrillator (ICD) in which capacitor systems are automatically reformed using a software-implemented computer system. The charge history and performance of the capacitor system are measured to perform intelligent calculations and to set the automatic capacitor reforming cycle. Individual capacitors among a group of many are isolatively charged as needed. Moreover, a sub optimal charge is used to automatically reform the capacitors to efficiently use battery energy. Further, excess charge is directed from one capacitor to another to thereby conserve energy. Specifically, the disclosure relates to an autonomous capacitor charging system which enhances ICD reliability to sustain real time provision of high current pulses.

Abstract: A method and apparatus for generating biphasic waveforms uses an implantable cardioverter defibrillator having two capacitor systems and a switching network. A first phase of the biphasic waveform is produced by configuring the two capacitor systems to selectively discharge first in a parallel combination, and then in a series combination. The second phase of the biphasic waveform is produced by reconfiguring the two capacitor systems in a parallel combination. By reverting to a parallel configuration for the second phase of the biphasic waveform, the output characteristics of the second phase of a biphasic waveform of the present invention more closely match a new model for understanding the effectiveness of the biphasic.

Abstract: Laser catheters according to the invention include multiple optical fibers for delivery of laser energy to a pre-determined treatment site in the therapeutic treatment of cardiac tissue. A fixation device fixes the distal end of the catheter to the treatment site. Temperature sensing devices disposed on the fixation device provide a temperature depth profile of the tissue treatment site, which can be used to control the treatment. Multi-piece, single-piece and porous tip catheters are disclosed.

Abstract: A capacitor-discharge implantable cardioverter defibrillator (ICD) has a relatively smaller energy storage capacity of less than about 1.0 Amp-hours. The smaller energy storage capacity of the ICD is achieved by selecting and arranging the internal components of the ICD to deliver a maximum defibrillation countershock optimized in terms of a minimum physiologically effective current (I.sub.pe) rather than a minimum defibrillation threshold energy (DFT). As a result of the optimization in terms of a minimum effective current I.sub.pe, there is a significant decrease in the maximum electrical charge energy (E.sub.c) that must be stored by the capacitor of the ICD to less than about 30 Joules, even though a higher safety margin is provided for by the device. Due to this decrease in the maximum E.sub.

Abstract: Cooled optical connector for alignment and coupling of bundled fibers of an optic cable. Coolant in a liquid or gaseous form is passed through a chamber in which a bundled fiber optic cable and nut portion of a standard optical connector is contained. Coolant in either form moves through the cooled optical connector absorbing thermal energy and cooling the interstitial and exposed fibers and areas and the standard optical connector itself.

Abstract: An implantable medical device, such as an implantable cardioverter defibrillator (ICD), utilizes a heat-shrink conforming shield to substantially isolate internal components and circuitry from the device housing and from each other. Preferably, the shield also protects the internal circuitry of the device from undesirable electro-magnetic coupling effects. The shape conforming isolation material provides an inexpensive, effective isolation barrier that helps shield the circuitry from undesired coupling effects and also protects the components from inadvertent shorts as well as potential damage during assembly and testing.

Abstract: A radio frequency (RF) ablation catheter system utilizes a flexible, tubular electrode that is selectively extendable from a distal end of a catheter body. The flexible, tubular electrode creates a continuous linear lesion when a longitudinal side of the electrode is arcuately positioned against an interior wall of the human body and the electrode is energized while a cooling fluid passes through the electrode. The catheter system also includes mechanisms for remotely manipulating and extending the electrode. Preferably, the catheter body include a catheter shaft and a flexible tip section such that the distal end of the catheter is steerable. The invention also includes a method of operating the RF catheter ablation system so as to create arcuate linear lesions.

Abstract: A system and method for reducing the perceived pain by a patient occurring during cardioversion/defibrillation countershocks to the heart. The system comprises an electrode subsystem for positioning at least one electrode in contact with a patient, a pain reducing stimulation subsystem for providing pain reducing electromagnetic stimulation to the electrode subsystem, a cardioversion/defibrillation countershock subsystem for treatment of cardiac fibrillation, and a control subsystem. The control subsystem provides synchronization of the pain reducing stimulation subsystem with the cardioversion/defibrillation countershock subsystem so that delivery of pain reducing stimulation to the patient begins prior to a cardioversion/defibrillation countershock.

Abstract: A system for passively anchoring mid-lead electrodes on an endocardial catheter lead includes at least one fibrosis-anchoring opening positioned along the exterior surface of the catheter lead body proximal or distal to the mid-lead electrodes for passively securing the catheter lead against the interior wall of the heart. Within the fibrosis-anchoring openings a suitable material is provided for anchoring the catheter lead body to the heart wall by fibrosis. Preferably, the fibrosis-anchoring openings comprise at least a pair of openings positioned only partially around the exterior of the catheter lead body at locations both proximal and distal to the mid-lead electrodes, with the catheter lead body between the fibrosis-anchoring openings being pre-formed to bias the mid-lead electrodes against the heart wall.

Abstract: A high voltage output system for use with an implantable cardioverter defibrillator (ICD) system provides for switched discharge pathways utilized to achieve a windshield wiper-like output. The high voltage output system includes at least two output capacitors each having at least a separately electrically accessible one of the cathode and anode of the capacitor system. A switching control system selectively discharges the at least two capacitor systems in a repeated alternating sequence such that the one of the cathode and anode of the capacitor systems is discharged through a common electrode and the other of the cathode and anode is electrically connected for at least a portion of the discharge to a second and third defibrillation electrode, respectively.

Abstract: An implantable cardioverter defibrillator capable of subcutaneous positioning within a patient delivers at least one electrical cardioversion/defibrillation countershocks to the heart of the patient. The implantable cardioverter defibrillator includes a housing, circuitry positioned within the housing to control delivery of the countershocks, and an energy source coupled with the circuitry to provide electrical energy to a capacitor in the circuitry that stores the electrical energy for delivery of the countershocks. Because the circuitry is susceptible to undesirable electromagnetic coupling effects of origin external to the circuitry, particularly the capacitive coupling effects between the circuitry and the housing of the device when at least a portion of the housing is utilized as an electrode, the implantable cardioverter defibrillator also includes a conductive shield, disposed between the housing and the circuitry, to shield the circuitry against such undesired coupling effects.