Abstract: A cardiac blood flow sensor includes a light source and a photodetector within a housing. The light source projects a beam through a fiber optic line having a first end optically connected to the housing and a distal tip positioned within the patient's heart. Light intermittently reflected off the moving blood cells is transmitted back through the optic line to the detector, which generates a varying signal proportional to the reflected light, and thus proportional to the blood flow rate within the heart. The flow sensor may be contained in a common housing with a defibrillator that is implanted in a patient. The sensor may remain inactive until a potentially unhealthy heart beat rate is detected, upon which the light source is activated. The defibrillator may be activated only if the flow sensor has detected a blood flow rate below a predetermined level.

Abstract: An implantable cardioverter defibrillator having a plurality of high voltage capacitors in the output stage which are coupled in parallel and a switching matrix for controlling the number of capacitors used to deliver the shock. For patients having lower DFTs, the number of capacitors in the output stage, as controlled by the switching matrix, can be reduced thus reducing the capacitor charging time prior to delivering a defibrillation shock. Additionally, if one of the capacitors experiences a degradation in performance, it can be switched out of the output circuit as long as the remaining capacitors can provide the necessary energy delivery for defibrillation. In another embodiment of the invention, if a particular defibrillation shock is ineffective, the back-up capacitors may be switched into the high voltage output circuit for delivery of the next shock.

Abstract: A method for the automated manufacture of defibrillation lead electrodes is disclosed. A metallic defibrillation electrode coil is first embedded in silicone rubber. The location of the coil is mapped using a machine vision system and then a CO.sub.2 laser is used to ablate the silicone overlying the coil to expose a controlled portion of the coil while leaving the remainder securely embedded in the silicone. The power density of the laser is below that which would affect the surface or bulk properties of the coil.

Abstract: An ICD system and method for its use which will detect the presence of sensing artifacts caused by lead conductor fracture, lead insulation failure or connector port fluid penetration. When such a failure results in an incorrect detection of a tachyarrhythmia, the presence of sensing artifacts or noise is noted and charging of high voltage capacitors and/or delivery of high voltage therapy is avoided. The system of the invention includes at least two pairs of sensing electrodes which provide two distinct electrogram signals to the sensing and analysis circuitry of a pulse generator. Each signal is analyzed for heart rate. The rates are compared and if the rates detected are significantly different therapy is not delivered to the patient. The sensing electrode pairs may include four independent electrodes or there may be one electrode in common with each sensing pair. In an alternative embodiment, the two signals are compared by performing a correlation analysis.

Abstract: A switch assembly for an implantable cardiac stimulation device which enables the implanting physician to selectively activate the pulse generator case or can of the device and/or to selectively activate an endocardial lead electrode inserted into a lead connector cavity or bore thereof. Also disclosed is an implantable cardiac stimulation device, e.g., an implantable cardioverter/defibrillator, which includes one or more such switch assemblies, to thereby enable the implanting physician to select any of a number of different electrode configuration options. For example, if two switch assemblies are used, the implanting physician is afforded six options.

Abstract: A transvenous lead system for cardiac stimulation with a pacemaker or implantable defibrillator having automatic activation of a passive fixation system. The lead includes an insulative lead body such as silicone rubber and has a proximal end with a connector for coupling the lead to the pacemaker or defibrillator. At least one conductor extends through the lead body for connection to a lead electrode. The lead further includes a plurality of flexible tines. In a first position, the tines are folded back along the lead body and exhibit a minimal profile. A hydrophilic material such as a hydrogel is disposed on the under side of each tine either as part of the tine or between the tine and the lead body. Upon exposure to body fluids when the lead is implanted, the hydrogel absorbs liquid and expands. This expansion forces the tines into a second, deployed position where the tines can engage trabeculae of the heart chambers to anchor the lead in place.

Abstract: A pulse generator circuit and method for using a defibrillation lead positioned close to the right ventricular apex to optimize energy delivery and sensing. This method includes operating a defibrillator-pacemaker system in a true bipolar sensing mode as long as high voltage therapy is not required. When required, the defibrillator-pacemaker system delivers a first high voltage therapy via an RV defibrillation electrode, and, using true bipolar sensing, determines whether the first high voltage therapy was successful. If the first high voltage therapy is deemed to be successful, then true bipolar sensing is resumed. Otherwise, the defibrillator-pacemaker system causes a ring electrode to be electrically connected to the RV defibrillation electrode, delivers a second high voltage therapy, and, using integrated bipolar sensing determines whether the second high voltage therapy was successful. In this way, because no new circuit elements are added within the lead, the lead size and complexity are not increased.

Abstract: An implantable defibrillator lead comprises a flexible core onto which is wound helically wound coils to form an electrode. These electrode coils are partially encapsulated by a flexible matrix which holds them in their wrapped position around the core. Due to its coiled coil structure, this electrode provides improved flexibility, and can be used endocardially, intravascularly, epicardially, or subcutaneously. The electrode may function alternately as a defibrillation electrode and as a sensing electrode in a lead with a separate pacing electrode.

Abstract: An implantable defibrillator lead having an improved integrated bipolar defibrillation electrode is disclosed. The defibrillation electrode is electrically connected to the lead conductor at the distal end, and has an increased surface area portion at the distal end, for bipolar sensing with a right ventricular pacing electrode.

Abstract: A defibrillator having a housing for enclosing and containing defibrillation pulse generator circuitry, particularly adapted to allow for ease of manufacture and use. At least one surface of the housing is electrically conductive and connected to the defibrillation pulse generator circuitry for delivering defibrillating energy to the heart. The defibrillator is provided with a case-activating lead connector cavity having two isolated conductive elements. By tightening a first setscrew onto a lead connector pin, an electrode of the lead becomes active. Tightening a second setscrew activates the can. Tightening both setscrews onto a plug pin activates the can alone. To use neither a lead in the case-activating port, nor an active can, only one setscrew may be tightened onto a conductive or nonconductive pin to plug the cavity without activating the can. By using this system, various electrode configurations can be used as required to provide the optimum system for a given patient.

Abstract: A gate driver circuit includes a timing circuit, an anti-Miller surge protection circuit, and charging and discharging circuits for driving an output transistor, such as an IGBT. The anti-Miller surge protection circuit prevents the output transistor from being accidentally turned on. The gate driver circuit provides a high impedance input, so as to allow such a gate driver circuit to be driven by a relatively smaller isolation transformer. Further, the timing circuit in the gate driver circuit of the present invention allows such isolation transformer a relative lower frequency of operation. In one embodiment, the capacitance of the output transistor's gate terminal is used to determine the time constant of the timing circuit.

Abstract: A method for defibrillating a patient's heart with an implantable defibrillator having defibrillation synchronized to the fibrillation waveform is disclosed. The defibrillator is used to detect fibrillation in a patient's heart, monitor at least one far-field fibrillation voltage across two spaced-apart electrodes while the high voltage capacitors are charging, then deliver a high energy shock during a period of ventricular fibrillation when the absolute values of the peak and trough voltages exceed a threshold based on a desired percentage greater than a running average of the absolute values of the peaks and troughs of the fibrillation voltages monitored during and after capacitor charging. The shock is then delivered synchronous with the next significant cardiac complex. The defibrillator also includes a safety timer so that if the threshold is not reached within a specified safe time limit, the high energy shock will be delivered without further delay.

Abstract: A programmable implantable medical device utilizable for delivering a configurable defibrillation waveform to a patient's heart. The device includes defibrillation electrode means adapted to be connected to the heart for delivering a multiphasic defibrillation waveform thereto. A programmable waveform generator connected to the heart generates the biphasic waveform such that the first phase of the defibrillation waveform has programmed tilt and the second phase has a duration which is a function of the duration of the first phase.

Abstract: A joint for cardiac stimulation lead has a sleeve that joins a conductor to an electrode. The conductor and electrode are inserted into passages formed through the sleeve and are bonded at least to the sleeve surface by laser welding, crimping, or resistance welding. The distal end of the conductor is attached to the sleeve and either the proximal end or the distal end of the electrode may be attached to the sleeve. The number, size, shape and positioning of passages in the sleeve are varied according to the desired lead configuration to allow passage of additional conductors through the joint.

Abstract: A capacitor having a housing defining a chamber, and having at least two internal alignment elements in the chamber. A plurality of capacitor layers, each having alignment holes formed therein to precisely fit the housing's alignment elements, is positioned within the chamber, with the alignment holes mating with the alignment elements. The housing may be electrically conductive and used to connect some capacitor elements, in which case the alignment elements include non conductive spacers that contact the alignment holes of the sheets. The housing may also include external index elements for precisely positioning the housing in registration with fixtures used for manufacturing processes requiring precise alignment.

Abstract: A cardiac blood flow sensor includes a light source and a photodetector within a housing. The light source projects a beam through a fiber optic line having a first end optically connected to the housing and a distal tip positioned within the patient's heart. A ruby positioned at the distal tip is heated by the beam, and fluoresces for a period of time after illumination ceases. The period of time depends on the temperature of the ruby, so that the fluorescent light is transmitted back through the optic line to the photodetector. The signal generated by the photodetector may be analyzed to estimate the blood flow rate, due to the thermal effect of blood flowing past the heated ruby. The flow sensor may be contained in a common housing with a defibrillator that is implanted in a patient. The sensor may remain inactive until a tachycardia or rapid heart rate is detected, upon which the light source is activated.

Abstract: An epicardial defibrillation electrode having a wide insulating border which insulates the heart from the body is disclosed. The wide insulating border forces defibrillation current to flow through the heart without passing through surrounding tissues, thus increasing the current density throughout the heart, to depolarize the majority of the cardiac tissue with a minimum of energy. By increasing defibrillation efficacy in this way, the conductive surface area of each electrode can be decreased, thus allowing room for implantation of a plurality of conductive electrode portions for controlling energy delivery to the heart both spatially and temporally.

Abstract: A defibrillation insulating device insulates the heart from the body. This forces current to flow through the heart without passing through surrounding tissues, thus increasing the current density throughout the heart, to depolarize the majority of the cardiac tissue with a minimum of energy.

Abstract: A method for defibrillating a patient's heart with an implantable defibrillator having defibrillation synchronized to the fibrillation waveform is disclosed. The defibrillator is used to detect fibrillation in a patient's heart, monitor at least one far-field fibrillation voltage across two spaced-apart electrodes while the high voltage capacitors are charging, then deliver a high energy shock during a period of ventricular fibrillation when the absolute values of the peak and trough voltages exceed a threshold based on a desired percentage greater than a running average of the absolute values of the peaks and troughs of the fibrillation voltages monitored during and after capacitor charging. The shock is then delivered synchronous with the next significant cardiac complex. The defibrillator also includes a safety timer so that if the threshold is not reached within a specified safe time limit, the high energy shock will be delivered without further delay.

Abstract: A body implantable electrode with rate controlled drug delivery is disclosed. A body implantable lead is provided for the delivery of stimulation energy to a desired body site includes a drug dispenser carried by the lead which retains a drug to be dispensed at least adjacent the desired body stimulation site. The drug may be one which is intended to counter thrombus formation, fibrosis, inflammation or arrhythmias, for example. The drug may be in liquid or powder form retained in a reservoir carried by the lead. The reservoir is formed as a pump which controls dispensing of the drug using a fluid drawing agent such as a salt.