Abstract: An improved electrolytic capacitor is provided by producing an anode foil which has areas which are not subject to stress during manufacturing being highly etched and those areas which are subject to stress during manufacturing being lightly etched or not etched at all. The process of the invention provides an etch mask to cover during the etch process those portions of the anode foil which will be subjected to stress during construction of the capacitor. The highly etched areas, which are very brittle, provide increased capacitance and thus improved energy density. For layered or stacked capacitors, a weld tab is covered with the etch mask to allow connection of the anode layers. Additionally, strong edges may be maintained thereby reducing the possibility of cracking that would normally occur during the stamping and assembly operations.

Abstract: Intracardiac lead for compliant fixation of a distal end of the lead to cardiac tissue. A fixation helix is disposed at the distal end of the lead. The fixation helix has a first end rigidly attached to the compliant fixation device and a second end that is sharpened to facilitate insertion of the fixation helix into cardiac tissue. The fixation helix can be designed to provide for either electrically active or inactive fixation. Once the lead is implanted in the cardiac tissue, the compliant fixation device, connecting the lead with the fixation helix, reduces the amount of lead movement that is transferred to the patient's tissue at the site of implantation of the fixation helix and reduces those forces from lead movement that could cause dislodgment of the fixation helix.

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 implantable cardiac stimulator having a housing defining an interior cavity and having an exterior surface, and a defibrillation pulse generator circuit contained within the cavity. The housing exterior surface has a number of ridges, and each ridge includes at least two surfaces that are angularly offset from each other at an edge. The ridges may be formed by creating grooves in the housing in a closely spaced arrangement.

Abstract: A method and apparatus for inducing fibrillation in a patient's heart by delivering a direct current stimulus to the heart from a DC-to-DC converter. The hardware of a conventional implantable cardioverter/defibrillator (ICD) is utilized with a modification to the control algorithms. Particularly, when it is desired to induce fibrillation in a patient's heart, typically during ICD implant defibrillation threshold (DFT) testing, a command is delivered from an external instrument to the ICD to deliver the fibrillation shock. The DC-to-DC converter which is normally used to charge the ICD high voltage capacitors is activated and immediately thereafter or following a short period to allow the high voltage capacitors to charge, the high voltage output switches of the output stage are closed. This delivers the output current from the DC-to-DC converter to the defibrillation electrodes and through the patient's heart. This stimulus is continued for a predetermined time of between about 30 milliseconds to 5 seconds.

Abstract: A system is provided to control operation of an implantable medical device based upon detected EMI (electromagnetic interference). A correlator produces a correlation function indicating the level of an EMI component of an input biomedical signal that includes a biomedical signal component and an EMI component, and that is monitored relative to a predetermined threshold to allow the device to operate in a normal manner as long as the intensity or level of the EMI component is such that it does not affect or interfere with device operation. One or more remedial measures may be selected in the event the level of the EMI component exceeds a predetermined threshold. The system is useful with any electronic device which receives an electronic information signal which may include an EMI component.

Abstract: A method of discriminating among cardiac rhythms of supraventricular and ventricular origin by exploiting the differences in their underlying dynamics reflected in the morphology of the waveform. A phase space representation of the dynamics of a waveform is obtained from the electrogram signal amplitude by using the technique of delay embedding. A first cardiac rhythm electrogram of known origin is sensed and a phase space representation or trajectory is generated for use as a template. A second or test cardiac rhythm electrogram is sensed and a phase space representation is generated from the detected waveform complex. This second phase space representation is compared to the template to distinguish between the origins of the first and second cardiac rhythms. If a test trajectory is sufficiently different from the template trajectory, the test complex is deemed to have different dynamics, and therefore be from a different origin than the template.

Abstract: An implantable device, such as a defibrillator, has a conforming housing that is adapted to follow to the contours of the patient's body at a device implantation site, while complying with pressures applied to the patient's body and with body flexion. In one form of the invention, the device housing is articulated at one or more hinge locations to provide a segmented housing that conforms to an implantation site through movement about the hinge axis. Another embodiment of the invention provides a flexible housing that surrounds a flex-circuit assembly.

Abstract: An implantable medical apparatus operable in conjunction with an attachable lead, and having a housing containing an electronic component, with a header connected to the housing and defining a cavity. A connector element is positioned within the cavity and is operably connected to the electronic component. A lens is connected to the header, such that the connector element may be viewed through the lens to facilitate confirmation of proper connection of a lead to the connector. The header may be transparent, and the lens either formed as part of the header, or detachable therefrom.

Abstract: A pulse generator having a housing for enclosing and containing pulse generator defibrillation circuitry, particularly adapted to allow for ease of manufacture and use, is disclosed. At least one surface of the housing is electrically conductive and connected to the pulse generator circuitry for delivering defibrillating energy to the heart. The defibrillator is provided with a case activating lead connector cavity having two connector blocks. By plugging in a lead with a pin long enough to contact the only first connector block, the lead becomes active. Using a plug with a longer pin to contact both blocks activates the can. To use neither a lead in the case activating port, nor an active can, a plug with a short or nonconductive pin may be used 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 method and apparatus for inducing fibrillation in a patient's heart by delivering an alternating current stimulus to the heart from a DC-to DC converter. The hardware of a conventional implantable cardioverter/defibrillator (ICD) is utilized with a modification to the control algorithms. Particularly, when it is desired to induce fibrillation in a patient's heart, typically during ICD implant defibrillation threshold (DFT) testing, a command is delivered from an external instrument to the ICD to deliver the fibrillation shock. The DC-to-DC converter which is normally used to charge the ICD high voltage capacitors is activated and immediately thereafter a first pair the high voltage output switches of the output stage are closed for about 4 milliseconds. This delivers an initial pulse of one polarity. Following an interval of about 4 milliseconds, a second pair of the high voltage output switches are closed for 4 milliseconds delivering an opposite polarity pulse.

Abstract: A fail-safe clock generator which has particular utility in implantable cardiac defibrillators includes a crystal oscillator for generating a crystal clock signal, a back-up circuit, and a one-shot generator. The back-up circuit includes a low frequency oscillator for generating a low frequency clock signal having a frequency less than that of the crystal clock signal, and an overspeed/underspeed detector responsive to the low frequency clock signal for detecting the frequency of the crystal clock signal during each period of the low frequency clock signal, and for generating a back-up mode control signal in response to detection of either an overspeed or underspeed failure mode over a plurality of consecutive periods of the low frequency clock signal.

Abstract: A suture sleeve having an elongated body defining a bore and having a relief aperture at a first intermediate position on the body and communicating with the bore. The sleeve includes a pair of actuator tabs connected to a second intermediate position on the body and extending therefrom, and at least a portion of the relief aperture is positioned between the tabs such that actuation of the tabs causes enlargement of the aperture. The sleeve may be movable between a tighter state in which a lead passing through the bore does not readily slide longitudinally within the bore, and a looser state, in which the lead may slide readily through the bore.

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: A lead having a defibrillation electrode that is deployed for defibrillation using artificial muscle. In an undeployed position, the defibrillation electrode is small in diameter so as to be easily implanted pervenously and nonobstructive to cardiac contraction and blood flow. In a deployed position the defibrillation electrode is larger in diameter for defibrillation shock delivery. Thus, the electrode forces an increased amount of current to flow through the heart muscle during shock delivery to depolarize the majority of the cardiac tissue with a minimum of energy, while not obstructing blood flow at other times when not used for energy delivery.

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 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 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.