Abstract: An implantable cardiac defibrillation electrode is provided, in which there is an electrically conductive wire mesh formed of crossed spirally wound cables. Each of the spirally wound cables comprises a plurality of stranded wire elements, with a central wire element and a plurality of outer wire elements wound adjacent the central wire element. In one embodiment, the crossed cables are formed in a twill weave pattern, alternating over and under at least two individual cables.

Abstract: A system is provided for fastening an implantable medical device, for example a defibrillator lead, to the heart. A lead electrode is placed in a desired position against the pericardium, pericardial tissue is grasped with a fastening tool, and the pericardial tissue is drawn away from epicardium and toward the fastening tool. A fastening member is applied to the pericardial tissue and to the lead electrode to secure the lead in the desired position. The application tool comprises a first pair of jaws for grasping membranous tissue and drawing the tissue away from other tissues and toward the tool. A second pair of jaws is provided for holding fastener members and delivering the fastener members to the membranous tissue.

Abstract: An implantable defibrillator lead comprises a flexible, conductive lead member having proximal and distal end portions. The distal end portion defines a plurality of separate, curvilinear electrodes which naturally extend laterally outwardly in a curved arrangement from the remainder of the lead. However, by desired means, the curvilinear electrodes may be temporarily extended out straight, substantially parallel to the axis of the remainder of said lead member, to facilitate implantation of the lead. This may be preferably accomplished by a flexible sheath that encloses the lead member in longitudinally slidable relation.

Abstract: A lead or other member may be implanted into the body, and typically at the heart, by a method which comprises and following: inserting one of a pair of pivotally attached jaws of an attachment tool through a hole in a body membrane, particularly the parietal pericardium surrounding the pericardial cavity. The other of the pivotally related jaws is placed outside of the body membrane in a position of registry with the first of the jaws. The jaws carry an attachment member which is to be attached for securance to the body membrane. The jaws are brought together in pressing relation with the membrane and attachment member positioned between the jaws, to cause attachment of the attachment member to the membrane. The lead may be pre-attached, or subsequently attached, to the attachment member after the above process steps.

Abstract: A medical device is provided for monitoring waveform complexes of intracardiac electrograms. The intracardiac electrogram is identified by determining, with respect to a waveform peak of the intracardiac electrogram, its amplitude, width and polarity. The identification criteria are averaged and stored to provide a standard complex. Subsequent complexes are compared to the stored standard complex. Such comparison includes comparing peaks of subsequent complexes with the peaks of a stored standard complex, aligning subsequent complexes with a stored standard complex, and providing a score associated with the comparisons and alignment.

Abstract: An antitachycardia device, either implanted or external, which delivers a fixed pulse width truncated exponential waveform defibrillation shock and automatically adjusts the pulse duration based upon the impedance measured or calculated following a delivered shock. The apparatus operates by measuring or calculating the high voltage system impedance, selecting a pulse width for that impedance value and using a pulse width derived from the selected pulse width for the next defibrillation shock.

Abstract: A method of manufacturing a medical electronic lead portion having an elastomeric mass and typically having a conductive metal member embedded in the elastomeric mass. The method includes the step of eroding elastomer of the mass from around the conductive metal member to form a predetermined shape by exposing the lead portion to a jet of gas containing entrained, particulate abrasive. Preferably, the particulate abrasive is softer than the conductive metal member to avoid scratching thereof. For example, soluble particulate abrasive such as sodium bicarbonate can be used.

Abstract: A boot manufactured from a bio-compatible material is used to smooth the external shape of an implantable medical device and to seal the device against fluid intrusion.

Abstract: An electrode system is provided for an implantable cardiac defibrillator. The electrode system includes a first endocardial lead having at least one electrode and a second epicardial or extrapericardial lead with an electrode that has a flexible configuration such that it is able to be straightened or compressed into an introducer but will expand when released from the introducer to provide a substantially larger surface area simulating the surface area of a patch electrode.

Abstract: An implantable cardiac deibrillator is provided having a battery, capacitive means, means coupled to the battery for charging the capacitive means, and means for coupling the capacitive means to a patient's heart, for delivering a high voltage shock to the heart. Current leakage from the capacitive means is detected. If the current leakage exceeds a predetermined amount, charging of the capacitive means is terminated. In one embodiment, voltage at the patient is directly sensed. In another embodiment, the voltage across a resistance located in series with the patient is sensed. In another embodiment, a test charge is provided for a short interval. The capacitive means is sensed to determine excessive loss of energy after the test charge. If excessive loss of energy is determined, charging is terminated.

Abstract: An implantable cardiac defibrillator is provided having an energy source, a capacitor, and means coupled to the energy source for charging the capacitor. The capacitor comprises a planar layered structure of anode plates, cathode plates and means separating the anode plates and cathode plates. A polymeric envelope containing electrolyte encloses the layered structure. Electrical contact means extend from the anodes and cathodes to outside the envelope.

Abstract: An electrode on a lead may be implanted at the heart by placing the lead through a hole in the parietal pericardium and positioning the distal end of the lead in a desired position relative to the heart. Thereafter one secures the lead in the desired position by attachment thereof to a fastener member, including the step of attaching the fastener member to the parietal pericardium by compressive action between a pair of opposed jaws of an attachment tool, with one of the jaws being positioned within and the other of the jaws positioned outside of the parietal pericardium. Also, a tool is disclosed for securing leads to a tissue site, particularly in accordance with the above method.

Abstract: Intrapericardial access is provided by clamping the wall of the pericardium between elongate jaw elements carrying axially aligned tubular guides and passing a guide wire through the guides and the pericardial tissue therebetween. In the preferred embodiment the jaw elements include interengageable ratchets for holding the elements in clamping engagement with the wall of the pericardium and aligned pointed extensions for piercing the pericardial tissue clamped between the elements. Further intrapericardial access is provided by an additional tubular guide carried by the jaw element intended to be disposed in the pericardium during placement of the guide wire.

Abstract: A method is disclosed for combined cardiac pacing and defibrillating with an implanted pacer/defibrillator having sensing and pacing leads connected to the atrium and the ventricle. P-waves and R-waves are sensed, and a V-V timer and a V-A timer are reset if an R-wave is sensed. If an R-wave is sensed during the V-V timer interval, a pacing stimulus to the ventricle is inhibited. If a P-wave is sensed during the V-A timer interval, a pacing stimulus to the atrium is inhibited. If an R-wave is sensed during the V-V timer interval, arrhythmia therapy is provided if an arrhythmia is determined to be present. If the sensed ventricular rate is greater than a selected tachycardia rate but is less than a selected fibrillation rate, than a determination is made whether the sensed atrial rate is greater than a selected fibrillation rate, and if so, the V-V and V-A timers are reset, but if the sensed atrial rate is not greater than a selected fibrillation rate, then arrhythmia therapy is provided.

Abstract: Intrapericardial access is provided by clamping the wall of the pericardium between elongate jaw elements carrying axially aligned tubular guides and passing a guide wire through the guides and the pericardial tissue therebetween. In the preferred embodiment the jaw elements include interengageable ratchets for holding the elements in clamping engagement with the wall of the pericardium and aligned pointed extensions for piercing the pericardial tissue clamped between the elements. Further intrapericardial access is provided by an additional tubular guide carried by the jaw element intended to be disposed in the pericardium during placement of the guide wire.

Abstract: An implantable medical device includes electrodes coupled to a patient's heart and sensing circuitry having inputs connected to the electrodes for sensing analog cardiac electrical signals from one of the atrial or ventricular channels. The sensing circuitry includes waveform digitization network means for converting the analog atrial or ventricular electrical signals into a parallel output format sign/magnitude digitized output signal.

Abstract: An implantable cardiac defibrillator employing a switched capacitor filter stage having charge steering resistors connected in series with corresponding switched capacitors that are coupled to a sensitive node of an operational amplifier. The stored channel charges in associated switches when they are tuned off are directed away from the sensitive node. The switches associated with the switched capacitors are operated by control signals having a generally trapezoidal shaped waveform so as to slowly turn off the same, thereby reducing clock feedthrough and charge injection induced offset voltage on the output of the operational amplifier.

Abstract: An implantable medical device includes electrodes coupled to a patient's heart and sensing circuitry having inputs connected to the electrodes for sensing cardiac electrical signals. The sensing circuitry includes a digital waveform analyzer system which performs direct analysis of digitized ECG heart signals from the atrial and/or ventricular channels. This eliminates the need for the system microprocessor to perform direct analysis on raw ECG data. The benefit being that complex software algorithms are not required, saving microprocessor memory space. System current drain is also reduced since the microprocessor need not be active during every ECG sample.

Abstract: A method is disclosed for combined cardiac pacing and defibrillating with an implanted pacer/defibrillator having sensing and pacing leads connected to the atrium and the ventricle. P-waves and R-waves are sensed, and V--V timer and a V--A timer are reset if an R-wave is sensed. If an R-wave is sensed during the V--V timer interval, a pacing stimulus to the ventricle is inhibited. If a P-wave is sensed during the V--A timer interval, a pacing stimulus to the atrium is inhibited. In an R-wave is sensed during the V--V timer interval, arrhythmia therapy is provided if an arrhythmia is determined to be present. If the sensed ventricular rate is greater than a selected tachycardia rate but is less than a selected fibrillation rate, then a determination is made whether the sensed atrial rate is greater than a selected fibrillation rate, and if so, the V--V and V--A timers are reset, but if the sensed atrial rate is not greater than a selected fibrillation rate, then arrhythmia therapy is provided.

Abstract: An implantable cardiac defibrillator employing a switched capacitor filter stage having charge steering resistors connected in series with corresponding switched capacitors that are coupled to a sensitive node of an operational amplifier. The stored channel charges in associated switches when they are turned off are directed away from the sensitive node. The switches associated with the switched capacitors are operated by control signals having a generally trapezoidal shaped waveform so as to slowly turn off the same, thereby reducing clock feedthrough and charge injection induced offset voltage on the output of the operational amplifier.