Abstract: An improved method and device for performing anti-tachycardia pacing (ATP) to convert a ventricular tachycardia (VT) to normal sinus rhythm. Pairs of pacing/sensing electrodes are placed in or on each of the left and right ventricles. Each pair of electrodes is shorted together to produce unipolar electrodes that are used for ATP.

Abstract: Improved methods and devices for performing anti-tachycardia pacing (ATP) to convert a ventricular tachycardia (VT) to normal sinus rhythm. In one embodiment one of a plurality of pacing configurations are selected for performing ATP. The selection can be based on the morphology of a signal indicative of the tachycardia.

Abstract: In an arrhythmia discrimination algorithm a timer is used to trigger the delivery of therapy when no diagnosis is made within a defined time during a tachycardia episode. Where one or more rhythm discriminators or qualifiers such as morphology, sudden onset, interval stability and AV association is enabled, the timer starts as soon as a ventricular interval or interval average is faster than a programmed maximum time to diagnosis (MTD) cutoff. If the timer times out before the algorithm diagnoses a particular rhythm, a programmed therapy is delivered. In the preferred embodiment, the therapy that is triggered is a function of the most recent detected ventricular rate and the programmed MTD therapy.

Abstract: An implantable cardiac stimulation device including a ventricular defibrillator and a rate adaptive cardiac pacer automatically adjusts post-pacing sensing parameters dependent upon pacing rate. The device includes a pulse generator that applies stimulation pulses to a heart at a calculated variable stimulation rate as a function of physiologic demand. A sensing circuit senses ventricular activity of the heart responsive to a plurality of sensing parameters including post-pace sensing parameters and a processor adjusts the post-pace sensing parameters responsive to the selected pacing rate.

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 two far-field fibrillation voltages across at least three 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 method for detecting cardiac arrhythmias which includes the steps of detecting a patient's cardiac activity, counting the number of intervals which satisfy a first selected criterion, and producing a sinus interval history count indicative of the number of such intervals which are counted, making a preliminary diagnosis of tachyarrhythmia upon detecting that the cardiac activity satisfies a second selected criterion, and, making a final diagnosis of tachyarrhythmia if the sinus interval history count is less than a selected maximum sinus interval history count, and otherwise, inhibiting a final diagnosis of tachyarrhythmia.

Abstract: A method and apparatus for performing electrophysiologic testing on a patient's heart using an implantable pulse generator system. The system includes an implantable pulse generator such as an implantable cardioverter-defibrillator having high voltage capacitors for storing electrical energy to defibrillate the patient's heart, a means for inducing a cardiac arrhythmia, an electrode system for discharging the stored energy into the patient's heart, and an external programmer for communication with and command of the implantable pulse generator. The method comprises the steps of charging the capacitors to a selected energy level upon command from the external programmer, inducing fibrillation in the patient's heart following the charging step, and discharging the capacitors through the electrodes into the patient's heart to defibrillate the patient's heart. The method and system provides flexibility in electrophysiologic testing by allowing the physician to control the time of delivery of high voltage therapy.

Abstract: A lead system for use with an implantable cardioverter/defibrillator is disclosed. The lead system includes a fixation hook positioned approximately half-way between the distal tip of the lead and the tricuspid valve. The distal tip of the lead is positioned at the apex of the right ventricle and may or may not be secured there by a second fixation means such as a screw tip or tines. The fixation hook allows the defibrillation electrode to be accurately positioned by the patient's surgeon and maintained in contact with the septum wall of the patient's heart. By providing such intimate contact between the defibrillation electrode and the septum wall, defibrillation thresholds are reduced.

Abstract: A lead system for use with an implantable pacemaker/cardioverter/defibrillator. The lead system includes a securable pace/sense electrode positioned between the distal tip of the lead and the tricuspid valve. The distal tip of the lead is positioned at the apex of the right ventricle and may or may not be secured there by a second fixation means such as a screw tip or tines. The securable pace/sense electrode allows the defibrillation electrode to be accurately positioned by the patient's surgeon and maintained in intimate contact with the septum wall of the patient's heart, thereby reducing defibrillation thresholds; it provides a sense signal from the region of the His bundle or AV node, which can be used with other electrodes to distinguish between various arrhythmias; and it provides more physiologic pacing leading to greater cardiac output.

Abstract: A header adapter which is a separately molded part and which is designed to be secured to receiving portions of the header and pulse generator case of an implantable cardiac stimulation device, such as a pacemaker or implantable cardioverter-defibrillator, in order to provide a different lead connector port configuration than that provided by the header of the device. The header adapter has a plurality of adapter lead connector ports and a plurality of lead connectors affixed to a rear portion (mounting side) thereof. The lead connectors extend outwardly from the rear portion of the header adapter, and are insertable into corresponding lead connector ports of the header of the implantable cardiac stimulation device to which the header adapter is to be secured.

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: 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 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 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 lead system for use with an implantable cardioverter/defibrillator is disclosed. The lead system includes a fixation hook positioned approximately half-way between the distal tip of the lead and the tricuspid valve. The distal tip of the lead is positioned at the apex of the right ventricle and may or may not be secured there by a second fixation means such as a screw tip or tines. The fixation hook allows the defibrillation electrode to be accurately positioned by the patient's surgeon and maintained in contact with the septum wall of the patient's heart. By providing such intimate contact between the defibrillation electrode and the septum wall, defibrillation thresholds are reduced.

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: 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.