Abstract: An alternative mechanism in an implantable device for meeting the physician's need for a stored electrogram and/or other stored physiologic signal associated with a detected arrhythmic or other physiological event without the undesirable current drain associated with continuous operation of a sense amplifier and a looping memory. The device regularly but intermittently activates a sense amplifier or other sensor and associated memory circuitry, independent of detection of arrhythmias. The device may temporarily store only a single record, replacing it with new records as they are stored, or may store multiple records, replacing the oldest stored record with the newest stored record. On detection of an arrhythmia or other defined physiological event, the device may simply transfer the one or more temporarily stored electrogram strips to permanent storage, for later use by the physician in diagnosing the condition of the patient prior to detection of the event.

Abstract: An implantable anti-tachyarrhythmia device which delivers atrial cardioversion or defibrillation pulses heart in response to detection of atrial tachyarrhythmias. The pulses are synchronized to atrial and ventricular events in such a fashion as to assure they occur outside of the vulnerable periods associated with both chambers. The device is provided with a pulse synchronizer which defines a first synchronization interval initiated following a sensed atrial event and a second synchronization interval initiated responsive to a sensed ventricular event and a pulse triggerer which triggers delivery of a cardioversion or defibrillation pulse responsive to the first and second synchronization intervals simultaneously being underway. In particular, the pulse triggerer may be responsive to initiation of the first synchronization interval during the second synchronization interval.

Abstract: An atrial cardioverter and a method of its operation. The cardioverter measures an interval between successive R-waves, defines a ventricular escape interval as a function of the measured interval between successive R-waves and delivers a ventricular pacing pulse at the expiration of the ventricular escape interval in the absence of R-waves during the ventricular escape interval. The cardioverter defines a synchronization interval following delivery of the ventricular pacing pulse, and delivers an atrial cardioversion pulse synchronized to an R-wave occurring after expiration of the synchronization interval, absent R-waves during the synchronization interval.

Abstract: A cardiac stimulator and a method of its use. The stimulator includes a lead system carrying a stimulation electrodes adapted to be located at multiple sites adjacent tissue of a patient's heart and is provided with stimulation pulse generators coupled to deliver stimulation pulses to the stimulation electrodes. The stimulator further includes depolarization sensors responsive to depolarizations of cardiac tissues at the tissue sites and, responsive to sensed depolarizations and stimulation pulses delivered to said sites by said stimulation electrodes determines exitable gaps of tissue at the sites. The stimulator calculates stimulus pulse delivery times at variable delivery times within the determined exitable gaps at the tissue sites to cause convergence of depolarization cycles at the tissue sites over a series of delivered stimulation pulses and delivers stimulation pulses to the stimulation electrodes at the calculated variable delivery times.

Abstract: A system and method for stimulating the baroreflex arc based on levels of indicators from the body includes a pacemaker for bradycardia support pacing should the indicators show the need for support pacing. Other indicators and a process take advantage of an assumed relationship between peripheral vascular resistance and pulmonary resistance to determine the level of nerve stimulation required. This level is adjusted or optimized based on its interaction with heart activity and changes in the other indicators. These other indicators are readily available to the implanted device and allow for a process to make an estimate of pulmonary vascular resistance, from which SVR is also estimated. The value determined for SVR is the primary value used to determine the level of nerve stimulation absent indicators for the need to provide bradicardia pacing. The pacemaker can be rate responsive, as can the process for determining the level of nerve stimulation to be delivered.

Abstract: A shape memory device includes a shape memory alloy member configured to have at least a portion of the shape memory alloy member be selectively activated. A heating device is coupled to the member and configured to provide heat to a selected section of the member and activate at least a portion of the selected section.

Abstract: An implantable cardioversion/defibrillation lead having an elongated insulative lead body carrying a tip electrode located at its distal end and a cardioversion/defibrillation electrode located on the lead body, proximal to the tip electrode. An elongated conductor coupled to the tip electrode extends proximally within the lead body. At the proximal end of the lead body is a first connector assembly carrying a first connector and a second connector assembly carrying a second connector. An elongated, stranded or cabled conductor is coupled to the cardioversion/defibrillation electrode and to the second connector and extends uninterrupted therebetween. A cylindrical transition member is coupled to the first connector by means of a coiled conductor. A press-fit sleeve having a longitudinal lumen extending therethrough compresses the stranded or conductor between the press-fit sleeve and the transition member to provide electrical interconnection between the stranded or cabled conductor and the transition member.

Abstract: An apparatus for deflecting a catheter or lead, for example a deflectable stylet or guidewire. The device includes an outer tubular member, a tension member mounted within the outer tubular member and coupled to the outer member and a handle mounted at the proximal end of the tubular member. The handle includes a major handle portion which has a rotatable knob located at its distal end, surrounding a proximal portion of the outer tubular member and provided with inwardly directed threading and an inner slider member provided with outwardly directed threading engaging the inwardly directed threading of the knob. The slider is advanced or retracted longitudinally within the handle by rotation of the knob but is rotationally fixed with regard to the major handle portion.

Abstract: An implantable lead which has an increased resistance to fracture and has the capability of continued function after fracture of a conductor. The lead is provided with a coiled conductor which may be monofilar or multifilar and which extends along the length of the lead, running from an electrical connector at the proximal end of the lead to an electrode at or near the distal end of the lead. In addition, the lead is provided with a stranded conductor which is electrically coupled to the coiled conductor at point along the lead body located proximal to the point of expected breakage of the coiled conductor and at a point along the lead body located distal to the point of expected breakage. The proximal and distal ends of the stranded conductor in some embodiments are also mechanically coupled to the coiled conductor.

Abstract: An implantable cardiac pacemaker and a method of its operation. The pacemaker delivers pacing pulses to a first chamber of a patient's heart and senses depolarizations of a second chamber of the patient's heart. The amplifier for sensing depolarizations of the second chamber of the patient's heart defines a base sensing threshold and, responsive to delivery of a pacing pulse to the first chamber of the patient's heart for defines an increased sensing threshold greater than the base sensing threshold. The increased sensing threshold persists for a defined period of time following delivery of a pacing pulse to the first chamber of the patient's heart and thereafter gradually decreases from the increased sensing threshold to the base sensing threshold.

Abstract: A method and apparatus for the simultaneous administration of multiple pacing therapies in which two or more pacing features which operate to cause the dynamic adjustment of a common operational parameter of a pacing system are activatable at the same time. In one embodiment, a prioritization among multiple pacing features is established, such that when two (or more) features which operate to cause adjustment of a common operational parameter, a lower-priority feature will not override an adjustment made by any higher-priority feature.

Abstract: An implantable pacing lead system for pacing a patient's heart, including a delivery catheter and a lead delivered by the delivery catheter. The lead takes the form of a single non-diverging filament having a proximal end and a distal end and carries an electrode mounted to a distal portion of the lead body. An active fixation device is mounted fixedly to, and extends laterally from, the lead body proximal to and longitudinally spaced from the electrode. During advancement of the lead through the vasculature the active fixation device is located within the delivery catheter. At the point of desired location of the active fixation device, it is advanced out of the delivery catheter and engaged with heart tissue. The lead body has greater torsional rigidity proximal to the active fixation device than distal to the active fixation device.

Abstract: An implantable anti-tachyarrhythmia device which delivers anti-tachyarrhythmia therapies to a patient's heart in response to detection of tachyarrhythmias. The device defines first criteria indicating the presence of atrial tachycardia and second criteria indicating the presence of atrial fibrillation, and compares the time elapsed since the either the first or second criteria were initially met to a defined time duration. In response to the defined duration having passed and either of the first or second criteria being met, the device triggers delivery of an appropriate anti-tachyarrhythmia therapy. The timer is reset on detection of termination of atrial tachyarrhythmia, but not on failure of the first and second criteria to be met. The first and second criteria are defined such that they can not be concurrently met.

Abstract: A medical electrical lead with a tip-ring assembly optimized to resist damage during extraction. The lead includes an elongated plastic tube and at least two elongated conductors mounted in the plastic tube. A tip-ring assembly is mounted to the distal end of the tube, the tip-ring assembly including a ring electrode coupled to one of the conductors, a tip electrode located distal to the ring electrode and coupled to another of the conductors and two molded plastic components separately fabricated of a plastic harder than the plastic tube, adhered to one another and together defining a circumferential groove in which the ring electrode is located and mechanically coupled to the tip electrode. The tip electrode may be provided with a proximally extending electrode shank covered by a tine sleeve which is fabricated of a plastic softer than the molded plastic components and is adhered to more distally located molded plastic component.

Abstract: An implantable medical device determines activity levels over a set of time periods, preferably on the order of seconds, minutes and hours and a display is enabled for days or weeks at recorded activity levels over a range of dates. This enables physician review of patient functional status. Additional physiologic data can be recorded along with the activity data, and this too may be reported out from the implanted device to a medical communications system for alarm purposes, titrating drugs or other monitoring tasks.

Abstract: A method of and apparatus for determining the physical posture of a patient's body, having a superior-inferior body axis, an anterior-posterior body axis and a lateral-medial body axis, in relation to earth's gravitational field. A medical device having first, second and, optionally, third accelerometers having sensitive axes mounted orthogonally within an implantable housing is adapted to be implanted with the sensitive axes nominally aligned with ideal X, Y and Z device axes correlated to patient body axes. Each accelerometer generates DC accelerometer signals having characteristic magnitudes and polarities on alignment of the sensitive axis with, against or normal to earth's gravitational field and DC accelerometer signals of varying magnitudes and polarities when not so aligned. The actual pitch and roll angles of the sensitive axes of the accelerometers in the implanted IMD with respect to the true gravitational axes are determined and the yaw angles are determined or estimated.

Abstract: A medical electrical lead and a reinforced silicone elastomer used therein. The silicone elastomer used therein is preferably made from a novel silica reinforced polysiloxane material, which after vulcanization by cross-linking exhibits improved mechanical properties. The medical electrical lead features a an electrode at a distal end thereof, a connector at a proximal end thereof and an elongated electrical conductor extending between the electrode and the connector, the conductor in electrical contact with the electrode at a distal end and in electrical contact with the connector at a proximal end, the conductor comprised of a plurality of wires or wire bundles wound in a multifilar coil configuration.

Abstract: An implantable electrical lead of the type having a rigid, insulative electrode head carrying an advanceable helical electrode. The electrode head is mounted to an elongated insulative lead body less rigid than said electrode head and which carries an extensible conductor coupled to the helical electrode and an inextensible conductor mechanically coupled to the proximal end of the lead. A second electrode is mounted to said lead body adjacent the electrode head and is coupled to the inextensible conductor. The inextensible electrical conductor is mechanically coupled to the electrode head such that poximally directed traction forces applied to the proximal end of the lead body are applied to the head by the inextensible conductor and not by the second electrode.

Abstract: A lead and a lead system for dispersion of a cardioversion/defibrillation electrode formed of one or more small diameter defibrillation electrodes in a heart chamber and for attaching a pace/sense electrode in contact with the heart. The small diameter defibrillation electrode or electrodes extend distally from the distal end of the lead body. If multiple electrodes are employed, they are preferably biased to spread apart when unrestrained and have a cross-section size small enough to be inserted into interstices of trabeculae in the ventricular chamber. The distal ends of the defibrillation electrodes may be free of attachment to the lead body or may be attached by a weak bond to the distal portion of the lead.

Abstract: A method and apparatus for detecting and treating atrial fibrillation. In response to detecting atrial fibrillation, the device derives an escape interval based on one or more preceding intervals between ventricular depolarizations. The escape interval is initiated in response to a ventricular depolarization, and in response to the expiration of the escape interval, an atrial cardioversion pulse is delivered. In one embodiment of the invention, the cardioverting pulse is delivered immediately upon expiration of the derived escape interval. In a second embodiment of the invention, a ventricular pacing pulse is delivered on expiration of the escape interval, with an atrial cardioversion pulse following after a short delay.