Abstract: A dual-chamber pacemaker for confirming pacemaker mediated tachycardia (PMT) after initial detection. The minimum V-V pacing interval is extended to be slightly longer than the interval of the sensed atrial rate. If the A-V Delay intervals in successive cycles remain constant, as opposed to progressively increasing in Wenckebach fashion, then PMT is confirmed.

Abstract: A leadless implantable cardiac arrhythmia alarm is disclosed which continuously assesses a patient's heart function to discriminate between normal and abnormal heart functioning and, upon detecting an abnormal condition, generates a patient-warning signal. The alarm is capable of sensing impedance measurements of heart, respiratory and patient motion and, from these measurements, generating an alarm signal when the measurements indicate the occurrence of a cardiac arrhythmia. Because it requires no external leads or feedthrough connectors, the hermetically-sealed patient alarm is minimally invasive and results in reduced trauma to a patient.

Abstract: A method, useable in implantable cardioverter defibrillators, for classifying heart rhythms of a patient by means of electrogram morphology. A number of features (metrics) of the electrogram are measured to form a description of the shape of individual electrograms, and the metrics are then converted into a cardiac rhythm diagnosis by means of a pattern classification technique.

Abstract: An implantable cardioverter/defibrillator device having an improved sensing system for automatically and rapidly adjusting to changing amplitudes of intracardiac electrogram "ICEG" signals during transitions between normal sinus rhythm and ventricular tachycardia/ventricular fibrillation of a patient's heart is disclosed. ICEG signals are sensed, amplified and filtered to remove high frequency and low frequency noise and artifacts therefrom. Crossings of positive and negative threshold levels by the filtered signals are detected and corresponding positive and negative output signals representative thereof are provided.

Abstract: A clinical programming system is disclosed for use with an implanted cardiac pacemaker to automatically determine the minimum pacing energy which is necessary to evoke a ventricular depolarization. The system utilizes a series of pacing pulses of progressively decreasing energies to stimulate the ventricle, and detects evoked responses through measurements of the integrals of the R-waves provided by a surface electrocardiogram. Upon loss of capture, the minimum pacing energy is a function of the energy of the last pacing pulse which evoked a ventricular depolarization.

Abstract: An implantable dual chamber ICD and method senses atrial (A-A) and ventricular (V-V) intervals, calculates the ratio (A/V interval ratio) of A-A intervals to V-V intervals, classifies heart rhythms with V-V intervals (i) above a revert rate threshold as not tachycardia, (ii) below a high rate threshold as treatable tachycardia, (iii) between the two thresholds and below an A-dominant A/V interval ratio threshold as a non-treatable tachycardia, (iv) between the revert rate threshold and the high rate threshold and above a V-dominant threshold as treatable tachycardia and, when the heart rhythm is intermediate all four thresholds, (v) utilizes one or a combination of advanced discriminators (e.g., ventricular windowing, ventricular interval variability, sudden onset, AV-delay creep, ventricular electrogram morphology, active sensing, minute ventilation, or right ventricular pressure) to classify whether the heart rhythm is a non-treatable or a treatable tachycardia.

Abstract: An implantable lead fixation apparatus, including two suture collars connected by a flexible retaining member of predetermined length, is provided for anchoring an elongate cylindrical electrode lead to a patient's body. Each suture collar comprises a flexible annular member having a central lumen that is adapted to enclose the lead. The suture collars each include provision for securing the lead against longitudinal movement of the lead with respect to the collar, and provision for anchoring the collar to the patient's body. The suture collars are positioned relatively proximally and distally with respect to the lead, and are secured on the lead with the proximal suture collar being separated from the distal suture collar by slightly less than the length of the retaining member.

Abstract: An apparatus and a method for discriminating between tachycardias of physiological origin, and those of pathological origin having similar atrial and ventricular rates, are disclosed. The apparatus includes two sensing electrodes for registering the electrograms from the atrium and the ventricle of the heart. There is further included a signal processing element for determining the times of atrial and ventricular events, and an algorithm for classifying the heart rhythm. The algorithm includes a means for discriminating between different types of heart rhythms having overlapping ventricular rates and having similar atrial and ventricular rates. The method utilizes an analysis of the relationships between successive atrial and ventricular intervals (i.e., atrial-atrial (AA), ventricular-ventricular (VV) and atrial-ventricular (AV) intervals) in discriminating between such heart rhythms.

Abstract: A pacemaker automatically adjusts sensitivity as a function of metabolic demand. The amplitude of cardiac signals is naturally reduced during exercise. The pacemaker measures a physiological parameter to determine the patient's metabolic demand. In response to increases in the patient's metabolic demand the sensitivity is increased and in response to decreases in the patient's metabolic demand the sensitivity is decreased.

Abstract: A time domain reflectometry (TDR) impedance sensor is provided for measuring body impedance along a lead or catheter implanted in a patient's cardiovascular system. The TDR sensor applies an electrical stimulus to the lead and measures reflections echoed from impedance variations along and distal to the lead, which are superimposed on the applied stimulus. The measured signals may be analyzed with respect to time-of-flight and distance along the lead to detect a plurality of physiologically meaningful signals.

Abstract: A method and apparatus for selectively controlling an oscillator-driven implantable stimulator to operate either in a quiescent state, in response to a command from an external communicating device, or in an active state in response either to removal of an activation pin or to an activating command from an external communicating device. Upon completion of manufacture of the stimulator, and before being placed on a shelf to await implantation in a patient, the activation pin is inserted into the stimulator and the external communicating device is triggered to send a deactivating command to the stimulator. The stimulator responds by generally disabling current sources to stimulator circuits, while maintaining current sources to a wake up circuit of the stimulator that is associated with communication operations. The stimulator is activated by subsequently transmitting an activating command from an external communicating device to the implantable stimulator, or by removing the activation pin.

Abstract: An implantable electrical device, including a sealed case and a connector assembly, and a method for making the same are disclosed. The sealed case has electrical circuitry therein and has at least one insulated electrical-feed-through coupled to the circuitry. The feed-through member extends from the interior of the case to the exterior of the case and includes an external electrical terminal. The connector assembly has an apertured housing adapted to receive the proximal end portion of an electrical lead in sealing engagement with the housing. The connector assembly also has at least one electrical contact therein adapted to be engaged by a terminal of the electrical lead, and at least one insulated feed-through member coupled to the contact and extending from the interior of the assembly to the exterior of the assembly, the feed-through member including an external electrical terminal.

Abstract: An improved implantable pacemaker/defibrillator device in which a first and relatively simplistic technique is employed to detect an abnormal heart rhythm and a second more precise algorithm is utilized for the more difficult problem of confirming the arrythmia. Since the complex, higher power consuming device is utilized only for confirmation, overall power consumption is minimized. Optionally, the precise algorithm may be utilized periodically to adjust the sensitivity of the detection circuitry.

Abstract: A transvenous cardioversion lead system capable of delivering electrical energy to cardiac tissue is provided. Lead system comprises an inner conductor surrounded by an insulative layer which, in turn, is surrounded by a second conductor mounted coaxially with the inner conductor. At least a portion of the second conductor is surrounded by an outer conductive sheath formed from a suitable material having an non-abrasive affect. This prevents damage to cardiac tissue during normal transvenous operating position while at the same time preventing thrombogenesis on the lead surface.

Abstract: An apparatus and a method for discriminating between tachycardias of physiological origin, and those of pathological origin having similar atrial and ventricular rates, are disclosed. The apparatus includes two sensing electrodes for registering the electrograms from the atrium and the ventricle of the heart. There is further included a signal processing element for determining the times of atrial and ventricular events, and an algorithm for classifying the heart rhythm. The algorithm includes a means for discriminating between different types of heart rhythms having overlapping ventricular rates and having similar atrial and ventricular rates. The method utilizes an analysis of the relationships between successive atrial and ventricular intervals (i.e., atrial-atrial (AA), ventricular-ventricular (VV) and atrial-ventricular (AV) intervals) in discriminating between such heart rhythms.

Abstract: A method is disclosed for greatly reducing pacing polarization of a porous platinum bioelectrical stimulation electrode substrate by applying an oscillating current to the electrode substrate while it is immersed in an electrolyte such as a sodium sulfate solution to electrochemically cause the formation of a thick, highly porous platinum hydrous oxide surface layer on the substrate. The surface layer is then slowly reduced to platinum, while maintaining an increased surface area structure therein, using a similar electrochemical process employing much lower levels of current. This method does not alter the electrode characteristics other than to increase the microsurface area. The reduced polarization follows from the known inverse relationship between microsurface area and polarization. An electrode made by the foregoing method is also disclosed.

Abstract: A neuromuscular stimulation apparatus and procedure, which employs multiple channels of stimulation for the purpose of supplying directional control of blood flow in addition to augmenting the force of contraction. The apparatus comprises multiple channel stimulation electrodes and a multiple channel cardiosynchronous stimulator to selectively stimulate various sections of the skeletal muscle. The amplitudes of the stimulation pulses and the time delay following a cardiac event may be selected for each channel to appropriately stimulate the muscle to control the order of contraction of particular muscle fibers and thereby to govern the direction of blood flow.

Abstract: An elongate endocardial lead is disclosed which includes at least one distal electrode for sensing electrical activity in, and delivering electrical pacing pulses to, a patient's malfunctioning heart, a plurality of proximal terminal pins for coupling the lead to a pacemaker device, and a distal pressure sensor for sensing haemodynamic pressure within the heart. The pressure sensor comprises an integrated circuit chip having a layer of piezo-resistive material and a non-conductive base member, with the layer of piezo-resistive material being carried by the base member and having a pressure sensing diaphragm area therein exposed to ambient pressure. The base member and layer of piezo-resistive material are constructed and arranged so as to form a hermetically sealed chamber therebetween, with the chamber being at substantially atmospheric pressure and being substantially coextensive with the pressure sensing diaphragm area.

Abstract: A P-wave detector in a single chamber ventricular cardiac pacemaker, which is adapted to perform VDD pacing, senses natural atrial activity in the form of P-waves from a standard lead implanted in the ventricle of the heart. The P-wave detector is electrically coupled to a ventricular sensing lead and, although the electrode of the lead is implanted in the ventricle, circuitry within the pacemaker perceives intrinsic cardiac electrical activity arising from all parts of the heart. The P-wave detector is adapted to differentiate P-wave signals arising within the atrium from other cardiac and non-cardiac signals using template matching techniques in which an acquired signal is compared with a previously stored P-wave template.

Abstract: An active fixation lead assembly including a dual-pitch screw mechanism and a free spinning mechanism, which provides an improved capability for firmly engaging a lead tip upon heart tissue while avoiding damage to the tissue due to overtorquing of the lead. The dual-pitch screw mechanism employs an extendable coupling screw, firmly attached to a helical fixation coil. The thread pitch of the extendable coupling screw is greater than the thread pitch of the helical fixation coil so that the coil portion will move through tissue faster per revolution than the coupling screw, thereby embracing the tissue more tightly against the lead and improving the electrical connection between the tissue and the electrode. Generally, the free spinning mechanism allows the fixation coil to rotate freely after the fixation coil has been fully extended.