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.

Abstract: An implantable cardioverting/defibrillating pacemaker and method for treating arrhythmias of a patient's heart are disclosed. Bradycardia support pacing is initially provided at a normal standby rate, in the absence of a tachycardia. Upon detection and confirmation of a tachycardia, antitachycardia therapy in the form of antitachycardia pacing pulse therapy and/or cardioversion or defibrillation therapy is delivered to the heart. Thereafter, upon reversion of the tachycardia, bradycardia support pacing is again delivered to the heart but at a greater rate than the earlier normal standby rate and only for a predetermined time period. At the end of such time period, the bradycardia support pacing rate is returned to the normal standby rate, either directly or in decremental steps.

Abstract: A method and apparatus for detecting and reverting pathological heart rhythms of a patient are disclosed. A plurality of electrical heart rhythm signals of the patient are sensed at two different locations within the heart. The cross-phase spectra of the sensed heart rhythm signals for each heartbeat are calculated and such heart rhythms are classified based upon the information contained in the cross-phase spectra. Appropriate therapy is then delivered to the patient's heart to revert those of the heart rhythms that are classified as pathological.

Abstract: A dual-chamber metabolic demand, rate adaptive pacemaker that automatically calibrates the correlation between a metabolic demand measurement and an appropriate metabolic demand pacing rate according to the true physiological needs of the body, as determined by a patient's sinus rate when the natural sinus rate is functioning in a reliable manner in the absence of cardiac arrhythmia.

Abstract: A method and apparatus for detecting cardiac arrhythmias are disclosed. The detecting method and apparatus sense cardiac electrical signals when the heart is functioning in a known cardiac state, such as a physiologically normal cardiac state, then define and store an array of amplitude windows wherein each sample in the array of amplitude windows corresponds to a sample of the known cardiac signal. Each amplitude window delineates a range of signal amplitudes bracketing the amplitude of the known cardiac electrical signal sample. The array of amplitude windows corresponds in time to periodically occurring known cardiac signal samples occurring within a predetermined time of interest.

Abstract: An anti-tachyarrythmia pacing system is disclosed which utilizes an intra-cardiac electrode to obtain a gradient for each cardiac cycle. When the gradient increases beyond a predetermined value, it is determined that tachyarrythmia is imminent and the pacing system responds by pacing the heart in a therapeutic manner to prevent the onset of such tachyarrythmia.

Abstract: An improved electrocardiac monitoring device is disclosed in which the sampling period utilized to sample the ECG signal is varied dynamically. Specifically, during rapidly varying portions of the ECG signal, the sampling rate is high. As the rate of change of the ECG signal decreases, the sampling rate is slowed so that only the minimum number of samples are taken to accurately reconstruct the analog ECG signal. The sampling period to be used is determined from the relative positions in time between a predetermined portion of the ECG signal and the portion of the ECG signal being sampled.

Abstract: A method and apparatus for aligning periodic cardiac signal waveforms for the purpose of signal averaging over a number of cardiac cycles. The aligning method and apparatus sense cardiac electrical signals over a number of cardiac cycles, store a template characterizing these signals, reduce the data rate of the same sensed signals by temporal data compression, and store a compressed template sequence. Subsequently, the method and apparatus perform signal averaging by monitoring cardiac electrical signals, storing samples of these signals, temporally compressing these samples and scan correlating the compressed samples with the previously stored compressed template sequence to derive correlation coefficients.

Abstract: A method and apparatus for delivering electrical therapy to the heart are disclosed. The apparatus detects and confirms the arrhythmia. However, during confirmation, if the arrhythmia is present but not too severe, it is allowed to continue in the hope that it will spontaneously revert. The arrhythmia is reconfirmed later and, if it is still present, electrical therapy is delivered to the heart. Thus, for mild arrhythmias, electrical shock therapy is withheld for a specified time period in the hope that the arrhythmia will revert spontaneously. More severe arrhythmias which are not hemodynamically sustaining are immediately electrically shocked in an effort to revert the heart back to normal sinus rhythm.

Abstract: An antiarrhythmia pacemaker and method detect and confirm the occurrence of an abnormal condition of a patient's heart selected from the group comprising tachycardia, fibrillation and precursors thereof, and, in response thereto, deliver an antiarrhythmia therapy to the patient which includes two components, electrical stimulation of the heart and electrical stimulation of a skeletal muscle graft which has been surgically grafted to the heart to augment performance of the heart. The antiarrhythmia pacemaker and method control electrical stimulation of the heart in terms of timing, frequency, amplitude, duration and other operational parameters, to provide such pacing therapies as antitachycardia pacing, cardioversion and defibrillation. A skeletal muscle graft stimulation electrode, which is driven by a skeletal muscle pulse stimulator, stimulates preselected nerve fibers within the skeletal muscle graft.

Abstract: A connector assembly for an implantable stimulating device employs a lead-locking spring clip to reliably provide a mechanical and electrical connection between the terminal pin of an electrode lead and the device, while reducing the user interaction required during implantation and disconnection. No tools are required to establish the connection. No user action, other than inserting the lead into the connector, is necessary to lock the lead into place. Disconnecting the lead requires only the application of a modest transverse compressing force to a release button on the connector assembly. In the event that a withdrawal force is applied to the lead without simultaneously applying the compressing force to the release button, the connector assembly increases its holding force on the electrode lead.

Abstract: An apparatus and method for the detection and treatment of arrhythmias using a processor having a neural network with a hierarchical arrangement including a first lower level for classifying individual waveforms, a second higher level for diagnosing detected arrhythmias and a third higher level for the application of therapy in response to a diagnosed arrhythmia. The neural network may be a back propogation neural network or an associative memory type neural network. The arrhythmias detected may be at least one of bradycardia, tachycardia and fibrillation. The apparatus may include a cardioverting/defibrillating pacemaker. In general, the apparatus acquires physiological signals representative of heart activity in a patient. A neural network receives the physiological signals and determines if any arrhythmia is present, and if present, selects therapy to be applied to the heart. A therapy generator then applies the therapy selected by the neural network.

Abstract: An improved ultrasonic transducer for a catheter tip has a thin strip of piezoelectric polymer film formed into a spiral ring and adhesively mounted on the support structure near the catheter tip. Electrical connection between the back face of the film and the support structure negative electrode is via capacitive coupling. Connection to the front face of the film is via a wire connected to the positive electrode of the catheter. A further embodiment suitable for a needle transducer is formed by coating the tip with a solution of PVDF co-polymer to form the actual transducer.

Abstract: A method and apparatus for detecting cardiac arrhythmias in a patient's heart is disclosed. The monitoring method and apparatus sense cardiac electrical signals when the heart is functioning in a known cardiac state, then characterize this known cardiac state by storing a temporally compressed template of time sequence samples. The method and apparatus allow testing during multiple different cardiac states and provide for storage of templates associated with each state. Subsequently, when the heart is functioning in an unknown cardiac state, the method and apparatus monitor cardiac electrical signals by temporally compressing samples and scan correlating these samples with the previously stored template sequences to derive correlation coefficients. The method and apparatus then use these correlation coefficients to characterize cardiac function.

Abstract: A method and apparatus for measuring subthreshold defibrillation electrode resistance are disclosed. A known subthreshold current pulse is sourced across the electrodes, the resulting voltage is measured and the electrode resistance is calculated from these values. The calculated electrode resistance may be utilized to adjust the energy level of a defibrillation shock used to treat a detected tachyarrhythmia. In one embodiment the calculated resistance and a predetermined leading edge voltage are used to calculate and adjust the duration of the defibrillation shock. In another embodiment the calculated electrode resistance and a predetermined shock duration are used to adjust the leading edge voltage of the defibrillation shock.

Abstract: An implantable medical device and method for providing therapy to a patient's inadequately functioning heart are disclosed. The device and method utilize a defibrillation electrode lead system to deliver defibrillation therapy to the patient's heart, and a defibrillator to provide the defibrillation therapy that is delivered by the defibrillation electrode lead system. The defibrillator includes a charge storing circuit for storing an electrical charge therein. Controls are employed for charging the charge storing circuit to an appropriately high energy level for use in defibrillation therapy, in response to a detected tachycardia condition, and for charging the charge storing circuit to an appropriately low energy level for selectively inducing an arrhythmia in the patient's heart.

Abstract: A method and apparatus for storing a representation of a cardiac signal by compressing the data using scan correlation and temporal data compression techniques. The method and apparatus sense cardiac signals when the heart is functioning in a known cardiac state, then characterize this known state by storing a temporally compressed template of time sequence samples. The method and apparatus may perform testing for multiple different cardiac states and store templates associated with each state. Subsequently when the heart is functioning in an unknown cardiac state, the method and apparatus monitor cardiac signals by temporally compressing samples and scan correlating these samples with the previously stored templates to derive correlation coefficients. These correlation coefficients are a basis for identifying and classifying cardiac signal waveforms.

Abstract: An implantable device and a method for the automatic detection of atrial arrhythmias and for providing low energy atrial cardioversion therapy for such arrhythmias, with minimal tissue damage and power drain, is disclosed. The device is capable of being incorporated within, and is disclosed as part of, an implantable automatic pacemaker defibrillator/cardioverter having the ability to also provide high energy ventricular defibrillation therapy, as well as dual chamber antitachycardia pacing therapy and bradycardia support pacing. Tripolar atrial and ventricular endocardial leads, each including tip and ring pacing electrodes and a braid cardioverting electrode therein, are employed in conjunction with a subcutaneous electrode lead in delivering therapy from the device to the patient, allowing the device to be implanted in and used by a patient without the need to open the patient's chest cavity.

Abstract: An antiarrhythmia pacemaker detects the occurrence of an abnormal condition of a patient's heart and, in response, delivers an antiarrhythmia therapy to the patient which includes two components, electrical stimulation of the heart and electrical stimulation of nerves or ganglia in the autonomic nervous system. The antiarrhythmia pacemaker controls electrical stimulation of the heart in terms of timing, frequency, amplitude, duration and other operational parameters, to provide such pacing therapies as antitachycardia pacing, cardioversion and defibrillation. A nerve stimulation electrode, which is driven by a nerve fiber pulse stimulator, stimulates preselected nerve fibers within the patient's autonomic nervous system. An arrhythmia therapy control responds to the detection and confirmation of an abnormal heart condition by controlling and coordinating the heart pulse stimulator and the nerve fiber stimulator to direct performance of a combined heart and nerve stimulation therapy.

Abstract: A rate-responsive pacemaker employing a rate control parameter of respiratory minute volume, derived over a unipolar lead. The pacemaker performs the minute volume measurement by periodically applying a measuring current between the lead and a reference point on the pacemaker case. This measuring current has frequency components in a range from approximately 10 kilohertz to 1000 megahertz. Application of this measuring current allows the pacemaker to detect the voltage which arises from the applied current and, from the detected voltage, to measure the patient's spatial impedance. Spatial impedance and minute volume vary as a function of the patient's pleural pressure. The pacemaker derives minute volume and rate-responsive pacing rate from the spatial impedance measurement.