Abstract: A method and apparatus for classifying and treating tachyarrhythmias. A cardiac stimulator includes an algorithm that uses dual chamber sensing to determine the type of tachyarrhythmia detected. If the tachyarrhythmia is of a type that responds well to ventricular therapy, such as a tachyarrhythmia originating in the ventricle rather than the atrium, the tachyarrhythmia is grouped into a treatable category. Accordingly, the cardiac stimulator applies therapy, or therapies, to the ventricle to remedy the ventricular tachyarrhythmia.

Abstract: A lead assembly for fixation to a human heart via thoracoscopy is provided. The lead assembly includes a lead that has a connector for connection to a cardiac stimulator, such as a pacemaker, a cardioverter/defibrillator, or a sensing instrument. A fixation mechanism is coupled to the lead that includes a tubular housing and a proximally projecting hook that is adapted to engage heart tissue. The hook is pivotable between a retracted position and an extended position. The lead and the hook are manipulated by a stylet. The lead assembly also includes a tubular introducer that is passed through the chest wall of a patient and used to place the lead proximate the epicardium.

Abstract: A method of preventing or reducing the incidence of staphylococci and other infections as a result of surgical or medical treatment procedures is implemented by inserting into or attaching to each sterile package containing a tool, implement, or implantable for use in such a procedure at least one impregnable swab containing a solution of H.sub.2 O.sub.2 packaged in a separate sterile pack, for use by the surgeon, therapist, or assistant in wiping down the tool, implement, or implantable, as the case may be, before use to maintain the sterility thereof in such procedure. The solution of H.sub.2 O.sub.2 is in a concentration of about 3% by volume. A plurality of separate sterile packs may be inserted in or attached to the sterile package, in which each of the sterile packs contains at least one swab impregnated with a solution of H.sub.2 O.sub.2 in such concentration.

Abstract: An implantable device for providing pacing and defibrillating stimuli to a heart, comprises: a power source, at least one electrode electrically connected to said power source, a sensor capable of providing data that can be used to determine a physiological pacing demand, and a control device. The control device controls the application of electrical stimuli to the heart. The control device calculates an adjusted pacing interval based on said demand, calculates an adjusted ventricular pace refractory period (VPRP.sub.current) that is a function of said pacing interval, and calculates a T-wave monitoring window. The end time, and optionally the start time also, of the T-wave window is a function of the pacing interval. The control device is also capable of adjusting the sensitivity of an amplifier based on signals received during the T-wave window.

Abstract: A lead assembly adapted for endocardial fixation to a human heart is provided. The lead assembly includes a lead body that has a proximal end provided with a connector for electrical connection to a cardiac stimulator. The cardiac stimulator may be a pacemaker, a cardioverter/defibrillator, or a sensing instrument. The distal end of the lead body is connected to a tubular electrode housing. The lead body consists of a noncoiled conductor cable surrounded by a coextensive insulating sleeve. In contrast to conventional leads, the lead body of the present invention does not require coiled conductor wires or an internal lumen. Manipulation of the lead body is via an external guide tube. Lead body diameters of 0.25 mm or smaller are possible.

Abstract: An implantable medical device for electrically stimulating the heart to beat includes a sense circuit for detecting cardiac electrical activity. The sense circuit includes a band pass filter with an adjustable frequency response. The frequency response can be repeatedly adjusted after implantation of the medical device and preferably is adjusted upon detection of the loss of normal sinus rhythm (NSR) in the heart's atria. The loss of NSR often indicates atrial fibrillation (AF), and the filter's frequency response is adjusted to increase the sensitivity of the sense circuit to the cardiac electrical activity typical during AF. The medical device is calibrated during implantation or at subsequent doctor visits with the aid of a calibration device external to the body. Cardiac electrical activity in the form of an electrogram is transmitted from the medical device to the external calibration device. The transmitted electrogram preferably includes both NSR and AF rhythms.

Abstract: Magnetically alterable material, such as magnetostrictive material, is used in combination with a suitable substrate and a suitable magnetic field to produce a stylet and lead assembly that curves in response to a suitable magnetic field.

Abstract: An implantable defibrillator, which may include cardioversion and pacemaker capabilities, which has EMI filters which are not susceptible to defibrillation shocks and which reduce or eliminate the effects of charging noise on sensing circuits used for continuous confirmation. A first filter capacitor is provided between a sense electrode, which may include pacing capabilities, and a ground reference within a hermetically sealed can containing a pulse/shock generator. A second filter capacitor is provided between a sensing/pacing reference electrode, which may also be a high voltage or shock electrode, and the ground reference. In addition, there is a third filter capacitor between the ground reference and the can. Preferably, the connections of the first, second and third filter capacitors are physically as well as electrically adjacent to each other. The filter capacitors are housed in the can and in or adjacent to a feedthrough assembly which passes through the can.

Abstract: A method and apparatus for detecting failure or impending failure of a lead and for providing a warning to a patient or a patient's physician. The impedance of the lead is repeatedly measured and compared with certain impedance limits. If the measured impedance falls outside of these impedance limits, an alarm may be given to the patient, or a warning may be given to the patient's physician.

Abstract: An implantable medical device for electrically stimulating the heart to beat includes a sense circuit for detecting cardiac electrical activity. The sense circuit includes an amplifier with a dynamically adjustable gain to provide increased sensitivity to the electrogram during atrial fibrillation. Alternatively, sensitivity control is provided by dynamically adjusting threshold limits associated with a threshold detector included in the sense circuit. The sensitivity level of the medical device to the electrogram can be repeatedly adjusted after implantation and preferably is increased upon detection of the loss of normal sinus rhythm (NSR) in the heart's atria. The medical device is calibrated with the aid of a calibration device external to the body to determine appropriate sensitivity levels. A method for calibrating and operating an implanted medical device with dynamically adjustable sensitivity is also disclosed for improving the medical device's sensitivity to atrial fibrillation.

Abstract: Various endocardial lead assemblies are disclosed that may be particularly useful for placement within the coronary sinus. One lead assembly includes an open-ended electrode that may be implanted in a patient by passing it along a previously implanted stylet. Another disclosed embodiment combines an open-ended electrode with one or more flow passages that improve blood flow through the body vessel in the area of the implanted electrode. Yet another disclosed embodiment uses an electrode that has flow passages but no opening. This electrode provides improved blood flow in the area of the electrode but may be implanted using conventional methods.

Abstract: A programmable pacemaker and program therefor are disclosed, wherein the pacer is programmed to operate in a first pacing mode whenever the measured atrial rate is less than a certain threshold switching rate R.sub.T, and to operate in a second pacing mode whenever the measured atrial rate is greater than the threshold switching rate R.sub.T. The threshold switching rate R.sub.T is varied based on either a programmed algorithm or the measured value of one or more sensed parameters. In another embodiment, a hysteresis is introduced, so that the rate at which the pacer switches back to its low-activity mode is lower than the rate that triggers a switch to the high-activity mode.

Abstract: An implantable medical device, such as a pacemaker, for electrically stimulating the heart to beat includes two or more node logic units connected by communication paths over which signals between nodes are conducted. Each node can provide pacing energy to an electrode and amplify electrical signals from the electrode. In response to detecting an electrical event from the electrode or pacing an electrode, each node generates a sense signal or a pace signal. The sense and pace signals form each node can be transmitted to all other nodes with or without a time delay. The time delays between nodes are provided by delay modules controlled by a processor. As such, the implantable medical device can be configured to provide a variety of pacemaker therapies.

Abstract: An interventional medical device has a capability to sense cardiac dysrhythmias and to selectively respond with one among a hierarchy of therapies appropriate to terminate the sensed dysrhythmia and return the heart of the patient in whom the device is adapted to be implanted to normal sinus rhythm. The device includes a therapy generator having a housing and electronics for conducting bidirectional communication with the patient. The bidirectional communication is carried out by detecting the occurrence of a predetermined dysrhythmia, such as atrial fibrillation, to alert the patient of such occurrence, and by responding to instructions from the patient following such alert for addressing the detected predetermined dysrhythmia. The detection is performed by electrodes mounted directly on the header of the device housing to both detect occurrence of the atrial fibrillation and for alerting the patient thereof by stimulating body tissue such as pectoral muscle in the vicinity of the header electrodes.

Abstract: An implantable cardiac stimulator delivers a first electrical shock via implantable stimulating electrodes at a time when there is substantially no flow of blood. At least one of the stimulating electrodes is disposed in a blood flow path of the cardiovascular system. The first shock is of insufficient energy level to cause defibrillation. An electrical potential is measured as a function of time between the blood-contacting electrode and a reference electrode following delivery of the first shock to obtain a first potential equilibration function under no-flow conditions. A second therapeutic electrical shock, of sufficient energy level to effect defibrillation, is delivered via the stimulating electrodes. A second potential equilibration function is measured following delivery of the second shock. The first and second potential equilibration functions are compared, and if the two functions are sufficiently different in morphology, it is determined that blood is flowing.

Abstract: An implantable, rate responsive pacemaker, sensitive to impedance changes in the heart, wherein the cardiac pacing rate and maximum cardiac pacing rate, or either of them, are adjusted as a function of an interval between either the administration of a pacing pulse or the detection of the R-wave and the occurrence of a maximum detected impedance, called the intercept interval. Because an intercept point in derivative of the impedance curve is detected, the apparatus and method are insensitive to electrode characteristics, electrode movement, body posture or other factors which could affect the magnitude of the detected impedance. The information contained in the intercept interval can also be combined with other sensed or calculated information to set the desired rates.

Abstract: An implantable system is provided for subcutaneous surgical implantation. The implantable system includes a smoothly contoured casing and an implantable apparatus designed to perform a desired medical function, such as cardiac stimulation, diagnosis, or drug infusion. The casing includes a chamber for enclosing the implantable apparatus. The casing is provided with one end that is separated from a second, and opposing, end by a slit. The shape of the casing and the separated ends enables implantation via a shorter incision than is possible using a comparably sized conventional implantable device. Some examples of possible implantable apparatus include cardiac stimulators and sensors, or drug infusion pumps.

Abstract: An implantable cardiac stimulator, which may include cardioversion and pacemaker capabilities, which has apparatus for detecting an externally applied shock, such as a defibrillation or cardioverting shock. In response to detection of such a shock, the cardiac stimulator has apparatus to adjust the parameters of applied therapy, or to select alternative therapy, including, but not limited to, adjusting the magnitude of stimulus pulses for a predetermined length of time. The risk of loss of capture, and consequent failure of cardiac function, following an externally applied shock is thereby reduced.

Abstract: An implantable medical device for electrically stimulating the heart to beat including a sense circuit for detecting cardiac electrical activity. The sense circuit includes a sense amplifier, band pass filter, and threshold detector. The threshold detector determines whether sensed cardiac electrical activity resulted from a normal heart beat or an ectopic beat such as a premature ventricular contraction. In a preferred embodiment, latches in the threshold detector are activated by output pulses from a pair of comparators. A positive comparator produces an output pulse upon detection of cardiac electrical activity exceeding a positive threshold voltage and a negative comparator produces an output pulse upon detection of cardiac electrical activity more negative than a negative threshold. Threshold logic produces output signals indicative of which comparator first produced an output pulse.

Abstract: A lead assembly includes a proximal end that has a connector for electrical connection to a cardiac stimulator, such as a pacemaker, a cardioverter/defibrillator, or a sensing instrument. The lead assembly includes an elongated proximal tubular portion that extends distally from the connector. The distal end of the proximal tubular portion is provided with a branch assembly that is joined distally to two elongated distal lead branches. The distal branches are provided, respectively, with lead tips that each function as electrodes for transferring electrical signals from and/or to the myocardium. The branch assembly includes structure for enabling a surgeon to selectively manipulate the distal branches using a single stylet passed through a single lumen in the proximal tubular portion.