Abstract: An implantable medical device electrically stimulates the heart to beat and senses electrical activity in the heart. The medical device generally includes a processor, a plurality of electrodes, and a sense amplifier. The medical device is capable of performing a variety of diagnostic tests, such as a sensing test in which a suitable sensitivity setting is computed for the sense amplifier. An external programmer is also provided to initiate the diagnostic tests. The programmer transmits a start signal to the implantable medical device and the medical device's processor initiates the diagnostic test specified by the programmer via the start signal. The implantable device is capable of completing the diagnostic test without further communication from the programmer or may initiate communication with the programmer during a refractory period in which signals from the programmer will not interfere with the diagnostic test. In the latter case, the programmer responds before the refractory period ends.

Abstract: A training unit generally includes a processor, a magnetic field sensor, a plurality of control switches, and a message and data output device. Placing a PEIS magnet, constructed in accordance with the ISOWD 14994 standard, adjacent to or in contact with the training unit activates the magnetic field sensor, a condition detectable by the processor. Activation of the switches determines which of three modes the training unit will operate. In an instructional mode, the process provides instructional messages to the operator via the message and data output device, which preferably includes a display and an audio speaker. In a coached mode, the training unit informs the operator when to place the magnet adjacent to or in contact with the training unit and when to remove the magnet in accordance with the timing intervals of the PEIS entry code. In a practice mode, the operator initiates and completes the entry code using a PEIS magnet without coaching.

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: 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: 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: 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: 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 cardiac stimulation catheter includes a helical electrode segment disposed about a central core of electrically non-conductive material for delivering an electrical pulse to the heart of the patient. The catheter may include a tubular electrode segment disposed on the catheter and electrically connected with the helical electrode. The helical and tubular electrode segments may be defibrillation electrode segments. The catheter may also include a demand pacer electrode for delivering a demand pacing pulse to the heart and/or a fixation mechanism for securing the catheter within the patient's heart.

Abstract: An energy transmission system for transmitting energy non-invasively from an external unit to an implanted medical device to recharge a battery in the medical device. An alternating magnetic field is generated by the external charging unit and a piezoelectric device in the implanted medical device vibrates in response to the magnetic flux to generate a voltage. The voltage is rectified and regulated to provide charging current to a rechargeable battery in the medical device. A series of piezoelectric devices may be connected in series to produce a larger voltage than can be produced by any one piezoelectric device. Acoustic waves generated by the external charging unit alternatively can be used to vibrate the piezoelectric device instead of a changing magnetic flux. The acoustic waves are generated by an external source coupled to a piezoelectric transducer.