Abstract: A cardiac event and arrhythmia detection system and method detects arrhythmic cardiac activity or other information from an electrogram signal of a heart. The system senses the electrogram signal through an electrogram lead, preliminarily processes the signal, and converts it to a plurality of discrete digital signals, each of which represents the magnitude of the electrogram signal at a prescribed sample time. The discrete digital signals are applied to both a cardiac event detector and a morphology detector. The morphology detector detects selected changes in the morphology (shape) of the electrogram signal, wherein such changes automatically control the sensitivity (gain and/or threshold) used to detect cardiac events. The occurrence of a prescribed amount of change in the detected morphology over time indicates the occurrence of a prescribed arrhythmic cardiac condition.

Abstract: An implantable pacemaker operates in a DDD mode and reverts to a modified DDI mode in response to sensing atrial depolarization early in the pacing cycle. The modified DDI mode, when invoked, provides additional atrial kick by generating an atrial stimulation pulse (A-pulse) when there is sufficient time left in the current pacing cycle for the atrial kick resulting from such A-pulse to be of hemodynamic and electrophysiologic benefit. A time window, T.sub.A, is defined that follows the post-ventricular atrial refractory period (PVARP) of the normal DDD pacing cycle. If a P-wave is sensed during T.sub.A, then the modified DDI mode is invoked. In such modified DDI mode, the time between the last ventricular event and the next scheduled V-pulse, absent the detection of an inhibiting R-wave, is preserved. Further, in such modified DDI mode, if there is sufficient time to supply an A-pulse before the next V-pulse is scheduled, such A-pulse will be generated to provide the additional atrial kick.

Abstract: A multi-conductor lead having a lead body including at least two conductors and at least one electrode at a distal end for delivering an electrical stimulus, the multi-conductor lead also including a connector assembly at a proximal end, the connector assembly including a pair of electrical contacts each connected to one of the two conductors of the multi-conductor lead and a rigid insulator interlocking and electrically separating the pair of electrical contacts.

Abstract: A pyroelectric suppressor circuit for preventing undesirable thermally induced signals generated by a piezoelectric physical activity sensor from reaching processor circuitry within an implantable medical device is provided. The thermally induced signals typically have frequencies below a frequency in the range from about 0.1 mHz to about 10 mHz. The suppressor circuit provides a high-pass filter that rejects signals that have frequencies associated with thermally induced signals. Signals having frequencies greater than a frequency in the range from about 0.1 mHz to about 10 mHz, which correspond to patient activity, are passed on to processing circuitry of the implantable medical device.

Abstract: A programming system is provided that allows a physician or medical personnel to optimize the settings of various arrhythmia detection criteria and/or parameters related to hemodynamic performance to be programmed into the implanted cardiac stimulating device. The cardiac stimulating device may be a pacemaker or cardioverter/defibrillator that detects heart arrhythmias by using various arrhythmia detection criteria. The cardiac stimulating device is capable of recording the patient's cardiac signals and/or sensor data. The programming system may play back the recorded signals to test the detection criteria and hemodynamic performance and may simulate the response of the device to the cardiac signal. Alternatively, the programming system may play back an artificially created or previously stored cardiac signal for test purposes. As a result, the recorded signal may be played back repeatedly without unnecessarily stressing the patient's heart.

Abstract: A self-sealing septum for isolating the setscrew used to secure a pacing lead connector pin to an implantable medical device such as a cardiac pacemaker. The septum comprises a generally cylindrical elastomer body having a central axis and a self-sealing passage coaxial with the axis for receiving a tool such as a hex key for driving the setscrew. The body of the septum contains a generally ring-shaped stiffener element for providing internal support and preventing damage to the septum passage caused by insertion of the hex key.

Abstract: A system and method for measuring and storing parametric data pertaining to the operating characteristics of an implantable medical device are provided. The parametric data may include the impedance of a lead that is attached to a patient's heart, and the internal impedance of a battery used to power the implantable medical device. The parametric data may be measured and stored at predetermined time intervals, as indicated by a clock provided within the implantable medical device. In addition, the parametric data measurements may be synchronized with the occurrence of a cardiac event, such as the application of a stimulation pulse to the patient's heart. A plurality of measurements for each type of parametric data may be stored, so that when the parametric data are later retrieved and displayed on an external programmer/analyzer, trends in the data can be readily observed.

Abstract: A pacemaker mediated tachycardia (PMT) is detected and suppressed in an implantable pacemaker operating in the VDD or VDDR modality. Such suppression is effectuated by extending the post ventricular atrial refractory period (PVARP) of the pacemaker to an extended PVARP that prevents retrograde P-waves from being tracked, thereby suppressing the PMT. The extended PVARP includes a retrograde window portion, following an absolute refractory portion. P-waves that occur during the retrograde window portion of the extended PVARP are deemed to be retrograde P-waves. The extended PVARP is returned to its original value whenever: (1) a P-wave is sensed following the extended PVARP, which P-wave is deemed to be a sinus P-wave, or (2) whenever a sufficient number of cardiac cycles elapse without the occurrence of a retrograde P-wave.

Abstract: A heart stimulator emits stimulation pulses to a heart, and has a regulator unit for regulating a variable function in the heart stimulator, a measurement device for measuring the return flow of blood to the heart, and a control device for controlling the regulation of the function by the regulator unit on the basis of changes in the return flow of blood. The regulator unit may be a pulse generator which generates and emits the stimulation pulses at a variable interval, the heart stimulator then becoming rate-adaptive and optimizing cardiac output. In this manner, heart rate is regulated on the basis of a variable directly related to the body's oxygenation needs.

Abstract: An arrangement, in particular a heart pacemaker, has a measuring device for recording a heart activity measurement parameter. In order to record the measurement parameter in such a way that it is rid of disturbing signals, and can thus be used to evaluate the physiological functions of the heart pacemaker, the arrangement contains switching means which evaluate the signal curve of a measurement parameter during a heart cycle (n+1) as a function of the frequency (f) or duration (t.sub.S) of the previous heart cycle (n).

Abstract: An implantable medical device including a piezoelectric accelerometer activity sensor. The activity sensor includes a thin film piezoelectric cell within a frame structure. A mass imposes a load based upon acceleration to apply lateral or transverse forces which cause the generation of an electrical potential within the piezoelectric cell, which can be used by a rate control algorithm within the device to control operation of the device.

Abstract: Implantable leads incorporating accelerometer-based cardiac wall motion sensors, and a method of fabricating such leads, are provided. The cardiac wall motion sensors transduce accelerations of cardiac tissue to provide electrical signals indicative of cardiac wall motion to an implantable cardiac stimulating device. The implantable cardiac stimulating device may use the electrical signals indicative of cardiac wall motion to detect and discriminate among potentially malignant cardiac arrhythmias. In response to a detected abnormal cardiac rhythm, the cardiac stimulating device may deliver therapeutic electrical stimulation to selected regions of cardiac tissue.

Abstract: A fluid flow rate measuring apparatus having a thermistor exposed to a flow of fluid and a driver circuit operable in an initial constant-voltage mode, in which it applies a substantially constant voltage across the thermistor, and a subsequent constant-current mode, in which it applies a substantially constant current through the thermistor, such current corresponding to the current level at the end of the constant-voltage mode. A voltage sensor measures the resultant voltage drop across the thermistor, which is a direct measurement of the fluid flow rate and which is substantially insensitive to variations in ambient temperature.

Abstract: The present invention includes a body implantable lead having a multipolar proximal connector, at least a first conductor coupled to at least one stimulating electrode, a sensor for sensing at least one physiologic parameter of the body, and a second and a third conductor coupled to the sensor. The sensor is hermetically sealed in a D-shaped housing. Sensor components are mounted onto a microelectronic substrate which is advantageously placed on an inner flat portion of the D-shaped housing. End caps having sealing rings, either glass frit or metal, are used to seal the ends of the shell. A hermetic seal is easily achieved by heating the sealing material until they re-flow between the end caps and the shell. Advantageously, the sensor terminals are sized to fit snugly within a narrow bore of the end cap which is then circumferentially welded closed. The D-shaped sensor is placed on a carrier having at least two lumens.

Abstract: A power converter apparatus adapted for use in a defibrillating cardiac pacemaker, to selectively provide a prescribed high voltage useful in treating a cardiac fibrillation. A pulse generator-cyclically applies a relatively low battery voltage V.sub.s to a step-up transformer, to controllably charge a high-voltage capacitor. The time durations of the cyclic applications of the battery voltage V.sub.s are controlled by digital feedback of several parameters, including peak transformer current, average transformer current., battery voltage V.sub.s, and the voltage on the high-voltage capacitor. If any of the measured parameters is determined to be outside a predetermined limit, the pulsing of the transformer is incrementally modified. A smooth, efficient charging of the high-voltage capacitor thereby is provided.

Abstract: An implantable pacemaker continuously records pacing events and their respective rates of occurrence in sequence, as they occur, into an Event Record stored in a circular buffer. The circular buffer always contains the most recent events and rates collected. The recording of the pacing events selectively occurs at every event, or at sampling rates of one event per fixed sample interval. A programming device, coupled to the implantable pacemaker through a telemetry link, selectively retrieves the recorded pacing events and rates from the Event Record and reports subsets thereof in condensed or summarized form using numerical and/or graphical formats. The pacing event data collected in the Event Record is three-dimensional in that each pacing event includes a pacemaker event, an associated pacemaker or heart rate, and a real time interval. The programming device also calculates and reports statistical information from the data collected in the Event Record.

Abstract: An implantable pacemaker continuously records pacing events and their respective rates of occurrence in sequence, as they occur, into an Event Record stored in a circular buffer. The circular buffer always contains the most recent events and rates collected. The recording of the pacing events selectively occurs at every event, or at sampling rates of one event per fixed sample interval. A programming device, coupled to the implantable pacemaker through a telemetry link, selectively retrieves the recorded pacing events and rates from the Event Record and reports subsets thereof in condensed or summarized form using numerical and/or graphical formats. The pacing event data collected in the Event Record is three-dimensional in that each pacing event includes a pacemaker event, an associated pacemaker or heart rate, and a real time interval. The programming device also calculates and reports statistical information from the data collected in the Event Record.

Abstract: An active discharge circuit for use within an implantable medical device, such as a pacemaker, rapidly discharges a coupling capacitor connected between a therapy circuit and body tissue. The active discharge circuit has a switching device, a charge transfer capacitor, and a clock. The clock is coupled to a control input of the switching device and provides a clock signal thereto. In response to the clock signal, the switching device sequentially and repeatedly couples the charge transfer capacitor to a discharge voltage supply so that charge transfers therebetween, and then couples the charge transfer capacitor to the coupling capacitor so that charge transfers therebetween. As the switch oscillates in response to the clock signal, the coupling capacitor is actively discharged.

Abstract: A processing system and method are provided for deriving an improved hemodynamic indicator from cardiac wall acceleration signals. The cardiac wall acceleration signals are provided by a cardiac wall motion sensor that responds to cardiac mechanical activity. The cardiac wall acceleration signals are integrated over time to derive cardiac wall velocity signals, which are further integrated over time to derive cardiac wall displacement signals. The cardiac wall displacement signals correlate to known hemodynamic indicators, and are shown to be strongly suggestive of hemodynamic performance. An implantable cardiac stimulating device which uses cardiac wall displacement signals to detect and discriminate cardiac arrhythmias is also provided.

Abstract: During the telemetering of telemetry signals between an implantable medical device and an external programmer, the transmitter power of the implantable device is dynamically adjusted. The programmer measures the strength of the telemetry signals transmitted by the implantable device. A power control signal is generated as a function of the measured signal strength, and the transmitter power of the implantable device is set to a power level specified by the power control signal. For example, if the measured signal strength falls below a predetermined minimum signal strength threshold, power must be increased. This process is repeated until the measured signal strength satisfies a predetermined signal strength condition.