Abstract: The prophylactic pacer/defibrillator is configured to deliver shocking therapy in response to a single episode of ventricular fibrillation, as well as delivering otherwise conventional pacing therapy. By providing “one shot” defibrillation capabilities a patient who is not at significant risk of ventricular fibrillation—and hence is not a candidate for a full-service implantable cardioverter defibrillator (ICD)—can receive defibrillation therapy in the event ventricular fibrillation should nevertheless occur. Once the prophylactic pacer/defibrillator has delivered shocks to terminate the single episode of ventricular fibrillation, the patient returns to his or her physician to have the device removed and a full-service ICD implanted, so that any additional episodes of ventricular fibrillation may be addressed by the full-service ICD.

Abstract: The prophylactic pacer/defibrillator is configured to deliver shocking therapy in response to a single episode of ventricular fibrillation, as well as delivering otherwise conventional pacing therapy. By providing “one shot” defibrillation capabilities a patient who is not at significant risk of ventricular fibrillation—and hence is not a candidate for a full-service implantable cardioverter defibrillator (ICD)—can receive defibrillation therapy in the event ventricular fibrillation should nevertheless occur. Once the prophylactic pacer/defibrillator has delivered shocks to terminate the single episode of ventricular fibrillation, the patient returns to his or her physician to have the device removed and a full-service ICD implanted, so that any additional episodes of ventricular fibrillation may be addressed by the full-service ICD.

Abstract: Methods and systems for increasing capacitor reformation efficiency in an implantable cardiac device (ICD) are presented. In one embodiment, a method and system provide for: (1) fully charging a first capacitor, (2) transferring energy from the first capacitor to an inductor, (3) transferring energy from the inductor to the second capacitor, and (4) completing charging of the second capacitor. In another embodiment, a method and system provide for: (1) fully charging a first capacitor, (2) sharing energy from the first capacitor with a second capacitor, and (3) completing charging of the second capacitor. In yet another embodiment, a method and system provide for: (1) fully charging a first capacitor, (2) sharing energy from the first capacitor with a second capacitor, (3) transferring remaining energy from the first capacitor to an inductor, (4) transferring energy from the inductor to the second capacitor, and (5) completing charging of the second capacitor.

Abstract: An implantable cardiac defibrillation assembly includes at least one implantable lead having a defibrillation electrode adapted for placement in a chamber of the heart. The lead includes a connector. The assembly further includes an implantable defibrillation device having a pulse generator that provides defibrillation pulses and that is configured to receive the connector to couple the defibrillation electrode to the pulse generator. The device further includes a system that evaluates and conditions the assembly to provide defibrillation therapy to the heart without requiring arrhythmia induction of the heart. The system may condition the device for defibrillation therapy by reforming the defibrillation output capacitor and evaluate defibrillation lead DC resistance, and R wave sensing and detection. In addition, the system may estimate defibrillation thresholds and electrical fields and condition the device by setting the device to provide an output voltage above the estimated threshold.

Abstract: A leakage detection system for use in an implantable cardiac stimulation device, such as an implantable cardioverter defibrillator. The leakage detection system employs one or more switches capable of disconnecting leaky electronic components from the power cell of the stimulation device, and of measuring electric currents to various components of this device. The leakage detection system includes a plurality of switches that are connected between selected components of the ICD, such as high-voltage capacitors, and the power cell. The switches can be selectively activated to disconnect the leaky or faulty components from the power cell, thereby preventing leakages from these components.

Abstract: Techniques are provided for generating pre-pulse pain inhibition (PPI) pulses and subsequent main cardioversion shocks. The PPI pulses are relatively low-voltage pulses each having a chevron-shaped waveform. The main shocks are relatively high-voltage shocks each having a plateau-shaped waveform. By employing plateau-shaped waveforms for the main shocks, a greater cardiac membrane response can be achieved at an equivalent peak voltage as compared to conventional shock waveforms. Peak voltage is a significant contributor to pain caused by cardioversion shocks. Hence, by using the plateau-shaped waveform, pain reduction can be achieved without loss of shock effectiveness. Moreover, by employing chevron-shaped PPI pulses in combination with plateau-shaped main shocks, a relatively simple shocking circuit having a single high-voltage shocking capacitor may be used, thus eliminating the need for both low-voltage PPI capacitors and higher voltage main shock capacitors.

Abstract: A cardiac stimulation device and method discriminates sinus events from non-sinus events and provide a uniquely prescribed response upon detection of a specific event.

Abstract: A leakage detection system for use in an implantable cardiac stimulation device, such as a cardioverter defibrillator. The leakage detection system includes a switch bank and a controller that regulates the switching arrangements of various switches. The leakage detection system causes pulse generators to generate a pulse-train waveform comprised of a sequence of pulses of opposite polarities, and to deliver these pulses in a preselected temporal relation. The controller detects the current leakage from the pulse generator to the tissues by sensing and analyzing the voltage or current of the pulse generator, leads, and electrodes. The pulsatility and alternating polarities of biphasic pulse-train waveforms increase the stimulation threshold of the motor or sensory nerves and excitable tissues.

Abstract: A high voltage converter circuit for an implantable cardiac device. The circuit includes a plurality of transistors that are connected in parallel to a battery and the primary winding of a transformer. A switching element is connected to the circuit so as to periodically connect and disconnect the capacitors to the primary winding of the transformer to thereby induce the capacitors to be charged and periodically discharged across the transformer into charging capacitors. A circuit also preferably includes a disconnect circuit that will disconnect the capacitors from the battery during periods of non-use to inhibit unwanted dissipation of the battery's energy.

Abstract: Increased myocardial voltage is achieved by configuring a shocking circuit of an ICD to generate a defibrillation pulse waveform having a positive phase with three distinct voltage peaks. The shocking circuit employs three capacitors along with switching circuitry for selectively discharging the capacitors so as to generate the defibrillation pulse waveform. More specifically, the switching circuitry generates a first step of the pulse waveform by discharging the capacitors while connected in parallel, then generates a second step of the pulse waveform by discharging the capacitors while the two of the three capacitors are connected in parallel and the third is connected in series, and finally generates a third step of the pulse waveform by discharging the capacitors while connected in series.

Abstract: A method of operating an implantable medical device containing a Lithium Silver Vanadium Oxide battery. In response to a detected need for therapy, a current flow is delivered from the battery to a charge storage device. After the battery is at least partly depleted by one or more such deliveries of current or other power consumption, the battery is recharged. The recharging may be initiated in response to a selected time threshold, a selected number of current flow delivery events, a selected voltage level, an excess charge time duration, or other operating characteristics. A limited number of recharging cycles may be provided if the charging is done under controlled conditions with respect to charge current and voltage.

Abstract: An implantable cardiac rhythm management device has a housing containing rhythm management circuitry. The circuitry includes a battery, a transformer, and a capacitor connected via charging circuitry that operates to transmit current from the battery to charge the capacitor. A number of leads connected to the circuitry operate to transmit a shock from the capacitor to cardiac tissue outside of the housing. The capacitor has a smaller volume than the combined volume of the battery and transformer, such that it reaches a selected charge voltage within a limited time interval. The device may operate to limit capacitor charging to less than a selected energy storage capability at a given voltage, and components may be selected to limit charging time to less than 2 seconds. The component selection and charge duration may be based on a time-based function of defibrillation threshold (DFT).

Abstract: An output circuit for use in an implantable cardiac defibrillation provides an output pulse having a waveform of virtually any desired shape. The device includes a sensing circuit that senses cardiac activity. An arrhythmia detector detects fibrillation responsive to the cardiac activity signal. The device further includes an output circuit that provides a stimulation output pulse when the arrhythmia detector detects a cardiac arrhythmia. The output circuit includes an H-bridge having a pair of switching devices which control the output pulse waveform with pulse-width modulation and a second pair of switching devices that control the output pulse polarity.

Abstract: An implantable cardiac stimulation device and method provides reliable sensing of cardiac events to support cardiac pacing or fibrillation detection. The device comprises a sensing circuit that senses the cardiac events in accordance with a plurality of threshold characterizing parameters. A parameter control adjusts the threshold parameters responsive to the rate of the sensed cardiac events in a manner which precludes positive feedback to prevent continued oversensing, undersensing, or noise sensing.

Abstract: In an implantable cardioverter-defibrillator and/or pacemaker, each having DDD pacing capabilities, an improved method of operation is described which dramatically increases the longevity of the implanted device by conserving battery power. The method comprises deactivating at least one unnecessary, power-consuming feature of the device until such feature is needed and then reactivating said feature only for so long as it is required by the patient. In a particular embodiment, the atrial sense amplifier is deactivated during normal operation of the implantable device, resulting in single-chamber sensing and pacing. Upon the occurrence of a predefined event, indicative of a need for dual-chamber sensing and pacing, the atrial sense amplifier is reactivated, the need for DDD pacing confirmed, and if appropriate, DDD pacing is begun. Once the patient's heart rate has returned to an acceptable level, the atrial sense amplifier is again deactivated and single-chamber sensing/pacing continued.

Abstract: An improved pacing system and related method for use in an implantable pacemaker or defibrillator are disclosed which operate using a predetermined subset of combinations of possible combinations for pacing stimulus pulse amplitude and pulse width, which subset of combinations are the most energy-efficient pairs, thereby ensuring reduced battery current drain. This is accomplished by ensuring that each combination has the lowest battery charge drain of any combination having at least the rheobase value of that particular combination as a function of cardiac chronaxie. The preferred embodiment of the pacing system of the present invention includes capture verification to enable a substantially reduced safety margin to further minimize the level of battery charge drain. The preferred embodiment of the pacing system of the present invention also includes the capability to produce a safety backup pulse, to ensure that the pacing system never misses a beat.

Abstract: Increased myocardial voltage is achieved by configuring a shocking circuit of an ICD to generate a defibrillation pulse waveform having a positive phase with three distinct voltage peaks. The shocking circuit employs three capacitors along with switching circuitry for selectively discharging the capacitors so as to generate the defibrillation pulse waveform. More specifically, the switching circuitry generates a first step of the pulse waveform by discharging the capacitors while connected in parallel, then generates a second step of the pulse waveform by discharging the capacitors while the two of the three capacitors are connected in parallel and the third is connected in series, and finally generates a third step of the pulse waveform by discharging the capacitors while connected in series.

Abstract: A display displays electrical activity of a heart. A receiver receives an electrical signal representing the electrical activity of a heart. The electrical signal includes event markers identifying occurrences of at least one type of cardiac event represented in the electrical signal. A display control circuit coupled to the display and to the receiver locates the display of the at least one type of cardiac event at a predetermined position on the display in response to the detection of one of the event markers. In at least one embodiment, the display overwrites the electrical signal. In another embodiment, a plurality of electrical signals may be stored and displayed simultaneously. In another embodiment, the stored plurality of electrical signals can be replayed to observe trends and patterns as the morphology changes.

Abstract: By redistributing the running totals for various preliminary classifications to other preliminary classifications based upon the values of the most recent cardiac events, the present invention biases the running totals (thereby biasing the duration criteria) to help overcome common discrimination problems which permits the stimulation device to make a correct and final therapy decision more quickly. To identify a patient's heart rhythm, various electrical events such as P-waves and R-waves, and their timing, relationship, and stability, are detected and a preliminary classification is made for each detected event. Running totals of the numbers of all events detected within each of the preliminary classifications are maintained, along with sliding totals covering only the most recently detected events. Then, the arrhythmia is identified based upon an analysis of both the running totals and the sliding totals.

Abstract: The implant guiding programmer is configured to automatically determine a defibrillation threshold (DFT) for a particular patient and to further determine an optimal implantation configuration for an implantable cardioverter fibrillator (ICD). In one implementation, to determine the DFT for the patient, the programmer correlates patient specific data with a predictive data base containing DFT information for an entire population of patients. The programmer additionally determines an optimal implantation configuration for the patient, wherein the optimal configuration is one which is capable of exceeding the DFT for the patient using minimal electrical pulse energy.