Abstract: An implantable defibrillation circuit can include an output circuit. The output circuit can include a first switch configured to controllably connect a first supply node to a first output node, a second switch configured to controllably connect a second supply node to the first output node through a first rectifier, and the second switch can be configured to inhibit the first switch from connecting the first supply node to the first output node when the second supply node is connected to the first output node through the second switch. In an example, the first and second switches can include insulated gate bipolar transistors.

Abstract: An implantable medical device and associated method sense cardiac signals for deriving a template representing a known EGM waveform morphology and for classifying an unknown waveform morphology. A boundary of the template, offset from the template, is computed and compared to an unknown waveform morphology for classifying the unknown waveform morphology.

Abstract: A system, method and implantable medical for concurrently providing a therapeutic output to a patient while communicating transcutaneously with an external device. The therapeutic output is provided to the patient with an implantable medical device wherein an electromagnetic signal is associated with at least one of recharging of a rechargeable power source and providing the therapeutic output. Bi-directional transcutaneous communication is conducted via via telemetry between the implantable medical device and an external device using a telemetry signal while the telemetry signal and the electromagnetic signal occur simultaneously.

Abstract: An active implantable medical device with atrial pacing for the treatment of diastolic heart failure. This device comprises circuits and leads for collecting right and left atrial events (16,18) and pacing the left atrium (18) and a sensor detecting myocardium contractions, preferably an endocardial acceleration sensor (20), delivering a signal representative of the myocardium contractions. Analysis of the signal allows a determination of the presence or absence of a detectable left atrial contraction distinguishable from the ventricular contraction. An interatrial delay is applied between the collection of a right atrial depolarization and the delivery of a left atrial pacing pulse. In the absence of left atrial contraction, the interatrial delay is iteratively reduced in successive cardiac cycles from an initial value to an adjustment value ensuring that a left atrial contraction appears, and then so maintained while the presence of a left atrial contraction continues.

Abstract: A feedthrough flat-through capacitor includes a capacitor having a first and second set of electrode plates, a first feedthrough passageway through the capacitor, a first lead disposed within the first feedthrough passageway and conductively coupled to the first set of electrode plates, a second feedthrough passageway through the capacitor disposed remote from the first feedthrough passageway, and a second lead disposed within the second feedthrough passageway and conductively coupled to the first set of electrode plates. The second set of electrode plates are typically conductively coupled to a ground. An EMI shield may be provided to electromagnetically isolate the first lead from the second lead.

Abstract: An output stage for use in a therapeutic defibrillator enables practical use of specialized output waveforms optimized for cardiac defibrillation. A pulse-width modulated (PWM) switching amplifier, connected to a high voltage source capacitor and to one or more output bridges corresponding to different electrode placements, is adapted to operate with high efficiency, demonstrated at about 80%. The amplifier is capable of delivering a defibrillating electric shock to a heart in the form of a time-varying output voltage waveform of arbitrary shape. Efficiency improvement is accomplished through the use of a high voltage reservoir capacitor network configured to minimize a voltage differential between the high voltage reservoir and the output voltage. The switching amplifier features both step-up and step-down amplifier capability. A PWM control unit is positioned within the circuit so as to reduce complexity by eliminating a need for additional isolation circuitry.

Abstract: Devices configured for and methods for inducing fibrillation in a patient using a controlled current AC signal applied via electrodes of an implanted ICD. In some embodiments, the AC signal is applied as a series of alternating constant current pulses. Some embodiments make use of a specialized H-bridge circuit for applying the AC signal. A low-side current controlling portion of an ICD's circuitry may make up part of the specialized H-bridge circuit. Further embodiments include devices embodying these methods.

Abstract: A system for the endocardial stimulation/defibrillation of the left ventricle. This system includes a generator (60) and an endocardial lead. The lead includes a lead body (26) whose distal end (30) extends into the right ventricle (14) and is provided with a mechanism to anchor (32) the distal end to the interventricular septum (20). The lead body carries on it a stimulating and/or defibrillation electrode (38) (64, 66). A microcable (42) extends into the lead body and beyond, with an intermediate portion (56) crossing from one side of the interventricular septum (20) to the other, and an active free portion (58) that emerges in the left ventricle (16). The microcable is coupled to the generator, to produce an electric field (62) between, on one hand, the stimulation electrode (38) or defibrillation electrode (64, 66) of the lead body and, on the other hand, a bare region of the active free portion (58) of microcable (42).

Abstract: According to some method embodiments, a left pulmonary artery electrode is positioned in a left pulmonary artery, and the left pulmonary artery electrode is used to sense atrial activity, or capture cardiac tissue, or deliver neural stimulation. According to some method embodiments, a right pulmonary artery electrode is positioned in a right pulmonary artery and a left pulmonary artery electrode is positioned in a left pulmonary artery, the right pulmonary artery electrode is used to sense atrial activity, or capture cardiac tissue, or deliver neural stimulation, and the left pulmonary artery electrode is used to sense atrial activity, or capture cardiac tissue, or deliver neural stimulation.

Abstract: The present invention relates to evaluating the effect of physiological conditions on the occurrence of ventricular fibrillation, identifying strategies for treatment or prevention of ventricular fibrillation or ventricular tachycardia, and evaluating a subject for induction of ventricular fibrillation from a condition of ventricular tachycardia.

Abstract: Embodiments of the present concept are directed to external defibrillators that include an electrode connection port having multiple connection options, and include a detection device to determine an electrode connection configuration so as to provide an appropriate electrical shock to a patient. The detection device detects the electrode connection configuration of a plug connector for connected electrodes to determine if the plug connector is in an adult orientation or a pediatric orientation. The external defibrillator is configured to a deliver an electrical shock with less energy when the pediatric orientation is detected rather than the adult orientation.

Abstract: A power supply for an implantable cardioverter-defibrillator for subcutaneous positioning between the third rib and the twelfth rib and using a lead system that does not directly contact a patient's heart or reside in the intrathoracic blood vessels and for providing anti-tachycardia pacing energy to the heart, comprising a capacitor subsystem for storing the anti-tachycardia pacing energy for delivery to the patient's heart; and a battery subsystem electrically coupled to the capacitor subsystem for providing the anti-tachycardia pacing energy to the capacitor subsystem.

Abstract: A magnetic switching device includes an electromagnet adapted to be arranged proximate to an exterior surface of an object having a magnetically-switchable device therein and a control circuit electrically connected to the electromagnet. The electromagnet is constructed to generate a magnetic field of sufficient strength and orientation to engage a switch in the magnetically-switchable device. The invention further includes an electrocautery system, including an electrocautery device, a control circuit electrically connected to the electrocautery device, and an electromagnet electrically connected to the control circuit. The electromagnet is adapted to be arranged proximate to an exterior surface of an object having a magnetically-switchable device therein. Operation of the electrocautery device causes the electromagnet to generate a magnetic field of sufficient strength to engage a switch in the magnetically-switchable device.

Abstract: A high voltage switching and control circuit is provided for an implantable medical device (IMD). The circuit includes a high voltage positive (HVP) node, configured to receive a positive high voltage signal from a high energy storage source, and a high voltage negative (HVN) node, configured to receive a negative high voltage signal from a high energy storage source. Additionally, the circuit includes first, second and third output terminals that are configured to be connected to electrodes for delivering high voltage energy. First and second SCR switches are connected to the first and second output terminals, respectively. The first and second SCR switches are connected in series with one another and are connected to one of the HVP and HVN nodes. The first and second SCR switches have gating terminals. A control circuit is connected to the gating terminals and delivers first and second gating signals to turn ON the first and second SCR switches, respectively.

Abstract: Various aspects of the present subject matter relate to a method. According to various method embodiments, cardiac activity is detected, and neural stimulation is synchronized with a reference event in the detected cardiac activity. Neural stimulation is titrated based on a detected response to the neural stimulation. Other aspects and embodiments are provided herein.

Abstract: A medical device and associated method for discriminating cardiac events includes determining whether a cardiac evidence counter is greater than a predetermined detection threshold, advancing from a concerned state to a convinced state in response to the evidence counter being greater than the predetermined detection threshold, determining whether a reduction in the cardiac evidence counter occurs while in the convinced state, determining whether one of a first rate corresponding to the first sensing vector and a second rate corresponding to the second sensing vector is less than a predetermined rate limit, and determining whether to advance from the convinced state to one of a therapy delivery state, the concerned state and the unconcerned state in response to determining whether one of the first rate and the second rate is less than a predetermined rate limit.

Abstract: A defibrillator includes a defibrillator mainframe and a defibrillating electrode. The defibrillator mainframe includes a main control unit and a master device electrically connected to the main control unit. The defibrillating electrode comprises a slave device supporting a bus protocol, the master device and slave device being interconnected through a bus.

Abstract: A system level scheme for networking of implantable devices, electronic patch devices/sensors coupled to the body, and wearable sensors/devices with cellular telephone/mobile devices, peripheral devices and remote servers is described.

Abstract: A method and system for treating an individual experiencing cardiac arrest using an automatic external defibrillator (AED) includes placing a first and a second electrode of the AED in electrical communication with an exterior surface of the individual. A need to apply a high voltage defibrillation signal to the individual is automatically determined. The method also includes automatically causing the AED to apply a medium voltage therapy (MVT) signal through the first and the second electrodes to the individual. The MVT signal is applied to induce a hemodynamic effect in the individual. Alternatively, or additionally, the MVT signal is applied to induce a respiratory effect in the individual. Optionally, the MVT signal is applied before determining the need to apply the defibrillation signal.

Abstract: The connector between the patient electrode pads and the base unit of an automatic external defibrillator (AED) system can be formed by capturing a printed circuit board (PCB) within a connector housing. The PCB can have conductive metal traces that serve as the contact points between the wires from the patient electrodes and the electronics within the AED base unit. The PCB in combination with the conductive metal traces can be shaped similar to a conventional two-prong or two-blade connector. Employing such a PCB-based connector may result in AED pads which are less complex and less costly to manufacture. The PCB can also support a configuration circuit that is positioned between the conductive metal traces and that allows the AED to read and store information about the attached pads. For example, the AED can use this data storage feature to check the expiration date of the pads.

Abstract: Devices, systems, and methods for leadlessly stimulating the heart. Through a magnetic signal generator positioned outside or inside the thoracic cavity, a magnetic signal is transmitted through the chest to stimulate electrical activity within the myocardial muscles. The magnetic signal may function as a pacemaker, cardioverter or defibrillator. Advantages of magnetic stimulation include, without limitation, non invasiveness, a reduction or even elimination in pain, and access to tissues covered by poorly conductive structures.

Abstract: Techniques are provided for use by implantable medical devices for controlling ventricular pacing, particularly during atrial fibrillation. In one example, during a V sense test for use in optimizing ventricular pacing, the implantable device determines relative degrees of variation within antecedent and succedent intervals detected between ventricular events sensed on left ventricular (LV) and right ventricular (RV) sensing channels. Preferred or optimal ventricular pacing delays are then determined, in part, based on a comparison of the relative degrees of variation obtained during the V sense test. In another example, during RV and LV pace tests, the device distinguishes QRS complexes arising due to interventricular conduction from QRS complexes arising due to atrioventricular conduction from the atria, so as to permit the determination of correct paced interventricular conduction delays for the patient. The paced interventricular conduction delays are also used to optimize ventricular pacing.

Abstract: Disclosed herein is an implantable pulse generator. The implantable pulse generator may include a header, a can and a feedthru. The header may include a lead connector block electrically coupled to a first conductor. The can may be coupled to the header and include a wall and an electronic component electrically coupled to a second conductor and housed within the wall. The feedthru may be mounted in the wall and include a header side with a first electrically conductive tab and a can side with a second electrically conductive tab electrically coupled to the first tab. The first tab is electrically coupled to the first conductor and the second tab is electrically coupled to the second conductor.

Abstract: An active implantable medical device for cardiac resynchronization therapy with effort based rate-responsive pacing is described. The device calculates a rate-responsive stimulation frequency based on output signal of an effort sensor between a base frequency (fbase) and a maximum frequency (fmax). The device determines a target stimulation frequency based on the difference between a first frequency and the maximum frequency (fmax). The first frequency is the higher frequency of the base frequency (fbase) and the spontaneous frequency of the patient. The device calculates a stimulation frequency that has an immediate increase in the pacing rate from the higher of the initial value of the current stimulation frequency, or the spontaneous frequency to the target stimulation frequency, within a predetermined time, or a predetermined number of cardiac cycles. A plurality of consecutive effort zones (Z1-Z4) is defined over the extent of the dynamic range of the output signal of the effort sensor.

Abstract: An apparatus and method for delivering an external shock pulse receive pacing pulses generated by a first device and a shock pulse generated by a second device. An output of the apparatus is coupled to patient electrodes and the apparatus controls delivery of the received pacing pulses to the output and delivery of the received shock pulse to the output. A control module, pacing control and shock control included in the apparatus cooperatively control delivery of the received shock pulse to the output at a predetermined delay after one of the received pacing pulses.

Abstract: Systems and methods related to the field of cardiac resuscitation, and in particular to devices for assisting rescuers in performing cardio-pulmonary resuscitation (CPR) are described herein.

Abstract: This document relates to batteries, e.g., batteries for medical devices such as defibrillators.

Abstract: Embodiments of the present concept are directed to external defibrillators that include a utility light for use by one or more rescuers using the defibrillator. In one implementation, an external defibrillator has a housing, an energy storage module for storing an electrical charge, a defibrillation port for guiding the stored electrical charge to a person, and a processor for determining when to guide the electrical charge. The defibrillator also includes a user interface that includes a screen showing indications by light, and a separate utility light coupled to the housing via a light-coupling structure. The utility light is structured to generate and cast a beam of light with a beam divergence angle of no more than 160 degrees in order to illuminate a certain point of the local environment. This illumination capability may help rescuers reach a person in need of medical attention and apply medical assistance to the person.

Abstract: Detection of T wave oversensing in an ICD is accomplished in order to prevent improper application of treatment to a patient. The ICD device senses for electrical impulses representing the R waves of a beating heart. In some instances the ICD device will sense T waves that it will assume to be R waves, because the ICD device expects or assumes that such sensed signals are R waves. Time intervals between each detected, assumed R waves are measured and a list of intervals is generated. The list is transformed into its frequency domain equivalent and analyzed for peaks and randomness criteria to determine whether T wave oversensing has occurred.

Abstract: Battery powered systems with long standby times, such as automatic external defibrillators (AEDs), may be required to indicate their operational status to a user by blinking lights or sounding speakers or buzzers. These active status indication activities consume power thereby reducing the battery life of the system. To conserve power and to be more effective in seeking attention from a human operator, the status alerts for the AED produced by an active status indicator (ASI) system can be more meaningful to humans or more unique relative to status alerts provided by conventional devices. Additionally, the ASI system may automatically adjust power consumed by the indicators in response to sensing environmental conditions of the AED.

Abstract: A computer-assisted method for quantitative characterization and treatment of ventricular fibrillation includes acquiring a time series of a ventricular fibrillation (VF) signal using a probe from a patient experiencing VF, subtracting the mean from the time series of the VF signal, calculating a cumulative VF signal after the mean is subtracted from the time series of the VF signal, segmenting the cumulative VF signal by a plurality of sampling boxes, calculating the root-mean-square of the cumulative VF signal as a function of the sampling box size , extracting an exponent of the root-mean-square of the cumulative VF signal as a function of the sampling box size, applying electrical defibrillation to the patient if the exponent is below a predetermined value, and applying cardiopulmonary resuscitation (CPR) to the patient if the exponent is above a predetermined value.

Abstract: An implantable electrode, for an implantable tissue stimulator, has an electrically conductive porous material comprising metal carbide, metal nitride, metal carbonitride, metal oxide or metal oxynitride and one or more coating layers on a surface thereof. The coating layer or at least one of the coating layers, is for contact with body tissue when the electrode is implanted. Each coating layer is an electrically conductive layer of polymer having a polypyrrole polymeric backbone or polythiophene polymeric backbone. The coating layer or layers are formed in situ by electropolymerisation. The polypyrrole or polythiophene may be substituted. The coating layer or layers can provide high charge storage capacitance and a fast discharging profile, as well as biocompatibility.

Abstract: The invention relates to a method for checking ECG signals measured by an ECG measuring device having at least three electrodes for the presence of interference errors. At least three voltages are measured on a closed circulation path across the electrodes of the ECG measuring device. A monitoring value is calculated from the three measured voltages. A presence of an error is checked by determining a deviation of the monitoring value from a reference value. An error signal is outputted if an error is presented. The ECG measuring device has a further processing unit for processing voltage signals between a different pair of electrodes and a monitoring unit for calculating the monitoring value.

Abstract: Techniques for determining whether one or more leads are not adequately connected to a patient, e.g., for ECG monitoring, are described. The techniques involve injection of an integrated signal (which includes a test signal) into one lead, and monitoring the driven lead and the response at the other leads, including the common mode and the difference between the other leads. These “lead-off” detection techniques may be provided by an external defibrillator that provides three-wire ECG monitoring. Techniques for determining a type of a cable coupled to a defibrillator are also described. The cable-type identification may allow a defibrillator to, for example, operate in either a three-wire ECG monitoring mode or a therapy mode, based on whether a three-wire ECG cable or a defibrillation cable is coupled to the defibrillator.

Abstract: Disclosed herein are various embodiments of methods, systems and devices for detecting atrial fibrillation (AF) in a patient. According to one embodiment, a patient places his or her left and right hands around left and right electrodes and a hand-held atrial fibrillation detection device acquires an electrocardiogram (ECG) from the patient over a predetermined period of time such as, by way of example, one minute. After acquiring the ECG from the patient, the device processes and analyzes the ECG and makes a determination of whether the patient has AF. The device may further be configured to provide a visual or audio indication of whether the patient has AF, or does not have AF. The device may be employed in a health care provider's office without the need for complicated or expensive diagnostic equipment, and is capable of providing an on-the-spot and low-cost diagnosis of AF.

Abstract: An example includes a capacitor case sealed to retain electrolyte, at least one anode disposed in the capacitor case, the at least one anode comprising a sintered portion disposed on a current collector formed of a framework defining cells extending to three axes, an anode conductor coupled to the current collector formed of a framework defining cells extending to three axes in electrical communication with the sintered portion, the anode conductor sealingly extending through the capacitor case to an anode terminal disposed on the exterior of the capacitor case with the anode terminal in electrical communication with the sintered portion, a cathode disposed in the capacitor case, a separator disposed between the cathode and the anode and a cathode terminal disposed on an exterior of the capacitor case and in electrical communication with the cathode, wherein the anode terminal and the cathode terminal are electrically isolated from one another.

Abstract: A wearable defibrillator and method of monitoring the condition of a patient are disclosed. The wearable defibrillator includes at least one therapy pad, at least one sensor and at least one processing unit operatively connected to the one or more therapy pads and the one or more sensors. The wearable defibrillator also includes at least one audio device operatively connected to the one or more processing units. The one or more audio devices are configured to receive audio input from a patient.

Abstract: An implantable cardioverter defibrillator (ICD) has a programmable ICD energy level corresponding to the maximum defibrillation energy deliverable with each defibrillation shock pulse. The ICD energy level is programmable within the maximum energy capacity of the defibrillation capacitor(s) of the ICD. In various embodiments, after a user enters the ICD energy level, one or more corresponding ICD performance parameters are presented. Restrictions are applied to the energy level programming of the ICD to ensure the predictability of the one or more ICD performance parameters.

Abstract: Described herein are implantable systems and devices, and methods for use therewith, that can be used to perform arrhythmia discrimination. A plurality of different sensing vectors are used to obtain a plurality of different IEGMs, each of which is indicative of cardiac electrical activity at a different ventricular region. The plurality of different IEGMs can include, e.g., an IEGM indicative of cardiac electrical activity at a first region of the patient's left ventricular (LV) chamber and an IEGM indicative of cardiac electrical activity at a second region of the patient's LV chamber. Additionally, the plurality of different IEGMs can further include an IEGM indicative of cardiac electrical activity at a region of a patient's right ventricular (RV) chamber. For each of the IEGMs, there is a determination of a corresponding localized R-R interval stability metric indicative of the R-R interval stability at the corresponding ventricular region. This can include, e.g.

Abstract: An implantable medical device may have a circuit failure mode. The disclosed circuit may have an integrated failure point designed to fail prior to those portions of the circuit. The integrated failure point may include a narrowed portion of a high voltage lead and a grounded lead having a narrow gap separating the grounded lead from the narrowed portion of the high voltage lead. During a high stress fault condition the narrowed portion of the high voltage lead acts as a fuse, forming a vaporized cloud of metal, which shorts current in the high voltage lead across the narrow gap to the grounded lead, thus protecting the remaining portion of the circuit from the high stress condition.

Abstract: An external defibrillator having a battery; a capacitor electrically communicable with the battery; at least two electrodes electrically communicable with the capacitor and with the skin of a patient; a controller configured to charge the capacitor from the battery and to discharge the capacitor through the electrodes; and a support supporting the battery, capacitor, electrodes and controller in a deployment configuration, the defibrillator having a maximum weight per unit area in the deployment configuration of 0.1 lb/in2 and/or a maximum thickness of 1 inch. The support may be a waterproof housing.

Abstract: A cardiac arrhythmia may be induced by delivering a sequence of pulses to a patient via one or more extravascular electrodes. In one example, one or more pacing pulses may be delivered to a patient via an extravascular electrode and a shock pulse may be delivered to the patient the extravascular electrode. In some examples, the pacing pulses and the shock pulse may be generated with energy from a common energy storage module and without interim charging of the module. For example, the pacing and shock pulses may be generated as the energy storage module dissipates. In another example, a cardiac arrhythmia may be induced in a patient by delivering a burst of pulses to a patient via an extravascular electrode. In some cases, the burst of pulses may be generated with energy from a common energy storage module and without interim charging of the energy storage module.

Abstract: A portable cardiac defibrillator for resuscitating individuals suffering cardiac events having an integrated short-range wireless transmitter or transceiver capable of using its access to another communications device for purpose summoning emergency aid (utilizing the cellular telephone system, satellite telephone system and/or marine or other radio frequencies), and/or providing voice communications with individuals who can provide aid, including in some embodiments allowing for the user to manually provide GPS coordinates in situations where cellular locator service is lacking. Additionally, the combined unit may provide a means for utilizing its communication facilities independent of the defibrillator component, and may utilize such facilities to provide diagnostics of the device to prompt for maintenance when necessary, and to alter or upgrade the device's functionality, including such alteration during its use in an emergency.

Abstract: A pulse generating implantable medical device comprises a power source , a control unit, a plurality of switching units, a timing unit, a pulse generating unit adapted to generate one or more stimulation pulses to be applied to human or animal tissue via one or more stimulation electrodes, and a coupling capacitor in series with each stimulation electrode. A stimulation pulse is adapted to be applied during a stimulation pulse timing cycle that includes a stimulation phase and a recharge phase, and that the timing of a stimulation pulse timing cycle is controlled by the control unit via the timing unit and the switching units. The implantable medical device further comprises an energy storage unit and that, during the recharge phase, one or more of the switching units is adapted to establish electrical connection between the one or many stimulation electrodes and the energy storage unit in order to collect and store energy from applied stimulation pulses.

Abstract: A component of an implantable medical device comprises a body comprising at least one external surface, the body comprising at least one of titanium, titanium-based alloys, and composites thereof, and a corrosion-resistant surface region at the at least one external surface, the corrosion-resistant surface region comprising at least one of titanium nitride, dititanium nitride, and a solid solution of nitrogen dissolved in the body, wherein the corrosion-resistant surface region is formed by thermal nitridation of the body.

Abstract: A medical device having a battery pack comprising an indicator, wherein the battery pack indicator indicates the status of the battery pack when the battery pack is disassociated from the medical device and indicates the status of the medical device when associated with the medical device.

Abstract: Implementations of various technologies described herein are directed toward a sensing architecture for use in cardiac rhythm management devices. The sensing architecture may provide a method and means for certifying detected events by the cardiac rhythm management device. Moreover, by exploiting the enhanced capability to accurately identifying only those sensed events that are desirable, and preventing the use of events marked as suspect, the sensing architecture can better discriminate between rhythms appropriate for device therapy and those that are not.

Abstract: A defibrillator electrode assembly with a slot-like storage case is described which protects the pads prior to use and retains them in either an electrically connected or electrically disconnected configuration. When the electrode assembly is slidably inserted into the case, an optional pinch clip within the case presses electrodes on opposite sides of a thick release liner into electrical contact with each other.

Abstract: A CRM system enhances intracardiac electrogram-based arrhythmia detection using a wireless electrocardiogram (ECG), which is a signal sensed with implantable electrodes and approximating a surface ECG. In one embodiment, the wireless ECG is sensed as a substitute signal for the intracardiac electrogram when the sensing of the intracardiac electrogram becomes unreliable.

Abstract: The invention is directed to tri-phasic pulse generation techniques that make use of a pre-stimulus phase, a stimulus phase, and a post-stimulus phase in a pulse generation cycle. During the pre-stimulus phase, an output capacitor is charged to a desired voltage level. During the stimulus phase, the capacitor is discharged, and during the post-stimulus phase recharging of the capacitor begins again. In accordance with the invention, charging of the output capacitor can be terminated during the post-stimulus phase after a measured voltage in the patient is greater than or equal to a threshold.