Abstract: An implantable stimulation device including a stimulation module and a data communication module. The stimulation device includes electrodes to delivery stimulation pulses, a voltage source, a DC-blocking capacitor and autoshort switch. The voltage source is connected to the electrodes via stimulation-pulse-switch(s) that controls delivery pacing pulses. The DC-blocking capacitor is connected with the voltage source and an electrode. The autoshort switch allows discharging of the DC-blocking capacitor via the electrodes when closed. The data communication module includes a data transmission control module connected to the autoshort switch and/or the at least one stimulation-pulse-switch, to alternatingly open and close the autoshort switch or the at least one stimulation-pulse-switch respectively, during an autoshort period following the delivery of a stimulation pulse or during a stimulation pulse period, respectively, to modulate an autoshort pulse or a stimulation pulse peak amplitude, respectively.

Abstract: An implantable medical device including a data communication device that includes a device that alters an oscillatory electric field imposed on body tissue surrounding the implantable device. The device that alters an oscillatory electric field modulates an impedance of a conductive medium surrounding the implantable device when the implantable device is within an oscillatory electric field. The device that alters an oscillatory electric field includes a device that generates an oscillatory electric field that is phase-synchronized with an oscillatory electric field imposed on a conductive medium surrounding the implantable device.

Abstract: An RF protection circuit mitigates potentially adverse effects that may otherwise result from electromagnetic interference (e.g., due to MRI scanning of a patient having an implanted medical device). The RF protection circuit may comprise a voltage divider that is deployed across a pair of cardiac electrodes that are coupled to internal circuitry of the implantable medical device. Each leg of the voltage divider may be referenced to a ground of the internal circuit, whereby the different legs are deployed in parallel across different circuits of the internal circuitry. In this way, when an EMI-induced (e.g., MRI-induced) signal appears across the cardiac electrodes, the voltages appearing across these circuits and the currents flowing through these circuits may be reduced. The RF protection circuit may be used in an implantable medical device that employs a relatively low capacitance feedthrough to reduce EMI-induced (e.g., MRI-induced) current flow in a cardiac lead.

Abstract: An RF protection circuit mitigates potentially adverse effects that may otherwise result from electromagnetic interference (e.g., due to MRI scanning of a patient having an implanted medical device). The RF protection circuit may comprise a voltage divider that is deployed across a pair of cardiac electrodes that are coupled to internal circuitry of the implantable medical device. Each leg of the voltage divider may be referenced to a ground of the internal circuit, whereby the different legs are deployed in parallel across different circuits of the internal circuitry. In this way, when an EMI-induced (e.g., MRI-induced) signal appears across the cardiac electrodes, the voltages appearing across these circuits and the currents flowing through these circuits may be reduced. The RF protection circuit may be used in an implantable medical device that employs a relatively low capacitance feedthrough to reduce EMI-induced (e.g., MRI-induced) current flow in a cardiac lead.

Abstract: Exemplary methods and apparatuses are disclosed that provide for determination of an atrio-ventricular delay on a beat-to-beat basis by determining a P-wave duration from electric signals corresponding to electric potentials in a heart, and determining the atrio-ventricular delay on a beat-to-beat basis such that the atrio-ventricular delay for an individual heart cycle depends on the P-wave duration of a same or an immediately preceding heart cycle.

Abstract: Techniques are provided for estimating defibrillation impedance of an implantable cardioverter/defibrillator (ICD). Briefly, at least two low-voltage resistance values are measured at different voltages using a pair of stimulation electrodes connected to the ICD. High-voltage defibrillation impedance is then estimated by the ICD based on a weighted combination of the measured resistance values. In one example, a set of weight coefficients, calculated during an initial calibration procedure, are applied to the measured resistance values to produce the estimate of the high-voltage defibrillation impedance. The weight coefficients are updated whenever a defibrillation shock is delivered, based on actual defibrillation impedance values measured during the shock.

Abstract: An implantable medical lead is disclosed herein. In one embodiment, the lead includes a body and an electrical pathway. The body may include a distal portion with an electrode and a proximal portion with a lead connector end. The electrical pathway may extend between the electrode and lead connector end and include a coiled inductor including a first portion and a second portion at least partially magnetically decoupled from the first portion. The first portion may include a first configuration having a first SRF. The second portion may include a second configuration different from the first configuration. The second configuration may have a second SRF different from the first SRF. For example, the first SRF may be near 64 MHz and the second SRF may be near 128 MHz.

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: Exemplary methods and apparatuses are disclosed that provide for determination of an atrio-ventricular delay on a beat-to-beat basis by determining a P-wave duration from electric signals corresponding to electric potentials in a heart, and determining the atrio-ventricular delay on a beat-to-beat basis such that the atrio-ventricular delay for an individual heart cycle depends on the P-wave duration of a same or an immediately preceding heart cycle.

Abstract: Implantable electromedical device or loop recorders or ILRs that solve the problem of very low arrhythmia detection specificities in, i.e., high number of false positives, based on detection and analysis of external noise, specifically muscle noise surrounding the electromedical device. Embodiments generally employ active detection of lead or device movement that induces signal artifacts indicative of external noise. One or more embodiments may detect lead or device movement through use of a piezoelectric transducer, for example located proximally to the device or in the lead of the electromedical.

Abstract: Systems and methods are provided for reducing heating within pacing/sensing leads of a pacemaker or implantable, cardioverter-defibrillator that occurs due to induced loop currents during a magnetic resonance imaging (MRI) procedure, or in the presence of other sources of strong radio frequency (RF) fields. For example, bipolar coaxial leads are described herein wherein the ring conductor of the lead is disconnected from the ring electrode in response to detection of MRI fields so as to convert the ring conductor into an RF shield for shielding the inner tip conductor of the lead so as to reduce the strength of loop currents induced therein and hence reduce tip heating.

Abstract: Disclosed herein is an implantable medical lead. In one embodiment, the lead includes a ring electrode, a tip electrode, first and second helically wound coaxial conductor coils, and a distal coil transition. The coils extend between the proximal and distal ends of the lead. The distal coil transition is proximal to the ring electrode and near the distal end and is where the first coil transitions from being outside the second coil proximal of the distal coil transition to being inside the second coil distal of the distal coil transition.

Abstract: A method for automatic threshold control and detection of lead failure in an implanted medical device obtains three sensing vectors for measurement of an electrocardiogram signal. A dynamic error signal is determined from the vectors, and may be used to set a detection threshold for insufficient ECG signals, and/or to passively monitor the device for indications of lead failure without performing an impedance measurement. Passive mode operation conserves battery power and enables continuous lead integrity checks. A quality factor may also be determined from the error signal, to indicate whether or not signal measurements are valid with respect to noise levels. If the detection threshold is allowed to decay between successive features of the electrocardiogram, the decay rate may be made adaptive such that it automatically adjusts to changes in heart rate or to changes in amplitude of the electrocardiogram features.

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: Constant voltage or current is applied to high-voltage leads to determine impedance across medical device leads. Thyristors are used for upper switching components in an H-bridge. Current is sourced into a thyristor's gate from a ground-referenced source. This current then passes from the gate to the cathode and out to the patient. By keeping the current sufficiently low, the thyristors will not conduct from the anode to the cathode. Current passes through the thyristor, lead and patient and is sensed as it returns from the other lead. The sensed current is used to regulate the injected current. Pulses of constant current on the order of tens of milliamperes can be injected and the resulting voltage can be measured. Alternatively, a constant voltage can be applied and the resulting current can be measured to determine lead impedance.

Abstract: An RF protection circuit mitigates potentially adverse effects that may otherwise result from electromagnetic interference (e.g., due to MRI scanning of a patient having an implanted medical device). The RF protection circuit may comprise a voltage divider that is deployed across a pair of cardiac electrodes that are coupled to internal circuitry of the implantable medical device. Each leg of the voltage divider may be referenced to a ground of the internal circuit, whereby the different legs are deployed in parallel across different circuits of the internal circuitry. In this way, when an EMI-induced (e.g., MRI-induced) signal appears across the cardiac electrodes, the voltages appearing across these circuits and the currents flowing through these circuits may be reduced. The RF protection circuit may be used in an implantable medical device that employs a relatively low capacitance feedthrough to reduce EMI-induced (e.g., MRI-induced) current flow in a cardiac lead.

Abstract: An implanted cardioverter defibrillator (ICD) delivers an electrical therapy signal to the heart of a patient. When ventricular fibrillation or another condition of the heart requiring high voltage therapy is sensed, the therapy signal is delivered to the heart. When a partial short-circuit or other low impedance condition occurs, an over-current protection circuit will stop delivery of a shocking pulse. The ICD will then reduce the voltage of the shocking pulse and try again to deliver electrical therapy. This process is repeated until a voltage level is found that is able to deliver the electrical therapy without causing an over-voltage condition. Alternate lead configurations may also be tried in an attempt to find a signal path that is not affected by the low impedance or short-circuit condition.

Abstract: An implantable cardiac defibrillation device diminishes fibrosis of a defibrillation electrode. The device includes an implantable lead having a defibrillation electrode adapted for implant in one of the superior vena cava and right ventricle of a heart, a pulse generator adapted to be coupled to the defibrillation electrode that provides defibrillation energy to the defibrillation electrode, and a power supply that maintains a negative voltage on the defibrillation electrode in the absence of defibrillating energy being provided to the defibrillation electrode.

Abstract: An implantable medical lead for coupling to an implantable pulse generator may be configured for improved safety. The lead may include: a first electrode; a second electrode in electrical communication with the first electrode; and an active circuit element in electrical communication with the first electrode and the second electrode. The active circuit element may be configured to change an impedance of the lead. The active circuit element may be configured to change the impedance of the lead in response to a pacing signal or a signal having opposite polarity to a pacing signal. A method of using an implantable medical lead for improved safety may include changing an impedance of an implantable medical lead from a relatively high impedance to a relatively low impedance and/or changing an impedance of an implantable medical lead from a relatively low impedance to a relatively high impedance.

Abstract: An implantable stimulation system includes a stimulation current generator encased in an implantable housing, one or more stimulation leads to deliver therapeutic stimulation from the generator to target patient tissue, and inductive elements arranged to condition the stimulation for delivery to the target tissue with increased efficiency and reduced pain sensation. The inductive elements are arranged external to the housing and integral with one or more of a stimulation lead or an external component of the housing, such as a header. The inductive elements serve to condition therapeutic stimulations such that varying the output of the generator allows the system to deliver arbitrary effective waveforms to the target tissue.