Abstract: An implantable device monitors and treats heart failure, pulmonary edema, and hemodynamic conditions and in some cases applies therapy. In one implementation, the implantable device applies a high-frequency multi-phasic pulse waveform over multiple-vectors through tissue. The waveform has a duration less than the charging time constant of electrode-electrolyte interfaces in vivo to reduce intrusiveness while increasing sensitivity and specificity for trending parameters. The waveform can be multiplexed over multiple vectors and the results cross-correlated or subjected to probabilistic analysis or thresholding schemata to stage heart failure or pulmonary edema. In one implementation, a fractionation morphology of a sensed impedance waveform is used to trend intracardiac pressure to stage heart failure and to regulate cardiac resynchronization therapy. The waveform also provides unintrusive electrode integrity checks and 3-D impedancegrams.

Abstract: An apparatus comprises an electrostimulation energy storage capacitor, a circuit path communicatively coupled to the electrostimulation energy storage capacitor and configured to provide quasi-constant current neural stimulation through a load from the electrostimulation energy storage capacitor, a current measuring circuit communicatively coupled to the circuit path and configured to obtain a measure of quasi-constant current delivered to the load, and a control circuit communicatively coupled to the current measuring circuit, wherein the control circuit is configured to initiate adjustment of the voltage level of the storage capacitor for a subsequent delivery of quasi-constant current according to a comparison of the measured load current to a specified load current value.

Abstract: In general, the disclosure is directed to techniques for identification and remediation of oversensed cardiac events using far-field electrograms (FFEGMs). Identification of oversensed cardiac events can be used in an ICD to prevent ventricular fibrillation (VF) detection, and thereby avoid delivery of an unnecessary defibrillation shock. Alternatively, or additionally, identification of oversensed cardiac events can be used in an ICD to support delivery of bradycardia pacing during an oversensing condition. In some cases, bradycardia pacing delivered in response to detection of oversensed cardiac events may include pacing pulses from multiple vectors to provide redundancy in the event the oversensing may be due to a lead-related condition.

Abstract: Approaches for rate initialization and overdrive pacing used during capture threshold testing are described. Cardiac cycles are detected and the cardiac events of a cardiac chamber that occur during the cardiac cycles are monitored. The number of intrinsic beats in the cardiac events is counted. Initialization for a capture threshold test involves maintaining a pre-test pacing rate for the capture threshold test if the number of intrinsic beats in the cardiac events is less than a threshold. The pacing rate is increased for the capture threshold test if the number of intrinsic beats in the cardiac events is greater than the threshold.

Abstract: Approaches for selecting an electrode combination of multi-electrode pacing devices are described. Electrode combination parameters that support cardiac function consistent with a prescribed therapy are evaluated for each of a plurality of electrode combinations. Electrode combination parameters that do not support cardiac function are evaluated for each of the plurality of electrode combinations. An order is determined for the electrode combinations based on the parameter evaluations. An electrode combination is selected based on the order, and therapy is delivered using the selected electrode combination.

Abstract: Methods of locating a tip of a central venous catheter (“CVC”) relative to the superior vena cava, sino-atrial node, right atrium, and/or right ventricle using electrocardiogram data. The CVC includes at least one electrode. In particular embodiments, the CVC includes two or three pairs of electrodes. Further, depending upon the embodiment implemented, one or more electrodes may be attached to the patient's skin. The voltage across the electrodes is used to generate a P wave. A reference deflection value is determined for the P wave detected when the tip is within the proximal superior vena cava. Then, the tip is advanced and a new deflection value determined. A ratio of the new and reference deflection values is used to determine a tip location. The ratio may be used to instruct a user to advance or withdraw the tip.

Abstract: A system and method for painlessly calculating an estimated defibrillation threshold, such as by using an implantable medical device and a controller. The estimated defibrillation threshold can be calculated using a delivered first energy to a first thoracic location, an electric field detected at a second thoracic location, and an electric field detected between a third thoracic location and a fourth thoracic location. The estimated defibrillation threshold represents an energy that, when delivered at the first thoracic location, can create an electric field strength in a target region of the heart that meets or exceeds a target electric field strength.

Abstract: Generally, the disclosure is directed one or more methods or systems of cardiac pacing employing a right ventricular electrode and a plurality of left ventricular electrodes. Pacing using the right ventricular electrode and a first one of the left ventricular electrodes and measuring activation times at other ones of the left ventricular electrodes. Pacing using the right ventricular electrode and a second one of the ventricular electrodes and measuring activation times at other ones of the left ventricular electrodes. Employing sums of the measured activation times to select one of the left ventricular electrodes for delivery of subsequent pacing pulses.

Abstract: The present disclosure pertains to cardiac pacing methods and systems, and, more particularly, to cardiac resynchronization therapy (CRT). In particular, the present disclosure pertains to determining the efficacy of CRT through use of an effective capture test (ECT). One or more embodiments comprises sensing a signal in response to a ventricular pacing stimulus. Through signal processing, a number of features are parsed from the signal. Exemplary features parsed from the signal include a maximum amplitude, a maximum time associated with the maximum amplitude, a minimum amplitude, and a minimum time associated with the minimum amplitude. The data is evaluated through use of the ECT. By employing the ECT, efficacy of CRT is easily and automatically evaluated.

Abstract: In an implantable heart stimulating device and a method of the operation thereof, device has a control circuit that detects an evoked responses to delivered pacing pulses and to carry out an automatic capture routine. The control circuit is arranged to automatically temporarily disable the automatic capture routine on the basis of at least one of the following criteria: a1) if more than a predetermined number of threshold searches have been performed during a certain time, and b1) if a variable time delay with which the device operates is changed such that a pacing pulse may be delivered by the device during the evoked response time window.

Abstract: An implantable medical device is connectable to an epicardial left ventricular lead having at least one epicardial electrode and a myocardium penetrating catheter with at least one endocardial electrode and present in a lumen of the lead. The device comprises a pulse generator controller that controls a ventricular pulse generator to generate pulses to be applied to the epicardial and endocardial electrodes. The controller uses an endocardial-to-epicardial time interval or epicardial-to-endocardial time interval to coordinate endocardial and epicardial activation of the left ventricle to thereby achieve cardiac pacing that closely mimics the natural electrical activation pattern of a healthy heart.

Abstract: Stimulation energy can be provided to a His-bundle to activate natural cardiac contraction mechanisms. Interval information can be used to describe a cardiac response to His-bundle stimulation, and the interval information can provide cardiac stimulation diagnostic information. For example, interval information can be used to discriminate between intrinsic conduction cardiac contractions and contractions responsive to His-bundle pacing.

Abstract: An ambulatory or implantable device, such as a pacer, defibrillator, or other cardiac rhythm management device, can tolerate magnetic resonance imaging (MRI) or other noise without turning on an integrated circuit diode by selectively providing a bias voltage that can overcome an expected induced voltage resulting from the MRI or other noise.

Abstract: The present disclosure pertains to cardiac pacing methods and systems, and, more particularly, to cardiac resynchronization therapy (CRT). In particular, the present disclosure pertains to determining the efficacy of CRT through use of an effective capture test (ECT). One or more embodiments comprises sensing a signal in response to a ventricular pacing stimulus. Through signal processing, a number of features are parsed from the signal. Exemplary features parsed from the signal include a maximum amplitude, a maximum time associated with the maximum amplitude, a minimum amplitude, and a minimum time associated with the minimum amplitude. The data is evaluated through use of the ECT. By employing the ECT, efficacy of CRT is easily and automatically evaluated.

Abstract: The present disclosure pertains to cardiac pacing methods and systems, and, more particularly, to cardiac resynchronization therapy (CRT). In particular, the present disclosure pertains to determining the efficacy of CRT through use of an effective capture test (ECT). One or more embodiments comprises sensing a signal in response to a ventricular pacing stimulus. Through signal processing, a number of features are parsed from the signal. Exemplary features parsed from the signal include a maximum amplitude, a maximum time associated with the maximum amplitude, a minimum amplitude, and a minimum time associated with the minimum amplitude. The data is evaluated through use of the ECT. By employing the ECT, efficacy of CRT is easily and automatically evaluated.

Abstract: The present disclosure pertains to cardiac pacing methods and systems, and, more particularly, to cardiac resynchronization therapy (CRT). In particular, the present disclosure pertains to determining the efficacy of CRT through use of an effective capture test (ECT). One or more embodiments comprises sensing a signal in response to a ventricular pacing stimulus. Through signal processing, a number of features are parsed from the signal. Exemplary features parsed from the signal include a maximum amplitude, a maximum time associated with the maximum amplitude, a minimum amplitude, and a minimum time associated with the minimum amplitude. The data is evaluated through use of the ECT. By employing the ECT, efficacy of CRT is easily and automatically evaluated.

Abstract: The present disclosure pertains to cardiac pacing methods and systems, and, more particularly, to cardiac resynchronization therapy (CRT). In particular, the present disclosure pertains to determining the efficacy of CRT through use of an effective capture test (ECT). One or more embodiments comprises sensing a signal in response to a ventricular pacing stimulus. Through signal processing, a number of features are parsed from the signal. Exemplary features parsed from the signal include a maximum amplitude, a maximum time associated with the maximum amplitude, a minimum amplitude, and a minimum time associated with the minimum amplitude. The data is evaluated through use of the ECT. By employing the ECT, efficacy of CRT is easily and automatically evaluated.

Abstract: An implantable heart stimulating device for indicating congestive heart failure (CHF) has a processor and a sensor combination that senses at least two heart events during one heart cycle at different locations of the heart. The processor is supplied with signals from the sensor combination relating to the sensed events, and determines therefrom at least one heart time interval between the sensed events in the same heart cycle. The processor determines a CHF indicator value representing a degree of CHF based on a variability measure calculated from at least two heart time intervals from at least two different heart cycles. The processor determines the CHF indicator value in relation to previous CHF indicator values.

Abstract: Techniques are described for detecting lead-related conditions for implantable electrical leads. In some of the described embodiments, an implantable electrical lead assembly is provided with a coupling member for connecting a conductor and associated insulator(s) to an electrode/sensing element. The implantable medical device controls and performs a measurement of an electrical property of the electrical lead during periods when the conductor is decoupled from the electrode/sensing element. An indication of a lead-related condition is derived based on the measured electrical property. The lead-related condition may be associated with an insulator of a lead body of the electrical lead.

Abstract: The present disclosure pertains to cardiac pacing methods and systems, and, more particularly, to cardiac resynchronization therapy (CRT). In particular, the present disclosure pertains to determining the efficacy of CRT through use of an effective capture test (ECT). One or more embodiments comprises sensing a signal in response to a ventricular pacing stimulus. Through signal processing, a number of features are parsed from the signal. Exemplary features parsed from the signal include a maximum amplitude, a maximum time associated with the maximum amplitude, a minimum amplitude, and a minimum time associated with the minimum amplitude. The data is evaluated through use of the ECT. By employing the ECT, efficacy of CRT is easily and automatically evaluated.

Abstract: Techniques are provided for use with an implantable medical device for detecting and assessing heart failure and for controlling cardiac resynchronization therapy (CRT) based on impedance signals obtained using hybrid impedance configurations. The hybrid configurations exploit right atrial (RA)-based impedance measurement vectors and/or left ventricular (LV)-based impedance measurement vectors. In one example, current is injected between the device case and a ring electrode in the right ventricle (RV) or RA. RA-based impedance values are measured along vectors between the device case and an RA electrode. LV-based impedance values are measured along vectors between the device case and one or more electrodes of the LV. Heart failure and other cardiac conditions are detected and tracked using the measured impedance values. CRT delay parameters are also optimized based impedance.

Abstract: The present disclosure pertains to cardiac pacing methods and systems, and, more particularly, to cardiac resynchronization therapy (CRT). In particular, the present disclosure pertains to determining the efficacy of CRT through use of an effective capture test (ECT). One or more embodiments comprises sensing a signal in response to a ventricular pacing stimulus. Through signal processing, a number of features are parsed from the signal. Exemplary features parsed from the signal include a maximum amplitude, a maximum time associated with the maximum amplitude, a minimum amplitude, and a minimum time associated with the minimum amplitude. The data is evaluated through use of the ECT. By employing the ECT, efficacy of CRT is easily and automatically evaluated.

Abstract: The invention provides methods and apparatus for determining in a non-tracking pacing mode (e.g., DDI/R, VVI/R) whether a ventricular pacing stimulus is capturing a paced ventricle, including some or all of the following aspects. For example, increasing a ventricular pacing rate a nominal amount to an overdrive pacing rate higher than a most recent heart rate and evaluating a conduction interval from a first pacing ventricle to a second sensing ventricle and then continuing to monitor the underlying rate to ensure that a threshold testing pacing rate will not exceed a predetermined minimum interval and providing pacing stimulation to the first ventricle and sensing the second ventricle to determine whether the pacing stimulation to the first ventricle was one of sub-threshold and supra-threshold. The methods and apparatus are especially useful in conjunction with ensuring actual delivery of a ventricular pacing regime (e.g., cardiac resynchronization therapy or “CRT”).

Abstract: An implantable medical device (IMD) receives an input associated with the presence of an environment having an external source that generates an interfering signal, such as an MRI device. The IMD adjusts a first set of one or more sensing parameters of a sensing module of the IMD in response to receiving the input associated with the presence of the environment. In this manner, the IMD operates in accordance with the adjusted sensing configuration in the presence of the interfering signal in an attempt to obtain a more detailed representation of the signal including noise caused by the interfering signal. The IMD analyzes the signals sensed using the first set of adjusted sensing parameters to determine if further adjustment is desired. If desired, the IMD adjusts a second set of one or more sensing parameters of the sensing module based on the analysis.

Abstract: The present disclosure pertains to cardiac pacing methods and systems, and, more particularly, to cardiac resynchronization therapy (CRT). In particular, the present disclosure pertains to determining the efficacy of CRT through use of an effective capture test (ECT). One or more embodiments comprises sensing a signal in response to a ventricular pacing stimulus. Through signal processing, a number of features are parsed from the signal. Exemplary features parsed from the signal include a maximum amplitude, a maximum time associated with the maximum amplitude, a minimum amplitude, and a minimum time associated with the minimum amplitude. The data is evaluated through use of the ECT. By employing the ECT, efficacy of CRT is easily and automatically evaluated.

Abstract: A system and method for monitoring at least one chamber of a heart (e.g., a left ventricular chamber) during delivery of extrasystolic stimulation to determine if the desired extra-systole (i.e., ventricular mechanical capture following refractory period expiration) occurs. The system includes an implantable or external cardiac stimulation device in association with a set of leads such as epicardial, endocardial, and/or coronary sinus leads equipped with motion sensor(s). The device receives and processes acceleration sensor signals to determine a signal characteristic indicative of chamber capture resulting from one or more pacing stimulus delivered closely following expiration of the refractory period.

Abstract: The invention relates to cardiac rhythm management systems, and more particularly, to rate adaptive cardiac pacing systems and methods. In an embodiment, the invention includes a cardiac rhythm management device. The device can include a pulse generator for generating electrical pulses to be delivered to a heart at a pacing rate, a processor in communication with the pulse generator, and one or more sensors for sensing pulmonary function and cardiac function. The processor can be configured to increase the pacing rate if the pulmonary function is increasing with time and the cardiac function is not decreasing with time, maintain the pacing rate if the pulmonary function is increasing with time and the cardiac function is decreasing with time, and decrease the pacing rate if the respiratory function is decreasing with time.

Abstract: Various techniques for facilitating selection of a pacing vector for pacing a chamber of a heart are described. One example method described includes, for each of a plurality of vectors, delivering a pacing pulse to capture a first heart chamber, determining a first time interval between the pacing pulse and a sensed event in a second heart chamber, determining a capture detection window in response to the determined first time interval, and enabling a capture detection module to iteratively decrease a pacing pulse magnitude delivered in the first heart chamber until an event in the second heart chamber is not sensed during the determined capture detection window.

Abstract: Approaches for rate initialization and overdrive pacing used during capture threshold testing are described. Cardiac cycles are detected and the cardiac events of a cardiac chamber that occur during the cardiac cycles are monitored. The number of intrinsic beats in the cardiac events is counted. Initialization for a capture threshold test involves maintaining a pre-test pacing rate for the capture threshold test if the number of intrinsic beats in the cardiac events is less than a threshold. The pacing rate is increased for the capture threshold test if the number of intrinsic beats in the cardiac events is greater than the threshold.

Abstract: A user may modify a stimulation parameter in a plurality of stimulation programs with a single adjustment. During stimulation therapy, the user, such as a patient, may desire to change a parameter of the plurality of stimulation programs. The patient may press a single button on an external programmer to make the parameter change, or global adjustment, to all of the plurality of stimulation programs. This global adjustment eliminates the need for the patient to navigate through each of the plurality of stimulation programs separately and adjust the parameter. Additionally, changing the plurality of stimulation programs may be desirable for uniform stimulation therapy between programs used by the patient. The external programmer may calculate an appropriate parameter change for each stimulation program to keep parameter ratios equal between the plurality of stimulation programs.

Abstract: In general, this disclosure describes techniques for monitoring ventricular capture of electrical stimulation based upon sensed ventricular pressures using an implantable medical device. One example method comprises obtaining a blood pressure signal for a first ventricle (e.g., right ventricle) of a patient, and determining whether stimulation captured a second, different ventricle (e.g., left ventricle) of the patient based upon the blood pressure signal for the first ventricle. Whether stimulation captured the second ventricle may be determined based on at least one value of a myocardial performance index that is determined based upon the blood pressure signal for the first ventricle. If a loss of capture is identified, the method may further comprise providing a warning signal and/or providing a therapy adjustment signal to adjust the electrical stimulation that is provided to the second ventricle.

Abstract: Various techniques for selecting a pacing vector based on pacing capture thresholds are described. One example method described includes for each of a plurality of vectors, iteratively delivering at least one pacing stimulus at each of a plurality of magnitudes within a predetermined range of magnitudes to a first chamber, determining if a depolarization occurred in a second chamber of the heart within a predetermined threshold time interval after the pacing stimulus that is less than an interval, identifying a pacing stimulus for which a depolarization in the second chamber does not occur within the predetermined threshold time interval, determining a capture threshold magnitude for the vector based on the magnitude of the pacing pulse for which a depolarization in the second chamber does not occur within the predetermined threshold time interval, and recording the capture threshold magnitudes.

Abstract: A cardiac medical device and associated method control delivery of dual chamber burst pacing pulses in response to detecting tachycardia. In one embodiment, a single chamber pacing pulse is delivered in response to detecting a tachycardia. Dual chamber pacing pulses are delivered subsequent to the single chamber pacing pulse. An intrinsic depolarization is sensed subsequent to delivering the dual chamber pacing pulses. The tachycardia episode is classified in response to the sensed intrinsic depolarization.

Abstract: An apparatus and method for placement of a lead for cardiac resynchronization therapy in a cardiovascular system of patient. A conductive tool is advanced along at least one branch of the cardiovascular system of the patient. Electrogram data of the cardiovascular system at each location of the conductive tool along the cardiovascular system using the conductive tool is obtained while the conductive tool is advanced. The electrogram data is analyzed to determine a morphological condition of tissue of the patient surrounding the location.

Abstract: According to some methods, for example, preprogrammed in a microprocessor element of an implantable cardiac pacing system, at least one of a number of periodic pacing threshold searches includes steps to reduce an evoked response amplitude threshold for evoked response signal detection. The reduction may be to a minimum value measurable above zero, for example, as determined by establishing a ‘noise floor’. Alternately, amplitudes of test pacing pulses and corresponding post pulse signals are collected and reviewed to search for a break, to determine a lower value to which the evoked response threshold may be adjusted without detecting noise. Subsequent to reducing the threshold, if no evoked response signal is detected for a test pulse applied at or above a predetermined maximum desirable pulse energy, an operational pacing pulse energy is set to greater than or equal to the maximum desirable in conjunction with a reduction in pacing rate.

Abstract: An apparatus and a system for seeking for an optimal configuration of a bi-, tri- or multi-ventricular cardiac resynchronization implantable medical device. This system includes ventricular pacing, a signal representative of an endocardial acceleration (EA) of a patient's heart, and isolating and pre-processing the EA signal to obtain an EA1 component and an EA2 component. The effectiveness of the current pacing configuration is evaluated by one or more composite indexes that combine at least two of the following parameters: peak-to-peak amplitude (PEA1) of the EA1 component; time occurrence (TstEA1) of the beginning of the EA1 component; time interval (LargEA1) between the beginning of the EA1 component and the moment of the energy peak of the EA1 component; and duration of systole (Syst), represented by the time interval between the beginning (TstEA1) of the EA1 component and the beginning (TstEA2) of the EA2 component.

Abstract: A cardiac rhythm management (CRM) system includes an implantable medical device that delivers anti-tachyarrhythmia therapies including anti-tachyarrhythmia pacing (ATP) and a hemodynamic sensor that senses a hemodynamic signal. The implantable medical device includes a hemodynamic sensor-controlled closed-loop ATP system that uses the hemodynamic signal for ATP capture verification. When ATP pulses are delivered according to a selected ATP protocol to terminate a tachyarrhythmia episode, the implantable medical device performs the ATP capture verification by detecting an effective cardiac contraction from the hemodynamic signal. The ATP protocol is adjusted using an outcome of the ATP capture verification.

Abstract: Methods and/or devices may be configured to track effectiveness of pacing therapy by monitoring two or more electrical vectors of the patient's heart during pacing therapy and analyzing at least one feature of a morphological waveform within each of the two or more electrical vectors.

Abstract: A cardiac rhythm management system provides for cardiac pacing that is delivered to a target portion of conductive tissue in a heart, such as the His bundle. In various embodiments, the system is configured to verify capture of the target portion and provide for selective pacing of the target portion. In various embodiments, the system is configured to detect responses of the target portion and adjacent myocardial tissue to delivery of pacing pulses and use an outcome of the detection to verify selective capture of the target portion (i.e., without directly exciting the adjacent myocardial tissue.

Abstract: A leadless implantable medical device (LIMD) comprises a housing configured to be implanted entirely within a single local ventricular chamber of the heart near a local apex region. A base on the housing is configured to be secured to tissue of interest, while a distal electrode is provided on the base and extends outward such that, when the device is implanted in the local chamber, the distal electrode is configured to engage the distal apex region at a distal activation site within the conduction network of the adjacent ventricular chamber.

Abstract: Methods and apparatus for accurately and painlessly measuring the impedance between defibrillation electrodes implanted in a patient utilize a high current test pulse delivered with a sufficiently high current to produce an accurate measurement of the defibrillation electrode impedance while limiting the duration of the test pulse such that the pain sensing cells in the patient do not perceive the test pulse. In one embodiment, the test pulse is generated from the high voltage transformer without storing energy in the high voltage capacitors and is delivered to the defibrillation electrodes in the patient utilizing the high voltage switching circuitry.

Abstract: Generally, the disclosure is directed one or more methods or systems of cardiac pacing employing a right ventricular electrode and a plurality of left ventricular electrodes. Pacing using the right ventricular electrode and a first one of the left ventricular electrodes and measuring activation times at other ones of the left ventricular electrodes. Pacing using the right ventricular electrode and a second one of the ventricular electrodes and measuring activation times at other ones of the left ventricular electrodes. Employing sums of the measured activation times to select one of the left ventricular electrodes for delivery of subsequent pacing pulses.

Abstract: Example techniques for communicating between two medical devices are described. One medical device may be an implantable medical device. Another medical device may be a lead-borne implantable medical device. The lead-borne implantable medical device may be referred to as a satellite. The implantable medical device may measure impedance of a path including at least two electrodes, at least one of which is on the lead, using an impedance measurement module. In some example implementations of this disclosure, the implantable medical device may also use the impedance measurement module to communicate with the satellite on the lead.

Abstract: Cardiac electrostimulation energy is delivered to a heart chamber of a subject according to a normal pacing mode using a set of implantable pacing electrodes. When a threshold test for the heart chamber is initiated and a sensing electrode independent from the set of pacing electrodes is unavailable for the heart chamber, cardiac electrostimulation energy is delivered to the subject according to a threshold test mode. The threshold test mode includes sensing a cardiac activity signal from a subject using a set of sensing electrodes that includes an electrode common to the set of pacing electrodes, and changing the electrostimulation energy and sensing a resulting cardiac activity signal using the set of sensing electrodes to determine the optimum electrostimulation energy for capture of the heart chamber.

Abstract: A method for selecting a target vein for left ventricular lead placement for cardiac resynchronization therapy includes determining electrical dispersion for the first coronary vein by calculating the difference between (i) activation time at a location of the vein that has the latest activation time of a plurality of locations in the vein and (ii) activation time at a location that has the earliest activation time of the plurality of locations. The method may further include (ii) determining whether the magnitude of the electrical dispersion for the vein meets or exceeds a predetermined threshold selecting the vein if the vein meets or exceeds the predetermined threshold; or (ii) selecting, among several veins, the vein that has the highest electrical dispersion.

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: Approaches for selecting an electrode combination of multi-electrode pacing devices are described. Electrode combination parameters that support cardiac function consistent with a prescribed therapy are evaluated for each of a plurality of electrode combinations. Electrode combination parameters that do not support cardiac function are evaluated for each of the plurality of electrode combinations. An order is determined for the electrode combinations based on the parameter evaluations. An electrode combination is selected based on the order, and therapy is delivered using the selected electrode combination.

Abstract: Methods and systems involve adjusting an energy used for safety pacing based on the capture threshold. The safety pacing energy may be adjusted prior to a capture threshold test. During the capture threshold test, backup safety paces are delivered using the adjusted pacing energy. Following suspension of automatic capture verification, the device may enter a suspension mode. During the suspension mode, safety pacing pulses are delivered using a pacing energy adjusted based on capture threshold.

Abstract: A new model is provided for understanding and exploiting impedance or admittance values measured by implantable medical devices, such as pacemakers or cardiac resynchronization devices (CRTs.) The device measures impedance along vectors extending through tissues of the patient between various pairs of electrodes. The device then converts the vector-based impedance measurements into near-field individual electrode-based impedance values. This is accomplished, in at least some examples, by converting the vector-based impedance measurements into a set of linear equations to be solved while ignoring far-field contributions to the impedance measurements. The device solves the linear equations to determine the near-field impedance values for the individual electrodes, which are representative of the impedance of tissues in the vicinity of the electrodes.

Abstract: A medical device includes pacing circuitry configured to deliver during a cardiac cycle a first pacing pulse to a first site using a first electrode as a cathode electrode for the first pacing pulse and to deliver a second pacing pulse to a second site using a second electrode as a cathode electrode for the second pacing pulse. Sensing circuitry is configured to generate a differential signal between cardiac electrical activity sensed at the first electrode and cardiac electrical activity sensed at the second electrode. Capture circuitry discriminates between single site capture and multi-site capture based on the differential signal.