Abstract: Apparatus and method for determining a mechanical property of an organ or a body part. The method includes positioning an impedance sensor within a blood vessel. The impedance sensor has at least two electrodes disposed within the blood vessel, which is mechanically coupled to the organ or body part. The method further includes determining the electrical impedance between the two electrodes to obtain an impedance signal correlated with the mechanical property of the organ or body part. The organ may be the heart, lungs, uterus, urinary bladder, part of the gastrointestinal tract and the brain. The impedance sensor includes at least two spaced apart electrodes capable of being disposed within a blood vessel. The sensor is operatively connected to an impedance determining unit which determines the impedance between the electrodes. The impedance sensor may be a part of an insertable or implantable lead or catheter like device.

Abstract: There is provided an electro-optically driven relay system (10) for switching the application of energy to a load (5). The subject relay system (10) comprises: a switch unit (100) operable responsive to a control signal; an electro-optic current generating unit (200) connected to the switch unit (100) for generating the necessary control signal responsive to an actuation signal; and, primary and supplemental drive units (300, 400) connected to the electro-optic current generating unit (200) for collectively generating the actuation signal. The primary drive unit (300) is operable responsive to a first input signal; and, the supplemental drive unit (400) is operable responsive to a second input signal to augment the actuation signal for at least a predetermined time duration. The switching response of the switch unit (100) is thereby accelerated.

Abstract: A method and devices for timing the delivery of non-excitatory signals for modifying myocardial contractility of a portion of the heart are disclosed. The method includes the steps of applying electrodes to a plurality of cardiac sites, sensing electrical activity in a first cardiac site through a first electrode for detecting a first electrical depolarization event within a beat cycle, sensing electrical activity in a second cardiac site through a second electrode for detecting a second electrical depolarization event within the beat cycle, and applying a non-excitatory signal to the heart at or near at least the second cardiac site through at least one of the electrodes in response to detecting the second electrical depolarization event within an alert window period. The alert window period starts at a first delay from the time of detection of the first electrical depolarization event and has a first duration.

Abstract: Apparatus and method for obtaining from a patient's heart data useful for on-line setting of the parameters of a detection time window in an excitable tissue control device. The method includes applying electrodes to a first cardiac site and a second cardiac site of a patient and electrically connecting the electrodes to a data collecting device. The device is then operated under a plurality of different cardiac conditions to obtain a plurality of different histogram data sets. Each histogram data set represents a cumulative time distribution histogram of cardiac depolarization events detected at the second cardiac site in a plurality of cardiac beats. Each histogram data set is defined by a plurality of histogram parameters having values indicative of the cardiac conditions common to the plurality of cardiac beats used to obtain the histogram data set.

Abstract: A fluid-phase electrode lead apparatus is disclosed, for the delivery of electrical signals to an excitable tissue.

Abstract: A method and devices for timing the delivery of non-excitatory signals for modifying myocardial contractility of a portion of the heart. The method includes the steps of applying electrodes to a plurality of cardiac sites, sensing electrical activity in a first cardiac site through a first electrode for detecting a first electrical depolarization event within a beat cycle, sensing electrical activity in a second cardiac site through a second electrode for detecting a second electrical depolarization event within the beat cycle, and applying a non-excitatory signal to the heart at or near at least the second cardiac site through at least one of the electrodes in response to detecting the second electrical depolarization event within an alert window period. The alert window period starts at a first delay from the time of detection of the first electrical depolarization event and has a first duration.

Abstract: A method for setting the parameters of an alert time window in an excitable tissue control device operative under a plurality of different cardiac conditions of a heart of a patient. The method includes providing said excitable tissue control device with a set of data including a plurality of sets of alert time window parameters. Each set of window parameters is uniquely associated with a different set of values of a plurality of cardiac condition defining parameters identifying one of the different cardiac conditions. Each set of window parameters includes at least a set of timing parameters usable for obtaining a beginning time point and an ending time point of the alert window. The sets of window parameters are obtained by processing data collected within a data collection session from a plurality of cardiac beats of the same patient under the different cardiac conditions.

Abstract: Apparatus and method for obtaining from a patient's heart data useful for on-line setting of the parameters of a detection time window in an excitable tissue control device. The method includes applying electrodes to a first cardiac site and a second cardiac site of a patient and electrically connecting the electrodes to a data collecting device. The device is then operated under a plurality of different cardiac conditions to obtain a plurality of different histogram data sets. Each histogram data set represents a cumulative time distribution histogram of cardiac depolarization events detected at the second cardiac site in a plurality of cardiac beats. Each histogram data set is defined by a plurality of histogram parameters having values indicative of the cardiac conditions common to the plurality of cardiac beats used to obtain the histogram data set.

Abstract: A memory device particularly useful in size-constrained electronic products, such as cardiac stimulators. To provide additional memory for such size-constrained products, memory chips are stacked one on top of another. The memory chips are configured to facilitate bonding without crossed contacts, using aligned bonding pads, vias, or castellations. Each memory chip also includes an address selection circuit that receives signals from one or more address lines to selectively enable and disable the memory chips in the stack.

Abstract: An implantable medical device for electrically stimulating the heart to beat generally includes a processor, a plurality of electrodes, a sense amplifier, a pulse generator, and a heart status monitor. The processor can determine when the patient has entered an environment of high electromagnetic interference. When this occurs, the processor forces the implantable device into a safe noise mode. While in the same noise mode (which preferably continues while the patient is experiencing the electromagnetic interference), the implantable device paces the heart on demand and inhibits pacing during the vulnerable period. The processor determines when the vulnerable period is occurring and when the heart needs to be paced by monitoring a status signal from the heart status monitor.

Abstract: Apparatus and methods adapted for in vivo chronic measurement of cardiac monophasic action potentials (MAPs). The methods include, inter alia, providing a sensing electrode in contact with cardiac tissue and a reference electrode in proximity to the sensing electrode, intermittently inducing a transient localized depolarization or transient injury-like electrical currents in at least some of the cells of the cardiac tissue underlying or adjacent to the sensing electrode and measuring the potential difference between the sensing electrode and the reference electrode during at least part of the duration of the depolarization or injury-like currents. Other methods for inducing depolarization or injury-like currents in the tissue include, inter alia, localized membrane electroporation, localized electrostatic production of depolarization using voltage clamp to produce a signal representative of MAPs, localized tissue heating, localized application of ultrasound and localized irradiation with light.

Abstract: A method and apparatus for evaluating heart rate variability of the heart of a person in order to forecast a cardiac event. A cardiac stimulator receives heart beat signals from the heart and determines a measurement of heart rate variability based on statistical data derived from the heart beat signals and sensing data derived from a sensor. This measurement of heart rate variability is compared with previously stored heart rate variability zones defining normal and abnormal heart rate variability. These zones are modifiable after the occurrence of a cardiac event. Once a cardiac event is detected, a pathway is computed which extends from a generally normal heart rate variability condition to an abnormal heart rate variability condition. Subsequent measurements of heart rate variability are compared with this pathway. Selective therapy regimes are initiated depending on the measurement of heart rate variability.

Abstract: A cardiac stimulator capable of measuring pacing impedance includes a tank capacitor for delivering charge to the heart via device leads, a shunt resistor, and high-impedance buffers for measuring pacing current through the shunt resistor. Soon after the leading edge of the stimulation pulse, the voltage across the shunt resistor, as sampled by a high-impedance buffer, indicates lead and cardiac tissue resistance. Just prior to opening the pacing switch to terminate the stimulation pulse, the voltage across the shunt resistor is sampled by a high-impedance buffer and held once again to allow the capacitance of the lead/heart tissue to be calculated. In alternative embodiments, a high-impedance buffer measures the voltage between the tank capacitor and ground immediately following the stimulation pulse to allow estimation of the lead/heart tissue capacitance.

Abstract: An implantable medical device including an enclosure and a header portion attached to the enclosure. The header includes a lead cavity into which a lead can be inserted. The lead cavity includes a compression device, such as a spring, for aligning a highly visible indicator plunger at least partially hidden from view inside the volume defined by an annular electrode, or other opaque object, partially surrounding the lead cavity. The plunger includes at least a portion that is easily visible to a surgeon during implantation of the medical device. When a lead is inserted into the lead cavity, the end of the lead pushes against the indicator plunger thereby moving the plunger and compressing the spring. When the lead is fully inserted into the lead cavity, the plunger becomes visible as it is pushed away from the volume defined by the annular electrode. In this way, the plunger provides a positive indication that the lead has been fully inserted into the header.

Abstract: A method and apparatus for evaluating heart rate variability of the heart of a person in order to forecast a cardiac event. A cardiac stimulator receives heart beat signals from the heart and determines a measurement of heart rate variability based on statistical data derived from the heart beat signals and sensing data derived from a sensor. This measurement of heart rate variability is compared with previously stored heart rate variability zones defining normal and abnormal heart rate variability. These zones are modifiable after the occurrence of a cardiac event. Once a cardiac event is detected, a pathway is computed which extends from a generally normal heart rate variability condition to an abnormal heart rate variability condition. Subsequent measurements of heart rate variability are compared with this pathway. Selective therapy regimes are initiated depending on the measurement of heart rate variability.

Abstract: A cardiorespiratory monitor that generates bioimpedance sensing signals that produce substantially no interference with bioimpedance signals generated by implanted devices. The monitor detects the bioimpedance signal generated by the implanted device, using a voltage detector or a telemetry circuit, for example. The monitor analyzes this detected signal to generate a bioimpedance sensing signal that will not interfere with the sensed signal. For instance, if the monitor produces a pulsed sensing signal, the pulses are delivered in an interval of the detected signal where no pulses are present. Similarly, if the monitor produces a high frequency AC sensing signal, the zero crossings of the AC sensing signal are positioned during the delivery of a pulse by the implanted device.

Abstract: A memory device particularly useful in size-constrained electronic products, such as cardiac stimulators. To provide additional memory for such size-constrained products, memory chips are stacked one on top of another. The memory chips are configured to facilitate bonding without crossed contacts, using aligned bonding pads, vias, or castellations. Each memory chip also includes an address selection circuit that receives signals from one or more address lines to selectively enable and disable the memory chips in the stack.

Abstract: An implantable medical device for electrically stimulating the heart to beat generally includes a processor, a plurality of electrodes, a sense amplifier, a pulse generator, and a heart status monitor. The processor can determine when the patient has entered an environment of high electromagnetic interference. When this occurs, the processor forces the implantable device into a safe noise mode. While in the same noise mode (which preferably continues while the patient is experiencing the electromagnetic interference), the implantable device paces the heart on demand and inhibits pacing during the vulnerable period. The processor determines when the vulnerable period is occurring and when the heart needs to be paced by monitoring a status signal from the heart status monitor.

Abstract: A technique for acquiring and accessing information from a medical implantable device. Analog waveforms of interest are sensed and processed by signal acquisition circuitry. Analog parameters of interest are applied to selector switches which are controlled by a logic circuit. The logic circuit is also coupled to an A/D converter for converting the analog signals to digital values. The digital values are stored in dedicated registers and are available for telemetry to an external device upon receipt of a request or prompt signal. When a digitized value is accessed and telemetered, the control logic circuit changes the conductive state of the selector switches to apply the corresponding analog signal to the A/D converter. The resulting digital value is applied to the corresponding register to refresh the accessed and telemetered value. The technique permits the external device to request and configure the implanted device to send only digitized values of interest.

Abstract: An implantable medical device for electrically stimulating the heart to beat generally includes a processor, a plurality of electrodes, a sense amplifier, a pair of comparators, inner and outer target logic units, and pulse generator. The processor controls the magnitudes of inner and outer target reference signals which are generated by the inner and outer target logic units, respectively. The outer target is adjusted to be approximately equal to the peak amplitude of the cardiac signal. The processor stores representations of the outer target reference in memory. Alternatively or additionally, the processor computes a histogram of the relative or absolute number of cardiac cycles that occur over a given period of time for each outer target setting. The processor can be directed to retrieve the outer target representations and/or the histogram from memory and transmit that information to an external programmer for use by a physician.