Abstract:
In specific embodiments, one or more cardiogenic impedance signal template is stored, where each template has a corresponding morphology. Additionally, one or more cardiogenic impedance signal is obtained using electrodes implanted within a patient, where each signal has a corresponding morphology. The morphology of one or more obtained cardiogenic impedance signal is compared to the morphology of one or more stored template, to determine one or more metric indicative of similarity between the compared morphologies. The one or more metric indicative of similarity is used to analyze the patient's cardiac condition, to discriminate among arrhythmias and/or to adjust a cardiac pacing parameter.
Abstract:
Techniques are provided for estimating left atrial pressure (LAP) or other cardiac performance parameters based on measured conduction delays. In particular, LAP is estimated based interventricular conduction delays. Predetermined conversion factors stored within the device are used to convert the various the conduction delays into LAP values or other appropriate cardiac performance parameters. The conversion factors may be, for example, slope and baseline values derived during an initial calibration procedure performed by an external system, such as an external programmer. In some examples, the slope and baseline values may be periodically re-calibrated by the implantable device itself. Techniques are also described for adaptively adjusting pacing parameters based on estimated LAP or other cardiac performance parameters. Still further, techniques are described for estimating conduction delays based on impedance or admittance values and for tracking heart failure therefrom.
Abstract:
An implantable system acquires intracardiac impedance with an implantable lead system. In one implementation, the system generates frequency-rich, low energy, multi-phasic waveforms that provide a net-zero charge and a net-zero voltage. When applied to bodily tissues, current pulses or voltage pulses having the multi-phasic waveform provide increased specificity and sensitivity in probing tissue. The effects of the applied pulses are sensed as a corresponding waveform. The waveforms of the applied and sensed pulses can be integrated to obtain corresponding area values that represent the current and voltage across a spectrum of frequencies. These areas can be compared to obtain a reliable impedance value for the tissue. Frequency response, phase delay, and response to modulated pulse width can also be measured to determine a relative capacitance of the tissue, indicative of infarcted tissue, blood to tissue ratio, degree of edema, and other physiological parameters.
Abstract:
Techniques are provided for detecting heart failure or other medical conditions within a patient using an implantable medical device, such as pacemaker or implantable cardioverter/defibrillator, or external system. In one example, physiological signals, such as immittance-based signals, are sensed within the patient along a plurality of different vectors, and the amount of independent informational content among the physiological signals of the different vectors is determined. Heart failure is then detected by the implantable device based on a significant increase in the amount of independent informational content among the physiological signals. In response, therapy may be controlled, diagnostic information stored, and/or warning signals generated. In other examples, at least some of these functions are performed by an external system.
Abstract:
An implantable system acquires intracardiac impedance with an implantable lead system. In one implementation, the system generates frequency-rich, low energy, multi-phasic waveforms that provide a net-zero charge and a net-zero voltage. When applied to bodily tissues, current pulses or voltage pulses having the multi-phasic waveform provide increased specificity and sensitivity in probing tissue. The effects of the applied pulses are sensed as a corresponding waveform. The waveforms of the applied and sensed pulses can be integrated to obtain corresponding area values that represent the current and voltage across a spectrum of frequencies. These areas can be compared to obtain a reliable impedance value for the tissue. Frequency response, phase delay, and response to modulated pulse width can also be measured to determine a relative capacitance of the tissue, indicative of infarcted tissue, blood to tissue ratio, degree of edema, and other physiological parameters.
Abstract:
Techniques are provided for estimating left atrial pressure (LAP) or other cardiac pressure parameters based on various parameters derived from impedance signals. In particular, effective LAP is estimated based on one or more of: electrical conductance values, cardiogenic pulse amplitudes, circadian rhythm pulse amplitudes, or signal morphology fractionation values, each derived from the impedance signals detected by the implantable device. Predetermined conversion factors stored within the device are used to convert the various parameters derived from the electrical impedance signal into LAP values or other appropriate cardiac pressure values. The conversion factors may be, for example, slope and baseline values derived during an initial calibration procedure performed by an external system, such as an external programmer. In some examples, the slope and baseline values may be periodically re-calibrated by the implantable device itself.
Abstract:
Techniques are provided for estimating left atrial pressure (LAP) or other cardiac performance parameters based on measured conduction delays. In particular, LAP is estimated based interventricular conduction delays. Predetermined conversion factors stored within the device are used to convert the various the conduction delays into LAP values or other appropriate cardiac performance parameters. The conversion factors may be, for example, slope and baseline values derived during an initial calibration procedure performed by an external system, such as an external programmer. In some examples, the slope and baseline values may be periodically re-calibrated by the implantable device itself. Techniques are also described for adaptively adjusting pacing parameters based on estimated LAP or other cardiac performance parameters. Still further, techniques are described for estimating conduction delays based on impedance or admittance values and for tracking heart failure therefrom.
Abstract:
Various techniques are provided for calibrating and estimating left atrial pressure (LAP) using an implantable medical device, based on impedance, admittance or conductance parameters measured within a patient. In one example, default conversion factors are exploited for converting the measured parameters to estimates of LAP. The default conversion factors are derived from populations of patients. In another example, a correlation between individual conversion factors is exploited to allow for more efficient calibration. In yet another example, differences in thoracic fluid states are exploited during calibration. In still yet another example, a multiple stage calibration procedure is described, wherein both invasive and noninvasive calibration techniques are exploited. In a still further example, a therapy control procedure is provided, which exploits day time and night time impedance/admittance measurements.
Abstract:
The present invention provides multi-functional medical catheters, systems and methods for their use. In one particular embodiment, a medical catheter (100) includes a flexible elongate body (105) having a proximal end (110) and a distal end (120). A plurality of spaced apart electrodes (130–136) are operably attached to the flexible body near the distal end. At least some of the electrodes are adapted for mapping a tissue and, in some embodiments, at least one of the electrodes is adapted for ablating a desired portion of the tissue. The catheter includes a plurality of tissue orientation detectors (140–146) disposed between at least some of the electrodes. In this manner, the medical catheter is capable of tissue mapping, tissue imaging, tissue orientation, and/or tissue treatment functions.
Abstract:
A system and method for denaturing corneal tissue of a cornea. The system may include an optical recognition system that-can recognize a feature of the corneal. The recognized feature is used to register a desired probe location relative to the cornea. The desired probe location is displayed by a monitor. The system further includes a probe that is coupled to an arm. The arm contains position sensors that provide position information of the probe. The position information is used to map and display the actual position of the probe. By watching the monitor the user can move the probe into the desired probe location relative to the cornea. Once the probe is properly positioned energy is delivered to denature corneal tissue.