The present invention relates to the field of implantable medical devices. More particularly, the present invention relates to cardiac pacing systems that are capable of measure and compare polarization signals to thereby determine an occurrence of a kidney failure.
Implantable pulse generators (or IPGS) are well known in the prior art. After a stimulus in the heart, a charge builds up at the electrode tip, which results in a polarization signal that decays over time. While an initial magnitude of the polarization signal is dependent upon the configuration of the electrode as well as any fibrosis around the electrode tip, ionic concentration in the blood ambient the heart is a major factor in the generation of the initial magnitude. For a patient having a significant risk of experiencing kidney failure, the ionic concentration may increase with each succeeding dialysis of the patient. However, the medical arts have failed to utilize various measurements of the polarization signal to ascertain any increases in the ionic concentration with each succeeding dialysis of the patient.
Thus, prior to the present invention, a need existed in the medical arts for facilitating a determination of a kidney failure by a patient.
Several methods have been proposed in the prior art for to determine various concentrations within the heart of a patient.
For example, U.S. Pat. No. 4,716,887 to Koning et al., entitled xe2x80x9cApparatus And Method For Adjusting Heart/Pacer Rate Relative To Cardiac PCO2 To Obtain A Required Cardiac Output,xe2x80x9d hereby incorporated by reference in its entirety, discloses pacing pulses to the right ventricle of the heart and a pCO2 sensor for sensing pCO2 of the blood in the heart. A microprocessor is programmed to relate the pCO2 with the required heart rate or change in rate, xe2x80xa2R, needed to supply a desired cardiac output and to cause the pacer to pace the heart at the required heart rate when the heart is not naturally paced.
U.S. Pat. No. 4,705,494 to King, entitled xe2x80x9cAutomatic Implantable Fibrillation Preventer,xe2x80x9d hereby incorporated by reference in its entirety, discloses a dual sensing of the probable onset of ventricular fibrillation or other harmful tachyarrythmias and delivering electrical cardioverting stimulation pulses in response thereto. One sensing technique utilizes an intracardiac ECG observed within three dimensional space. The other sensing technique employs a chemically sensitive semiconductor device which measures the level of ionic potassium found within the intracardiac blood.
U.S. Pat. No. 4,899,750 to Ekwall. entitled xe2x80x9cLead Impedance Scanning System For Pacemakersxe2x80x9d, hereby incorporated by reference in its entirety, discloses making separate measurements of lead impedance during each heart signal and each pacing pulse. A moving average of measures parameters is maintained and recurring deviations from the norms are noted in separate event counters for subsequent analysis of the noted events as possible indications of impending failure of an implanted lead.
As discussed above, the most pertinent prior art patents are shown in the following table:
All the patents listed in Table 1 are hereby incorporated by reference herein in their respective entireties. As those of ordinary skill in the art will appreciate readily upon reading the Summary of the Invention, the Detailed Description of the Preferred Embodiments and the Claims set forth below, many of the devices and methods disclosed in the patents of Table 1 may be modified advantageously by using the teachings of the present invention.
The present invention is therefore directed to providing a method and system for managing therapies in a cardiac pacing system. Such a system of the present invention overcomes the problems, disadvantages and limitations of the prior art described above, and provides a more efficient and accurate means of determining kidney failure in a patient.
The present invention has certain objects. That is, various embodiments of the present invention provide solutions to one or more problems existing in the prior art respecting the determination of kidney failure in a patient. Those problems include, without limitation: the lack of knowledge relating to an interpretation of any deflections in a polarization signal as an indication of kidney failure; inability to use ambient heart conditions as indication of kidney failure; inability to track likelihood of kidney failure with succeeding dialysis sessions; inability to determine risk of kidney failure using measurements of the polarization signal; and inability to correlate polarization signal magnitude with potential kidney failure.
In comparison to known techniques for determining kidney failure, various embodiments of the present invention may provide the following advantages, interalia, i.e., use of an implantable medical device in determining an occurrence of kidney failure in a patient; ability to determine ionic concentration in the blood ambient the heart; ability to correlate ionic concentration in the blood with magnitude of a polarization signal; ability to measure potential risk of kidney failure with each succeeding dialysis based on ionic concentration; ability to correlate risk of kidney failure with polarization signals measured by an implantable medical device; and use of one implantable medical device to provide pacing stimulation and concomitantly, to measure potential kidney failure.
Some embodiments of the present invention include one or more of the following features: (a) an IPG capable of measuring ionic concentration in the blood; (b) an IPG capable of determining magnitudes of polarization signals; (c) an IPG capable of correlating ionic concentration with magnitudes of polarization signals; (d) an IPG capable of determining potential kidney failure based on ambient heart conditions; (e) an IPG capable of correlating polarization signals with risk of kidney failure over a period of time (f) methods of determining potential kidney failure based on ambient heart conditions; and (g) methods of correlating magnitudes of polarization signals with risk of kidney failure over time.
At least some embodiments of the invention provide methods for determining kidney failure, such as: (a) a first magnitude of a first polarization signal being determined during a first visit of the patient for a dialysis treatment, a second magnitude of a second polarization signal being determined during a second visit of the patient for a dialysis treatment, and a deflection differential between the first magnitude and the second magnitude being determined and the probability or existence of kidney failure being determined for the patient when the deflection differential exceeds or is greater than an established threshold; (b) a series of discrete and individual historical or chronological polarization signal trends being calculated by comparing a series of presently measured polarization signals respecting previously measured polarization signals, where the polarization trend signals are calculated and stored in memory at predetermined intervals for subsequent retrieval or signal processing; (c) discrete or individual polarization trend signals being employed to alert or warn the patient or a health care professional that the patient has a probability of or is experiencing kidney failure in response to a predetermined polarization trend signal threshold being reached or exceeded; (d) a warning or alert being provided to a remote health care provider through internet or telephonic communication between the implantable medical device and a remote computer, server or database; (e) in response to a warning or alert being generated, the patient and/or health care provider being prompted to arrange dialysis treatment for the patient within a specified time period.