Non-barometric determination of arrhythmia hemodynamic effects using signals sensed by implantable device

Abstract

The present disclosure relates to non-barometric determination of arrhythmia hemodynamic effects using signals sensed by an implantable device. Certain aspects of the present disclosure provide methods, devices, and computer-readable media for determining hemodynamic stability of a subject. In one example method, an optical signal is transmitted via at least one optical fiber of a set of one or more optical fibers disposed in part in a heart of a subject, where the at least one optical fiber in the set is configured to bend with mechanical movement of the heart. A reflected portion of the optical signal is received via at least one optical fiber, wherein a change in at least one parameter of the reflected portion of the received optical signal is indicative of mechanical movement of the heart. A hemodynamic stability of the heart is determined based on the received reflected portion. The hemodynamic stability of the subject may be further determined based on thermal, ultrasound, and / or impedance signals measured in or near the heart.

Description

[0001] This application is a divisional application of an application with an application date of August 5, 2019, application number 201980058913.X, and invention name “Non-pneumatic determination of hemodynamic effects of arrhythmia using signals sensed by an implantable device”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims the benefit of U.S. Patent Application No. 16 / 530,299, entitled “Non-Pneumatic Determination of Hemodynamic Effects of Arrhythmias Using Signals Sensed by an Implantable Device” and filed on August 2, 2019, which U.S. Patent Application No. 62 / 714,217, entitled “Non-Pneumatic Determination of Hemodynamic Effects of Arrhythmias Using Signals Sensed by an Implantable Device” and filed on August 3, 2018, which are expressly incorporated herein by reference in their entirety. Background Art Technical Field

[0004] The present disclosure relates generally to implantable medical devices, and more particularly to determining the hemodynamic effects of arrhythmia in a subject using signals sensed by such implantable devices.

[0005] Related Background

[0006] Deaths from heart disease (approximately 610,000 per year in the United States) are the leading cause of death in the United States and developed countries, with a mortality rate higher than all types of cancer combined. Contrary to common belief, a heart attack is not usually the immediate and direct cause of cardiac death. Rather, most cardiac deaths occur without warning (hence the term sudden cardiac death or SCD), primarily from fatal ventricular arrhythmias (VAs) originating in the ventricles. Fortunately, most of these SCDs caused by VAs are now preventable with the advent of implantable cardioverter / defibrillators (ICDs). ICD implantation has been demonstrated to be the most reliable therapy for reducing SCD mortality in large, randomized, multicenter clinical trials. Currently, accepted clinical indications for ICD implantation include: (1) primary prevention in patients at high risk for SCD who have not had a prior SCD event (e.g., patients with a history of a major heart attack) and (2) secondary prevention in patients who have survived a SCD event. It is important to note that the likelihood of surviving a SCD event without an ICD is very low (<4% if the SCD occurs outside of a hospital). Many of these survivors may suffer brain damage and fall into a vegetative state even if he or she is resuscitated.

[0007] ICDs save lives by delivering a high-energy shock (typically 10-35J) to the heart in an effort to “reset” the electrical activity of the ventricles in an effort to restore normal heart rhythm. Although the delivery of shocks saves lives, these shocks often cause significant discomfort and increase patient morbidity. Both physical and psychological trauma can ensue. Current ICD technology relies entirely on analysis of the heart’s electrical activity or electrocardiogram (i.e., ECG-based technology) to determine whether a shock should be delivered. This technology inevitably leaves patients vulnerable to (1) inappropriate shocks and / or (2) premature shocks.

[0008] An inappropriate shock is an ICD shock that occurs when a nonfatal arrhythmia is misinterpreted as a fatal arrhythmia. A recent study (Journal of American College Cardiology 2011, 57:556–62) showed that 13% of 1,544 ICD patients experienced at least one inappropriate shock during a follow-up period of 41±18 months. In addition, inappropriate shocks increased the risk of all-cause mortality by nearly 50% (hazard ratio or HR: 1.6, p=0.01, where the p value is the probability of observation and p values ​​less than 0.05 are generally considered statistically significant, i.e., as auxiliary evidence for the observation). Each subsequent shock increased the risk of death, and after 5 inappropriate shocks, the HR could reach 3.7. It is worth mentioning that atrial fibrillation was the most common predictor of inappropriate shocks (HR: 2.0, P<0.01), especially for patients under 70 years old (HR: 1.8, p=0.01). Other causes of inappropriate shocks include, but are not limited to, electrical noise and / or interference from external sources, such as strong magnetic fields or electrical interference (e.g., during certain types of welding processes). Noise can be caused by internal causes, such as broken wires in the leads and improper or damaged internal electrical connections. Such noise and / or interference can cause false positive detection of irregular heart rhythms, resulting in inappropriate ICD shocks.

[0009] A premature shock is an ICD shock delivered when a potentially fatal arrhythmia is detected while the patient is still hemodynamically stable and has adequate blood pressure and full consciousness. An ICD is typically unable to predict the duration of an abnormal heart rhythm. For example, an abnormal heart rhythm may last for 10 beats, 20 beats, or for about half an hour or more. Currently, ICDs are configured to deliver a shock after a preset duration, regardless of the patient's hemodynamic state (e.g., a shock is delivered even if the patient still maintains adequate blood pressure). Ideally, in such situations, an ICD shock should be rejected and a less drastic and painless treatment, such as overdrive pacing or anti-tachycardia pacing (ATP), should be applied.

[0010] Therefore, both types of adverse ICD shocks are shortcomings inherited from current ECG-based ICD technology and represent an unmet need for optimal management of patients at increased risk for SCD. Minimizing inappropriate and premature shocks has become the single most important and challenging unsolved problem in today's ICD technology. Therefore, it is desirable to assess the hemodynamic effects or consequences of an ICD shock during an arrhythmia just before it is delivered, so that unnecessary shocks can be aborted as long as the patient is hemodynamically stable. The most intuitive way to assess hemodynamics is to directly record intracardiac or intravascular pressure changes or barometric pressure signals. However, all pressure sensing or barometric pressure technologies depend on displacement of mass, membrane or diaphragm. These technologies work well in acute settings, but for long-term implanted devices, the pressure or barometric pressure sensor is inevitably wrapped by tissue fibrosis, which eventually renders the sensor useless for a period of time (e.g., weeks, months or years), while the expected life of implantable devices has been extended to 7-10 years, or even longer. Currently, no ICD technology available determines hemodynamics during arrhythmia that could minimize or eliminate harmful inappropriate and premature ICD shocks. Summary of the invention

[0011] Certain aspects of the present disclosure generally relate to determining the hemodynamic effects of an arrhythmia using non-pneumatic pressure signals sensed internally and processed by an implantable device. Examples of such non-pneumatic pressure signals may include optical, electrical, thermal, and / or ultrasonic signals.

[0012] Certain aspects of the present disclosure provide a method for determining the hemodynamic stability of a subject. The method generally includes transmitting an optical signal via at least one optical fiber of a group of one or more optical fibers disposed in the heart of the subject, wherein at least one optical fiber in the group is configured to bend with mechanical movement of the heart, the mechanical movement being associated with contraction and relaxation of the heart during a cardiac cycle; receiving a reflected portion of the optical signal via the at least one optical fiber, wherein a change in at least one parameter of the received reflected portion of the optical signal indicates mechanical movement of the heart; and determining the hemodynamic stability of the subject based on the received reflected portion of the optical signal.

[0013] In one aspect, determining hemodynamic stability of the subject includes determining that the subject is hemodynamically unstable if a change in at least one parameter of the reflected portion of the received light signal is below a configurable threshold.

[0014] In one aspect, the method further includes receiving an electrocardiogram signal from one or more electrodes disposed in the subject; and detecting an arrhythmia of the subject based on the electrocardiogram signal, wherein the hemodynamic stability of the subject is determined in response to detecting the arrhythmia; and the determined hemodynamic stability indicates the hemodynamic effects of the detected arrhythmia. For some aspects, the electrocardiogram signal may include one or more types of noise and / or interference. In this case, detecting the arrhythmia may further include analyzing the one or more types of noise and / or interference, and determining a scenario based on the noise and / or interference analysis. The scenario may, for example, indicate at least one of a magnetic field, external electrical interference, damaged internal electrical connection, or lead breakage. For some aspects, detecting the arrhythmia may further include analyzing the one or more types of noise and interference, and detecting the arrhythmia based on the noise and interference analysis and the received reflected portion of the light signal.

[0015] In one aspect, the reflected portion includes a portion of the optical signal reflected from within or proximate to one or more ventricles of the heart.

[0016] In one aspect, the reflected portion includes a portion of the optical signal reflected by at least one optical sensor, such as a fiber Bragg grating sensor within at least one optical fiber.

[0017] In one aspect, determining the hemodynamic stability of a subject includes analyzing changes in at least one parameter of a reflected portion of a received optical signal over a period of time, wherein the change in at least one parameter is a function of at least one of a curvature or a curvature of at least one optical fiber; and determining whether the subject is hemodynamically stable based on the analysis.

[0018] On the one hand, the method also includes receiving a reflected portion of at least one additional optical signal through at least one additional optical fiber in the group, wherein determining the hemodynamic stability of the subject also includes analyzing changes in at least one parameter of the received reflected portion of the at least one additional optical signal over the period of time; combining the results of analyzing the received reflected portion of the optical signal and analyzing the received reflected portion of at least one additional optical signal; and determining whether the subject is hemodynamically stable based on the combined results.

[0019] In one aspect, at least one additional optical fiber can be placed within the subject's heart or in a region within the subject outside of the subject's heart.

[0020] On the one hand, the method also includes receiving electrical signals from electrodes arranged in the subject; analyzing the electrical signals over the period of time; combining the results of analyzing the reflected portion of the received light signal and analyzing the electrical signals; and determining whether the subject is hemodynamically stable during the detected arrhythmia based on the combined results.

[0021] In one aspect, the electrical signal is at least one of an electrocardiogram signal or an impedance signal.

[0022] In one aspect, the at least one optical fiber is disposed in at least one lead of an implantable cardioverter / defibrillator (ICD) implanted in the subject.

[0023] In one aspect, transmitting the optical signal, receiving the reflected portion, and determining the hemodynamic stability of the subject are performed by an implantable device implanted in the subject, either standalone or as part of an ICD, and comprising an optical fiber or a group of optical fibers.

[0024] In one aspect, at least one optical fiber is disposed in a ventricle of the heart.

[0025] On the one hand, at least one parameter used to determine hemodynamic stability includes one or more of the amplitude, phase, delay or wavelength of the reflected portion of the received optical signal, or the rate of change of these parameters, or the drift of their baseline values ​​during one or more cardiac cycles.

[0026] In one aspect, the method further comprises automatically applying an electrical shock to the heart based on a determination of the hemodynamic stability of the subject during the detected arrhythmia.

[0027] On the one hand, the method also includes receiving a thermal signal indicating the temperature of at least a portion of the heart from a temperature sensor disposed in or near the heart of the subject; analyzing at least one parameter of the reflected portion of the received light signal and changes in the thermal signal over a period of time; and combining the results of analyzing the reflected portion of the received light signal and analyzing the thermal signal, wherein the hemodynamic stability of the subject is determined based on the combined results.

[0028] On the one hand, the method also includes receiving a reflected portion of an ultrasound signal from at least one ultrasound sensor arranged in the subject; analyzing changes in at least one parameter of the reflected portion of the received light signal and changes in the reflected portion of the received ultrasound signal over a period of time; and combining the results of analyzing the reflected portion of the received light signal and analyzing the reflected portion of the received ultrasound signal, wherein the hemodynamic stability of the subject is determined based on the combined results.

[0029] Certain aspects of the present disclosure provide an implantable system for implanting in a subject to determine the hemodynamic stability of the subject. The implantable system generally includes an optical fiber or a group of optical fibers configured to be placed in the heart of the subject, wherein at least one optical fiber in the group is configured to bend with the mechanical movement of the heart; at least one light source configured to introduce an optical signal into the at least one optical fiber; at least one receiver configured to receive a reflected portion of the optical signal via the at least one optical fiber, wherein a change in at least one parameter of the received reflected portion of the optical signal indicates the mechanical movement of the heart; and at least one processor configured to determine the hemodynamic stability of the subject based on the received reflected portion of the optical signal.

[0030] In one aspect, the at least one processor is configured to determine hemodynamic stability of the subject by determining that the subject is hemodynamically unstable if the change in the at least one parameter is below a configurable threshold.

[0031] In one aspect, the at least one processor is further configured to receive an electrocardiogram signal from an electrode disposed in the subject; and detect an arrhythmia of the subject based on the electrocardiogram signal, wherein the hemodynamic stability of the subject is determined in response to detecting the arrhythmia; and the determined hemodynamic stability indicates the hemodynamic effect of the detected arrhythmia. For some aspects, the electrocardiogram signal may include one or more types of noise and / or interference. In this case, detecting the arrhythmia may further include analyzing the one or more types of noise and / or interference, and determining a scenario based on the noise and / or interference analysis. The scenario may, for example, indicate at least one of a magnetic field, external electrical interference, damaged internal electrical connection, or lead breakage. For some aspects, detecting the arrhythmia may further include analyzing the one or more types of noise and interference, and detecting the arrhythmia based on the noise and interference analysis and the received reflected portion of the light signal.

[0032] In one aspect, the implantable system further includes one or more leads having a plurality of electrodes configured to be routed in a subject to sense electrocardiogram signals, wherein the at least one optical fiber is disposed within a first group of the one or more leads.

[0033] In one aspect, the implantable system further includes a capacitive element configured to deliver an electrical shock to the heart through a second set of the one or more leads.

[0034] In one aspect, the first set of leads is different from the second set of leads.

[0035] In one aspect, at least one of the at least one light source or the at least one receiver is disposed in the first set of leads.

[0036] In one aspect, one or more leads are configured to receive an electrocardiogram signal, and at least one processor is further configured to analyze changes in at least one parameter of a reflected portion of a received light signal and the electrocardiogram signal over a period of time; and combine the results of analyzing the reflected portion of the received light signal and analyzing the electrocardiogram signal, wherein at least one processor is configured to determine whether the subject is hemodynamically stable based on the combined results.

[0037] In one aspect, the implantable system further includes a memory coupled to the at least one processor and configured to store an electrical representation of at least one of the received reflected portion of the optical signal or the electrocardiogram signal.

[0038] In one aspect, the implantable system further comprises at least one temperature sensor configured for placement in or near the subject's heart, the at least one temperature sensor configured to measure the temperature of at least a portion of the heart, wherein changes in the temperature of the portion of the heart are indicative of hemodynamic stability of the subject.

[0039] In one aspect, at least one processor is further configured to analyze changes in at least one parameter of the received light signal reflected portion and changes in temperature over a period of time; and combine the results of analyzing the received light signal reflected portion and analyzing the temperature, wherein at least one processor is configured to determine the hemodynamic stability of the subject based on the combined results.

[0040] In one aspect, the implantable system further comprises at least one ultrasound transmitter configured to transmit an ultrasound signal into the heart of the subject; and at least one ultrasound sensor configured to receive a reflected portion of the ultrasound signal, wherein changes in the reflected portion of the received ultrasound signal indicate mechanical movement of the heart.

[0041] In one aspect, at least one processor is also configured to analyze changes in at least one parameter of the received light signal reflection portion and the received ultrasound signal reflection portion over a period of time; and combine the results of analyzing the received light signal reflection portion and analyzing the received ultrasound signal reflection portion, wherein at least one processor is configured to determine the hemodynamic stability of the subject based on the combined results.

[0042] In one aspect, the implantable system also includes at least one optical sensor (e.g., a fiber Bragg grating sensor) disposed within at least one optical fiber and having at least one characteristic wavelength range, the at least one fiber Bragg grating being configured to reflect at least a portion of an optical signal within the at least one characteristic wavelength range to produce a reflected portion of the optical signal.

[0043] In one aspect, the reflected portion includes a portion of the optical signal reflected from within or proximate to one or more ventricles of the heart.

[0044] In one aspect, the at least one processor is configured to determine the hemodynamic stability of the subject by: analyzing a change in at least one parameter of a reflected portion of an optical signal over a period of time, wherein the change in the at least one parameter is a function of at least one of a curvature or a curvature of at least one optical fiber; and determining whether the subject is hemodynamically stable based on the analysis. In one aspect, the at least one receiver is configured to receive a reflected portion of at least one additional optical signal via at least one additional optical fiber in the set of optical fibers, wherein the at least one processor is further configured to analyze the reflected portion of at least one additional optical signal received during the period of time; and combining the results of analyzing the received reflected portion of the optical signal and analyzing the reflected portion of the at least one additional optical signal received, wherein the at least one processor is configured to determine the hemodynamic stability of the subject based on the combined results.

[0045] In one aspect, at least one additional optical fiber can be placed within the subject's heart or in a region within the subject outside of the subject's heart.

[0046] In one aspect, the at least one light source comprises at least one of a light emitting diode (LED) or a laser diode, wherein the at least one receiver comprises a photodetector.

[0047] In one aspect, at least one of the at least one light source, at least one receiver, or at least one processor is disposed in an implantable device (eg, an ICD) implanted in a subject.

[0048] In one aspect, a portion of at least one optical fiber is configured for placement in or in close proximity to one or more ventricles of the heart. In one aspect, the at least one parameter includes one or more of the amplitude, phase, delay, or wavelength of the reflected portion of the received optical signal, the rate of change of these parameters, or a drift of its baseline value (e.g., a drift or other change of baseline amplitude, baseline phase, baseline delay, or baseline wavelength) over one or more cardiac cycles.

[0049] Certain aspects of the present disclosure provide a non-transitory computer-readable medium having instructions stored thereon that, when executed by at least one processor, cause the processor to perform operations for determining hemodynamic stability of a subject. The operations generally include transmitting an optical signal via at least one optical fiber of a group of one or more optical fibers disposed in a heart of the subject, wherein at least one optical fiber in the group is configured to bend with mechanical movement of the heart; receiving a reflected portion of the optical signal via the at least one optical fiber, wherein a change in at least one parameter of the received reflected portion of the optical signal indicates mechanical movement of the heart; and determining the hemodynamic stability of the subject based on the received reflected portion of the optical signal.

[0050] In one aspect, determining the hemodynamic stability of the subject includes determining that the subject is hemodynamically unstable if a change in at least one parameter is below a configurable threshold.

[0051] In one aspect, the operation further includes receiving an electrocardiogram signal from an electrode disposed in a subject; and detecting an arrhythmia of the subject based on the electrocardiogram signal, wherein the hemodynamic stability of the subject is determined in response to detecting the arrhythmia; and wherein the determined hemodynamic stability indicates the hemodynamic effects of the detected arrhythmia. For some aspects, the electrocardiogram signal may include one or more types of noise and / or interference. In this case, detecting the arrhythmia may further include analyzing the one or more types of noise and / or interference, and determining a scenario based on the noise and / or interference analysis. The scenario may, for example, indicate at least one of a magnetic field, external electrical interference, damaged internal electrical connection, or lead breakage. For some aspects, detecting the arrhythmia may further include analyzing the one or more types of noise and interference, and detecting the arrhythmia based on the noise and interference analysis and the received reflected portion of the light signal.

[0052] In one aspect, the reflected portion includes a portion of the optical signal reflected from within or proximate to one or more ventricles of the heart.

[0053] In one aspect, the reflected portion includes a portion of the optical signal reflected by at least one optical sensor (eg, a fiber Bragg grating sensor) within at least one optical fiber.

[0054] In one aspect, determining the hemodynamic stability of a subject includes analyzing changes in at least one parameter of a reflected portion of a received optical signal over a period of time, wherein the change in at least one parameter is a function of at least one of a curvature or a curvature of at least one optical fiber; and determining whether the subject is hemodynamically stable based on the analysis.

[0055] On the one hand, the operation also includes receiving a reflected portion of at least one additional optical signal through at least one additional optical fiber in the group, wherein the determining includes analyzing a change in at least one parameter of the received reflected portion of the at least one additional optical signal over the period of time; combining the results of analyzing the received reflected portion of the optical signal and analyzing the received reflected portion of at least one additional optical signal; and determining whether the subject is hemodynamically stable based on the combined results, wherein discrimination of extracardiac motion artifacts or noise is enhanced.

[0056] On the one hand, the operation also includes receiving an electrocardiogram signal from electrodes arranged in the subject; analyzing the electrocardiogram signal during a period of time; and combining the results of analyzing the reflected portion of the received light signal and analyzing the electrocardiogram signal, wherein the hemodynamic stability of the subject is determined based on the combined results.

[0057] In one aspect, the at least one optical fiber is disposed in at least one lead, either as a stand-alone lead or as an integral part of a lead of an ICD or another implantable device implanted into a subject.

[0058] In one aspect, transmitting, receiving, and determining are performed by an implantable device implanted within a subject and coupled to the set of optical fibers.

[0059] In one aspect, at least one optical fiber is disposed in a ventricle of the heart.

[0060] On the one hand, the at least one parameter includes one or more of a change in the amplitude, phase, delay or wavelength of the reflected portion of the received optical signal; a rate of change of these parameters; and / or a drift of its baseline value over one or more cardiac cycles.

[0061] In one aspect, the operations further include automatically applying an electrical shock to the heart based on a determination of the hemodynamic stability of the subject during the detected arrhythmia.

[0062] On the one hand, the operation also includes receiving a temperature signal indicating the temperature of at least a portion of the heart from a temperature sensor disposed in the heart of the subject; analyzing changes in at least one parameter of the received light signal reflection portion and the temperature signal over a period of time; and combining the results of analyzing the received light signal reflection portion and analyzing the temperature signal, wherein the hemodynamic stability of the subject is determined based on the combined results.

[0063] On the one hand, the operation also includes receiving a reflected portion of an ultrasound signal from an ultrasound sensor arranged in the subject; and combining the results of analyzing the received reflected portion of the optical signal and the received reflected portion of the ultrasound signal, wherein the hemodynamic stability of the subject is determined based on the combined results.

[0064] Certain aspects of the present disclosure provide a method for determining the hemodynamic stability of a subject. The method generally includes transmitting an ultrasonic signal to at least one anatomical reference structure in the heart of the subject using an ultrasonic transmitter within a given time period; receiving a reflected portion of the ultrasonic signal using an ultrasonic receiver within the given time period; analyzing the reflected portion of the ultrasonic signal within the time period to determine a change in the distance between the ultrasonic receiver and the at least one anatomical reference structure during a cardiac cycle, wherein the change indicates mechanical movement of the heart; and determining the hemodynamic stability of the subject based on the mechanical movement of the heart.

[0065] In one aspect, an ultrasound transmitter and an ultrasound receiver are placed in a region outside of the heart within a subject.

[0066] In one aspect, an ultrasound transmitter and an ultrasound receiver are integrated within an ICD that is implanted within a subject.

[0067] In one aspect, an ultrasound transmitter and an ultrasound receiver are placed within the heart of a subject.

[0068] In one aspect, an ultrasound transmitter and an ultrasound receiver are disposed in at least one lead of an ICD implanted in a subject.

[0069] In one aspect, the method further includes receiving an electrocardiogram signal from one or more electrodes disposed in the subject; and detecting an arrhythmia of the subject based on the electrocardiogram signal, wherein the hemodynamic stability of the subject is determined in response to detecting the arrhythmia; and the determined hemodynamic stability indicates the hemodynamic effects of the detected arrhythmia. For some aspects, the electrocardiogram signal may include one or more types of noise and / or interference. For some cases, detecting an arrhythmia may further include analyzing the one or more types of noise and / or interference, and determining a scenario based on the noise and / or interference analysis. The scenario may, for example, indicate at least one of a magnetic field, external electrical interference, damaged internal electrical connection, or lead breakage. For other cases, detecting an arrhythmia may further include analyzing the one or more types of noise and interference, and detecting an arrhythmia based on the noise and interference analysis and the reflected portion of the ultrasound signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] In order that the manner in which the above-mentioned features of the present disclosure are understood in detail, a more specific description briefly summarized above may be made by reference to various aspects, some of which are illustrated in the accompanying drawings. It should be noted, however, that the accompanying drawings illustrate only certain typical aspects of the present disclosure and are therefore not to be considered limiting of its scope, as the description may admit of other equally effective aspects. Figure 1An implantable cardioverter / defibrillator (ICD) is shown as an example implantable device in accordance with certain aspects of the present disclosure. Figure 2 An example ultrasound transceiver configuration is shown in which the ultrasound transceiver is built into the ICD leads in accordance with certain aspects of the present disclosure.

[0071] Figure 3 An example ultrasound transceiver configuration is shown in which one or more ultrasound transceivers are built into an ICD generator in accordance with certain aspects of the present disclosure.

[0072] Figure 4 is a flow chart of example operations for determining hemodynamic stability of a subject in accordance with certain aspects of the present disclosure.

[0073] Figure 5

[0013] Shown is a portion of an implantable system for determining hemodynamic stability in a subject using optical signals, according to certain aspects of the present disclosure.

[0074] Fig. 6A , Figure 6B and Figure 6C Shown are example recorded optical signals during a representative experiment including monitoring mechanical motion of a subject's heart based on the optical signals, according to certain aspects of the present disclosure.

[0075] Figure 7 Example operations for determining hemodynamic stability of a subject using ultrasound signals in accordance with certain aspects of the present disclosure are shown. DETAILED DESCRIPTION

[0076] Certain aspects of the present disclosure provide methods and apparatus for determining the hemodynamic effects of an arrhythmia (e.g., a lethal ventricular arrhythmia) in a subject by sensing mechanical motion of the subject's heart using an optical signal sensed by an implantable device (e.g., an ICD). In certain aspects, one or more optical fibers are placed in the subject's heart, which may extend to adjacent vascular segments of the heart, wherein the optical fibers bend as the heart contracts and relaxes (during systole and diastole). At least one parameter (e.g., amplitude, phase shift / delay, and / or wavelength) associated with the optical signal passing through the optical fiber changes as the optical fiber is bent, wherein changes in the parameters of the optical signal indicate mechanical motion of the heart. At least one processor of the implantable device, for example, in response to detecting an arrhythmia (e.g., based on an electrocardiogram signal), analyzes changes in the parameters of the optical signal and determines whether the mechanical motion of the heart is sufficiently reduced to indicate hemodynamic instability in the subject during the detected arrhythmia. If this analysis indicates that the subject is experiencing a life-threatening arrhythmia associated with hemodynamic instability, the processor (eg, in the case of an ICD) may activate the ICD to deliver an ICD shock to the subject's heart in an attempt to restore the heart's normal rhythm.

[0077] Various aspects of the present disclosure are described more fully below with reference to the accompanying drawings. However, the present disclosure can be implemented in many different forms and should not be interpreted as being limited to any specific structure or function presented throughout the present disclosure. Instead, these aspects are provided so that the present disclosure will be thorough and complete, and the scope of the present disclosure will be fully conveyed to those skilled in the art. Based on the teachings of this article, it should be understood by those skilled in the art that the scope of the present disclosure is intended to cover any aspect of the present disclosure disclosed herein, whether independent of any other aspect of the present disclosure or implemented in combination with any other aspect of the present disclosure. For example, a device may be executed or a method may be practiced using any number of aspects set forth herein. In addition, the scope of the present disclosure is intended to cover such a device or method, which uses other structures, functions, or structures and functions in addition to or in addition to the various aspects of the present disclosure set forth herein to practice. It should be understood that any aspect of the present disclosure disclosed herein may be embodied by one or more elements of a claim.

[0078] As used herein, the term "determining" encompasses a wide variety of actions. For example, "determining" may include arithmetic, calculation, processing, derivation, investigation, lookup (e.g., lookup in a table, database, or another data structure), ascertainment, etc. Also, "determining" may include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory), etc. Also, "determining" may include parsing, selecting, choosing, establishing, etc.

[0079] As used herein, the term "subject" may refer to a human or another animal, such as a pig or a dog.

[0080] Example implantable device

[0081] An implantable device may include any device that can be implanted in a subject. Examples include an implantable cardioverter / defibrillator (ICD), a pacemaker capable of pacing the heart at one or more locations, an implantable electrocardiograph (or EKG) device (capable of recording EKG signals), and the like.

[0082] Figure 1 An ICD 100 having leads 102 fed through a blood vessel (e.g., a vein) to a heart 120 is shown as an example of an implantable device for use with certain aspects of the present disclosure. Although the term "ICD" is used throughout the present disclosure for ease of description, the reader will understand that the term "ICD" may be replaced by "implantable device" throughout the text, and certain aspects of the present disclosure will perform the techniques described herein with any suitable implantable device capable of performing similar functions. Figure 1 A four-chambered heart 120 is shown having a right atrium 122, a left atrium 124, a right ventricle 126, and a left ventricle 128. Figure 1 A four-chambered heart is shown in FIG. 4 as a non-limiting example, but aspects of the present disclosure may also be applied to hearts having more or less than four chambers (eg, a three-chambered heart), for example due to congenital defects.

[0083] The ICD 100 may include: (1) a generator 104 and (2) a number of leads 102, which are typically metal wires with a plurality of electrodes 103 embedded in the leads. The generator 104 may include a housing unit or "can" (typically made of titanium or another suitable metal). The housing unit may contain integrated circuits (ICs) (e.g., at least one processor and associated memory, as well as analog, digital, and / or hybrid (e.g., hybrid) electronic integrated circuits), a battery, capacitive elements (e.g., capacitors) for storing charge and delivering shocks, and / or other hardware components (e.g., signal processing) for detecting arrhythmias and delivering ICD shocks in accordance with aspects of the present disclosure. Although in the Figure 1 Three leads 102 are shown in FIG. 1 as a non-limiting example, but aspects of the present disclosure may use more or less than three leads.

[0084] The ICD generator 104 is typically implanted subcutaneously in the left or right chest region, but can be implanted in any of a variety of suitable regions within the subject. For example, the ICD generator 104 can alternatively be implanted subcutaneously in the upper abdomen or other regions of the body adjacent to the heart. The ICD lead 102 is connected to the generator 104 at one end and inserted into different cardiac chambers (e.g., right atrium 122 and right ventricle 126) at the other end (e.g., through the subclavian or axillary vein) or into the pericardial space around the heart. At least some of the electrodes on the ICD lead 102 can be used to transmit current, for example, to excite the myocardium (similar to a pacemaker) or to vibrate the heart in order to reset a lethal VA (e.g., defibrillation or ICD shock) with high energy. At least some of the electrodes on the ICD lead 102, which may be the same or different from the electrodes used to transmit current, can be used to sense the electrical activity of the heart 120 (e.g., an electrocardiogram). In certain aspects, ICD 100 may detect cardiac arrhythmias from abnormal electrical activity sensed by one or more of these electrodes 103 based on existing techniques (eg, electrocardiogram-based techniques).

[0085] In some aspects, in addition to or in lieu of the ICD lead 102, the ICD 100 also includes a set of optical fibers configured for placement in the heart 120. The set of optical fibers may extend to adjacent vascular segments of the heart, wherein at least one optical fiber in the set is configured to bend with mechanical movement of the heart. The ICD 100 may include at least one light source or optical transmitter (e.g., a light emitting diode (LED) or a laser diode) configured to introduce an optical signal (e.g., an optical signal) into at least one optical fiber in the set. The ICD 100 may also include at least one optical receiver (e.g., a photodetector) configured to receive a reflected portion of the optical signal via an optical fiber. The optical transmitter may convert an electrical signal into an optical signal (e.g., an optical signal that may be composed of one or more frequency components on a visible spectrum and / or an invisible spectrum) under the control of at least one processor in the ICD 100 and may emit the optical signal into at least one optical fiber. The optical receiver may receive the reflected portion of the optical signal from at least one optical fiber and convert the received optical signal into an electrical signal (e.g., using a photodetector), which is then fed back to at least one processor for analysis. In one aspect, both the light source and the light receiver are built into a single component (e.g., an optical transceiver) on an integrated circuit (IC) that is coupled to an optical fiber at one end and to the rest of the circuitry at the other end, which may include a signal processing unit and / or at least one processor on the other end.

[0086] In certain aspects, at least one processor disposed in the generator 104 can analyze changes in one or more parameters of the received optical signal. For example, the at least one processor can analyze changes in the amplitude (e.g., intensity) of the received optical signal due to changes in the angle of incidence, and / or can analyze changes in the phase shift / delay of the received optical signal due to changes in the optical path length, or can analyze changes in the wavelength of the received optical signal due to bending of one or more optical fibers. In one aspect, changes in amplitude, changes in phase shift / delay, and shifts in wavelength of the optical signal indicate changes in the amount of bending of the optical fiber determined by mechanical movement of the heart due to the contractile function of the heart.

[0087] In certain aspects, at least one processor disposed in the generator 104 can determine the hemodynamic stability of the subject (e.g., during an electrocardiogram-based detected arrhythmia) based on such analysis of one or more parameters of the received optical signal (e.g., changes in amplitude, phase shift / delay, and / or wavelength) and its correlation with direct hemodynamic measurements, such as, but not limited to, blood pressure, cardiac output, cardiac filling pressures, and / or cardiac chamber volumes, in the form of regression formulas, lookup table (LUT) data, quantitative or semi-quantitative cutoff values, and / or other reference data derived deterministically or stochastically. In this manner, the at least one processor can determine, based on the analysis, whether the mechanical function of the heart is sufficient to maintain hemodynamic stability during a detected arrhythmia.

[0088] The at least one processor can determine whether the heart is experiencing a potentially fatal arrhythmia (e.g., a fatal ventricular arrhythmia (VA)) based on the determined hemodynamic state of the subject. In one aspect, a portion of at least one optical fiber is configured for placement in a ventricle (e.g., right ventricle 126) of the heart 120, and the at least one processor is configured to determine whether the heart is experiencing a potentially fatal VA.

[0089] The set of optical fibers can be used to continuously monitor the mechanical motion of the heart in certain aspects or only when an arrhythmia is detected in other aspects. The optical fibers in the set can be implemented as one or more independent leads, or incorporated as part of one or more ICD leads.

[0090] In one aspect, each optical fiber in the group physically bends with the mechanical motion of the heart, typically having a maximum bend or deviation from its resting "relaxed" position at the end of systole at the end of diastole. As the optical fiber bends, one or more parameters (e.g., amplitude, phase shift / delay, and / or wavelength) of the optical signal propagating through the optical fiber also change. When the heart beats normally with strong mechanical motion, the changes in these parameters reach their maximum, indicating normal hemodynamic stability. When the contractile function of the heart is impaired (e.g., during faster lethal ventricular tachycardia) or essentially stops (e.g., during ventricular fibrillation), the changes in one or more of these optical signal parameters may be greatly reduced or become minimal or even flattened due to fibrillatory motion. In addition, the baseline levels of these parameters at the end of diastole may vary with the ventricular end-diastolic volume, and the rate of change during the cardiac cycle may also be related to changes in the contractility and relaxation of the ventricles. The algorithm stored in the ICD memory can configure at least one processor disposed in the generator 104 to sense changes in the received optical signals and determine whether the mechanical or contractile function of the heart remains normal or is impaired. On the one hand, the mechanical movement of the heart indicates the hemodynamic stability of the subject. If an arrhythmia is detected, the algorithm can configure at least one processor to determine whether the subject is hemodynamically unstable, and if so, an ICD shock or other appropriate therapy can be triggered to restore normal heart rhythm. As described above, such determination of hemodynamic stability / instability can be based on the optical signals, utilizing their correlation with direct hemodynamic measurements, such as but not limited to blood pressure, cardiac output, cardiac filling pressures, and / or cardiac chamber volumes, in the form of regression formulas, lookup table data, quantitative or semi-quantitative cutoff values, and / or other reference data derived deterministically or stochastically.

[0091] In certain aspects, because the triggering of an ICD shock is based not only on the detection of an arrhythmia from an electrical signal (e.g., an electrocardiogram), but also on the hemodynamic stability of the subject from sensing the mechanical movement of the heart, the occurrence of inappropriate or premature ICD shocks to the heart can be greatly reduced or eliminated.

[0092] In one aspect, one end of the one or more optical fibers is connected to the generator 104 and the other end is inserted into a different cardiac chamber (e.g., right atrium 122 and right ventricle 126) (e.g., via a subclavian or axillary vein). In one aspect, the one or more optical fibers are disposed within the lead 102. In another aspect, the one or more optical fibers can be configured as a standalone lead (e.g., not used as an ICD or pacemaker lead).

[0093] In one aspect, the light source and light receiver (or optical transceiver) are disposed within the generator 104. For example, the ICD 100 can include one or more optical transceivers to send and receive optical signals via one or more optical fibers. In one aspect, the optical signal can include light at any wavelength in the visible and / or invisible wavelengths (e.g., ultraviolet (UV) or infrared (IR) light).

[0094] In one aspect, the light source and receiver (or optical transceiver) can be disposed within an ICD or pacemaker lead or within a separate lead having one or more optical fibers therein for sending and receiving optical signals via the one or more optical fibers. In this case, an electrical wire (e.g., a metal wire) can connect the optical transceiver with the generator 104 to provide power to the transceiver (e.g., from a battery housed in a can).

[0095] In one aspect, an optical receiver or transceiver receives a portion of the transmitted optical signal reflected from within the same or different optical fiber, which may be routed to and partially disposed in the heart of the subject and may extend into an adjacent vascular segment of the heart. In one aspect, at least one optical fiber may have one or more optical reflection mechanisms, such as a fiber Bragg grating (FBG) configured with at least one characteristic wavelength and / or another optical reflection component (e.g., a fiberscope) disposed in the optical fiber. A receiver or transceiver may receive a portion of the optical signal reflected by at least one of the optical reflection mechanisms (e.g., FBGs).

[0096] In certain aspects, at least one processor of the generator 104 can be configured to combine the results of an analysis of electrical signals (e.g., an electrocardiogram) from the electrodes with the results of an analysis from the optical signals in order to more accurately determine a potentially fatal arrhythmia. For example, at least one processor can detect an arrhythmia based on the electrocardiogram signal, and in response, can further determine the hemodynamic stability of the subject based on the optical signals. If the subject is determined to be hemodynamically unstable, the at least one processor can decide to deliver an electric shock to the heart. Thus, at least one processor can determine the hemodynamic effects of an arrhythmia based on the optical signals (e.g., based on the electrical signal detection), and can decide to deliver an electric shock to the heart in the presence of a detected arrhythmia based on a determination of the hemodynamic instability of the heart.

[0097] In some aspects, multiple optical fibers are routed to and partially arranged in the heart and can extend into adjacent vascular segments of the heart to provide redundancy and distinguish the effects of mechanical motion of the heart from the effects of external or extracardiac motion. In this case, at least one processor of the generator 104 can be configured to receive multiple optical signals from multiple optical fibers and combine the results of analyzing the multiple optical signals to try to detect the hemodynamic stability of the heart. In this case, one or more additional optical fibers / sensors can be placed in different areas of the heart to monitor the mechanical motion of these different areas. The results from these different optical fibers / sensors can be combined to determine the hemodynamic stability of the heart. In one aspect, multiple optical sensors can be integrated into one or more ICD leads that traverse the heart at different locations on the ICD leads. Additionally or alternatively, one or more additional optical fibers / sensors can be placed in areas outside the heart of the subject to monitor non-cardiac body motion. These non-cardiac body motions determined based on these additional optical sensors can be eliminated in order to determine the motion of the heart.

[0098] In certain aspects, the ICD 100 includes one or more temperature sensors configured for placement in the subject's heart 120. The temperature sensor measures the temperature of at least a portion of the heart, wherein changes in the temperature of the portion of the heart can indicate reduced blood flow during an arrhythmia, which in turn can indicate an abnormal heart rhythm. In certain aspects, at least one processor of the generator 104 is configured to analyze temperature changes within the heart over a period of time and combine the thermal data with results of analyzing optical signals received over the same period of time. At least one processor can be configured to determine whether the heart is functioning properly based on the combined optical and thermal results and using correlations between the optical and thermal signals and direct hemodynamic measurements, such as but not limited to blood pressure, cardiac output, cardiac filling pressures, and / or cardiac chamber volumes, and therefore determine whether the subject is hemodynamically stable, wherein the correlations are in the form of regression formulas, lookup table data, quantitative or semi-quantitative cutoffs, and / or other reference data derived deterministically or stochastically.

[0099] In certain aspects, changes in the temperature of the heart can be measured based on changes in one or more parameters of an optical signal transmitted via an optical fiber routed to the heart and partially disposed in the heart. In one aspect, the temperature measurement by the optical fiber placed in the heart can change as the temperature of the heart changes, thereby changing the wavelength / frequency of the optical signal transmitted via the optical fiber. Therefore, changes in the wavelength / frequency of the optical signal are indicative of changes in the temperature of the heart. A photodetector receiving the optical signal can detect changes in the wavelength / frequency of the received optical signal, and a change in the temperature of the heart can be determined based on the changes in the wavelength / frequency of the detected optical signal.

[0100] In certain aspects, the ICD 100 includes at least one ultrasound transmitter (e.g., a piezoelectric transducer) configured to transmit an ultrasound signal to at least one anatomical reference structure within the heart 120 (e.g., an intraventricular septum) and / or surrounding the heart (e.g., a sternum), and at least one ultrasound sensor configured to receive a reflected portion of the ultrasound signal. For certain aspects, the ultrasound transmitter and ultrasound sensor can be physically integrated into an ultrasound transceiver. The reflected ultrasound signal can be analyzed to determine a change in the distance between the transceiver and at least one anatomical reference during a heartbeat or cardiac cycle, which can indicate mechanical movement of the heart. In one aspect, the ultrasound transmitter and / or ultrasound receiver (or transceiver) are configured for attachment to a lead and can be arranged as a separate lead or incorporated into the ICD lead 102.

[0101] Figure 2 An example ultrasound transceiver configuration 200 is shown in accordance with certain aspects of the present disclosure, wherein the ultrasound transceiver is built into an ICD lead 102. One or more ultrasound transceivers 202 may be built into the ICD lead 102 and may be configured to transmit ultrasound signals and detect portions of the transmitted ultrasound signals reflected from various structures having different ultrasound features 204 within the heart (e.g., ventricular free walls and interventricular septum) and / or outside the heart (e.g., the subject's sternum). In certain aspects, multiple ultrasound transmitters (or transceivers) may be embedded into the ICD lead 102. In this case, each transmitter (or transceiver) may be configured to transmit ultrasound signals in different directions within the subject's heart. For example, at least one transceiver may be mounted on the tip of the lead with the ultrasound beam facing forward, or conversely, one or more transceivers may be mounted on the side of the lead with the ultrasound beam pointing laterally. In one aspect, a combination of forward and lateral configurations may be used, i.e., one or more ultrasound transceivers may be mounted on the tip and one or more ultrasound transceivers may be mounted laterally. In one aspect, data from reflected ultrasound signals received from different directions within the heart can be combined to generate a more accurate representation of heart motion. In one aspect, the collected data can be used to generate a real-time three-dimensional model of the heart to help monitor the mechanical motion of the heart in real time.

[0102] In this example configuration, an electrical wire (e.g., a metal wire) may connect the transceiver 202 with the generator 104 to provide power to the transceiver (e.g., from a battery housed in a can). Additionally, the transceiver may transmit data collected from the received reflected ultrasound signals to the generator 104 by transmitting the data over an additional data line disposed between the transceiver and the generator 104, or by transmitting the data wirelessly to the generator 104.

[0103] Data related to the reflected ultrasound signal can also be retrieved from the ICD, for example, via telemetry (e.g., a telemetry wand), and analyzed by an external processing system (e.g., which includes one or more processors outside the subject's body), for example, to generate a real-time model of the heart. Such a processing system can also be a radio frequency (RF) (e.g., ) or other remote communication technology to communicate with the ICD part of a remote centralized patient monitoring center.

[0104] In one aspect, the ultrasound transmitter and / or ultrasound receiver (or transceiver) is configured for placement in a suitable area of ​​the subject outside the heart 120 of the subject. For example, the ultrasound transceiver may be integrated into the generator 104 of the ICD 100, or may be implanted in a suitable area of ​​the subject as a separate device (i.e., separate from the generator 104). For example, the transceiver may be implanted subcutaneously in the left or right thoracic region, or in any of a variety of other suitable areas within the subject, such as in the upper abdomen or other areas of the body adjacent to the heart. When implanted as a separate device, an electrical wire (e.g., a metal wire) may connect the ultrasound transceiver to the generator 104 to provide power to the transceiver (e.g., from a battery contained in a can). In addition, the transceiver may transmit data collected from the received reflected ultrasound signal to the generator 104 by transmitting data on an additional data line arranged between the transceiver and the generator 104, or by wirelessly transmitting the data to the generator 104. When used in an external configuration, the ultrasound transceiver may be configured to transmit ultrasound signals in the general direction of the heart. In one aspect, signals reflected from ICD leads 102 placed within the heart can be more apparent than signals reflected from cardiac tissue. Since ICD leads 102 are at least partially made of metal, the leads will have a stronger reflection than cardiac tissue. In one aspect, since ICD leads 102 move with the mechanical movement of the heart, cardiac motion can be tracked by tracking the movement of ICD leads 102.

[0105] Figure 3An example ultrasound transceiver configuration 300 is shown according to certain aspects of the present disclosure, wherein the ultrasound transceiver is built into the ICD generator 104. The ultrasound transceiver 302 is integrated into the ICD generator housing. The transceiver 302 transmits ultrasound signals in the general direction of the heart and detects signals reflected from different heart surfaces, structures within the heart, and at least some portions of the ICD lead 102 placed within the heart. Since the reflections from the ICD lead 102 are much stronger and distinguishable from reflections from other organic heart tissues, the movement of the ICD lead can be easily tracked. The received ultrasound signals can be analyzed (e.g., by one or more processors) to track the movement of the ICD lead 102 and determine cardiac motion based on the tracked movement of the ICD lead 102. For example, the ultrasound signals can be analyzed to determine changes in the distance between the transceiver and at least one anatomical reference during a heartbeat or cardiac cycle, which can indicate mechanical motion of the heart. In one aspect, the surface of the ultrasound transceiver can be shaped to be flat, concave, or convex to optimize the detection of the ICD lead.

[0106] An advantage of this approach is that stray ultrasound signals reflected from other organs (eg, the lungs) may not affect the determination because the reflection from the ICD lead 102 will be clearly distinguishable from the other reflections.

[0107] In one aspect, at least a portion of the lead motion can be caused by the subject's whole body motion. In one aspect, one or more accelerometers can be used to detect other body motions of the subject, and these body motions can be eliminated from determining the lead motion caused by the heart motion.

[0108] In some aspects, at least one processor in the generator 104 is configured to analyze the received ultrasound signals over a period of time and combine the ultrasound data with the results of analyzing the received optical signals over the same period of time. At least one processor can be configured to determine whether the heart is functioning properly and, therefore, whether the subject is hemodynamically stable based on the combined optical and ultrasonic results and using correlations between the optical and ultrasonic signals and direct hemodynamic measurements, such as but not limited to blood pressure, cardiac output, cardiac filling pressures, and / or cardiac chamber volumes, in the form of regression formulas, lookup table data, quantitative or semi-quantitative cutoffs, and / or other reference data derived deterministically or stochastically. In some aspects, the ICD 100 can be connected to electrodes embedded in separate leads or incorporated into the ICD leads 102 to measure impedance changes within at least one chamber of the heart (e.g., the right ventricle 126) during a heartbeat or cardiac cycle. In one aspect, the impedance within the ventricle changes with changes in the volume of the heart due to mechanical contraction and relaxation of the heart. Thus, changes in impedance indicate mechanical movement of the heart. In certain aspects, at least one processor in the generator 104 is configured to analyze the received impedance signal over a period of time and combine the results with the results of analyzing the received optical signal over the same period of time. The at least one processor is configured to determine whether the heart is functioning properly and, therefore, whether the subject is hemodynamically stable based on the combined optical and impedance results and utilizing correlations between the impedance and optical signals and direct hemodynamic measurements such as, but not limited to, blood pressure, cardiac output, cardiac filling pressures, and / or cardiac chamber volumes in the form of regression formulas, lookup table data, quantitative or semi-quantitative cutoffs, and / or other reference data derived deterministically or stochastically.

[0109] In certain aspects, at least one processor can be configured to determine the hemodynamic stability of the subject based on the optical signal, thermal signal, ultrasound signal, or impedance signal independently, or based on a combination of two or more of these foregoing signals, and utilizing their correlation with direct hemodynamic measurements, such as but not limited to blood pressure, cardiac output, cardiac filling pressures, and / or cardiac chamber volumes, wherein the correlation is in the form of regression formulas, lookup table (LUT) data, quantitative or semi-quantitative cutoff values, and / or other reference data derived deterministically or stochastically.

[0110] In some aspects, radio frequency (RF) signals can be used to detect changes in the mechanical movement of the heart. For example, the electrode 103 can be configured to transmit RF signals within the heart and receive RF signals reflected from within the heart (e.g., RF signals reflected from heart tissue / walls). At least one processor can analyze the reflected RF signals and determine whether the heart is mechanically compromised, and thereby determine the hemodynamic stability of the subject. For some aspects, this use of RF signals can be combined with any other techniques described herein, such as using electrocardiograms, light, heat, ultrasound, and / or impedance signals to determine hemodynamic stability.

[0111] In some aspects, the ICD itself (more specifically, a processor within the ICD) or another implantable device (e.g., a second device other than the ICD) can perform a quantitative analysis of at least one of the optical signals, electrocardiographic signals, thermal signals, impedance signals, or ultrasonic signals sensed and / or stored by the implantable device to determine whether the heart is experiencing a fatal arrhythmia. Alternatively, data related to at least one of the received optical signals, electrocardiographic signals, thermal signals, impedance signals, or ultrasonic signals (e.g., stored and / or currently sensed signals) can be retrieved, for example, via telemetry (e.g., a telemetry wand) and analyzed by an external processing system (e.g., one or more processors thereof outside the subject's body). Such a processing system can also be a system that processes the signal received via radio frequency (RF) (e.g., ) or other remote communication technology to communicate with the ICD part of a remote centralized patient monitoring center.

[0112] In certain aspects, the at least one processor can be configured to determine whether the heart is experiencing an arrhythmia based on the electrocardiogram signal, and to determine the hemodynamic effects of the detected arrhythmia based on one or a combination of optical signals, thermal signals, impedance signals, or ultrasound signals sensed and / or stored by the implantable device to determine whether the detected arrhythmia is lethal. The at least one processor can be configured to: if the subject is determined to be hemodynamically unstable, such as by utilizing a correlation with a direct hemodynamic measurement, such as but not limited to blood pressure, cardiac output, cardiac filling pressures, and / or cardiac chamber volumes, the correlation being in the form of a regression formula, lookup table data, quantitative or semi-quantitative cutoff values, and other reference data derived deterministically or stochastically.

[0113] Figure 44 is a flow chart of example operations 400 for determining hemodynamic stability of a subject (e.g., a human patient or an animal) according to certain aspects of the present disclosure. Operations 400 may be performed by an implantable device such as ICD 100. For certain aspects, at least some of operations 400 may be performed by a telemetry device (e.g., via radio frequency (RF), such as or other wireless communication technology) and one or more processors coupled to the telemetry device and configured to read the signals received from the implantable device via the telemetry device. For example, the system may include a wireless communication method (e.g., technology, other RF signals or other telecommunication technologies) to communicate with the ICD programmer. The system can also be a programmer that communicates with the ICD via RF (e.g. ) or other wireless communication technologies. At block 402, operation 400 begins by transmitting an optical signal via at least one optical fiber of a group of one or more optical fibers partially disposed in a heart of a subject, the optical fiber may extend into an adjacent blood vessel segment of the heart, wherein at least one optical fiber in the group is configured to bend with mechanical movement of the heart.

[0114] At block 404, a reflected portion of the optical signal is received via at least one optical fiber, wherein a change in at least one parameter of the received reflected portion of the optical signal indicates mechanical motion of the heart. In one aspect, the at least one parameter includes one or more of amplitude, phase, or delay of the optical signal.

[0115] At block 406, hemodynamic stability of the subject is determined based on the received reflected portion of the light signal.

[0116] In one aspect, determining the hemodynamic stability of the subject includes determining that the subject is hemodynamically unstable if mechanical motion of the heart is below a configurable threshold (eg, for a period of time).

[0117] In one aspect, an electrocardiogram signal (also referred to as an electrocardiogram signal) is sensed by one or more electrodes arranged in a subject, and an arrhythmia is detected in the subject based on the electrocardiogram signal. In response to detecting the arrhythmia, the hemodynamic stability of the subject is determined, wherein the determined hemodynamic stability indicates the hemodynamic effect of the detected arrhythmia. In certain aspects, in order to determine the hemodynamic stability of the subject, a change in at least one parameter of a reflected portion of a received optical signal is analyzed over a period of time, wherein the change in at least one parameter is a function of at least one of the degree of bending or the rate of bending of at least one optical fiber (e.g., as reflected by the first-order derivative of the reflected portion of the received optical signal). Based on the analysis, it is determined whether the subject is hemodynamically stable. In one aspect, the change in at least one parameter indicates mechanical movement of the heart, and therefore, analyzing these changes indicates whether the mechanical or contractile function of the heart is normally manifested or impaired. In one aspect, if the analysis of the optical signal indicates that the mechanical movement of the heart is sufficiently impaired to indicate hemodynamic instability, it can be determined that an ICD shock will be delivered to the heart in an effort to restore the normal rhythm of the heart.

[0118] In some aspects, the ICD initially detects a potentially fatal arrhythmia based solely on electrical signals (e.g., an internal electrocardiogram). However, the ICD currently does not decide whether to deliver an ICD shock based solely on the detected arrhythmia. Instead, in response to detecting an arrhythmia, the ICD monitors and analyzes optical signals as described above in an attempt to determine the hemodynamic effects of the detected arrhythmia. When hemodynamic instability of the subject is detected in response to the detected arrhythmia, the ICD decides to deliver an electric shock to the subject's heart. For example, if hemodynamic instability is detected, indicating that the mechanical function of the heart is severely impaired, sufficient to cause hypotension, the ICD may decide to deliver an electric shock in an attempt to restore the normal rhythm of the heart. On the other hand, if hemodynamic stability is determined, indicating that the reduction in the mechanical function of the heart is not sufficient to cause hypotension, the ICD shock may be prevented, thereby minimizing or avoiding inappropriate and / or premature ICD shocks.

[0119] In some aspects, operation 400 also includes receiving reflected portions of one or more additional optical signals via one or more additional optical fibers in the group. Changes in at least one parameter of the additional received optical signals are analyzed over the same time period, and the results of analyzing the received first optical signal and analyzing the received additional optical signals are combined. Determining whether the subject is hemodynamically stable based on the combined results can increase the sensitivity and specificity of the hemodynamic determination, especially in the presence of external or extracardiac mechanical motion or noise. This is because cardiac motion can cause different effects in optical fibers placed at different locations in the heart or along different sides of the same ICD lead, while extracardiac motion often causes similar effects on all intracardiac optical fibers.

[0120] In some aspects, operation 400 also includes: receiving an electrocardiogram signal and other electrical signals, such as impedance measurements, from one or more electrodes disposed in a subject (e.g., a heart of the subject) during the same time period; and analyzing the electrocardiogram signal and other electrical signals, such as impedance measurements. The results of analyzing the reflected portion of the received light signal and analyzing the electrocardiogram and electrical signals are combined. In this case, it can be determined whether the subject is hemodynamically stable during the arrhythmia based on the combined results.

[0121] In some aspects, operation 400 also includes receiving a thermal signal indicating a temperature change of at least a portion of the heart from a temperature sensor disposed in the heart of the subject. The thermal signal is analyzed over the same time period and the analysis results are combined with the results of analyzing the reflected portion of the received optical signal. In this case, it can be determined whether the subject is hemodynamically stable based on the combined results.

[0122] In some aspects, operation 400 also includes: receiving a reflected portion of an ultrasound signal from an ultrasound sensor disposed in the subject during the same time period and analyzing the reflected portion of the received ultrasound signal. The result of analyzing the reflected portion of the received ultrasound signal is combined with the result of analyzing the received optical signal. In this case, it can be determined whether the subject is hemodynamically stable based on the combined result.

[0123] In one aspect, the reflected portion of the optical signal comprises a portion of the optical signal reflected from within a portion of the heart (e.g., a ventricle). In one aspect, the reflected portion of the optical signal comprises a portion of the optical signal reflected by at least one optical reflection mechanism (e.g., a fiber Bragg grating) within at least one optical fiber.

[0124] According to certain aspects, the implantable device is capable of delivering an electrical shock to the heart of a subject, for example, based on a determination that the heart is experiencing a potentially fatal arrhythmia (e.g., a fatal ventricular arrhythmia) and that the subject is hemodynamically unstable. In this case, the implantable device may include an implantable cardioverter / defibrillator (ICD). For other aspects, the implantable device includes a pacemaker, an internal electrocardiogram (ECG) device, or other device that can activate an audible warning and / or provide a signal to the subject via RF (e.g., ) or other wireless communication technologies to remotely send alarm signals to external devices or centralized patient monitoring / management centers.

[0125] According to certain aspects, the implantable device can have multiple leads with multiple electrodes for sensing internal electrocardiogram signals and measuring impedance. For certain aspects, the implantable device includes at least two leads with at least four electrodes. In one aspect, at least one optical fiber in the set of optical fibers is placed in an ICD lead implanted in a subject or as a separate lead (also referred to herein as an independent lead).

[0126] In one aspect, at least one optical fiber in the set is at least partially disposed in a ventricle of a heart of the subject. In this case, determining whether the heart is experiencing a fatal arrhythmia includes determining whether the subject is hemodynamically stable when the heart is experiencing a ventricular arrhythmia (VA).

[0127] According to certain aspects, the subject is a human patient. For other aspects, for example, the subject can be a pig or a dog.

[0128] In certain aspects, the implantable device can store internal ECG signals (and their derivatives) that can be processed in digital or analog form during single or multiple VA events (which can originate from single or multiple ventricular sites) to facilitate comparison, analysis, and VA localization by healthcare providers during device interrogation.

[0129] According to certain aspects, electrical noise and / or interference sensed by electrodes implanted in a subject may be mistakenly diagnosed as part of a "detected arrhythmia". The implanted electrodes may include, for example, one or more electrodes 103 in one or more leads 102 of an ICD 100 or other implanted device. For example, the electrodes may be subject to external interference (e.g., interference from a strong magnetic field or certain types of welding) and / or internal noise from a broken lead or damaged internal electrical connection. Certain aspects of the present disclosure may be able to distinguish between such types of noise and true arrhythmias based on signals that are immune to electrical noise and interference, including non-pneumatic signals described herein, such as light, heat, and / or ultrasound signals. For example, the type of noise and true arrhythmias may be distinguished by comparing one or more features of an electrical signal with one or more features of at least one non-pneumatic signal. Example features of the signal that may be analyzed include frequency domain content (e.g., frequency values, bandwidth, and / or other characteristics of the spectrum) and / or time domain content (e.g., amplitude and / or time characteristics) of the non-pneumatic, noise, and / or interference signals. Distinguishing between noise and true arrhythmia types can be based primarily on: (1) not much change from their respective baselines, (2) not much hemodynamic compromise, or (3) both being non-pneumatic signals (e.g., optical, thermal, and / or ultrasonic signals) that are expected to occur during true arrhythmias. For example, based on simultaneous analysis of one or more of these non-pneumatic signals and the electrocardiogram signal, the optical, thermal, and / or ultrasonic signals can exclude such electrical noise from being misdiagnosed as arrhythmias.

[0130] Figure 5 A portion of an implantable system 500 for determining hemodynamic instability during a detected arrhythmia is shown in accordance with certain aspects of the present disclosure.

[0131] As shown, the implantable system 500 includes a light source 502 that outputs an optical signal (e.g., an optical signal in the visible spectrum and / or the invisible spectrum). As described above, the light source 502 may include a light emitting diode (LED) or a laser diode. The optical signal generated by the light source 502 may be coupled to an optical fiber 506 via an optical circulator 504. The optical fiber 506 is configured to be at least partially placed in the heart of the subject. A fiber Bragg grating 510 may be provided near the distal segment of the optical fiber 506 to be placed in the heart of the subject. The fiber Bragg grating 510 is configured to reflect at least a portion of the optical signal transmitted by the light source 502 at a characteristic range of wavelengths (also referred to as the Bragg wavelength). The light reflection from the fiber Bragg grating 510 is transmitted back to the optical circulator 504 and an optical sensor 512, such as a photodetector. The sensor 512 converts the reflection of the Bragg wavelength into an electrical signal, the amplitude of which may also reflect the energy loss of the reflected optical signal when passing through the optical fiber, which is a function of the incident angle determined by the bending amount of the optical fiber. Sensor 512 can also detect the time delay in the reflected light signal as the signal passes through the optical fiber, which is a function of the path length determined by the amount of fiber bending. Alternatively, an optical mirror or other optical reflector other than a fiber Bragg grating can be placed at the end of the optical fiber to reflect the light signal.

[0132] As shown, light source 502 and optical sensor 512 are coupled to a processor 514 that controls the optical output from light source 502 and receives and processes electrical signals received from optical sensor 512 to determine whether the subject's mechanical or contractile function is normal or maintained, and therefore whether the subject is hemodynamically stable.

[0133] In one aspect, Figure 5 As shown, the optical fiber 506 can be embedded in the ICD lead 102 of the ICD 100 (e.g., as shown in FIG. Figure 1 In one aspect, the light source 502, light sensor 512, optical circulator 504, and processor 514 and associated memory may be housed in a generator unit (e.g., Figure 1 The generator 104 shown is either a discrete component or as part of an application specific integrated circuit (ASIC).

[0134] Fig. 6A , Figure 6B and Figure 6C 1 shows example recorded optical signals during a representative experiment including monitoring mechanical motion of a subject's heart based on the optical signals according to certain aspects of the present disclosure. Fig. 6A , 6B and 6C show the variation of the wavelength of the monitored optical signal over time.

[0135] Fig. 6A A baseline sinus rhythm of 95 beats per minute (bpm) is shown. During the cardiac cycle, the optical signal is associated with the movement of the ventricles and is also affected by respiration, which can be identified and isolated from the ECG signal based on its respective spectral and temporal characteristics. Figure 6B The effects of ventricular tachycardia (VT) are shown. Ventricular pacing (v-pacing) is used to simulate VT originating from the left ventricle. Figure 6B As can be seen from the curve, a decrease in the amplitude of the wavelength change is noted during VT (e.g., 240 bpm), reflecting a decrease in the contractile function of the ventricle and, therefore, its mechanical movement. A slight but significant downward drift in the optical signal is also noted during VT, indicating that the size or volume of the ventricle changes (increases) during consecutive cardiac cycles. Figure 6B The bottom two traces show that the optical signal did not recover immediately after restoration of sinus rhythm, which is consistent with the usual residual hemodynamic effects of sustained VT.

[0136] Figure 6C shows the effects of ventricular fibrillation. Rapid ventricular pacing can induce ventricular fibrillation. Figure 6C As can be seen from the curve, the optical signal is further weakened during ventricular fibrillation, which is consistent with completely impaired cardiac contractile function.

[0137] Figure 7 Example operations 700 are shown for determining hemodynamic stability of a subject using ultrasound signals in accordance with certain aspects of the present disclosure.

[0138] The operations 700 begin at block 702 by transmitting ultrasound signals toward at least one anatomical reference structure within a subject's heart using an ultrasound transmitter for a given period of time.

[0139] At block 704 , the ultrasound receiver receives a reflected portion of the ultrasound signal within a given period of time.

[0140] At block 706, the reflected portion of the ultrasound signal is analyzed during the time period to determine a change in a distance between the ultrasound receiver and at least one anatomical reference structure during the cardiac cycle, wherein the change is indicative of mechanical motion of the heart.

[0141] At block 708, hemodynamic stability of the subject is determined based on the mechanical motion of the heart.

[0142] In one aspect, the ultrasound transmitter and ultrasound receiver are placed in a region outside the heart of the subject. For example, the ultrasound transmitter and ultrasound receiver may be integrated into an ICD implanted in the subject.

[0143] In one aspect, the ultrasound transmitter and the ultrasound receiver are placed in the heart of the subject. For example, the ultrasound transmitter and the ultrasound receiver may be arranged in at least one lead of an ICD implanted in the subject.

[0144] Any of the above operations, such as operation 400, may be included as instructions in a computer-readable medium to be executed by a processing system. (Non-transitory) computer-readable media may include any suitable memory or other storage device for storing instructions, such as a read-only memory (ROM), a random access memory (RAM), a flash memory (e.g., a USB flash drive), an electrically erasable programmable ROM (EEPROM), a compact disk ROM (CD-ROM), a floppy disk, or a digital versatile disk ROM (DVD-ROM). The method disclosed herein includes one or more steps or actions for implementing the described method. Without departing from the scope of the claims, the method steps and / or actions may be interchangeable with each other. In other words, unless a specific order of steps or actions is specified, the order and / or use of specific steps and / or actions may be modified without departing from the scope of the claims. As used herein (including the appended claims), a phrase referring to "at least one" in a list of items refers to any combination of those items, including single members. As an example, "at least one of x, y, and z" is intended to cover: x, y, z, xy, xz, yz, xyz, and any combination thereof (e.g., xyy and xxyz).

[0145] While the foregoing is directed to certain aspects of the present disclosure, other and further aspects may be devised without departing from the basic scope of the present disclosure, and the scope of the present disclosure is determined by the claims that follow.

Claims

1. An implantable system for implantation in a subject to determine the hemodynamic stability of the subject, comprising: at least one optical fiber configured for placement in at least one of a heart of a subject or near a ventricle of a heart of the subject, wherein the at least one optical fiber comprises at least one fiber Bragg grating (FBG) and is configured to bend with contraction and relaxation of the heart; at least one light source configured to introduce an optical signal into the at least one optical fiber; at least one receiver configured to receive a reflected portion of the optical signal via the at least one FBG of the at least one optical fiber; as well as At least one processor configured to: analyzing a reflected portion of the received optical signal for a change in at least one parameter, wherein the change in at least one parameter comprises a shift in a Bragg wavelength, and wherein the shift in the Bragg wavelength indicates an amount of bending of the at least one optical fiber due to contraction and relaxation of the heart; as well as The hemodynamic stability of the subject is determined based on the shift in the Bragg wavelength.

2. The implantable system of claim 1, further comprising one or more leads, wherein the at least one optical fiber is disposed within a first lead of the one or more leads.

3. The implantable system of claim 1, wherein at least one of the at least one light source, the at least one receiver, or the at least one processor is disposed in an implantable device.

4. The implantable system of claim 3, wherein the implantable device comprises a generator, and wherein the at least one processor is disposed within the generator.

5. The implantable system of claim 3, wherein the implantable device comprises a generator, and wherein the at least one light source and the at least one receiver are disposed within the generator.

6. The implantable system of claim 3, wherein the at least one processor is disposed in another device.

7. An implantable system according to claim 6, wherein the other device is disposed externally to the subject.

8. The implantable system of claim 6, wherein the other device is configured for implantation in a subject.

9. The implantable system of claim 1 , wherein the at least one receiver is configured to receive a reflected portion of at least one additional optical signal via at least one additional optical fiber, wherein the at least one processor is configured to: analyzing changes in said at least one parameter of the received reflected portion of said at least one additional optical signal; and The results of analyzing the received reflected portion of the light signal and analyzing the received reflected portion of the at least one additional light signal are combined, wherein the at least one processor is configured to determine hemodynamic stability of the subject based on the combined results.

10. The implantable system of claim 9, wherein the at least one additional optical fiber is disposed outside the heart, and wherein the combined result is indicative of hemodynamic stability of the subject in the presence of non-cardiac body motion.

11. An implantable system according to claim 1, wherein the at least one optical fiber is located in a first region of the heart for monitoring mechanical movement of the first region, and the system further comprises at least one additional optical fiber located in a second region of the heart for monitoring mechanical movement of the second region.

12. The implantable system of claim 1 , wherein the at least one processor is further configured to: receiving electrocardiogram signals from electrodes disposed in the subject; Analyzing electrocardiogram signals; and The results of analyzing the received reflected portion of the light signal and analyzing the electrocardiogram signal are combined, wherein the at least one processor is configured to determine whether the subject is hemodynamically stable based on the combined results.

13. The implantable system of claim 1, wherein the at least one optical fiber is disposed within a cavity of the heart or within an adjacent blood vessel segment of the heart.

14. A non-transitory computer readable medium having stored thereon instructions that, when executed by at least one processor, cause the at least one processor to perform operations for determining hemodynamic stability of a subject, the operations comprising: transmitting an optical signal via at least one optical fiber of a group of one or more optical fibers disposed in at least one of a heart of the subject or near a ventricle of the heart of the subject, wherein the at least one optical fiber of the group is configured to bend with contraction and relaxation of the heart; receiving a reflected portion of the optical signal via the at least one optical fiber, wherein a change in at least one parameter of the received reflected portion of the optical information indicates an amount of bending of the at least one optical fiber due to contraction and relaxation of the heart, wherein the at least one parameter change includes a shift in the Bragg wavelength; The hemodynamic stability of the subject is determined based on the shift in the Bragg wavelength.

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