Heart rate recovery assessment

Abstract

Some aspects relate to systems, devices, and methods of assessing heart rate recovery. A patient's heart rate can be measured during a plurality of heart rate recovery events. Each heart rate recovery event of the plurality of heart rate recovery events includes a duration of time following an activity that causes an increase in heart rate. Heart rate recovery information can be determined based on the measured heart rate during each heart rate recovery event of the plurality of heart rate recovery events, and a cardiac status of the patient can be generated from the determined heart rate recovery information within the plurality of heart rate recovery events.

Description

[0001] The present disclosure relates to systems, devices, and methods configured to generally assess a patient, and in particular, to assess a patient with a condition such as heart failure.

[0002] Heart failure (HF) is a complex disease that can be broadly defined as the inability of the heart to pump sufficiently to cope with its venous return and / or to provide sufficient output to meet the metabolic demands of the body. Heart failure is an increasingly common, life-threatening cardiovascular disorder characterized by significant disability, frequent hospitalization, and high mortality. HF is increasingly prevalent in the elderly (up to 10% of the population) and has become the most common cause of hospitalization in people over 65 years of age. HF is a major cause or contributing factor of hospitalization and, as such, is becoming a significant contributing factor of healthcare expenditure.

[0003] Cardiac output is a function of stroke volume, which reflects the pumping ability of the heart, and heart rate (HR). With increasing age, or in the presence of conditions that limit the pumping ability of the heart, there is a gradual reliance on an increase in HR during, for example, exercise, where an increase in cardiac output is required. In addition, chronotropic incompetence (CI), which is characterized by an inadequate rise in HR during exercise, progression of chronic heart failure (CHF), use of medication to treat CHF, hypertension, or other diseases can also occur and / or reflect a worsening cardiac status or side effects of medication.

[0004] A patient's health can be assessed to determine and track the progression of HF in the patient through medical history and physical examination. This can involve spending a significant amount of time and cost with the patient at the physician's office to develop a management plan for the patient's treatment. The management plan can include pharmacological therapy such as beta-blockers, ACE inhibitors, and diuretics. More aggressive therapy can include biventricular pacing and other implantable cardiac device therapy. The management plan can also include an exercise regimen.

[0005] Exercise diagnosis can be helpful in assessing a patient's health. During exercise, heart rate is a parameter or indicator of the amount of work required to provide blood and oxygen to the body. The maximum heart rate for a level of exercise corresponds to the accommodation of the heart. Other parameters such as heart rate intensity, percent of oxygen consumption (VO2%) reserve, metabolic equivalents (METS), and work load also provide data indicative of the accommodation of the heart.

[0006] Measurements of a patient's ability to track a natural heart response to stress, such as exercise, like heart rate recovery (HRR) can be used to assess the health of a patient. Post-exercise heart rate recovery can be assessed as a clinical marker of good vagal tone and cardiac health. As heart rate increases due to decreased vagal tone, heart rate also decreases with reactivation of vagal tone. Delayed response to heart rate decrease can be a good prognostic marker of overall mortality and cardiac health. An implantable device or an extracorporeal device can be used to provide diagnostic parameters to a physician to monitor a patient's medical condition.

[0007] Heart rate recovery includes a decrease in a patient's heart rate indicating, for example, that an elevated heart rate has stopped after the patient performs an exercise regimen. Heart rate recovery events can be used to demonstrate the health or strength of a heart. Patient data related to heart condition and heart rate recovery can be obtained in a variety of ways. Typically, a patient directly communicates health data to medical personnel during an office visit, however, this can limit the time period in which health data can be collected. Some data can be automatically generated and wirelessly transmitted to a computer system or healthcare system. Trends or patterns of measurements indicative of changes in a patient, including heart rate recovery, can be used to determine a patient's heart condition and medical treatment. SUMMARY

[0008] The present disclosure relates generally to systems, devices, and methods for assessing heart rate recovery to determine a patient's heart condition.

[0009] According to the principles of the present disclosure, some aspects relate to a method including measuring a patient's heart rate during a plurality of heart rate recovery events. Each heart rate recovery event of the plurality of heart rate recovery events includes a duration after an activity that causes an elevated heart rate. The method further includes determining heart rate recovery information based on the measured heart rate during each heart rate recovery event of the plurality of heart rate recovery events, and generating a heart condition of the patient from the determined heart rate recovery information within the plurality of heart rate recovery events.

[0010] According to the principles of the present disclosure, other aspects relate to a device including a sensor apparatus and a processing apparatus. The sensor apparatus includes a heart rate sensor to sense a patient's heart rate. The processing apparatus is operably coupled to the sensor apparatus. The processing apparatus includes processing circuitry configured to monitor a patient's heart rate during a plurality of heart rate recovery events using the heart rate sensor, determine heart rate recovery information based on the measured heart rate during each heart rate recovery event of the plurality of heart rate recovery events, and generate a heart condition of the patient from the determined heart rate recovery information within the plurality of heart rate recovery events. Each heart rate recovery event of the plurality of heart rate recovery events includes a duration after an activity that causes an elevated heart rate.

[0011] According to the principles of the present disclosure, other aspects relate to a system including a sensing device, a processing device, and a notification device. The sensor device includes a heart rate sensor for sensing a heart rate of a patient. The processing device is operably coupled to the sensor device. The processing device includes processing circuitry configured to monitor a heart rate of a patient using the heart rate sensor during a plurality of heart rate recovery events, determine heart rate recovery information based on the measured heart rate during each of the plurality of heart rate recovery events, and generate a cardiac state of the patient over the plurality of heart rate recovery events according to the determined heart rate recovery information. Each of the plurality of heart rate recovery events comprises a duration of time following an activity that causes an increase in heart rate. The notification device is for notifying the patient to begin the activity that causes the increase in heart rate.

[0012] According to the principles of the present disclosure, other aspects relate to a method including measuring a perturbation effect of a patient during a plurality of perturbation recovery events, determining perturbation recovery information based on the measured perturbation effect during each of the plurality of perturbation recovery events, and generating a cardiac state of the patient according to the determined perturbation recovery information over the plurality of perturbation recovery events. Each of the plurality of perturbation recovery events comprises a duration of time following the patient being perturbed.

[0013] According to the principles of the present disclosure, other aspects relate to an apparatus including a sensor device and a processing device. The sensor device includes a heart rate sensor for sensing a heart rate of a patient. The processing device is operably coupled to the sensor device. The processing device includes processing circuitry configured to measure a perturbation effect of a patient during a plurality of perturbation recovery events, determine perturbation recovery information based on the measured perturbation effect during each of the plurality of perturbation recovery events, and generate a cardiac state of the patient according to the determined perturbation recovery information over the plurality of perturbation recovery events. Each of the plurality of perturbation recovery events comprises a duration of time following the patient being perturbed.

[0014] The details of one or more aspects of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the technologies described in this disclosure will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a diagram of an illustrative system including an illustrative implantable medical device (IMD).

[0016] Figure 2A is a diagram of an illustrative IMD of Figure 1 .

[0017] Figure 2B is a magnified view of a distal end of an electrical lead disposed in a left ventricle of Figure 2A .

[0018] Figure 3A is a block diagram of an illustrative IMD of a system such as Figures 1-2B .

[0019] Figure 3B is another block diagram of illustrative IMD (e.g., implantable pulse generator) circuitry and associated leads employed in a system of Figures 1-2B .

[0020] Figure 4 illustrates a flow diagram of an example method of generating a cardiac status of a patient in accordance with aspects of the present disclosure.

[0021] Figure 5A is an illustrative block diagram of an apparatus for determining heart rate recovery information and generating a cardiac status of a patient in accordance with aspects of the present disclosure.

[0022] Figure 5B is an illustrative block diagram of a system for determining heart rate recovery information and generating a cardiac status of a patient in accordance with aspects of the present disclosure.

[0023] Figure 6 illustrates a flow diagram of an example method of generating a cardiac status of a patient in accordance with aspects of the present disclosure.

[0024] Figure 7 is an example graphical illustration of a heart rate recovery information trend for generating a cardiac status of a patient in accordance with aspects of the present disclosure. DETAILED DESCRIPTION

[0025] It should be understood that various aspects disclosed herein can be combined in different combinations than the combinations expressly presented in the specification and drawings. It should also be understood that, depending on the example, certain acts or events of any of the processes described herein can be performed in a different sequence, can be added, modified or omitted (e.g., all described acts or events can not be necessary to perform the techniques), unless expressly limited otherwise. In addition, while certain aspects of this disclosure are described as being performed by a single module or device, it should be appreciated that the techniques of this disclosure can be performed by a combination of modules or devices associated with, for example, an implantable medical device.

[0026] Illustrative cardiac therapy systems and apparatuses can be further described herein with reference to Figures 1-3B , which can utilize illustrative systems, methods, and processes described herein with respect to Figures 4-7 .

[0027] Figure 1 This is a conceptual diagram illustrating a therapeutic system 10 that can be used to deliver pacing therapy to a patient 14. The patient 14 can be, but does not necessarily have to be, a person. The therapeutic system 10 may include an implantable medical device 16 (IMD) that can be coupled to leads 18, 20, 22. The IMD 16 may be, for example, an implantable pacemaker, cardioverter-defibrillator, and / or a defibrillator, which delivers or provides electrical signals (e.g., pacing, etc.) to the heart 12 of the patient 14 via electrodes coupled to one or more of leads 18, 20, 22 and / or senses electrical signals from said heart.

[0028] Leads 18, 20, and 22 extend into the heart 12 of the patient 14 to sense the electrical activity of the heart 12 and / or deliver electrical stimulation to the heart 12. Figure 1 In the example shown, the right ventricle (RV) lead 18 extends through one or more veins (not shown), the superior vena cava (not shown), and the right atrium 26, and enters the right ventricle 28. The left ventricle (LV) coronary sinus lead 20 extends through one or more veins, the vena cava, and the right atrium 26, and enters the coronary sinus 30 to reach the region adjacent to the free wall of the left ventricle 32 of the heart 12. The right atrium (RA) lead 22 extends through one or more veins and the vena cava, and enters the right atrium 26 of the heart 12.

[0029] The IMD 16 can sense electrical signals associated with depolarization and repolarization of the heart 12 via electrodes coupled to at least one of leads 18, 20, and 22. In some instances, the IMD 16 delivers pacing therapy (e.g., pacing pulses) to the heart 12 based on the electrical signals sensed within the heart 12. The IMD 16 can be operable to adjust one or more parameters associated with the pacing therapy, such as AV delay and various other timing, pulse width, amplitude, voltage, burst length, etc. Furthermore, the IMD 16 can be operable to deliver pacing therapy using various electrode configurations, which can be monopolar, bipolar, quadrupole, or other multipolar configurations. For example, a multipolar lead system can contain several electrodes that can be used to deliver pacing therapy. Thus, a multipolar lead system can provide or supply multiple electrical vectors for pacing from it. The pacing vector may include at least one cathode and at least one anode, the at least one cathode being at least one electrode located on at least one lead, and the at least one anode being at least one electrode located on at least one lead (e.g., the same lead or different leads) and / or on the housing or canister of the IMD. While improvements in cardiac function as a result of pacing therapy may depend primarily on the cathode, electrical parameters such as impedance, pacing threshold voltage, current consumption, and lifespan may be more dependent on the pacing vector, which includes both a cathode and an anode. The IMD 16 may also provide defibrillation and / or cardioversion therapy via electrodes located on at least one of leads 18, 20, 22. Further, the IMD 16 may detect arrhythmias of heart 12, such as fibrillation of ventricles 28, 32, and provide defibrillation therapy to heart 12 in the form of electrical pulses. In some instances, the IMD 16 may be programmed to deliver a therapeutic process, e.g., pulses with increasing energy levels, until the fibrillation of heart 12 ceases.

[0030] Figures 2A-2B It shows in more detail Figure 1 A conceptual diagram of the IMD 16 and leads 18, 20, 22 of the therapy system 10. Leads 18, 20, 22 can be electrically coupled to a therapy delivery module (e.g., for delivering pacing therapy), a sensing module (e.g., for sensing one or more signals from one or more electrodes), and / or any other module of the IMD 16 via connector block 34. In some instances, the proximal ends of leads 18, 20, 22 may contain electrical contacts electrically coupled to corresponding electrical contacts within connector block 34 of the IMD 16. Additionally, in some instances, leads 18, 20, 22 may be mechanically coupled to connector block 34 by means of a retaining screw, connecting pin, or other suitable mechanical coupling mechanism.

[0031] Each of the leads 18, 20, 22 includes an elongated insulated lead body that can carry a plurality of conductors (e.g., coiled conductors, straight conductors, etc.) separated from one another by insulation (e.g., a tubular insulating jacket). In the illustrated example, bipolar electrodes 40, 42 are located near the distal end of the lead 18. In addition, bipolar electrodes 44, 45, 46, 47 are located near the distal end of the lead 20, and bipolar electrodes 48, 50 are located near the distal end of the lead 22.

[0032] The electrodes 40, 44, 45, 46, 47, 48 can take the form of ring electrodes, and the electrodes 42, 50 can take the form of extendable helical tip electrodes that are retractably mounted within insulated electrode heads 52, 54, 56, respectively. Each of the electrodes 40, 42, 44, 45, 46, 47, 48, 50 can be electrically coupled to a respective one of the conductors (e.g., coiled conductors and / or straight conductors) within the lead body of its associated lead 18, 20, 22, and thereby to a respective one of the electrical contacts on the proximal end of the lead 18, 20, 22.

[0033] In addition, the electrode surface area of the electrodes 44, 45, 46, and 47 can be about 5.3 mm 2 to about 5.8 mm 2 The electrodes 44, 45, 46, and 47 can also be referred to as LV1, LV2, LV3, and LV4, respectively. The LV electrodes on the lead 20 (i.e., left ventricular electrode 1 (LV1) 44, left ventricular electrode 2 (LV2) 45, left ventricular electrode 3 (LV3) 46, and left ventricular 4 (LV4) 47, etc.) can be spaced apart at variable distances. For example, the electrode 44 can be a distance of, for example, about 21 millimeters (mm) from the electrode 45, the electrodes 45 and 46 can be spaced apart from one another by a distance of, for example, about 1.3 mm to about 1.5 mm, and the electrodes 46 and 47 can be spaced apart from one another by a distance of, for example, about 20 mm to about 21 mm.

[0034] The electrodes 40, 42, 44, 45, 46, 47, 48, 50 can further be used to sense electrical signals (e.g., morphological waveforms within electrograms (EGMs)) attendant to the depolarization and repolarization of the heart 12. The electrical signals are conducted through the respective leads 18, 20, 22 to the IMD 16. In some examples, the IMD 16 can also deliver pacing pulses through the electrodes 40, 42, 44, 45, 46, 47, 48, 50 to cause depolarization of cardiac tissue of the patient's heart 12. In some examples, as Figure 2AAs shown in the middle, IMD 16 includes one or more housing electrodes, such as housing electrode 58, which can be integrally formed with or otherwise coupled to an outer surface of a housing 60 (e.g., a hermetically sealed housing) of IMD 16. Any of electrodes 40, 42, 44, 45, 46, 47, 48, 50 can be combined with housing electrode 58 for unipolar sensing or pacing. It is generally understood by those skilled in the art that other electrodes can also be selected to define pacing and sensing vectors or for pacing and sensing vectors. Further, any of electrodes 40, 42, 44, 45, 46, 47, 48, 50, 58, when not used to deliver pacing therapy, can be used to sense electrical activity during pacing therapy.

[0035] As referenced above Figure 2A As described in further detail below, housing 60 can enclose a therapy delivery module, which can include a stimulation generator for generating cardiac pacing pulses and defibrillation or cardioversion shocks, and a sensing module for monitoring electrical signals of the patient's heart (e.g., the patient's heart rhythm). Leads 18, 20, 22 can also include elongated electrodes 62, 64, 66, respectively, which can take the form of coils. IMD 16 can deliver defibrillation shocks to heart 12 through any combination of elongated electrodes 62, 64, 66 and housing electrodes 58. Electrodes 58, 62, 64, 66 can also be used to deliver cardioversion pulses to heart 12. Further, electrodes 62, 64, 66 can be made of any suitable electrically conductive material, such as but not limited to platinum, platinum alloy, and / or other materials known to be useful in implantable defibrillation electrodes. Since electrodes 62, 64, 66 are not generally configured to deliver pacing therapy, any of electrodes 62, 64, 66 can be used to sense electrical activity and can be used in combination with any of electrodes 40, 42, 44, 45, 46, 47, 48, 50, 58. In at least one embodiment, RV elongated electrode 62 can be used to sense electrical activity of the patient's heart during delivery of pacing therapy (e.g., in combination with housing electrode 58 or a defibrillation electrode-to-housing electrode vector).

[0036] Figures 1-3B The illustrated configuration of therapy system 10 is merely one example. In other examples, a therapy system can include epicardial leads and / or patch electrodes in place of or in addition to transvenous leads 18, 20, 22. Figure 1 The illustrated transvenous leads 18, 20, 22. Additionally, in other examples, therapy system 10 can be implanted in and / or around the heart space without transvenous leads (e.g., leadless / wireless pacing systems) or with leads implanted (e.g., transvenously or using methods) to the left chambers of the heart (in addition to being placed in the right chambers of the heart as illustrated Figure 1The illustrated transvenous leads can be in addition to or in lieu of the transvenous leads placed in the right chambers of the heart). Further, in one or more embodiments, IMD 16 need not be implanted within patient 14. For example, IMD 16 can deliver various cardiac therapies to heart 12 through percutaneous leads that extend through the skin of patient 14 to locations within or outside of heart 12. In one or more embodiments, system 10 can utilize wireless pacing (e.g., transferring energy to an intracardiac pacing component(s) by ultrasound, inductive coupling, RF, etc.) and sensing cardiac activation using electrodes on a housing / can and / or subcutaneous leads.

[0037] In other examples of therapy systems that provide electrical stimulation therapy to heart 12, such therapy systems can include any suitable number of leads coupled to IMD 16, and each of the leads can extend to any location within or proximate to heart 12. For example, other examples of therapy systems can include three transvenous leads at the locations shown. Still further, other therapy systems can include a single lead extending from IMD 16 into right atrium 26 or right ventricle 28 or two leads extending into respective ones of right atrium 26 and right ventricle 28. Figures 1-3B

[0038] Figure 3A is a functional block diagram of one illustrative configuration of IMD 16. As shown, IMD 16 can include control module 81, therapy delivery module 84 (e.g., which can include a stimulation generator), sensing module 86, and power source 90. Control module or device 81 can include processor 80, memory 82, and telemetry module, or device 88. Memory 82 can include computer-readable instructions that, when executed by processor 80, for example, cause IMD 16 and / or control module 81 to perform various functions attributed to IMD 16 and / or control module 81 described herein. Further, memory 82 can include any volatile, nonvolatile, magnetic, optical, and / or electrical media, such as a random access memory (RAM), read only memory (ROM), nonvolatile RAM (NVRAM), electrically-erasable programmable ROM (EEPROM), flash memory, and / or any other digital media.

[0039] ​The processor 80 of the control module 81 can include any one or more of a microprocessor, a controller, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), and / or equivalent discrete or integrated logic circuitry. In some examples, the processor 80 can include multiple components, such as any combination of one or more microprocessors, one or more controllers, one or more DSPs, one or more ASICs, and / or one or more FPGAs, as well as other discrete or integrated logic circuitry. The functionality attributed to the processor 80 herein can be embodied as software, firmware, hardware, or any combination thereof.

[0040] The control module 81 can control the therapy delivered by the therapy delivery module or device 84 to the heart 12 according to one or more selected therapy programs, which can be stored in the memory 82 (e.g., electrical stimulation therapy such as pacing). More specifically, the control module 81 (e.g., the processor 80) can control various parameters of electrical stimulation delivered by the therapy delivery module 84, such as, for example, A-V delays, V-V delays, pacing pulses with amplitudes, pulse widths, frequencies, or electrode polarities, etc., as specified by one or more selected therapy programs (e.g., A-V and / or V-V delay adjustment programs, pacing therapy programs, pacing resumption programs, capture management programs, etc.). As shown, the therapy delivery module 84 is electrically coupled to the electrodes 40, 42, 44, 45, 46, 47, 48, 50, 58, 62, 64, 66, e.g., by conductors of the respective leads 18, 20, 22, or, in the case of the housing electrode 58, by an electrical conductor disposed within the housing 60 of the IMD 16. The therapy delivery module 84 can be configured to generate and deliver electrical stimulation therapy, such as pacing therapy, to the heart 12 using one or more of the electrodes 40, 42, 44, 45, 46, 47, 48, 50, 58, 62, 64, 66.

[0041] For example, the therapy delivery module 84 can deliver pacing stimulation (e.g., pacing pulses) by the ring electrodes 40, 44, 45, 46, 47, 48 coupled to the leads 18, 20, 22 and / or the helix tip electrodes 42, 50 of the leads 18, 22. Further, for example, the therapy delivery module 84 can deliver defibrillation shocks to the heart 12 by at least two of the electrodes 58, 62, 64, 66. In some examples, the therapy delivery module 84 can be configured to deliver pacing, cardioversion, or defibrillation stimulation in the form of electrical pulses. In other examples, the therapy delivery module 84 can be configured to deliver one or more of these types of stimulation in the form of other signals, such as sine waves, square waves, and / or other substantially continuous time signals.

[0042] IMD 16 can further include a switch module or device 85, and control module 81 (e.g., processor 80) can use switch module 85 to, for example, select which of the available electrodes to use for therapy, such as pacing pulses for pacing therapy, or which of the available electrodes to use for sensing, by way of a data / address bus. Switch module 85 can include an array of switches, a matrix of switches, multiplexers, or any other type of switching device suitable to selectively couple sensing module or device 86 and / or therapy delivery module 84 to one or more selected electrodes. More specifically, therapy delivery module 84 can include a plurality of pacing output circuits. Each of the plurality of pacing output circuits can be selectively coupled to one or more of electrodes 40, 42, 44, 45, 46, 47, 48, 50, 58, 62, 64, 66 (e.g., a pair of electrodes for delivering therapy to a bipolar or multipolar pacing vector), for example, using switch module 85. In other words, each electrode can be selectively coupled to one of the pacing output circuits of therapy delivery module using switch module 85.

[0043] Sensing module 86 is coupled (e.g., electrically coupled) to sensing devices, among other sensing devices, which can include electrodes 40, 42, 44, 45, 46, 47, 48, 50, 58, 62, 64, 66 to monitor electrical activity of heart 12, such as electrocardiogram (ECG) / electrogram (EGM) signals, etc. The ECG / EGM signals can be used to measure or monitor activation times (e.g., ventricular activation times, etc.), heart rate (HR), heart rate variability (HRV), heart rate turbulence (HRT), deceleration / acceleration capacity, deceleration sequence morbidity, T-wave alternans (TWA), P-wave to P-wave intervals (also referred to as P-P intervals or A-A intervals), R-wave to R-wave intervals (also referred to as R-R intervals or V-V intervals), P-wave to QRS complex intervals (also referred to as P-R intervals, A-V intervals, or P-Q intervals), QRS complex morphology, ST segment (i.e., the segment connecting the QRS complex and the T wave), T wave changes, QT interval, electrical vector, etc.

[0044] Switch module 85 can also be used with sensing module 86 to select which of the available electrodes to use or to enable to, for example, sense electrical activity of the patient's heart (e.g., one or more electrical vectors of the patient's heart using any combination of electrodes 40, 42, 44, 45, 46, 47, 48, 50, 58, 62, 64, 66). Likewise, switch module 85 can also be used with sensing module 86 to select which of the available electrodes not to use (e.g., to disable) to, for example, sense electrical activity of the patient's heart (e.g., one or more electrical vectors of the patient's heart using any combination of electrodes 40, 42, 44, 45, 46, 47, 48, 50, 58, 62, 64, 66), etc. In some examples, control module 81 can select electrodes to act as sensing electrodes by providing signals through switch module within sensing module 86, e.g., through a data / address bus.

[0045] In some examples, sensing module 86 includes channels that include amplifiers having a relatively wider passband than R-wave or P-wave amplifiers. Signals from selected sensing electrodes can be provided to a multiplexer and thereafter converted by an analog-to-digital converter to a multi-bit digital signal for storage in memory 82, e.g., as an electrogram (EGM). In some examples, storage of such EGMs in memory 82 can be under the control of a direct memory access circuit.

[0046] In some examples, control module 81 can operate as an interrupt driven device and can respond to interrupts from the pacemaker timing and control module, where the interrupts can correspond to the occurrence of sensed P-waves and R-waves and the generation of cardiac pacing pulses. Any necessary mathematical calculations can be performed by processor 80 and any updating of values or intervals controlled by the pacemaker timing and control module can occur following such interrupts. A portion of memory 82 can be configured as a plurality of recirculating buffers capable of holding one or more series of measured intervals that can be analyzed by, for example, processor 80 in response to the occurrence of pacing or sensing interrupts to determine whether the patient's heart 12 is currently exhibiting atrial or ventricular tachyarrhythmia.

[0047] The telemetry module 88 of the control module 81 can include any suitable hardware, firmware, software, or any combination thereof for communicating with another device, such as a programmer. For example, under the control of the processor 80, the telemetry module 88 can receive downlink telemetry from and send uplink telemetry to a programmer with the aid of an antenna, which can be internal and / or external. The processor 80 can provide, e.g., data to be uplinked to the programmer and control signals for the telemetry circuit within the telemetry module 88, e.g., by way of an address / data bus. In some examples, the telemetry module 88 can provide received data to the processor 80 through a multiplexer.

[0048] The various components of the IMD 16 are further coupled to a power source 90, which can include a rechargeable or non-rechargeable battery. A non-rechargeable battery can be selected to last for several years, while a rechargeable battery can be inductively charged from an external device, e.g., on a daily or weekly basis.

[0049] Figure 3B is another embodiment of a functional block diagram of an IMD 16 depicting bipolar RA lead 22, bipolar RV lead 18, and bipolar LV CS lead 20 without LA CS pacing / sensing electrodes and coupled to an implantable pulse generator (IPG) circuit 31 having programmable modes and parameters of the type known in the pacing art as dual-chamber DDD / R. In turn, sensor signal processing circuit 91 is coupled indirectly to timing circuit 43 and to microcomputer circuitry 33 by way of a data and control bus. The IPG circuit 31 is shown in a functional block diagram that is generally divided into microcomputer circuit 33 and pacing circuit 21. Pacing circuit 21 includes digital controller / timer circuit 43, output amplifier circuit 51, sense amplifier circuit 55, RF telemetry transceiver 41, activity sensor circuit 35, and numerous other circuits and components described below.

[0050] Crystal oscillator circuit 89 provides a basic timing clock to pacing circuit 21 when battery 29 provides power. Power-on reset circuit 87 responds to initial connection of the circuit to the battery for defining initial operating conditions, and similarly, resets the operating state of the device in response to detecting a low battery condition. Reference mode circuit 37 generates stable voltage references and currents for analog circuits within pacing circuit 21. Analog-to-digital converter (ADC) and multiplexer circuit 39 digitizes analog signals and voltages to provide, e.g., real-time telemetry of cardiac signals from sense amplifier 55 for uplink transmission by RF transmitter and receiver circuit 41. Voltage reference and bias circuit 37, ADC and multiplexer 39, power-on reset circuit 87, and crystal oscillator circuit 89 can correspond to any of those used in illustrative implantable cardiac pacemakers.

[0051] If the IPG is programmed in rate response mode, the signal output by one or more physiological sensors is used as a rate control parameter (RCP) to derive a physiological escape interval. For example, the escape interval is adjusted in proportion to a patient activity level generated in a patient activity sensor (PAS) circuit 35 in the illustrative IPG circuit 31 depicted. The patient activity sensor 27 is coupled to the IPG housing and can take the form of a piezoelectric crystal transducer. The output signal of the patient activity sensor 27 can be processed and used as an RCP. The sensor 27 generates an electrical signal in response to sensed body activity, which is processed by the activity circuit 35 and provided to the digital controller / timer circuit 43. Similarly, the illustrative systems, devices, and methods described herein can be practiced in conjunction with alternative types of sensors, such as oxygenation sensors, pressure sensors, pH sensors, and respiration sensors, perfusion sensors, heart rate sensors, for providing rate responsive pacing capabilities. Alternatively, QT time can be used as a rate indicating parameter, in which case no additional sensors are needed. Similarly, the illustrative embodiments described herein can also be practiced in non-rate responsive pacemakers.

[0052] Data transmission to and from an external programmer is accomplished through telemetry antenna 57 and associated RF transceiver 41, which is used to both demodulate received downlink telemetry and to transmit uplink telemetry. Uplink telemetry capabilities can include the ability to transmit stored digital information, e.g., operating modes and parameters, EGM histograms and other events, as well as real-time EGMs of atrial and / or ventricular electrical activity and marker channel pulses indicating the occurrence of sensed and paced depolarizations in the atrium and ventricles.

[0053] Microcomputer 33 contains a microprocessor 80 and associated system clock and on-processor RAM chip 82A and ROM chip 82B, respectively. In addition, microcomputer circuit 33 includes a separate RAM / ROM chip 82C to provide additional memory capacity. Microprocessor 80 is normally operated in a reduced power mode and is interrupt driven. Microprocessor 80 is awakened in response to defined interrupt events, which can include A-TRIG, RV-TRIG, LV-TRIG signals generated by timers in digital timer / controller circuit 43, as well as A-EVENT, RV-EVENT and LV-EVENT signals generated by sense amplifier circuit 55, among others. The specific values of intervals and delays timed by digital controller / timer circuit 43 are controlled by microcomputer circuit 33 through data and control buses from programmed parameter values and operating modes. In addition, if programmed to operate as a rate responsive pacemaker, timing interrupts can be provided, e.g., every cycle or every two seconds, to allow the microprocessor to analyze activity sensor data and update the underlying A-A, V-A or V-V escape interval, if applicable. In addition, microprocessor 80 can also be used to define variable, programmable A-V delay intervals, V-V delay intervals and energy delivered to each ventricle and / or atrium.

[0054] In one embodiment, microprocessor 80 is a custom microprocessor adapted to fetch and execute instructions stored in RAM / ROM units 82 in a conventional manner. However, other embodiments are contemplated that can be suitable to practice the present disclosure. For example, an off-the-shelf, commercially available microprocessor or microcontroller or custom, hard-wired logic or state machine type circuit can perform the functions of microprocessor 80.

[0055] Digital controller / timer circuit 43 operates under the general control of microcomputer 33 to control timing and other functions within pacing circuit 21 and includes a set of timing and associated logic circuits, some of which are depicted in relation to the present disclosure. The depicted timing circuits include URI / LRI timers 83A, V-V delay timers 83B, intrinsic interval timers 83C for timing elapsed V-EVENT to V-EVENT intervals or V-EVENT to A-EVENT intervals or V-V conduction intervals, escape interval timers 83D for timing A-A, V-A and / or V-V pacing escape intervals, A-V delay interval timers 83E for timing A-LVp delays (or A-RVp delays) from a prior A-EVENT or A-TRIG, post-ventricular timers 83F for timing post-ventricular time periods, and date / time clock 83G.

[0056] An A-V delay interval timer 83E is loaded with the appropriate delay interval for one ventricular chamber (e.g., A-RVp delay or A-LVp) to time out from a previous A-PACE or A-EVENT. The interval timer 83E triggers the delivery of a pacing stimulus and can be based on one or more previous cardiac cycles (or based on a data set empirically derived for a given patient).

[0057] An event post timer 83F times out a post-ventricular time period following an RV-EVENT or LV-EVENT or RV-TRIG or LV-TRIG and a post-atrial time period following an A-EVENT or A-TRIG. The duration of the event post time periods can also be selected as programmable parameters stored in the microcomputer 33. The post-ventricular time period includes a post-ventricular atrial blanking period (PVARP), a post-atrial ventricular blanking period (PAVBP), a ventricular blanking period (VBP), and a ventricular refractory period (VRP), although other time periods can be suitably defined depending at least in part on the operational circuitry employed in the pacing engine. The post-atrial time period includes an atrial refractory period (ARP) during which A-EVENTS are ignored for the purpose of resetting any A-V delays and an atrial blanking period (ABP) during which atrial sensing is disabled. It should be noted that the start of the post-atrial time period and the A-V delays can begin substantially contemporaneously with the start or end of each A-EVENT or A-TRIG, or in the latter case, at the end of an A-PACE that can follow an A-TRIG. Similarly, the start of the post-ventricular time period and the V-A escape interval can begin substantially contemporaneously with the start or end of a V-EVENT or V-TRIG, or in the latter case, at the end of a V-PACE that can follow a V-TRIG. The microprocessor 80 also optionally calculates the A-V delays, the V-V delays, the post-ventricular time period, and the post-atrial time period, which vary in response to one or more sensor-based escape intervals established in response to the RCP and / or the intrinsic atrial and / or ventricular rates.

[0058] The output amplifier circuit 51 contains the RA pacing pulse generator (and the LA pacing pulse generator, if provided), the RV pacing pulse generator, the LV pacing pulse generator, and / or any other pulse generators configured to provide atrial and ventricular pacing. To trigger the generation of an RV-PACE or LV-PACE pulse, the digital controller / timer circuit 43 generates an RV-TRIG signal when the A-RVp delay (in the case of RV pre-excitation) provided by the A-V delay interval timer 83E (or the V-V delay timer 83B) times out or an LV-TRIG when the A-LVp delay (in the case of LV pre-excitation) times out. Similarly, the digital controller / timer circuit 43 generates an RA-TRIG signal that triggers the output of an RA-PACE pulse (or an LA-TRIG signal that triggers the output of an LA-PACE pulse, if provided) at the end of the V-A escape interval timed by the escape interval timer 83D.

[0059] The output amplifier circuit 51 includes a switching circuit for coupling selected pairs of pacing electrodes from among the lead conductors and the IND-CAN electrode 20 to the RA pacing pulse generator (and the LA pacing pulse generator, if provided), the RV pacing pulse generator, and the LV pacing pulse generator. The pacing / sense electrode pair selection and control circuit 53 selects the lead conductors and associated pairs of pacing electrodes to be coupled to the atrial and ventricular output amplifiers within the output amplifier circuit 51 for effecting RA, LA, RV, and LV pacing.

[0060] The sense amplifier circuit 55 contains sense amplifiers for atrial and ventricular pacing and sensing. High-impedance P-wave and R-wave sense amplifiers can be used to amplify the voltage difference signal generated across a sense electrode pair due to the passage of a cardiac depolarization wavefront. High-impedance sense amplifiers use high gain to amplify low amplitude signals and rely on passband filtering, time domain filtering, and amplitude threshold comparisons to distinguish P-waves or R-waves from background electrical noise. The digital controller / timer circuit 43 controls the sensitivity settings of the atrial and ventricular sense amplifiers 55.

[0061] The sense amplifiers can be decoupled from the sensing electrodes during a blanking period before, during, and after the delivery of a pacing pulse into any of the pacing electrodes of the pacing system to avoid saturation of the sense amplifiers. The sense amplifier circuit 55 includes blanking circuitry for decoupling selected pairs of lead conductors and the IND-CAN electrode 20 from the inputs of the RA sense amplifier (and LA sense amplifier, if provided), the RV sense amplifier, and the LV sense amplifier during ABP, PVABP, and VBP. The sense amplifier circuit 55 also includes switching circuitry for coupling selected sensing electrode lead conductors and the IND-CAN electrode 20 to the RA sense amplifier (and LA sense amplifier, if provided), the RV sense amplifier, and the LV sense amplifier. Again, the sense electrode selection and control circuit 53 selects the conductors and associated pairs of sensing electrodes to be coupled to the output amplifier circuit 51 and the atrial and ventricular sense amplifiers within the sense amplifier circuit 55 for RA, LA, RV, and LV sensing along the desired unipolar and bipolar sensing vectors.

[0062] A right atrial depolarization or P-wave in the RA-SENSE signal sensed by the RA sense amplifier results in a RA-EVENT signal that is communicated to the digital controller / timer circuit 43. Similarly, a left atrial depolarization or P-wave in the LA-SENSE signal sensed by the LA sense amplifier, if provided, results in a LA-EVENT signal that is communicated to the digital controller / timer circuit 43. A ventricular depolarization or R-wave in the RV-SENSE signal sensed by the ventricular sense amplifiers results in a RV-EVENT signal that is communicated to the digital controller / timer circuit 43. Similarly, a ventricular depolarization or R-wave in the LV-SENSE signal sensed by the ventricular sense amplifiers results in a LV-EVENT signal that is communicated to the digital controller / timer circuit 43. The RV-EVENT, LV-EVENT, and RA-EVENT, LA-SENSE signals can be inappropriately or non-inappropriately sensed, and can be inadvertently triggered by electrical noise signals or aberrantly conducted depolarization waves rather than true R-waves or P-waves.

[0063] The techniques described in this disclosure, including those attributed to IMD 16 and / or various constituent components, can be implemented, at least in part, in hardware, software, firmware or any combination thereof. For example, various aspects of the techniques can be implemented within one or more processors, including one or more microprocessors, DSPs, ASICs, FPGAs, or any other equivalent integrated or discrete logic circuitry, as well as any combinations of such components, embodied in programmers, such as physician or patient programmers, stimulators, image processing apparatuses, or other devices. The terms "module," "processor" or "processing circuitry" can generally refer to any of the

[0064] When implemented in software, the functions attributed to the systems, devices and techniques described in this disclosure can be embodied as instructions on a computer-readable medium, such as RAM, ROM, NVRAM, EEPROM, FLASH memory, magnetic data storage media, optical data storage media, or the like. The instructions can be executed by one or more processors to support one or more aspects of the functionality described in this disclosure.

[0065] Such hardware, software, and / or firmware can be implemented within the same device or within separate devices to support the various operations and functions described in this disclosure. In addition, any of the described units, modules or components can be implemented together or separately as discrete but interoperable logic devices. Depiction of different features as modules or units is intended to highlight different functional aspects and does not necessarily imply that such modules or units must be realized by separate hardware or software components. Rather, functionality associated with one or more modules or units can be performed by separate hardware or software components, or integrated within common or separate hardware or software components.

[0066] According to the present disclosure, illustrative devices, systems, and methods can be used to generate a cardiac status or a cardiac trend based on a patient's cardiac health. The cardiac status can provide useful information about a trend or pattern of a patient's determined cardiac health over an extended period of time. The patient's cardiac status can be useful for assessing and quantifying a patient's health, specifically the health of the patient's heart, and for assessing and managing the patient's treatment and cardiac management care. For example, illustrative devices, systems, and methods can be used to assist in configuring and / or adjusting one or more cardiac therapy settings of a cardiac therapy delivered to a patient, such as, for example, optimizing the A-V interval or delay and A-V interval or delay of a pacing therapy (e.g., left-ventricular-only or left- single-ventricular pacing therapy) and the V-V interval or delay of a pacing therapy (e.g., biventricular pacing therapy). In another example, illustrative devices, systems, and methods can be used to assist in configuring and / or adjusting a drug therapy delivered to a patient in response to the patient's cardiac status. In another example, illustrative devices, systems, and methods can be used to assist in configuring and / or adjusting a physical therapy of a patient in response to the patient's cardiac status.

[0067] As described further below, the cardiac status can be useful for relating reduced physical activity to an undesirable patient condition, such as, for example, the onset or progression of heart failure. The devices, systems, and methods can generally be described as being used to quantify and assess a patient's physical response to, for example, a perturbation, and generate a cardiac status of the patient based on data generated from a plurality of physical responses of the patient to, for example, a perturbation. A basic assumption of heart rate recovery is that a patient's heart rate will increase accordingly with an increase in activity. However, there can be instances where the heart rate does not increase accordingly with an increase in activity, and an undesirable patient condition can be determined.

[0068] In this regard, one example of a perturbation can be a deviation from a patient's normal heart rate. However, perturbations can occur in different ways or forms and at different time scales (a few heartbeats to minutes, hours, days of heartbeats). Some examples of perturbations include a syncope event (e.g., cardiac arrest) or premature depolarization (atrial or ventricular) or the onset of pneumonia. Other health states (e.g., disease states) to consider can include chronic obstructive pulmonary disease (COPD) states and anemia states. Other examples of perturbations, particularly for HF patients, can include strenuous activity (e.g., exercise) or arrhythmia.

[0069] Figure 4A flowchart illustrating an example method 100 of generating a patient's cardiac status using perturbation recovery information is shown. A perturbation to the heart can cause an increase in the demand for oxygen in the patient. In response to the perturbation, the cardiac output can need to be increased to supply more oxygen to the organs and / or tissues with increased demand for oxygen. More oxygen can be supplied by supplying more oxygen to the lungs (e.g., by breathing faster and / or harder) or by increasing the efficiency of delivering oxygen to the organs in need. One way to increase the efficiency of delivering oxygen to the organs is to increase the cardiac output. Cardiac output is a function of the volume of blood pumped by the heart (SV) and the heart rate (HR). Cardiac output can be increased by increasing the stroke volume of the patient (e.g., the volume of blood pumped from the left ventricle per beat) and / or the heart rate (e.g., the number of beats of the heart per minute). The method 100 can include, at 102, measuring a perturbation effect during each of a plurality of perturbation recovery events. The measurements track the patient's natural or normal cardiac response capacity to stress (e.g., a perturbation), such as can measure, for example, heart rate recovery (HRR). During heart rate recovery, the patient's heart rate typically decreases over a duration of time following an activity that causes an increase in heart rate (e.g., a peak heart rate activity or a perturbation).

[0070] In a normal healthy person, the body's response to a perturbation has a typical or normal response time, degree of change, and pattern of change (e.g., time course of change signal morphology). In an acute or chronic disease state, these body responses will differ from the typical body responses experienced by a normal healthy person. For example, for a patient with acute HF, the condition can worsen following a sudden increase in activity that causes a significant increase in heart rate, and it can take longer to recover and return to baseline. The heart of an HF patient is typically not as good as that of a patient without HF, so the heart of an HF patient can have to maintain the increased heart rate for a longer duration to compensate, which can typically result in decompensated heart failure. Similarly, the patient's breathing can include breathing faster and / or harder for an extended period of time following a sudden increase in activity.

[0071] After the cardiovascular system is perturbed, the patient's body reacts through compensatory mechanisms to cope with the perturbation and to restore the cardiovascular system to its pre-perturbation state and / or to prepare for another perturbation. In other words, during a perturbation recovery event or over a period of time after the patient is perturbed, the patient's body reacts to recover from the perturbation. When the patient has a chronic disease, the patient's body can not be able to restore the cardiovascular system to normal, or can need more than a typical period of time (or a different time distribution, but the same or less time) to restore balance during a perturbation recovery event. The method 100 can include, at 104, determining perturbation recovery information or data based on the measured perturbation effects during each of the plurality of perturbation recovery events. The perturbation recovery information can include any information related to the patient's cardiac health. For example, the perturbation recovery information can include a difference in the patient's respiration or heart rate over a period of time, a duration for the patient's respiration or heart rate to return to a baseline, or a duration for the patient's respiration or heart rate to recover to another predetermined level, among others. The method 100 can also include, at 106, generating a cardiac state of the patient based on the perturbation recovery information from the plurality of perturbation recovery events, as further described below.

[0072] Figure 5A is an illustrative block diagram of an apparatus 150 for determining heart rate recovery information and generating a cardiac state of a patient in accordance with aspects of the present disclosure. The apparatus 150 can be an external apparatus or an internal, implanted apparatus. There are various types of apparatuses 150, implanted and external, that can be used to monitor patient information in accordance with aspects of the present disclosure. Some non-limiting examples of suitable implanted apparatuses include pacemakers, implantable cardioverter / defibrillators (ICDs), cardiac resynchronization therapy (CRT) devices, insertable cardiac monitors, subcutaneous devices, and non-therapeutic monitoring devices. Examples of suitable external apparatuses include smart wristbands, patches, smartwatches, chest straps, on- or smart phone combined with a smart phone, and the smart phone itself.

[0073] The apparatus 150 can be used to sense and monitor various patient health status information, e.g., a patient's heart rate, activity level, heart rate variability, arrhythmic state, respiration rate, fluid status, etc. The patient health status information can be stored and / or transmitted to another apparatus to generate patient alerts and provide feedback to a clinician regarding the patient. Such information can be used to optimize the patient's therapy apparatus and manage the patient's health. In one example, the apparatus 150 can use heart rate recovery information determined over a plurality of heart rate recovery events to generate or can be used to generate a cardiac state, as further described below.

[0074] Device 150 can include sensing device 186 and processing device 180. Sensing device 186 can include a variety of sensors to sense one or more data from a patient, which can be useful to generate a cardiac state of the patient, e.g., a heart rate and activity level of the patient. Sensing device 186 can be similar to the sensors described above with respect to sensing module 86, and further described below. Processing device 180 can include processing circuitry, similar to the processing circuitry described above with respect to processor 80, and further described below.

[0075] In one example, device 150 can use sensing device 186 to sense, process, and monitor activity information, e.g., patient movement information based on accelerometer signals, pulse wave velocity signals, electrocardiogram signals, intracardiac electrogram signals, blood pressure measurements, and / or perfusion rates. In other words, sensing device 186 can include activity sensors to collect activity values, levels, and signals. In one example, sensing device 186 includes an accelerometer, among other suitable sensors.

[0076] Further, sensing device 186 can include sensors for measuring pressure, temperature, posture, impedance, etc., as well as various combinations of such sensor signal outputs. Still further, sensing device 186 can include sensors that sense heart rate, activity level, and other biological information of the patient. In some examples, sensing device 186 can sense and measure at least one of respiratory rate and respiratory effort, heart rate and short-term heart rate variability, blood pressure and short-term fluid shifts of the patient. The sensed measurements can be transmitted from sensing device 186 to processing device 180 for processing in order to quantify the patient’s physical response to a perturbation, e.g., to generate a cardiac state of the patient.

[0077] Processing device 180 can determine heart rate recovery information for each of the plurality of heart rate recovery events, and determine a trend in the determined heart rate recovery information within the plurality of heart rate recovery events to generate a cardiac state of the patient. Each heart rate recovery can be referred to as a “heart rate recovery event.” In one example, processing device 180 can determine, for example, a heart rate recovery of the patient within each of a plurality of heart rate recovery events based on sensed heart rate and activity level received from sensing device 186. Each of the plurality of heart rate recovery events includes a decrease in heart rate of the patient over a duration of time following an activity that causes an increase in heart rate (e.g., a peak heart rate activity) for a sustained prescribed period of time. For example, a heart rate of the patient increases during exercise; after stopping the exercise, the heart rate of the patient decreases from the increased heart rate to a lower heart rate (e.g., a pre-increased heart rate) over a determined period of time. In some embodiments, processing device 180 can determine a start and termination of the activity that causes the increase in heart rate based on, for example, the peak heart rate activity.

[0078] A cardiac status can be generated based on at least some of the plurality of heart rate recovery events. The generated cardiac status can provide trend and diagnostic information about the patient's heart. The processing device 180 can determine a cardiac risk score for the patient based on the generated cardiac status. The processing device 180 can determine a pacing frequency of cardiac therapy to be delivered to the patient's heart by a pacing device based on the generated pattern / trend. The pacing device can be a separate device from the device 150 or can be the same device. In some examples, the patient with an implanted cardiac therapy device (i.e., a pacing device) will suspend pacing during the heart rate recovery events and activation of the sensing device 186 monitoring the heart rate recovery events. In some examples, the system 200 can include a plurality of electrodes and therapy delivery circuitry operably coupled to the plurality of electrodes (not shown) to deliver cardiac therapy to the patient's heart based on the generated cardiac status.

[0079] Figure 5B is a illustrative block diagram of a system 200 for determining heart rate recovery information and generating a cardiac status of a patient in accordance with aspects of the present disclosure. The system 200 includes a sensing device 286 and a processing device 280, similar to the sensing device 186 and the processing device 180 as described above. In this example, the system 200 also includes a notification device 282 and a communication device 288. One or more of the sensing device 286, the processing device 280, the notification device 282, and the communication device 288 can be included in one or more implanted or external devices. For example, the devices 286, 280, 282, and 288 can be included in a single device 150, such as an external patch or an ICD. In another example, the notification device 282 and the communication device 288 can be included in one device (e.g., a smart wristband) and the sensing device 286 and the processing device 280 can be included in another device (e.g., a subcutaneous device). Other types and combinations of devices 286, 280, 282, and 288 included in devices are acceptable.

[0080] In some examples, the communication device 288 can be used to transmit or communicate the patient's activity information, heart rate recovery information, and / or cardiac status from the system 200 to a physician located remotely from the patient (e.g., to a physician office when the patient is not located at the physician office) or the internet (e.g., the cloud), etc. The communication can be over a network, such as a local area network (LAN) and / or a wide area network (WAN). The communication network can include an intranet communication network, an internet communication network, or similar high-speed communication network including wireless communication networks.

[0081] In some examples, the transmitted communication can also include alerts, status updates, medical device adjustment notifications, and other information communications. In some examples, Figure 5BThe communication device 288 illustrated in the middle can be configured to externally communicate heart rate recovery information, heart status, reminders, alerts, or any other information to another device (e.g., a computing device such as a server, smartwatch, smartphone, tablet, etc.). The device can store data, programs, instructions, or any other machine-readable data.

[0082] In some examples, the notification device 282 can be used to signal or notify the patient to begin and / or terminate an activity (e.g., an exercise regimen). For example, the notification device 282 can be employed to prompt the patient to begin or terminate a specified exercise regimen for a certain period of time. The notification device 282 can provide a notification to the user that is tactile, audible, visual, or a combination of tactile, audible, and visual.

[0083] In one example, the sensing device 286 can sense the patient's heart rate to establish a baseline heart rate prior to signaling the patient to begin the activity through the notification device 282. In one example, the processing device 280 can thereafter determine or confirm that the patient complies with the request to begin the activity by sensing and monitoring both the activity level and the heart rate of the patient during the activity event. After the patient maintains an increased activity level for a specified amount of time, the system 200 can employ the notification device 282 to notify the patient to terminate the exercise and begin rest. The sensing device 286 can sense the heart rate at the termination of the activity and at the completion of the predetermined recovery period. The heart rate recovery for the heart rate recovery event can be determined by the processing device 280 using the difference or delta between the heart rate at the termination of the activity and the heart rate at the completion of the predetermined recovery period.

[0084] In one example, if the processing device 280 determines that a heart rate recovery event has not occurred over an extended period of time (e.g., 7 days), the patient can be notified or prompted by the notification device 282 to request heart rate recovery information and begin a prescribed activity or exercise regimen. In one example, the notification can also be communicated by the communication device 288 to a remote device such as a monitoring device (e.g., a computing device) at a physician's office.

[0085] Figure 6A flowchart illustrating an example method 300 of generating a patient's cardiac status is shown in accordance with aspects of the present disclosure. According to the illustrative example method 300, at 302, a patient's heart rate can be measured or sensed during each of a plurality of heart rate recovery events. Each of the plurality of heart rate recovery or heart rate recovery events can be measured immediately after an increase in activity level, such as a workout regimen, for a determined period of time. The workout regimen can be prescribed or proscribed to occur for a predetermined duration of time that is substantially the same for each of the plurality of heart rate recovery events for the patient. Alternatively, the prescribed or proscribed duration of time can be based on the patient's cardiac health. For example, a relatively healthy patient can use a longer duration than a patient with less healthy heart. One example workout regimen can include a patient repeatedly and consecutively walking up an elevated platform or staircase at a proscribed rate for a duration of time, such as three minutes, and then walking down the elevated platform or staircase. In one instance, a relatively healthy patient's heart rate recovery can be 20 beats per minute (bpm), while a patient experiencing acute HF can have a heart rate recovery of 5 bpm.

[0086] In some instances, at 304, the patient's heart rate recovery information can be determined based on the measured heart rate during each of the plurality of heart rate recovery events. In some instances, determining the heart rate recovery information includes sensing or measuring a baseline heart rate (HR1) of the patient during a period of inactivity or low activity. This period of inactivity or low activity can be identified opportunistically by the device or actively collected as a result of the device prompting the patient to stop activity. The patient then begins a workout regimen by increasing their activity level to a predetermined or threshold level for a predetermined or threshold activity duration and sensing or measuring a second heart rate (HR2) at the end of the activity duration. In other words, an activity that causes an increase in heart rate can be performed, resulting in the second heart rate. When the patient's activity level decreases to an inactivity or low activity level, a third heart rate (HR3) can be sensed at the end of a predetermined or threshold recovery duration after the end of the activity. The heart rate recovery can be determined by subtracting HR3 from HR2. In other words, the change in heart rate from the period of activity to the recovery period after the activity can be determined and used as the heart rate recovery information.

[0087] The recovery period following the activity that caused the increase in heart rate can be between about 15 seconds to about 3 hours, during which heart rate recovery information can be determined. In one or more embodiments, the recovery period can be greater than or equal to about 15 seconds, greater than or equal to about 25 seconds, greater than or equal to about 45 seconds, greater than or equal to about 1 minute, greater than or equal to about 2 minutes, greater than or equal to about 5 minutes, greater than or equal to about 15 minutes, greater than or equal to about 30 minutes, and / or less than or equal to about 3 hours, less than or equal to about 2 hours, less than or equal to about 55 minutes, less than or equal to about 40 minutes, less than or equal to about 25 minutes, less than or equal to about 10 minutes, less than or equal to about 4 minutes, etc.

[0088] During a time period encompassing a plurality of heart rate recovery events, for example, a cardiac status of the patient can be generated at 306 based on the heart rate recovery information determined during the plurality of heart rate recovery events.

[0089] The method 300 can include prompting the patient to begin an activity that causes an increase in heart rate (e.g., an exercise regimen) such that a heart rate recovery event can be monitored. Alternatively, the method can include determining whether the patient has begun an activity that causes an increase in heart rate (e.g., an exercise regimen) such that a heart rate recovery event can be monitored during. For example, an inherent period of activity (e.g., exercise) that satisfies or exceeds a predetermined criterion or threshold based on the patient's activity level and the increase in heart rate can be automatically sensed.

[0090] The patient's compliance with the prescribed exercise regimen can affect the determination of whether additional heart rate recovery events are needed to generate a cardiac status of the patient. For example, the patient's compliance with the prescribed exercise regimen can result in a less defined or more abrupt onset and offset of activity than prompted to the patient. Regardless, the device or system can determine that the patient is exercising based on sensed activity information, such as heart rate, and determine heart rate recovery when the exercise regimen ceases. In other words, sensing and monitoring the patient's heart rate during a heart rate recovery event can be initiated based on sensed activity level of the patient indicative of a cessation of the increase in heart rate.

[0091] As discussed above with respect to Figure 5B At least one of the determined heart rate recovery information or the generated cardiac status can be communicated to an extracorporeal or external device. In one example, cardiac therapy delivered by an implantable medical device (e.g., a pacemaker or a subcutaneous drug delivery device) can be determined and / or adjusted based on the generated cardiac status. In one example, the generated cardiac status can be employed or implemented as a risk score for future heart failure events.

[0092] Figure 7is an example graphical representation of a trend of heart rate recovery information over time that can be used to provide a cardiac status 400. The cardiac status indicated by line 400 can be generated using a plurality of heart rate recovery events 402 that indicate a trend of heart rate recovery information generated from heart rate recovery events occurring over an extended period of time, e.g., days, weeks, or months. In other words, a patient's cardiac status can be based on the generated trend of heart rate recovery information. Each of the individual heart rate recovery events 402 are graphically indicated in Figure 7 More or fewer heart rate recovery events 402 can be used to generate the cardiac status 400 and the plurality of heart rate recovery events 402 contained in Figure 7 are used for illustrative purposes only, as do the shape and slope of the cardiac status 400 generated from the plurality of heart rate recovery events 402. As indicated by the time axis, the heart rate recovery events 402 can be recorded in chronological order over time to generate the cardiac status 400 of the patient. As the graph illustrates, the sensed information of each heart rate recovery taken over several heart rate recovery events 402 can be compiled to generate the cardiac status 400 that indicates the cardiac health of the patient. The cardiac status 400 can be generated continuously or periodically as additional heart rate recovery events.

[0093] In one example, a plurality of heart rate recovery events 402 can be taken in a given day (or other time period) with the goal of preserving data from the most similar intrinsic exercise sessions (in terms of activity level, duration, maximum heart rate, etc.) in order to make the most meaningful and accurate comparisons of heart rate recovery over time. This can allow for "personalization" of exercise regimens for a given patient. For example, a healthy patient can be able to achieve a higher level of activity over a longer period of time compared to a patient with a poorer health status. In one example, the illustrative device, system, or method can monitor and record a patient's exercise patterns to generate a trend of the patient's exercise patterns over time and determine or develop a tracking pattern related to the time at which the sensed and monitored activity information is most useful. Such information can be collected without the patient being in a physician's office.

[0094] ​For example, the generated cardiac status described herein can be useful for anticipating or predicting future heart failure events or, for example, patient CHF prognosis and disease progression. The cardiac status of a patient over a long period of time can assist a physician in diagnosing the patient's cardiac condition and, in some examples, can assist in determining appropriate adjustments to cardiac therapy delivered to the patient. For example, the generated cardiac status can be used to determine adjustments to pacing (e.g., A-V delay) delivered to the patient. Objective measures of long-term trends in patient activity and cardiac health, as generated by the cardiac status, can be useful for early or ongoing identification of heart disease and timely therapy. For example, different recovery patterns can be observed in patients with both COPD and HF when COPD worsens versus when HF worsens, and thus determining and generating the cardiac status of a patient can aid in differential diagnosis.

[0095] In response to the collected data and the generated cardiac status, a healthcare system can respond in a variety of ways. Some healthcare systems can be capable of generating health alerts based on the cardiac status generated by the device 150 or system 200. One example healthcare system can be described in U.S. Patent Application 2010 / 0030293 to Sarkar et al., which is incorporated by reference herein in its entirety, which is capable of generating alerts in response to a cardiac status for a patient to seek medical treatment, which is incorporated by reference herein in its entirety. For example, the device 150 or system 200 can detect a worsening of heart failure in a patient based on the cardiac status, and upon detecting the worsening of heart failure, can provide an alert to the patient so that the patient can seek medical attention prior to experiencing a heart failure event. In other examples, an alert can alternatively or additionally be provided to a physician's office, such as over the internet and a computing device at the physician's office.

[0096] Example Embodiments

[0097] Example 1. A method comprising:

[0098] measuring a heart rate of a patient during a plurality of heart rate recovery events, wherein each heart rate recovery event of the plurality of heart rate recovery events comprises a duration of time following an activity that causes an increase in heart rate;

[0099] determining heart rate recovery information based on the measured heart rate during each heart rate recovery event of the plurality of heart rate recovery events;

[0100] generating a heart rate recovery information trend from the determined heart rate recovery information within the plurality of heart rate recovery events over a period of time;

[0101] generating a cardiac status of a heart failure patient based on the generated heart rate recovery information trend; and

[0102] detecting worsening heart failure in a heart failure patient based on the cardiac state.

[0103] Embodiment 2. The method of embodiment 1, wherein the duration is substantially the same for each of the plurality of heart rate recovery events for a heart failure patient.

[0104] Embodiment 3. The method of any one of embodiments 1-2, wherein the duration is based on a cardiac health of a heart failure patient.

[0105] Embodiment 4. The method of any one of embodiments 1-3, further comprising:

[0106] prompting a heart failure patient to initiate an activity that causes the heart rate to increase.

[0107] Embodiment 5. The method of any one of embodiments 1-4, further comprising:

[0108] sensing an activity level of a heart failure patient,

[0109] wherein measuring the heart rate of a heart failure patient during a heart rate recovery event is initiated based on a sensed decrease in the activity level of the heart failure patient.

[0110] Embodiment 6. The method of any one of embodiments 1-5, further comprising:

[0111] communicating at least one of the determined heart rate recovery information and the generated cardiac state to an extracorporeal device.

[0112] Embodiment 7. The method of any one of embodiments 1-6, further comprising:

[0113] initiating cardiac therapy by an implantable medical device on a heart failure patient based on the generated cardiac state.

[0114] Embodiment 8. The method of any one of embodiments 1-7, further comprising issuing an alert to a heart failure patient to seek medical care in response to detecting worsening.

[0115] Embodiment 9. An apparatus comprising:

[0116] a sensor device comprising a heart rate sensor to sense a heart rate of a heart failure patient; and

[0117] a processing device operably coupled to the sensor device and comprising processing circuitry configured to:

[0118] monitoring heart rate of the heart failure patient using the heart rate sensor during a plurality of heart rate recovery events, wherein each heart rate recovery event of the plurality of heart rate recovery events comprises a duration of time following an activity that causes an increase in heart rate,

[0119] determining heart rate recovery information based on the measured heart rate during each heart rate recovery event of the plurality of heart rate recovery events; and

[0120] generating a heart rate recovery information trend from the determined heart rate recovery information within the plurality of heart rate recovery events over a certain time period;

[0121] generating a cardiac status of the heart failure patient based on the generated heart rate recovery information trend; and

[0122] detecting a worsening of heart failure of the heart failure patient based on the cardiac status.

[0123] Embodiment 10. The apparatus of embodiment 9, further comprising:

[0124] a notification device for notifying the heart failure patient to begin an activity that causes the increase in heart rate.

[0125] Embodiment 11. The apparatus of embodiment 10, wherein the processing circuitry is further configured to sound an alarm for medical attention to the heart failure patient using the notification device in response to detecting a worsening.

[0126] Embodiment 12. The apparatus of any one of embodiments 9-11, wherein the processing device further comprises communication circuitry configured to communicate at least one of the heart rate recovery information and the cardiac status to another external apparatus.

[0127] Embodiment 13. The apparatus of any one of embodiments 9-12, wherein the sensing device further comprises an activity level sensor for sensing an activity level of the heart failure patient, and wherein the processing circuitry is further configured to sense the activity level of the patient using the activity level sensor to determine to terminate the activity based on a decrease in the sensed activity level.

[0128] Embodiment 14. The apparatus of any one of embodiments 9-13, wherein the processing circuitry is further configured to determine a therapy to be delivered to the heart failure patient based on the generated cardiac status.

[0129] Example 15. The apparatus of any of Examples 9-14, wherein the processing circuitry is further configured to determine, based on the generated cardiac status, a pacing frequency of a cardiac therapy to be delivered by a pacing apparatus to a heart of the heart failure patient.

[0130] Example 16. The apparatus of any of Examples 9-15, further comprising:

[0131] at least one pacing electrode; and

[0132] therapy delivery circuitry operably coupled to the at least one electrode to deliver a cardiac therapy to a heart of the heart failure patient based on the generated cardiac status.

[0133] Example 17. A system comprising:

[0134] a sensor device comprising a heart rate sensor to sense a heart rate of a heart failure patient;

[0135] a processing device operably coupled to the sensor device and comprising processing circuitry configured to:

[0136] measure a heart rate of the heart failure patient during a plurality of heart rate recovery events, wherein each heart rate recovery event of the plurality of heart rate recovery events comprises a duration of time following an activity that causes an increase in heart rate;

[0137] determine heart rate recovery information based on the measured heart rate during each heart rate recovery event of the plurality of heart rate recovery events; and

[0138] generate a heart rate recovery information trend over a period of time;

[0139] detect a worsening of heart failure of the heart failure patient based on the generated heart rate recovery information trend; and

[0140] a notification device to notify the heart failure patient to begin the activity that causes the increase in heart rate.

[0141] Example 18. The system of Example 17, wherein the processing device further comprises communication circuitry configured to transmit at least one of the heart rate recovery information and the generated heart rate recovery information trend to another external apparatus.

[0142] Example 19. The system of any of Examples 17-18, wherein the sensing device further comprises an activity level sensor for sensing an activity level of the heart failure patient, and wherein the processing circuitry is further configured to sense an activity level of the heart failure patient using the activity level sensor to determine to terminate the activity based on a decrease in the sensed activity level.

[0143] Example 20. The system of any of Examples 17-19, wherein the processing circuitry is further configured to determine a pacing frequency of a cardiac therapy to be delivered by a pacing device to a heart of the heart failure patient based on the generated heart rate recovery information trend.

[0144] Example 21. A method comprising:

[0145] measuring a perturbation effect of a patient during a plurality of perturbation recovery events, wherein each perturbation recovery event of the plurality of perturbation recovery events comprises a duration of time after the patient is perturbed;

[0146] determining perturbation recovery information based on the measured perturbation effect during each perturbation recovery event of the plurality of perturbation recovery events; and

[0147] generating a cardiac state of the patient from the determined perturbation recovery information within the plurality of perturbation recovery events.

[0148] Example 22. The method of Example 21, further comprising:

[0149] generating a heart rate recovery information trend over a period of time; wherein the generated cardiac state of the patient is based on the generated heart rate recovery information trend.

[0150] Example 23. The method of Example 21, wherein the patient perturbation comprises a syncope event.

[0151] Example 24. The method of Example 21, wherein the patient perturbation comprises premature depolarization.

[0152] Example 25. The method of Example 21, wherein the patient perturbation comprises an infection.

[0153] Example 26. An apparatus comprising:

[0154] a sensor device comprising a heart rate sensor for sensing a heart rate of a patient; and

[0155] a processing device operably coupled to the sensor device and comprising processing circuitry configured to:

[0156] measuring perturbation effects of a patient during a plurality of perturbation recovery events, wherein each perturbation recovery event of the plurality of perturbation recovery events comprises a duration of time after the patient is subjected to a perturbation,

[0157] determining perturbation recovery information based on the measured perturbation effects during each perturbation recovery event of the plurality of perturbation recovery events; and

[0158] generating a cardiac state of the patient from the determined perturbation recovery information within the plurality of perturbation recovery events.

[0159] Embodiment 26. The apparatus of Embodiment 26, wherein the processing device further comprises communication circuitry configured to transmit at least one of the heart rate recovery information and the cardiac state to another external apparatus.

[0160] Embodiment 27. The apparatus of Embodiment 26, wherein the patient perturbation comprises a syncope event.

[0161] Embodiment 28. The apparatus of Embodiment 26, wherein the patient perturbation comprises premature depolarization.

[0162] Embodiment 29. The apparatus of Embodiment 26, wherein the patient perturbation comprises an infection.

[0163] It should be understood that various aspects disclosed herein can be combined in different combinations than the combinations expressly presented in the specification and attached drawings. It should also be understood that certain actions or events that are described in association with one or more processes or methods described herein can be performed in different orders than expressly described in the specification and attached drawings. Additionally, although certain aspects of the disclosure are described as being performed by a single module or unit for purposes of clarity, it should be understood that techniques of the disclosure can be performed by a combination of units or modules associated with, for example, a medical device.

[0164] In one or more examples, the described techniques can be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions can be stored as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media can include computer-readable storage media, which corresponds to a tangible medium such as data storage media (e.g., RAM, ROM, EEPROM, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer).

[0165] Instructions can be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term "processor," as used herein can refer to any of the foregoing structure or any other physical structure suitable for implementation of the described techniques. Moreover, the described techniques can be

[0166] Although the present disclosure has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and scope of the disclosure.

Claims

1. An apparatus comprising: a sensor device including a heart rate sensor to sense a heart rate of a heart failure patient; and a processing device operably coupled to the sensor device and including processing circuitry configured to: monitor the heart rate of the heart failure patient during a plurality of heart rate recovery events using the heart rate sensor, wherein each heart rate recovery event of the plurality of heart rate recovery events includes a duration of time following an activity that causes an elevated heart rate, determine heart rate recovery information based on the monitored heart rate during each heart rate recovery event of the plurality of heart rate recovery events, wherein the heart rate recovery information for each heart rate recovery event of the plurality of heart rate recovery events includes a difference between the elevated heart rate and a recovery heart rate measured at completion of the heart rate recovery event; generate a heart rate recovery information trend from the determined heart rate recovery information within the plurality of heart rate recovery events over a certain time period; generate a cardiac status of the heart failure patient based on the generated heart rate recovery information trend; and in response to the cardiac status indicating that the difference between the elevated heart rate and the recovery heart rate exhibits a downward trend during the plurality of heart rate recovery events, detect a worsening of heart failure of the heart failure patient.

2. The apparatus of claim 1, further comprising: a notification device to notify the heart failure patient to begin the activity that causes the elevated heart rate.

3. The apparatus of claim 2, wherein the processing circuitry is further configured to sound an alarm for medical attention to the heart failure patient using the notification device in response to detecting the worsening.

4. The apparatus of claim 1, wherein the processing device further includes communication circuitry configured to communicate at least one of the heart rate recovery information and the cardiac status to another external apparatus.

5. The apparatus of claim 1, wherein the sensor device further includes an activity level sensor to sense an activity level of the heart failure patient, and wherein the processing circuitry is further configured to sense the activity level of the heart failure patient using the activity level sensor to determine to terminate the activity based on a decrease in the sensed activity level.

6. The apparatus of claim 1, wherein the processing circuitry is further configured to determine a therapy to be delivered to the heart failure patient based on the generated cardiac status.

7. The apparatus of claim 1, wherein the processing circuitry is further configured to determine a pacing frequency of a cardiac therapy to be delivered by a pacing apparatus to a heart of the heart failure patient based on the generated cardiac status.

8. The apparatus of claim 1, further comprising: at least one pacing electrode; and therapy delivery circuitry operably coupled to the at least one pacing electrode to deliver a cardiac therapy to a heart of the heart failure patient based on the generated cardiac status.

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