Patent Publication Number: US-2023144375-A1

Title: Pvc adjusted af detection

Description:
CLAIM OF PRIORITY 
     This application is a continuation of U.S. patent application Ser. No. 16/845,552, filed Apr. 10, 2020, which claims the benefit of priority under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application Ser. No. 62/833,217, filed on Apr. 12, 2019, which are herein incorporated by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     This document relates generally to medical devices, and more particularly, but not by way of limitation, to systems, devices, and methods for adjusting atrial fibrillation (AF) detection or classification using premature ventricular contraction (PVC) information. 
     BACKGROUND 
     Heart failure (HF) is a reduction in the ability of the heart to deliver enough blood to meet bodily needs. HF patients commonly have enlarged heart with weakened cardiac muscles, resulting in reduced contractility and poor cardiac output of blood. Signs of HF include pulmonary congestion, edema, difficulty breathing, etc. HF is often a chronic condition, but can also occur suddenly, affecting the left, right, or both sides of a heart. Causes of HF include, among others, coronary artery disease, myocardial infarction, high blood pressure, atrial fibrillation, valvular heart disease, alcoholism, infection, cardiomyopathy, or one or more other conditions leading to a decreased pumping efficiency of the heart. 
     An arrhythmia is an abnormal heart rhythm, or any heart rhythm (e.g., fast, slow, irregular, etc.) that is not a normal heart rhythm. Arrhythmias include, among others: bradycardia; tachycardia; premature, extra, or skipped heart beats; heart defects; and atrial or ventricular fibrillation affecting one or more chambers of the heart. Atrial fibrillation (AF) is as an abnormal heart rhythm characterized by rapid and irregular activity in the left or right atria of the heart. AF is commonly associated with a reduction in cardiac output, an increased risk of heart failure (HF), dementia, and stroke. Risk factors for AF include, among others, high blood pressure, heart failure (HF), valvular heart disease, COPD, obesity, and sleep apnea. 
     Premature ventricular contractions (PVCs) (also referred to as premature ventricular complexes, ventricular premature beats, or ventricular extrasystoles or palpitations) are premature or extra heartbeats that begin in the left or right ventricles of the heart, often originating sooner than the next expected heartbeat, disrupting a normal heart rhythm that originates in the sinoatrial (SA) node in the right atrium of the heart. PVCs are often associated with injury to the heart muscle, such as from coronary artery disease, congenital heart disease, high blood pressure, or HF. 
     An ambulatory medical device (AMD), such as an implantable, wearable, or other external medical device, can be configured to monitor, detect, or treat various conditions, including HF, arrhythmias, etc. 
     SUMMARY 
     This document discusses, among other things, systems and methods to receive cardiac electrical information of a subject, detect a premature ventricular contraction (PVC) event in a first detection window using the received cardiac electrical information, determine a count of detected PVC events in the first detection window, remove cardiac electrical information associated with the detected PVC event from the first detection window based on the determined count of detected PVC events, and detect an indication of atrial fibrillation of the subject for the first detection window using remaining cardiac electrical information in the first detection window. 
     In an example, the system can include a signal receiver circuit configured to receive cardiac electrical information of a subject and an assessment circuit configured to detect a premature ventricular contraction (PVC) event in a first detection window using the received cardiac electrical information from the first detection window, determine a count of detected PVC events in the first detection window, remove cardiac electrical information associated with the detected PVC event from the first detection window based on the determined count of detected PVC events, and detect an indication of atrial fibrillation of the subject for the first detection window using remaining cardiac electrical information in the first detection window. 
     In another example, the system can include a signal receiver circuit configured to receive cardiac electrical information of a subject and an assessment circuit configured to detect a premature ventricular contraction (PVC) event using the received cardiac electrical information, detect, using the received cardiac electrical information, an indication of atrial fibrillation of a subject using one of multiple atrial fibrillation detection modes, each of the multiple atrial fibrillation detection modes configured to detect atrial fibrillation of the subject, determine a count of detected PVC events in a first detection window, and transition between different first and second atrial fibrillation detection modes of the multiple atrial fibrillation detection modes based on the determined count of PVC events in the first detection window. 
     Example 1 is a system, comprising: a signal receiver circuit configured to receive cardiac electrical information and premature ventricular contraction (PVC) information of a subject; and an assessment circuit configured to: detect atrial fibrillation (AF) of the subject using the received cardiac electrical information; and adjust the AF detection using the received PVC information. 
     In Example 2, the subject matter of Example 1 optionally includes wherein the assessment circuit is configured to determine a PVC state of the subject using the received PVC information and to adjust AF detection using the determined PVC state. 
     In Example 3, the subject matter of Example 2 optionally includes wherein the assessment circuit is configured to detect a PVC event using the received PVC information and to count detected PVC events in a first detection window. 
     In Example 4, the subject matter of Example 3 optionally includes wherein the assessment circuit is configured to determine the PVC state of the subject and to adjust the AF detection using the count of PVC events in the first detection window. 
     In Example 5, the subject matter of any one or more of Examples 3-4 optionally include wherein the received PVC information comprises an indication of a detected PVC event. 
     In Example 6, the subject matter of any one or more of Examples 3-5 optionally include wherein, if the PVC event count is below a first threshold, the assessment circuit is configured to determine a low-PVC state, and the system is configured to detect AF of the subject using a low-PVC burden mode, and wherein, if the PVC event count meets or exceeds the first threshold, the medial-device system is configured to determine a high-PVC state, and the system is configured to detect AF of the subject using a high-PVC burden mode. 
     In Example 7, the subject matter of Example 6 optionally includes wherein the assessment circuit is configured to detect AF in the first detection window using the received cardiac electrical information in the first detection window, wherein, to adjust the AF detection in the high-PVC burden mode, the assessment circuit is configured to remove detected PVC events from the first detection window. 
     In Example 8, the subject matter of Example 7 optionally includes wherein, to adjust the AF detection in the high-PVC burden mode, the assessment circuit is configured to remove detected PVC events, and cardiac electrical information from an interval at least one of preceding or proceeding the detected PVC events from the first detection window. 
     In Example 9, the subject matter of any one or more of Examples 3-8 optionally include wherein, if the PVC event count is below a first threshold, the assessment circuit is configured to determine a low-PVC state, and the assessment circuit is configured to detect AF of the subject using a low-PVC burden mode, wherein, if the PVC event count meets or exceeds the first threshold, but is below a second threshold higher than the first threshold, the medial-device system is configured to determine a high-PVC state, and the assessment is configured to detect AF of the subject using a high-PVC burden mode, and wherein, if the PVC event count meets or exceeds the second threshold, the system is configured to suspend AF detection. 
     In Example 10, the subject matter of any one or more of Examples 1-9 optionally include wherein the assessment circuit is configured to control storage of received cardiac electrical information using the received PVC information. 
     Example 11 is a method, comprising: receiving cardiac electrical information and premature ventricular contraction (PVC) information of a subject using a signal receiver circuit; detecting, using an assessment circuit, atrial fibrillation (AF) of the subject using the received cardiac electrical information; and adjusting, using the assessment circuit, AF detection using the received PVC information. 
     In Example 12, the subject matter of Example 11 optionally includes determining, using the assessment circuit, a PVC state of the subject using a count of PVC events in a first detection window. 
     In Example 13, the subject matter of any one or more of Examples 11-12 optionally include detecting, using the assessment circuit, a PVC event using the received PVC information; counting, using the assessment circuit, detected PVC events in a first detection window; and determining, using the assessment circuit, a PVC state of the subject using the count of PVC events in the first detection window, wherein adjusting AF detection comprises using the determined PVC state. 
     In Example 14, the subject matter of Example 13 optionally includes wherein determining the PVC state of the subject comprises determining: a low-PVC state if the PVC event count is below a first threshold; and a high-PVC state if the PVC event count meets or exceeds the first threshold, but is below a second threshold, and wherein detecting AF of the subject includes using: a low-PVC burden mode if the PVC event count is below the first threshold; and a high-PVC burden mode if the PVC event count meets or exceeds the first threshold, but is below the second threshold. 
     In Example 15, the subject matter of Example 14 optionally includes suspending AF detection if the PVC event count meets or exceeds the second threshold higher than the first threshold. 
     In Example 16, the subject matter of any one or more of Examples 14-15 optionally include wherein detecting AF comprises detecting an AF episode in the first detection window using the received cardiac electrical information in the first detection window, and wherein, in the high-PVC burden mode, adjusting AF detection comprises removing detected PVC events from the detection window and detecting AF using the remaining cardiac electrical information in the first detection window. 
     In Example 17, the subject matter of Example 16 optionally includes wherein, in the high-PVC burden mode, adjusting AF detection comprises removing detected PVC events and cardiac electrical information from an interval at least one of preceding or proceeding the detected PVC events from the first detection window. 
     Example 18 is a system, comprising: a signal receiver circuit configured to receive cardiac electrical information and premature ventricular contraction (PVC) information of a subject; and an assessment circuit configured to: detect atrial fibrillation (AF) of the subject using the received cardiac electrical information of the subject; determine a PVC state of the subject using a count of PVC events in a first detection window, including: if the PVC event count is below a first threshold, determine a low-PVC state; and if the PVC event count meets or exceeds the first threshold, determine a high-PVC state; and adjust the AF detection using the determined PVC state, including: detect AF of the subject using a low-PVC burden mode in the low-PVC state; and detect AF of the subject using a high-PVC burden mode in the high-PVC state, wherein an AF detection threshold is different in the high-PVC burden mode than in the low-PVC burden mode. 
     In Example 19, the subject matter of Example 18 optionally includes wherein the assessment circuit is configured to suspend atrial fibrillation detection if the PVC event count meets or exceeds a second threshold higher than the first threshold. 
     In Example 20, the subject matter of any one or more of Examples 18-19 optionally include wherein the assessment circuit is configured to detect AF in the first detection window using the received cardiac electrical information in the first detection window, wherein, to adjust the AF detection in the high-PVC burden mode, the assessment circuit is configured to remove detected PVC events and cardiac electrical information from an interval at least one of preceding or proceeding the detected PVC events from the first detection window. 
     In Example 21, subject matter (e.g., a system or apparatus) may optionally combine any portion or combination of any portion of any one or more of Examples 1-20 to comprise “means for” performing any portion of any one or more of the functions or methods of Examples 1-20, or at least one “non-transitory machine-readable medium” including instructions that, when performed by a machine, cause the machine to perform any portion of any one or more of the functions or methods of Examples 1-20. 
     This summary is intended to provide an overview of subject matter of the present patent application. It is not intended to provide an exclusive or exhaustive explanation of the disclosure. The detailed description is included to provide further information about the present patent application. Other aspects of the disclosure will be apparent to persons skilled in the art upon reading and understanding the following detailed description and viewing the drawings that form a part thereof, each of which are not to be taken in a limiting sense. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings, which are not necessarily drawn to scale, like numerals may describe similar components in different views. Like numerals having different letter suffixes may represent different instances of similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document. 
         FIG.  1    illustrates an example medical-device system including a signal receiver circuit and an assessment circuit. 
         FIG.  2    illustrates an example patient management system and portions of an environment in which the system may operate. 
         FIG.  3    illustrates an example of a Cardiac Rhythm Management (CRM) system and portions of an environment in which the CRM system can operate. 
         FIGS.  4 - 5    illustrate example episodes including PVCs. 
         FIG.  6    illustrates generally an example method including detecting AF of a subject. 
         FIG.  7    illustrates a block diagram of an example machine upon which any one or more of the techniques discussed herein may perform. 
     
    
    
     DETAILED DESCRIPTION 
     The present inventors have recognized, among other things, systems and methods to adjust atrial fibrillation (AF) detection to account for the occurrence of premature ventricular contractions (PVCs), such as using detected PVC events or PVC information to adjust one or more AF detection parameters, in certain examples, increasing the robustness of AF detection for the subject. 
     PVC events include mis-timed, “premature” events, often falsely detected as, or contributing to the false detection of, an AF event. Existing AF detection or classification can account for a number or rate of PVC events; however, they do not adequately tolerate above-average occurrences of PVCs, but generally attempt to distinguish PVC events from irregular rhythms, such as AF. 
     The present inventors have recognized, among other things, that in certain examples, such as the number or rate of PVC events is below a first threshold, it can be advantageous to not discriminate or distinguish PVC events, but to proceed with AF detection on all valid beats or intervals within a detection window. When the number or rate of PVC events increases above the first threshold, such between first and second thresholds, it can be advantageous to discriminate or distinguish PVC events, in certain examples, removing them from the detection window. In an example, otherwise valid beats or intervals preceding, proceeding, or both preceding and proceeding a detected PVC event can be removed from the detection window with the PVC event. In an example, when the number or rate of PVC events increases above the second threshold, AF detection can cease and a user may be informed. In other examples, more or less thresholds can be used, increasing the number of zones or sub-zones of AF or PVC detection adjustment. 
     Examples of AF detection algorithms can be found, for example, in the commonly assigned Krueger et al. U.S. patent application Ser. No. 14/825,669, titled “Atrial Fibrillation Detection Using Ventricular Rate Variability” (herein, “the &#39;669 application”); Perschbacher et al. U.S. patent application Ser. No. 15/082,440, titled “Atrial Fibrillation Detection” (herein, “the &#39;440 application”); Krueger et al. U.S. patent application Ser. No. 15/341,565, titled “Method and Apparatus for Enhancing Ventricular Based Atrial Fibrillation Detection Using Atrial Activity” (herein, “the &#39;565 application”); and Perschbacher et al. U.S. patent application Ser. No. 15/864,953, titled “Atrial Fibrillation Discrimination Using Heart Rate Clustering” (herein, “the &#39;953 application”), each of which are hereby incorporated by reference in their entireties, including their disclosure of AF detection and AF detection algorithms including, for example: AF detection using pairs of ventricular information detected from a ventricle, including rate changes and rate change characteristics, and determination of valid heart beats or intervals using various characteristics, including threshold rates, intervals, morphology criterion, etc., such as disclosed in the &#39;669 application; AF detection using a distribution of ventricular depolarization intervals, such as disclosed in the &#39;440 application; AF detection using atrial activity scores from an atrial detection window prior to a detected ventricular polarization, such as disclosed in the &#39;565 application; AF discrimination using clustered depolarization information, such as disclosed in the &#39;953 application, etc. 
     The present inventors have recognized, among other things, that an AF detection algorithm for a subject can be automatically adjusted using a determined PVC burden of the subject. For example, the PVC burden can be determined and categorized using a number of PVC events (or candidate PVC events) detected in a specified time window, in a specified number of cardiac intervals, a specified number of valid cardiac intervals, etc. In other examples, the PVC burden can be determined and categorized using a rate of PVC events (or candidate PVC events) to non-PVC events, etc. PVC events (or candidate PVC events) can be detected using one or more PVC detection criteria. The PVC burden can be scored, categorized, etc., and used to adjust one or more AF detection algorithms, such as one or more parameters of the one or more AF detection algorithms. Adjustments can include, for example, the cardiac electrical information (e.g., specific beats or intervals from a detection window, etc.) considered or removed for AF detection. For example, if the PVC burden is high, cardiac electrical information indicative of a PVC event can be removed from a detection window, and non-PVC events, or events below a PVC threshold or measure, can be considered. In other examples, cardiac electrical information preceding, proceeding, or both preceding and proceeding (e.g., one or more specific beats or intervals before, after, or before and after a PVC event, etc.) can be removed from consideration. Moreover, specific PVC detection criteria can be adjusted between or within the different determined PVC burdens. For example, as the PVC burden increases, the criteria used to determine a PVC event (e.g., frequency, morphology, timing, amplitude, etc.) can become less exclusive to account for the higher probability of the PVC event. 
     In an example, the PVC burden can be categorized, such as in one or more categories (e.g., low and high; low, high, and very high; first-fourth; etc.). In an example, a low PVC burden can include a normal burden, such as an expected PVC burden that one or more of the example AF detection algorithms above are designed to tolerate without interruption or suspension, etc. One or more additional PVC burdens beyond the low PVC burden can be determined, such as high and very-high PVC burdens, etc., and the one or more AF detection algorithms can be adjusted according to the determined one or more additional PVC burdens. 
     In certain examples, AF detection can include detection windows, such as measured by one or more of time (e.g., 30-second windows, 2-minute windows, or one or more other time periods, etc.), cardiac intervals (e.g., a number of cardiac intervals, etc.), valid cardiac intervals (e.g., within one or more time boundaries (ms), such as above a low threshold, below a high threshold; a change from one or more previous or average intervals; etc.), etc. 
     In an example, the low PVC burden can include a determined PVC burden below a first threshold (e.g., 30% of the beats (or valid beats) in a detection window, etc.). A high PVC burden can include a determined PVC burden above the first threshold, and in certain examples, below a second threshold (e.g., 70% of the beats (or valid beats) in the detection window, etc.). A very-high PVC burden can include a determined PVC burden above the second threshold. In other examples, one or more other percentages, ranges, or number or levels of categories can be used. In certain examples, such as depending on the robustness of the AF detection algorithm, or desired sensitivity or specificity, the first threshold can range between 10% and 50%, and the second threshold can range between 50% and 90%. In an example, only a first threshold can be used (e.g. between 10 and 90%), defining two zones. In other examples, three or more threshold can be used, defining 4 or more zones with different ranges or boundaries, etc. 
     In an example, when the low PVC burden is determined, a first AF detection algorithm, or a first set of AF parameters, can be used to detect or categorize AF in the subject. When the high PVC burden is determined, a second detection algorithm or set of AF parameters tuned to tolerate a higher number or rate of PVC events can be used to detect or classify AF in the subject. When the very-high PVC burden is determined, AF detection and/or classification can be suspended. In an example, as mentioned above, first and second thresholds can be positioned at 30% and 70%, respectively, or in other examples, at one or more other thresholds defining a number of ranges, etc. In certain examples, adjustments to the AF detection and/or classification using the determined PVC burden may increase sensitivity or specificity of AF or PVC detection, or avoid mis-detection or mis-classification. Increased sensitivity or specificity of detection can increase data collection and storage efficiency, providing a more robust patient monitoring system, in certain examples, using less storage or data processing than existing systems. 
     In certain examples, storage decisions can be made depending on the determined PVC burden. For example, AF detection windows or sub-windows can be stored including PVCs, such as for subsequent review, while non-PVC detection windows or sub-windows can be discarded and not stored. Varying device operation with determined PVC burdens can also save power, extending device lifespan. For example, AF detection can cease for a time period following a determined very-high PVC burden. In certain examples, an alert corresponding to the determined very-high PVC burden can be provided. AF detection can resume after a period of time (e.g., 10 minutes, 30 minutes, 1 hour, 6 hours, 12 hours, 1 day, etc.), in response to one or more triggers (e.g., a change in a state of the subject, a percentage change in heart rate, a change in posture, etc.). In other examples, the frequency of AF detection can be adjusted for a period following determination of a very-high PVC burden. 
     Moreover, improved detection or classification of AF in sophisticated, regulatory-compliant medical systems, components, or machinery may increase the efficiency of medical system resources, improving the functioning of modern regulated technological systems and methods not capable of being performed or managed by generic computers, components, or machinery. 
     Ambulatory medical devices (AMDs), including implantable or wearable medical devices, can be configured to monitor, detect, or treat various cardiac conditions associated with a reduced ability of a heart to sufficiently deliver blood to a body, such HF, arrhythmias, hypertension, etc. An AMD can include a single device or a plurality of medical devices or monitors implanted in a subject&#39;s body or otherwise positioned on or about the subject to monitor subject physiologic information of the subject, such as heart sounds, respiration (e.g., respiration rate, tidal volume, etc.), impedance (e.g., thoracic impedance, cardiac impedance, etc.), pressure (e.g., blood pressure), cardiac activity (e.g., heart rate), physical activity, posture, plethysmography, or one or more other physiologic parameters of a subject, or to provide electrical stimulation or one or more other therapies or treatments to optimize or control contractions of the heart. 
     In an example, the AMD can include one or more of: a respiration sensor configured to receive respiration information (e.g., a respiration rate (RR), a respiration volume (tidal volume), etc.); an acceleration sensor (e.g., an accelerometer, a microphone, etc.) configured to receive cardiac acceleration information (e.g., cardiac vibration information, pressure waveform information, heart sound information, endocardial acceleration information, acceleration information, activity information, posture information, etc.); an impedance sensor (e.g., intrathoracic impedance sensor, transthoracic impedance sensor, etc.) configured to receive impedance information, a cardiac sensor configured to receive cardiac electrical information; an activity sensor configured to receive information about a physical motion (e.g., activity, steps, etc.); a posture sensor configured to receive posture or position information; a pressure sensor configured to receive pressure information; a plethysmograph sensor (e.g., a photoplethysmography sensor, etc.); or one or more other sensors configured to receive physiologic information of the subject. 
     Traditional cardiac rhythm management (CRM) devices, such as pacemakers, defibrillators, or cardiac resynchronizers, include subcutaneous devices configured to be implanted in a chest of a subject, having one or more leads to position one or more electrodes or other sensors at various locations in or near the heart, such as in one or more of the atria or ventricles. Separate from, or in addition to, the one or more electrodes or other sensors of the leads, the CRM device can include one or more electrodes or other sensors (e.g., a pressure sensor, an accelerometer, a gyroscope, a microphone, etc.) powered by a power source in the CRM device. The one or more electrodes or other sensors of the leads, the CRM device, or a combination thereof, can be configured detect physiologic information from, or provide one or more therapies or stimulation to, the subject. 
     Implantable devices can additionally include leadless cardiac pacemakers (LCP), small (e.g., smaller than traditional implantable CRM devices, in certain examples having a volume of about 1 cc, etc.), self-contained devices including one or more sensors, circuits, or electrodes configured to monitor physiologic information (e.g., heart rate, etc.) from, detect physiologic conditions (e.g., tachycardia) associated with, or provide one or more therapies or stimulation to the heart without traditional lead or implantable CRM device complications (e.g., required incision and pocket, complications associated with lead placement, breakage, or migration, etc.). In certain examples, an LCP can have more limited power and processing capabilities than a traditional CRM device; however, multiple LCP devices can be implanted in or about the heart to detect physiologic information from, or provide one or more therapies or stimulation to, one or more chambers of the heart. The multiple LCP devices can communicate between themselves, or one or more other implanted or external devices. 
     Wearable or external medical sensors or devices can be configured to detect or monitor physiologic information of the subject without required implant or an in-patient procedure for placement, battery replacement, or repair. However, such sensors and devices, in contrast to implantable medical devices, may have reduced patient compliance, increased detection noise, or reduced detection sensitivity. 
     For each ambulatory medical device (AMD) described above (e.g., implantable medical device (IMD) or wearable medical devices (WMD)), each additional sensor can increase system cost and complexity, reduce system reliability, or increase the power consumption and reduce the usable life of the ambulatory device. Accordingly, it can be beneficial to use a single sensor to determine multiple types of physiologic information, or a smaller number of sensors to measure a larger number of different types of physiologic information. 
     In an example, an accelerometer, microphone, or acoustic sensor can sense or detect acceleration information of the subject including or indicative of cardiac acceleration information (e.g., heart sound information, such as from pressure waveforms due to cardiac vibrations; endocardial acceleration information, such as from acceleration information detected on or within a cardiac chamber; cardiac vibration information; etc.) of the subject. In certain examples, the same or different accelerometer, microphone, acoustic sensor or one or more other activity, posture, or exertion sensors can receive exertion information (e.g., activity information, posture information, etc.) of the subject. Exertion information can include physical activity information of the subject occurring at a different frequency than cardiac acceleration information. Accordingly, the sampling rate to detect physical activity information of the subject is often much lower than that required to detect cardiac acceleration information (e.g., exertion is often detected at a sampling rate of 50 Hz or less, whereas cardiac acceleration information is often detected at a sampling rate of 1 kHz or higher). 
     In an example, a single sensor can detect acceleration information at a detection period and sampling rate such that both cardiac acceleration information and exertional information can be determined from the detected acceleration information over the same or overlapping time periods. However, such determination of the separate cardiac acceleration information and the exertion information from the same acceleration information can require substantial processing time and resources. Accordingly, when a single sensor is used to detect cardiac acceleration information and exertion information, the cardiac acceleration information and the exertion information are more often detected in non-overlapping time periods (e.g., the single sensor detects one of the cardiac acceleration information or the exertional information at a time) at different sampling rates and with different pre-processing (e.g., filters, signal conditioning, etc.), such as to reduce the processing resources required to sense and process the separate information in the AMD or medical-device system having limited or different storage, processing, power, and performance capabilities. 
     In other examples, different sensors (or a single sensor with different physical sensing portions or components) can be used to detect the cardiac acceleration information and the exertion information. For example, it can be advantageous to detect physical activity or exertion information using a more rigid sensor tuned to sense activity having a higher magnitude and lower frequency response than cardiac acceleration information; whereas it can be advantageous to detect cardiac acceleration information using sensor having higher sensitivity and sampling frequency (e.g., a microphone instead of an accelerometer, etc.). In certain examples, separate axes of a multi-axis sensor can be used to detect different information at different sampling rates. 
       FIG.  1    illustrates an example system (e.g., a medical device, etc.)  100  including a signal receiver circuit  102  and an assessment circuit  104 , each having an input and an output. The signal receiver circuit  102  can be configured to receive subject information, such as physiologic information of a subject, a patient (or a group of subjects or patients) from one or more sensors. In an example, the signal receiver circuit can be configured to receive cardiac electrical information of the subject, such as from a cardiac sensor (e.g., including one or more electrodes configured to sense electrical activity of the subject, such as cardiac electrical activity, and an amplifier configured to amplify the received cardiac electrical activity, etc.) or one or more other devices or sensors, etc. In an example, the signal receiver circuit can be configured to receive premature ventricular contraction (PVC) information of the subject, such as from one or more other devices or sensors. In an example, the system can include a PVC determination circuit configured to receive cardiac electrical information and to determine one or more PVC events using the received cardiac electrical information (e.g., using a timing, a morphology, a frequency, etc. of the cardiac electrical information, etc.). 
     The assessment circuit  104  can be configured to receive information from the signal receiver circuit  102 , and to determine one or more parameters (e.g., composite physiologic parameters, stratifiers, one or more pacing parameters, etc.), such as described herein. In an example, the assessment circuit  104  can be configured to detect atrial fibrillation (AF) of the subject, such as an AF event or a potential AF event of the subject, using the received cardiac electrical information. In an example, the assessment circuit  104  can be configured to adjust the AF detection using the received PVC information. 
     The assessment circuit  104  can be configured to determine a subject condition, or an indication, risk, or stratification of worsening subject condition, using the received information. The assessment circuit  104  can provide acute or chronic monitoring of the subject condition, and in certain examples can be configured to provide an output to a user, such as a score, an alert, a trend, or indication to the subject or a clinician. In certain examples, the assessment circuit  104  can be configured to provide an indication that the subject seek medical treatment or be hospitalized in response to a determined change, or otherwise determine one or more therapy parameters, such as to be provided to a clinician for consideration, or to propose, control, or otherwise manage one or more therapies to the subject or one or more functions, modes, or operations of one or more components of a medical-device system. In other examples, the assessment circuit  104  can be configured to provide an output to another circuit, machine, or process, such as to control, adjust, or cease a therapy of a medical device, a drug delivery system, etc., or otherwise alter one or more processes or functions of a medical-device system. 
       FIG.  2    illustrates an example patient management system  200  and portions of an environment in which the system  200  may operate. The patient management system  200  can perform a range of activities, including remote patient monitoring and diagnosis of a disease condition. Such activities can be performed proximal to a patient  201 , such as in a patient home or office, through a centralized server, such as in a hospital, clinic, or physician office, or through a remote workstation, such as a secure wireless mobile computing device. 
     The patient management system  200  can include one or more ambulatory devices, an external system  205 , and a communication link  211  providing for communication between the one or more ambulatory devices and the external system  205 . The one or more ambulatory devices can include an implantable medical device (IMD)  202 , a wearable medical device  203 , or one or more other implantable, leadless, subcutaneous, external, wearable, or ambulatory medical devices configured to monitor, sense, or detect information from, determine physiologic information about, or provide one or more therapies to treat various cardiac conditions of the patient  201 , such as high blood pressure, an ability of a heart to sufficiently deliver blood to a body, including atrial fibrillation (AF), congestive heart failure (CHF), hypertension, or one or more other cardiac or non-cardiac conditions (e.g., dehydration, hemorrhage, renal dysfunction, etc.). 
     In an example, the IMD  202  can include one or more traditional cardiac rhythm management (CRM) devices, such as a pacemaker or defibrillator, implanted in a chest of a subject, having a lead system including one or more transvenous, subcutaneous, or non-invasive leads or catheters to position one or more electrodes or other sensors (e.g., a heart sound sensor) in, on, or about a heart or one or more other position in a thorax, abdomen, or neck of the subject  201 . In another example, the IMD  202  can include a monitor implanted, for example, subcutaneously in the chest of subject  201 . 
     The IMD  202  can include an assessment circuit configured to detect or determine specific physiologic information of the subject  201 , or to determine one or more conditions or provide information or an alert to a user, such as the subject  201  (e.g., a patient), a clinician, or one or more other caregivers. The IMD  202  can alternatively or additionally be configured as a therapeutic device configured to treat one or more medical conditions of the subject  201 . The therapy can be delivered to the subject  201  via the lead system and associated electrodes or using one or more other delivery mechanisms. The therapy can include anti-arrhythmic therapy to treat an arrhythmia or to treat or control one or more complications from arrhythmias, such as syncope, congestive heart failure (CHF), or stroke, among others. In other examples, the therapy can include delivery of one or more drugs to the subject  201  using the IMD  202  or one or more of the other ambulatory devices. Examples of the anti-arrhythmic therapy include pacing, cardioversion, defibrillation, neuromodulation, drug therapies, or biological therapies, among other types of therapies. In other examples, therapies can include cardiac resynchronization therapy (CRT) for rectifying dyssynchrony and improving cardiac function in CHF patients. In some examples, the IMD  202  can include a drug delivery system, such as a drug infusion pump to deliver drugs to the patient for managing arrhythmias or complications from arrhythmias, hypertension, or one or more other physiologic conditions. In yet other examples, the IMD  202  can include a therapy circuit or module configured to treat hypertension (e.g., a neuro-stimulation therapy circuit, a drug delivery therapy circuit, a stimulation therapy circuit, etc.). 
     The wearable medical device  203  can include one or more wearable or external medical sensors or devices (e.g., automatic external defibrillators (AEDs), Holter monitors, patch-based devices, smart watches, smart accessories, wrist- or finger-worn medical devices, such as a finger-based photoplethysmography sensor, etc.). In other examples, the wearable medical device  203  can include an acoustic sensor or accelerometer to detect acoustic information (e.g., heart sounds) or the sound or vibration of blood flow, an impedance sensor to detect impedance variations associated with changes in blood flow or volume, a temperature sensor to detect temperature variation associated with blood flow, a laser Doppler vibrometer or other pressure, strain, or physical sensor to detect physical variations associated with blood flow, etc. 
     The patient management system  200  can include, among other things, a respiration sensor configured to receive respiration information (e.g., a respiration rate (RR), a respiration volume (tidal volume), etc.), a heart sound sensor configured to receive heart sound information, a thoracic impedance sensor configured to receive impedance information, a cardiac sensor configured to receive cardiac electrical information, an activity sensor configured to receive information about a physical motion (e.g., activity, posture, etc.), a plethysmography sensor, or one or more other sensors configured to receive physiologic information of the subject  201 . 
     The external system  205  can include a dedicated hardware/software system, such as a programmer, a remote server-based patient management system, or alternatively a system defined predominantly by software running on a standard personal computer. The external system  205  can manage the subject  201  through the IMD  202  or one or more other ambulatory devices connected to the external system  205  via a communication link  211 . In other examples, the IMD  202  can be connected to the wearable device  203 , or the wearable device  203  can be connected to the external system  205 , via the communication link  211 . This can include, for example, programming the IMD  202  to perform one or more of acquiring physiological data, performing at least one self-diagnostic test (e.g., a device operational status, etc.), analyzing the physiological data to detect a cardiac arrhythmia, or optionally delivering or adjusting a therapy to the subject  201 . Additionally, the external system  205  can send information to, or receive information from, the IMD  202  or the wearable device  203  via the communication link  211 . Examples of the information can include real-time or stored physiological data from the subject  201 , diagnostic data, such as detection of cardiac arrhythmias or events of worsening heart failure, responses to therapies delivered to the subject  201 , or device operational status of the IMD  202  or the wearable device  203  (e.g., battery status, lead impedance, etc.). The communication link  211  can be an inductive telemetry link, a capacitive telemetry link, or a radio-frequency (RF) telemetry link, or wireless telemetry based on, for example, “strong” Bluetooth or IEEE 802.11 wireless fidelity interfacing standards. Other configurations and combinations of patient data source interfacing are possible. 
     By way of example and not limitation, the external system  205  can include an external device  206  in proximity of the one or more ambulatory devices, and a remote device  208  in a location relatively distant from the one or more ambulatory devices, in communication with the external device  206  via a communication network  207 . Examples of the external device  206  can include a medical device programmer. 
     The remote device  208  can be configured to evaluate collected subject or patient information and provide alert notifications, among other possible functions. In an example, the remote device  208  can include a centralized server acting as a central hub for collected data storage and analysis. The server can be configured as a multi- or distributed computing and processing system. The remote device  208  can receive data from multiple subjects or patients. The data can be collected by the one or more ambulatory devices, among other data acquisition sensors or devices associated with the subject  201 . The server can include a memory device to store the data in a patient database. The server can include an alert analyzer circuit to evaluate the collected data to determine if specific alert condition is satisfied. Satisfaction of the alert condition may trigger a generation of alert notifications, such to be provided by one or more human-perceptible user interfaces. In some examples, the alert conditions may alternatively or additionally be evaluated by the one or more ambulatory devices, such as the IMD. By way of example, alert notifications can include a Web page update, phone or pager call, E-mail, SMS, text or “Instant” message, as well as a message to the subject or patient and a simultaneous direct notification to emergency services and to the clinician. Other alert notifications are possible. The server can include an alert prioritizer circuit configured to prioritize the alert notifications. For example, an alert of a detected medical event can be prioritized using a similarity metric between the physiological data associated with the detected medical event to physiological data associated with the historical alerts. 
     The remote device  208  may additionally include one or more locally configured clients or remote clients securely connected over the communication network  207  to the server. Examples of the clients can include personal desktops, notebook computers, mobile devices, or other computing devices. System users, such as clinicians or other qualified medical specialists, may use the clients to securely access stored patient data assembled in the database in the server, and to select and prioritize patients and alerts for health care provisioning. In addition to generating alert notifications, the remote device  208 , including the server and the interconnected clients, may also execute a follow-up scheme by sending follow-up requests to the one or more ambulatory devices, or by sending a message or other communication to the subject  201  (e.g., the patient), clinician or authorized third party as a compliance notification. 
     The communication network  207  can provide wired or wireless interconnectivity. In an example, the communication network  207  can be based on the Transmission Control Protocol/Internet Protocol (TCP/IP) network communication specification, although other types or combinations of networking implementations are possible. Similarly, other network topologies and arrangements are possible. 
     One or more of the external device  206  or the remote device  208  can output the detected medical events to a system user, such as the patient or a clinician, or to a process including, for example, an instance of a computer program executable in a microprocessor. In an example, the process can include an automated generation of recommendations for anti-arrhythmic therapy, or a recommendation for further diagnostic test or treatment. In an example, the external device  206  or the remote device  208  can include a respective display unit for displaying the physiological or functional signals, or alerts, alarms, emergency calls, or other forms of warnings to signal the detection of arrhythmias. In some examples, the external system  205  can include an external data processor configured to analyze the physiological or functional signals received by the one or more ambulatory devices, and to confirm or reject the detection of arrhythmias. Computationally intensive algorithms, such as machine-learning algorithms, can be implemented in the external data processor to process the data retrospectively to detect cardia arrhythmias. 
     Portions of the one or more ambulatory devices or the external system  205  can be implemented using hardware, software, firmware, or combinations thereof. Portions of the one or more ambulatory devices or the external system  205  can be implemented using an application-specific circuit that can be constructed or configured to perform one or more functions or can be implemented using a general-purpose circuit that can be programmed or otherwise configured to perform one or more functions. Such a general-purpose circuit can include a microprocessor or a portion thereof, a microcontroller or a portion thereof, or a programmable logic circuit, a memory circuit, a network interface, and various components for interconnecting these components. For example, a “comparator” can include, among other things, an electronic circuit comparator that can be constructed to perform the specific function of a comparison between two signals or the comparator can be implemented as a portion of a general-purpose circuit that can be driven by a code instructing a portion of the general-purpose circuit to perform a comparison between the two signals. “Sensors” can include electronic circuits configured to receive information and provide an electronic output representative of such received information. 
     The patient management system  200  can include a therapy device, such as a drug delivery device configured to provide therapy or therapy information (e.g., dosage information, etc.) to the subject  201 , such as using information from one or more of the ambulatory devices. In other examples, one or more of the ambulatory devices can be configured to provide therapy or therapy information to the subject  201 . The therapy device can be configured to send information to or receive information from one or more of the ambulatory devices or the external system  205  using the communication link  211 . In an example, the one or more ambulatory devices, the external device  206 , or the remote device  208  can be configured to control one or more parameters of the therapy device  210 . 
     The external system  205  can allow for programming the one or more ambulatory devices and can receives information about one or more signals acquired by the one or more ambulatory devices, such as can be received via a communication link  211 . The external system  205  can include a local external IMD programmer. The external system  205  can include a remote patient management system that can monitor patient status or adjust one or more therapies, such as from a remote location. 
     In various examples, the assessment circuit may be implemented using one or more of the IMD  202 , the wearable medical device  203 , or at the external system  205 , such as using data extracted from the one or more ambulatory devices or data stored in a memory within the external system  205 . In other examples, portions of the assessment circuit may be distributed between the one or more ambulatory devices and the external system  205 . 
       FIG.  3    illustrates an example of a Cardiac Rhythm Management (CRM) system  300  and portions of an environment in which the CRM system  300  can operate. The CRM system  300  can include an ambulatory medical device, such as an implantable medical device (IMD)  302  that can be electrically coupled to a heart  301  through one or more leads, such as one or more of a first, second, or third lead  307 - 309  coupled to the IMD  302  using a header  303 , and an external system  305  that can communicate with the IMD  302 , such as via a communication link  311 . 
     The IMD  302  can include an implantable cardiac device, such as a pacemaker, an implantable cardioverter-defibrillator (ICD), or a cardiac resynchronization therapy defibrillator (CRT-D). The IMD  302  can include one or more monitoring or therapeutic devices, such as a subcutaneous implanted device, a wearable external device, a neural stimulator, a drug delivery device, a biological therapy device, or one or more other ambulatory medical devices. The IMD  302  may be coupled to or substituted by a monitoring medical device, such as a bedside or other external monitor. 
     The IMD  302  can include a hermetically sealed CAN  304  that can house an electronic circuit that can sense a physiologic signal in the heart  301  and can deliver one or more therapeutic electrical pulses to a target region, such as in the heart, through the one or more leads. In certain examples, the CRM system  300  can include only a single lead (e.g., the second lead  308 , etc.), only two leads (e.g., the first and second leads  307 ,  308 , or three or more leads, etc. 
     The first lead  307  can include a proximal end that can be configured to be connected to the IMD  302  and a distal end that can be configured to be placed at a target location, such as in the right atrium (RA)  331  of the heart  301 . The first lead  307  can have a first pacing-sensing electrode  351  that can be located at or near its distal end, and a second pacing-sensing electrode  352  that can be located at or near the first pacing-sensing electrode  351 . The first and second pacing-sensing electrodes  351 ,  352  can be electrically connected to the IMD  310 , such as via separate conductors in the first lead  307 , such as to allow for sensing of the right atrial activity and optional delivery of atrial pacing pulses. 
     The second lead  308  can be a defibrillation lead that can include a proximal end that can be connected to the IMD  310  and a distal end that can be placed at a target location, such as in the right ventricle (RV)  332  of the heart  301 . The second lead  308  can have a first pacing-sensing electrode  352  that can be located at distal end, a second pacing-sensing electrode  353  that can be located near the first pacing-sensing electrode  352 , a first defibrillation coil electrode  354  that can be located near the electrode  353 , and a second defibrillation coil electrode  355  that can be located at a distance from the distal end, such as for superior vena cava (SVC) placement. The electrodes  352 - 355  can be electrically connected to the IMD  302 , such as via separate conductors in the second lead  308 . The first and second pacing-sensing electrodes  352 ,  353  can allow for sensing of a ventricular electrogram and can optionally allow delivery of one or more ventricular pacing pulses, and the first and second defibrillation coil electrodes  354 ,  355  can allow for delivery of one or more ventricular cardioversion/defibrillation pulses. 
     In an example, the second lead  308  can include only three electrodes. The first pacing-sensing electrode  352  and the first defibrillation coil electrode  354  can be used for sensing or delivery of one or more ventricular pacing pulses, and the electrodes the first defibrillation coil electrode  354  and the second defibrillation coil electrode  355  can be used for delivery of one or more ventricular cardioversion or defibrillation pulses. 
     The third lead  309  can include a proximal end that can be connected to the IMD  302  and a distal end that can be configured to be placed at a target location, such as in a left ventricle (LV)  334  of the heart  301 . The third lead  309  may be implanted through the coronary sinus  333  and may be placed in a coronary vein over the LV, such as to allow for delivery of one or more pacing pulses to the LV. The third lead  309  can include a first distal electrode  361  that can be located at a distal end of the third lead  309  and a second distal electrode  362  that can be located near the first distal electrode  361 . The first and second distal electrodes  361 ,  362  can be electrically connected to the IMD  302 , such as via separate conductors in the third lead  309 , such as to allow for sensing of the LV electrogram and optionally allow delivery of one or more resynchronization pacing pulses from the LV. 
     The IMD  302  can include an electronic circuit that can sense a physiologic signal. The physiologic signal can include an electrogram or a signal representing mechanical function of the heart  301 . The hermetically sealed CAN  304  may function as an electrode, such as for sensing or pulse delivery. For example, an electrode from one or more of the first, second, or third leads  307 - 309  may be used together with the CAN  304 , such as for unipolar sensing of an electrogram or for delivering one or more pacing pulses. A defibrillation electrode from the second lead  308  may be used together with the CAN  304 , such as for delivering one or more cardioversion/defibrillation pulses. 
     In an example, the IMD  302  can sense impedance, such as between electrodes located on one or more of the first, second, or third leads  307 - 309  or the CAN  304 . The IMD  302  can be configured to inject current between a pair of electrodes, sense the resultant voltage between the same or different pair of electrodes, and determine impedance using Ohm&#39;s Law. The impedance can be sensed in a bipolar configuration in which the same pair of electrodes can be used for injecting current and sensing voltage, a tripolar configuration in which the pair of electrodes for current injection and the pair of electrodes for voltage sensing can share a common electrode, or tetrapolar configuration in which the electrodes used for current injection can be distinct from the electrodes used for voltage sensing. In an example, the IMD  302  can be configured to inject current between an electrode on the second lead  308  and the CAN  304 , and to sense the resultant voltage between the same electrodes or between a different electrode on the second lead  308  and the CAN  304 . A physiologic signal can be sensed from one or more physiologic sensors that can be integrated within the IMD  302 . The IMD  302  can also be configured to sense a physiologic signal from one or more external physiologic sensors or one or more external electrodes that can be coupled to the IMD  302 . Examples of the physiologic signal can include one or more of heart rate, heart rate variability, intrathoracic impedance, intracardiac impedance, arterial pressure, pulmonary artery pressure, RV pressure, LV coronary pressure, coronary blood temperature, blood oxygen saturation, one or more heart sounds, physical activity or exertion level, physiologic response to activity, posture, respiration, body weight, or body temperature. 
     The arrangement and functions of these leads and electrodes are described above by way of example and not by way of limitation. Depending on the need of the subject and the capability of the implantable device, other arrangements and uses of these leads and electrodes are anticipated and included herein. 
     The external system  305  can allow for programming of the IMD  302  and can receives information about one or more signals acquired by IMD  302 , such as can be received via a communication link  311 . The external system  305  can include a local external IMD programmer. The external system  305  can include a remote patient management system that can monitor patient status or adjust one or more therapies, such as from a remote location. 
     The communication link  311  can include one or more of an inductive telemetry link, a radio-frequency telemetry link, or a telecommunication link, such as an internet connection. The communication link  311  can provide for data transmission between the IMD  302  and the external system  305 . The transmitted data can include, for example, real-time physiologic data acquired by the IMD  302 , physiologic data acquired by and stored in the IMD  302 , therapy history data or data indicating IMD operational status stored in the IMD  302 , one or more programming instructions to the IMD  302 , such as to configure the IMD  302  to perform one or more actions that can include physiologic data acquisition, such as using programmably specifiable sensing electrodes and configuration, device self-diagnostic test, or delivery of one or more therapies. 
     Portions of the IMD  302  or the external system  305  can be implemented using hardware, software, or any combination of hardware and software. Portions of the IMD  302  or the external system  305  may be implemented using an application-specific circuit that can be constructed or configured to perform one or more particular functions or can be implemented using a general-purpose circuit that can be programmed or otherwise configured to perform one or more particular functions. Such a general-purpose circuit can include a microprocessor or a portion thereof, a microcontroller or a portion thereof, or a programmable logic circuit, or a portion thereof. For example, a “comparator” can include, among other things, an electronic circuit comparator that can be constructed to perform the specific function of a comparison between two signals or the comparator can be implemented as a portion of a general-purpose circuit that can be driven by a code instructing a portion of the general-purpose circuit to perform a comparison between the two signals. While described with reference to the IMD  302 , the CRM system  500  could include a subcutaneous medical device (e.g., subcutaneous ICD, subcutaneous diagnostic device), wearable medical devices (e.g., patch-based sensing device), or other external medical devices. 
       FIGS.  4 - 5    illustrate example episodes  400 ,  500  including PVCs.  FIG.  4    illustrates generally an example episode  400  of AF that was rejected due to PVCs using a prior art AF detection algorithm, and  FIG.  5    illustrates generally an example episode  500  of a false positive AF classification due to PVCs using a prior art AF detection algorithm. 
     The example episodes  400 ,  500  include cardiac electric signals  401 ,  501  and corresponding rate distributions  402 ,  502 . Normal depolarizations are illustrated in the cardiac electrical signals  401 ,  501  without boxes, such as first depolarizations  403 ,  503 . The cardiac electrical signals  401 ,  501  illustrate time on the horizontal axis in seconds (e.g.,  162 - 176 , etc.) and a vertical axis represents a normalized magnitude of the cardiac electrical signals  401 ,  501 , such as detected by a cardiac sensor (e.g., an electrocardiogram detected by one or more electrodes, etc.). 
     In an example, PVCs can be detected, for example, using one or more of rate, morphology, amplitude, or frequency information of a cardiac electrical signal. In certain examples, PVCs can be detected as wide QRS complex, wider than a normal or expected depolarization (e.g., the first depolarization  403 , etc.). In  FIG.  4   , four PVCs  404  are detected in the cardiac electrical signal  401 . In  FIG.  5   , six PVCs  504  are detected in the cardiac electrical signal  501 . Ventricular events are illustrated with markers  405 ,  505  in each of the cardiac electrical signals  401 ,  501 . 
     The rate distributions  402 ,  502  illustrate an index of individual rates of ventricular events, including ventricular events  406 ,  506  of the cardiac electrical signals  401 ,  501 , syncing at origins  407 ,  507 , on the horizontal axis and a vertical axis representing heart rate. In certain examples, AF can be detected using the rate distributions  402 ,  502 , such as characteristics of the rate distributions, including intervals between successive events, classification or categorization of the different intervals, etc. In an example, candidate AF events can be detected, and then classified as an AF event or a non-AF event using one or more other circuits, methods, or confirmation using previous, subsequent, or additional information. 
       FIG.  6    illustrates generally an example method  600  including detecting AF of a subject. In an example, detecting AF can including detecting candidate AF events, and in certain examples, classifying the candidate AF events as AF or non-AF. 
     At  601 , cardiac electrical information is received, such as using a signal receiver circuit of a component of a medical system, such as a first ambulatory medical device, a medical device programmer, etc. The cardiac electrical information can be received from a cardiac sensor or one or more other devices (e.g., a second ambulatory medical device, etc.). 
     At  602 , PVC information is optionally determined, such as by a first assessment circuit using the received cardiac electrical information. In an example, one or more PVC events can be determined of a subject, such as using the received cardiac electrical information (e.g., a morphology, a rate, a magnitude, a frequency, or one or more other characteristics or a comparison to one or more templates or previous cardiac electrical information, etc.). In an example, determining PVC information can include determining a PVC state of the subject, such as using one or more detected PVC events, their proximity, the number of detected PVC events in a specific number of cardiac cycles, etc. 
     At  603 , PVC information can be received, such as from the first assessment circuit or one or more other devices (e.g., the second ambulatory medical device, etc.) using the signal receiver circuit. In an example, the PVC information can include a determination of one or more PVC states, including, for example, separate low, high, and very-high PVC states, or one or more other determinations of different PVC states of the subject, etc. 
     At  604 , AF detection can be adjusted using the received PVC information, such as using one or more determined PVC events or states of the subject. In an example, an assessment circuit can adjust AF detection using the received PVC information. The assessment circuit can count a number of detected PVC events in a first time period, such as a first detection window, etc., and determine a PVC state of the subject using the count of PVC events in the first time period. The AF detection can be adjusted using the determined PVC state. 
     For example, a first AF detection mode (e.g., a low-PVC burden mode) can tolerate a first number of PVC events (e.g., below 30% of cardiac intervals as PVC events, etc.). The assessment circuit can determine a low-PVC state if the PVC event count is below a first threshold, such as in a specific detection window, etc., and use the low-PVC burden mode to detect AF, such as using one or more of the AF detection algorithms described above, even in detection window having the first number of PVC events. 
     In a second AF detection mode (e.g., a high-PVC burden mode) can remove detected PVC events, for example, from a detection window. Once removed from the detection window, AF detection can proceed on the remaining cardiac electrical information (e.g., beats or intervals) in the window. In an example, the detection algorithm, in the context of the remaining cardiac electrical information, can remain the same as in the first AF detection mode, but the information being considered has been altered. However, the threshold for individual beats or intervals to remain in the window for consideration increases, as in this mode, more intervals are removed from the detection window. The assessment circuit can determine a high-PVC state if the number of PVC events is above the first number of PVC events (e.g., at or above 30% of cardiac intervals as PVC events, etc.), such as in a specific detection window, etc. In certain examples, the beats or intervals before, after, or both before and after the detected PVC event can be removed from the detection window as well, and AF detection can proceed on the remaining cardiac electrical information in the window. 
     AF detection can be suspended in a third AF detection mode if the number of PVC events is above a second number of PVC events (e.g., at or above 70% of the cardiac intervals as PVC events, etc.), such as in a specific detection window, etc. In an example, one or more other thresholds can be used. Further, in certain examples, when AF detection is suspended or disabled, an alert can be issued or provided that AF classification has been suspended. Suspending AF in the third AF detection mode can reduce power consumption of the device, as the number and amount of PVCs may make it difficult to detect a condition with confidence outside of the PVCs themselves. 
     In other examples, the PVC burden or state can be determined, or an indication of the PVC burden or state can be received, such as from a user or one or more other processes. In other examples, adjusting AF detection can include adjusting AF classification, such that candidate AF events are detected, but one or more classification parameters or thresholds of such detected AF events can change. In other examples, AF detection parameters can include rate thresholds (e.g., rates above or below upper or lower thresholds are not considered as valid beats or intervals for AF detection), sequential rate or interval change thresholds between successive or ordered beats or intervals, etc. 
       FIG.  7    illustrates a block diagram of an example machine  700  upon which any one or more of the techniques (e.g., methodologies) discussed herein may perform. Portions of this description may apply to the computing framework of one or more of the medical devices described herein, such as the IMD, the external programmer, etc. Further, as described herein with respect to medical device components, systems, or machines, such may require regulatory-compliance not capable by generic computers, components, or machinery. 
     Examples, as described herein, may include, or may operate by, logic or a number of components, or mechanisms in the machine  700 . Circuitry (e.g., processing circuitry) is a collection of circuits implemented in tangible entities of the machine  700  that include hardware (e.g., simple circuits, gates, logic, etc.). Circuitry membership may be flexible over time. Circuitries include members that may, alone or in combination, perform specified operations when operating. In an example, hardware of the circuitry may be immutably designed to carry out a specific operation (e.g., hardwired). In an example, the hardware of the circuitry may include variably connected physical components (e.g., execution units, transistors, simple circuits, etc.) including a machine-readable medium physically modified (e.g., magnetically, electrically, moveable placement of invariant massed particles, etc.) to encode instructions of the specific operation. In connecting the physical components, the underlying electrical properties of a hardware constituent are changed, for example, from an insulator to a conductor or vice versa. The instructions enable embedded hardware (e.g., the execution units or a loading mechanism) to create members of the circuitry in hardware via the variable connections to carry out portions of the specific operation when in operation. Accordingly, in an example, the machine-readable medium elements are part of the circuitry or are communicatively coupled to the other components of the circuitry when the device is operating. In an example, any of the physical components may be used in more than one member of more than one circuitry. For example, under operation, execution units may be used in a first circuit of a first circuitry at one point in time and reused by a second circuit in the first circuitry, or by a third circuit in a second circuitry at a different time. Additional examples of these components with respect to the machine  700  follow. 
     In alternative embodiments, the machine  700  may operate as a standalone device or may be connected (e.g., networked) to other machines. In a networked deployment, the machine  700  may operate in the capacity of a server machine, a client machine, or both in server-client network environments. In an example, the machine  700  may act as a peer machine in peer-to-peer (P2P) (or other distributed) network environment. The machine  700  may be a personal computer (PC), a tablet PC, a set-top box (STB), a personal digital assistant (PDA), a mobile telephone, a web appliance, a network router, switch or bridge, or any machine capable of executing instructions (sequential or otherwise) that specify actions to be taken by that machine. Further, while only a single machine is illustrated, the term “machine” shall also be taken to include any collection of machines that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies discussed herein, such as cloud computing, software as a service (SaaS), other computer cluster configurations. 
     The machine (e.g., computer system)  700  may include a hardware processor  702  (e.g., a central processing unit (CPU), a graphics processing unit (GPU), a hardware processor core, or any combination thereof), a main memory  704 , a static memory (e.g., memory or storage for firmware, microcode, a basic-input-output (BIOS), unified extensible firmware interface (UEFI), etc.)  706 , and mass storage  708  (e.g., hard drive, tape drive, flash storage, or other block devices) some or all of which may communicate with each other via an interlink (e.g., bus)  730 . The machine  700  may further include a display unit  710 , an alphanumeric input device  712  (e.g., a keyboard), and a user interface (UI) navigation device  714  (e.g., a mouse). In an example, the display unit  710 , input device  712 , and UI navigation device  714  may be a touch screen display. The machine  700  may additionally include a signal generation device  718  (e.g., a speaker), a network interface device  720 , and one or more sensors  716 , such as a global positioning system (GPS) sensor, compass, accelerometer, or one or more other sensors. The machine  700  may include an output controller  728 , such as a serial (e.g., universal serial bus (USB), parallel, or other wired or wireless (e.g., infrared (IR), near field communication (NFC), etc.) connection to communicate or control one or more peripheral devices (e.g., a printer, card reader, etc.). 
     Registers of the processor  702 , the main memory  704 , the static memory  706 , or the mass storage  708  may be, or include, a machine-readable medium  722  on which is stored one or more sets of data structures or instructions  724  (e.g., software) embodying or utilized by any one or more of the techniques or functions described herein. The instructions  724  may also reside, completely or at least partially, within any of registers of the processor  702 , the main memory  704 , the static memory  706 , or the mass storage  708  during execution thereof by the machine  700 . In an example, one or any combination of the hardware processor  702 , the main memory  704 , the static memory  706 , or the mass storage  708  may constitute the machine-readable medium  722 . While the machine-readable medium  722  is illustrated as a single medium, the term “machine-readable medium” may include a single medium or multiple media (e.g., a centralized or distributed database, and/or associated caches and servers) configured to store the one or more instructions  724 . 
     The term “machine-readable medium” may include any medium that is capable of storing, encoding, or carrying instructions for execution by the machine  700  and that cause the machine  700  to perform any one or more of the techniques of the present disclosure, or that is capable of storing, encoding, or carrying data structures used by or associated with such instructions. Non-limiting machine-readable medium examples may include solid-state memories, optical media, magnetic media, and signals (e.g., radio frequency signals, other photon-based signals, sound signals, etc.). In an example, a non-transitory machine-readable medium comprises a machine-readable medium with a plurality of particles having invariant (e.g., rest) mass, and thus are compositions of matter. Accordingly, non-transitory machine-readable media are machine-readable media that do not include transitory propagating signals. Specific examples of non-transitory machine-readable media may include: non-volatile memory, such as semiconductor memory devices (e.g., Electrically Programmable Read-Only Memory (EPROM), Electrically Erasable Programmable Read-Only Memory (EEPROM)) and flash memory devices; magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks. 
     The instructions  724  may be further transmitted or received over a communications network  726  using a transmission medium via the network interface device  720  utilizing any one of a number of transfer protocols (e.g., frame relay, internet protocol (IP), transmission control protocol (TCP), user datagram protocol (UDP), hypertext transfer protocol (HTTP), etc.). Example communication networks may include a local area network (LAN), a wide area network (WAN), a packet data network (e.g., the Internet), mobile telephone networks (e.g., cellular networks), Plain Old Telephone (POTS) networks, and wireless data networks (e.g., Institute of Electrical and Electronics Engineers (IEEE) 802.11 family of standards known as Wi-Fi®, IEEE 802.16 family of standards known as WiMax®), IEEE 802.15.4 family of standards, peer-to-peer (P2P) networks, among others. In an example, the network interface device  720  may include one or more physical jacks (e.g., Ethernet, coaxial, or phone jacks) or one or more antennas to connect to the communications network  726 . In an example, the network interface device  720  may include a plurality of antennas to wirelessly communicate using at least one of single-input multiple-output (SIMO), multiple-input multiple-output (MIMO), or multiple-input single-output (MISO) techniques. The term “transmission medium” shall be taken to include any intangible medium that is capable of storing, encoding, or carrying instructions for execution by the machine  700 , and includes digital or analog communications signals or other intangible medium to facilitate communication of such software. A transmission medium is a machine-readable medium. 
     Various embodiments are illustrated in the figures above. One or more features from one or more of these embodiments may be combined to form other embodiments. Method examples described herein can be machine or computer-implemented at least in part. Some examples may include a computer-readable medium or machine-readable medium encoded with instructions operable to configure an electronic device or system to perform methods as described in the above examples. An implementation of such methods can include code, such as microcode, assembly language code, a higher-level language code, or the like. Such code can include computer readable instructions for performing various methods. The code can form portions of computer program products. Further, the code can be tangibly stored on one or more volatile or non-volatile computer-readable media during execution or at other times. 
     The above detailed description is intended to be illustrative, and not restrictive. The scope of the disclosure should, therefore, be determined with references to the appended claims, along with the full scope of equivalents to which such claims are entitled.