News Column

Patent Issued for Implantable Heart Monitoring Device and Method

June 23, 2014



By a News Reporter-Staff News Editor at Clinical Trials Week -- Pacesetter, Inc. (Sylmar, CA) has been issued patent number 8750975, according to news reporting originating out of Alexandria, Virginia, by NewsRx editors (see also Pacesetter, Inc.).

The patent's inventors are Blomqvist, Andreas (Taby, SE); Broome, Michael (Ekero, SE).

This patent was filed on August 20, 2013 and was published online on June 10, 2014.

From the background information supplied by the inventors, news correspondents obtained the following quote: "The present invention relates to an implantable heart monitoring device, with which it is possible to monitor the heart condition. The invention also concerns a corresponding method.

"Several different devices for monitoring the performance of a heart are known. Often these devices are also able to deliver stimulation pulses to the heart. The devices are often able to sense the electrical activity in the heart. It is also known to determine an impedance value measured between different electrodes positioned in or at the heart. It is also known to sense other physiological parameters, such as pressure, oxygen level etc.

"US 2001/0012953 A1 describes bi-ventricular pacing. An impedance may be measured between electrodes on the right and the left sides of the heart. The variation of the impedance with time is detected. The detected impedance variation may be used in order to synchronize the contraction of the ventricles.

"US 2001/0021864 A1 describes different manners of using the proximal and distal electrodes of different leads in order to inject a current and to measure an impedance. The measured impedance value may be used in order to maximize the cardiac flow.

"US 2007/0049835 A1 relates to an implantable cardioverter-defibrillator or pacemaker whose standard circuitry is used to trend a physiological cardiac parameter using intra-cardiac impedance measurements.

"US 2007/0100249 A1 describes an implantable medical apparatus for detecting diastolic heart failure, DHF. The apparatus includes circuitry for determining, as the DHF parameter, the time duration of a predetermined phase of diastole.

"US 2007/0055170 A1 describes a device for detecting the state of a heart on the basis of intracardial impedance measurement. The device has an impedance measuring unit as well as an analysis unit, which is connected to the impedance measuring unit and is implemented to derive a cardiac function parameter from a time curve of the impedance ascertained using the impedance measuring unit. The analysis unit derives a cardiac function parameter characterizing the behaviour of a heart during the diastole.

"U.S. Pat. No. 6,314,323 describes a heart stimulator in which the cardiac output is determined by measuring the systolic pressure.

"The article 'Hemodynamic Effects of Tachycardia in Patients with Relaxation Abnormality Abnormal Stroke Volume Response as Overlooked Mechanism of Dyspnea Associated with Tachycardia in Diastolic Heart Failure' by Dae-Won Sohn et al., Journal of the American Society of Echocardiography, February 2007, pp. 171-176, describes a comparative study of two groups of individuals: healthy individuals and individuals with stable relaxation abnormality. The article describes how left ventricular pressure and stroke volume varies for the two groups when the heart is paced with 80 beats per minute and 120 beats per minute."

Supplementing the background information on this patent, NewsRx reporters also obtained the inventors' summary information for this patent: "An object of the present invention is to provide an implantable heart monitoring device with which it is possible to detect or monitor the status of the heart of a patient who suffers from a heart failure, in particular a diastolic dysfunction. A further object is to provide such a device, which with quite simple means makes it possible to detect or monitor the status of the heart condition of a patient who suffers from such heart deficiency.

"The above objects are achieved by an implantable heart monitoring device having at least one memory and a control circuit configured to communicate with a number of implanted electrode and/or sensor members adapted to be positioned in a heart or in relation to a heart of a living being such that the control circuit, by means of these members, is able to detect the heart rate of the living being and to derive information correlated to the stroke volume of said heart, wherein the control circuit is configured to carry out the following steps:

"a) detect the heart rate,

"b) derive said information correlated to the stroke volume at said detected heart rate, and

"c) store the detected heart rate and the derived information correlated to the stroke volume in said memory,

"wherein the control circuit is configured to automatically carry out steps a) to c) at a number of different occasions at different, naturally varying, heart rates, such that the memory contains information that indicates the stroke volume as a function of the heart rate.

"The information concerning the stroke volume as a function of the heart rate constitutes important information about the status of the heart. In particular, when a patient suffers from a diastolic dysfunction, the stoke volume tends to decrease more with increasing heart rate than for a patent without such dysfunction. The more the stroke volume decreases with increasing heart rate, the worse is the dysfunction in question. Since according to the present invention, information concerning the stroke volume as a function of the heart rate is obtained, the device according to the invention provides important information concerning the status of the heart. Furthermore, the device carries out the mentioned steps automatically, which means that for example no physician needs to be present for carrying out the steps. The device does not have to have a complicated construction in order to provide the information. For example, an implantable heart stimulation device can with simple measures be constructed to constitute a device according to the invention.

"It should be noted that with naturally varying heart rate is in this document meant that the heart rate is the heart rate of a heart that at the occasion in question is not paced at all by a heart stimulating device, or, if the heart is paced, then the pacing pulses are delivered in accordance with the intrinsic rate of the heart.

"It should also be noted that as a measure of the heart rate, for example the duration of the heart beat can be used (since the duration of a heart beat is the inverse of the heart rate). The duration can be detected, for example as the RR-interval, i.e. the time between two R-waves. The heart rate may thus be determined for an individual heart beat.

"According to an embodiment of the invention, the control circuit is configured to carry out the steps for at least three different heart rates such that the information that indicates the stroke volume as a function of the heart rate can be determined with a sufficiently high accuracy.

"Since the control circuit is configured to carry out the steps for at least three different heart rates, the stored information concerning stroke volume as a function of the heart rate can be determined with a high accuracy. Preferably, the control circuit is configured to carry out the steps for more than three different heart rates, for example for at least 5 different heart rates. Thereby it can be determined with even higher accuracy how the stroke volume varies as a function of the heart rate. Consequently, very accurate information about the status of the heart can be obtained.

"According to an embodiment, the control circuit is configured to carry out the steps for different heart rates, which differ from each other such that the highest heart rate is at least 10%, preferably at least 25%, higher than the lowest heart rate. Thereby, the stoke volume as a function of the heart rate can be determined for a relatively large variation of the heart rate, which means that a very good information concerning the status of the heart is obtained.

"According to a further embodiment, the control circuit is configured to create a warning message if the obtained information that indicates the stroke volume as a function of the heart rate fulfils a predetermined criterion.

"The predetermined criterion may for example be that the information that indicates the stroke volume as a function of the heart rate indicates that the stroke volume decreases when the heart rate increases. Another criterion may be that the information that indicates the stroke volume as a function of the heart rate indicates that the stroke volume decreases more than a predetermined amount when the heart rate increases.

"With such a warning message, for example the patient in question or a physician can be alerted. The warning message may be any kind of warning message. The warning message may for example be stored in the memory. Such a warning message may for example be transferred in a wireless manner to an external device, located outside of the living being. Such a warning message may be communicated to the living being in which the device is implanted or to a physician.

"According to a further embodiment, the control circuit is configured to, for a certain heart rate, derive the information correlated to the stroke volume during a plurality of heart beats, such that a more accurate information correlated to the stroke volume at the heart rate in question is obtained than if the information is derived only during one heart beat.

"It should be noted that when it is said that the control circuit is configured to, for a certain heart rate, derive the information correlated to the stroke volume during a plurality of heart beats, this does not mean that the heart rate must be exactly the same for the number of heart beats. For example, the information correlated to the stroke volume for a certain heart rate may be derived for 10 different heart beats with heart rates varying between 72 and 75. From this procedure it is possible to determine for example an average measure of the stroke volume, and an average heart rate within the interval 72 to 75. Thereby a measure of the stroke volume at the heart rate in question is obtained. Hereby a more accurate information correlated to the stroke volume at the heart rate in question is obtained than if the information is derived only during one heart beat.

"According to a further embodiment, the control circuit is configured such that the number of different occasions takes place within a first time period.

"The time period may for example be less than 24 hours, preferable less than 1 hour, for example less than 20 minutes.

"According to a further embodiment, the control circuit is configured such that the number of different occasions will also take place within at least one second time period, at a later time than the first time period, such that the memory comprises information that indicates the stroke volume as a function of the heart rate both within the first time period and within said second time period, wherein said memory contains information as to whether the indicated stroke volume as a function of the heart rate has changed between said first and second time periods.

"The first and second time periods should thus not overlap with one another. The second time period may for example take place at least 1 day, or at least one week, after the first time period. By determining the stroke volume as a function of the heart rate during different time periods, it is possible to monitor how the heart condition has changed between these time periods.

"According to a further embodiment, the control circuit is configured to create a warning message if the indicated stroke volume as a function of the heart rate has changed more than a predetermined amount between said first and second time periods. For example, a warning message may be created if the function determined in the second time period indicates that the diastolic dysfunction has become worse, for example indicated by the fact that the stroke volume decreases more with increasing heart rate than during the first time period.

"The warning message may be any kind of warning message, for example as explained above.

"According to a further embodiment, the device has a detector for detecting the physical activity of the living being, and the control circuit is configured to be able to determine the occasions when the steps are to be carried out in dependence on physical activity sensed by the detector for detecting the physical activity.

"Since, the control circuit is configured to select said number of occasions in dependence on the physical activity sensed by said detector, it is possible to obtain the information that indicates the stroke volume as a function of the heart rate within a relatively short time. With the help of the sensed physical activity, it is thus possible to determine whether the physical activity of the living being changes, such that the heart rate is likely to change. It is thereby possible to obtain the information correlated to the stroke volume for different heart rates in a relatively short time. For example, each of the mentioned first and second time periods may be shorter than 20 minutes.

"Alternatively, it is of course also possible for the device to directly monitor the heart rate of the living being and to select the different occasions when suitable, different heart rates are detected, such that the information that indicates the stroke volume as a function of the heart rate is obtained.

"According to a further embodiment, the control circuit is configured to derive the information correlated to the stroke volume of said heart by carrying out an impedance measurement that indicates how the amount of blood in the left ventricle of the heart varies with time, which measurement thus creates a signal that varies with time, and thereby constitutes a curve that indicates how the amount of blood in the left ventricle of the heart varies with time.

"Such an impedance measurement is an advantageous, and relatively simple, manner of determining the information that is correlated to the stroke volume.

"According to a further embodiment, the control circuit is configured to derive the information correlated to the stroke volume either from the aforementioned curve, from a filtered such curve, from a template based on different such curves from different heart beats or from a template based on different filtered such curves from different heart beats.

"The detected impedance curve may thus be filtered, for example in order to filter out artifacts and in order to make the curve smoother. A template can be created based on a measurement during a plurality of heart beats. The template is thus a representative curve based on measurements for a plurality of heart beats. The template may thus be a kind of average, or typical curve based on measurements for different heart beats.

"According to a further embodiment, said information correlated to the stroke volume is derived by considering one or both of the following:

"a) an area defined by the curve, filtered curve or template,

"b) a peak-to-peak value of the curve, filtered curve or template.

"In for example these manners, a good indication of the stroke volume can be obtained.

"According to a further embodiment, the control circuit is configured to determine whether the contraction of the ventricle at the occasion in question belongs to a special category, and if this is the case, then the control circuit is either configured not to store the derived information in the memory, or to store the derived information separately in said memory such that the memory contains information that the derived information relates to the special category such that the stored information in the memory is distinguished from the information obtained when the contraction does not belong to the special category.

"According to a further embodiment, the control circuit is configured to determine whether the contraction of the ventricle at the occasion in question belongs to any of a number of different special categories, and depending on to which special category the contraction belongs, the control circuit is either configured not to store the derived information in the memory, or to store the derived information separately in the memory, depending on the category, such the stored information in the memory for the different special categories can be distinguished from one another.

"For example, the control circuit can be configured to be able to detect one or more of the following special categories (in addition to normal sinus rhythm):

"a) whether the contraction of the ventricle at the occasion in question is a premature ventricular contraction,

"b) whether the contraction of the ventricle at the occasion in question relates to atrial fibrillation,

"c) whether the contraction of the ventricle at the occasion in question is a supraventricular extra-systole,

"d) whether the contraction of the ventricle at the occasion in question is caused by left ventricular pacing,

"e) whether the contraction of the ventricle at the occasion in question is caused by right ventricular pacing,

"f) whether the contraction of the ventricle at the occasion in question is caused by biventricular pacing.

"For different such special categories, the heart may behave differently, such that the mentioned information that indicates the stroke volume as a function of the heart rate may depend on the type (or category) of heart beat. For example, for heart beats that are premature ventricular contractions (PVCs), the mentioned information that indicates the stroke volume as a function of the heart rate may change more when the heart condition becomes worse than for heart beats that are not PVCs. Consequently, it is an advantage of the invention that the information that indicates the stroke volume as a function of the heart rate is stored separately for, for example, PVCs. The stored information based on PVC beats may thus be more sensitive to a change in the heart condition and will therefore be suitable to use in order to monitor a change in the heart condition.

"Another aspect of the invention relates to a method of monitoring a heart of a living being with the help of an implantable heart monitoring device. The method includes the following steps:

"a) detect the heart rate,

"b) derive information correlated to the stroke volume of the heart at the detected heart rate, and

"c) store the detected heart rate and the derived information correlated to the stroke volume,

"wherein the method also includes the following steps:

"carry out steps a) to c) at a number of different occasions at different, naturally varying, heart rates, such that information that indicates the stroke volume as a function of the heart rate is obtained.

"Such a method provides advantages corresponding to those described above in connection with the device according to the invention."

For the URL and additional information on this patent, see: Blomqvist, Andreas; Broome, Michael. Implantable Heart Monitoring Device and Method. U.S. Patent Number 8750975, filed August 20, 2013, and published online on June 10, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8750975.PN.&OS=PN/8750975RS=PN/8750975

Keywords for this news article include: Diastole, Diagnosis, Cardiology, Heart Rate, Hemodynamics, Cardio Device, Heart Disease, Heart Failure, Stroke Volume, Cardiac Output, Medical Devices, Pacesetter Inc., Myocardial Contraction, Cardiovascular Diseases, Diagnostic Techniques and Procedures, Cardiovascular Physiological Phenomena.

Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2014, NewsRx LLC


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Source: Clinical Trials Week


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