Patent ID: 12207965

DETAILED DESCRIPTION OF SEVERAL EMBODIMENTS

A cross-sectional view of a human heart10is depicted inFIG.1. The heart10has a muscular heart wall11, an apex19, and four chambers: right atrium12; right ventricle14; left atrium16; and left ventricle18. Blood flow is controlled by four main valves: tricuspid valve20; pulmonary valve22; mitral valve24; and aortic valve26. Blood flows through the superior vena cava28and the inferior vena cava30into the right atrium12of the heart10. The right atrium12pumps blood through the tricuspid valve20(in an open configuration) and into the right ventricle14. The right ventricle14then pumps blood out through the pulmonary valve22and into the pulmonary artery32(which branches into arteries leading to the lungs), with the tricuspid valve20closed to prevent blood from flowing from the right ventricle14back into the right atrium. Free edges of leaflets of the tricuspid valve20are connected via the right ventricular chordae tendinae34to the right ventricular papillary muscles36in the right ventricle14for controlling the movements of the tricuspid valve20.

After leaving the lungs, the oxygenated blood flows through the pulmonary veins38and enters the left atrium16of the heart10. The mitral valve24controls blood flow between the left atrium16and the left ventricle18. The mitral valve24is closed during ventricular systole when blood is ejected from the left ventricle18into the aorta40. Thereafter, the mitral valve24is opened to refill the left ventricle18with blood from the left atrium16. Free edges of leaflets42a,42pof the mitral valve24are connected via the left ventricular chordae tendinae44to the left ventricular papillary muscles46in the left ventricle18for controlling the mitral valve30. Blood from the left ventricle18is pumped through the aortic valve26into the aorta40, which branches into arteries leading to all parts of the body except the lungs. The aortic valve26includes three leaflets48which open and close to control the flow of blood into the aorta40from the left ventricle18of the heart as it beats.

In prior art echocardiogram systems, phased array data can be processed to create images of the heart and local blood flows. An example of a prior art echocardiogram output display50is depicted inFIG.2, including an image52of the heart with local blood flows depicted with reference colors54, a chart of maximum blood flow velocities through the mitral valve56, and a chart of EKG output58. While phased arrays used to create such echocardiogram displays can provide detailed information about the heart, they require skilled operator input and assessment and are relatively complex and expensive, as well as requiring relatively high power levels.

A simple transducer device and system according to the invention uses one or a few discrete, non-phased-array ultrasound transducers that collect echo in a beam or beams that target one or more heart valves, and uses signal processing to monitor key parameters of the different valves. It is intended for at-home monitoring of patients suffering from heart valve disease (e.g. aortic stenosis, mitral regurgitation, etc.) for a few days to a few weeks. It can diagnose and document changes in heart valve function during normal life functions (e.g., at work, at home, during exercise, etc.), including changes that were not detected in an ultrasound exam in the hospital or clinic. If such changes are detected by the at-home system of the invention, the system can document the changes, and communicate the changes to a smart phone, which will relay the information back to the physician via a remote computer (such as the physician's smart cell phone or laptop computer or other remote computer device).

A key element of the invention is measuring blood flow velocity in the aortic and mitral valves using echo Doppler via a simple ultrasound transducer or transducers taped on the patient's chest.FIG.3Adepicts a patient60with heart62monitored by a simple transducer64positioned on the patient's chest66adjacent the heart apex68according to an embodiment of the invention. The transducer64produces an ultrasonic beam70directed toward one or more heart valves72. EKG measurements from one or more EKG electrodes74on the patient's chest66may also be used, and may provide an EKG signal76as depicted in the EKG chart78ofFIG.3B. Blood flow measurements80determined from the Doppler echo from the transducer64are depicted in the blood flow chart81ofFIG.3C. While all the blood flow within the beam70field of view contributes to the Doppler velocity signal and thus the total blood measured blood flow80, the highest velocities associated with the largest frequency shifts come from the jets through the aortic valve and through the mitral valve. The pressure and flow velocity through the pulmonic and tricuspid valves and flow within the various heart chambers are typically much smaller. In patients with no significant aortic or mitral regurgitation, as depicted inFIG.3C, the aortic and mitral jets can be separated by their different timing and direction. Peak aortic flow82occurs in systole and its direction is negative (away from the transducer on the chest), while peak mitral flow84occurs in diastole and its direction is positive (towards the transducer64on the chest66).

If the patient60has significant aortic or mitral valve regurgitation, such as the mitral regurgitation as depicted inFIG.4C, the regurgitative flow86of the mitral valve is away from the transducer at the same time that the proper systolic flow through the aortic valve occurs. More specifically, if the patient has significant mitral regurgitation, the systolic phase is a superposition of forward flow82through the aortic valve and regurgitant flow86through the mitral valve, both in a direction away from the transducer62.

For the patient with significant mitral regurgitation, it is important to separate the systolic total flow contribution of the regular flow through the aortic valve from regurgitant flow through the mitral valve in order to properly assess and diagnose the regurgitation. Similarly, for a patient with aortic regurgitation, it is important to separate the diastolic total flow contribution of the regular mitral flow from the regurgitant aortic flow. To simplify the determination of regurgitant flow, the present invention ignores low velocities (such as those within heart chambers or from the tricuspid and pulmonary valves), and makes the assumption that peak velocities have only two contributions: a mitral jet and an aortic jet. To be able to separate the contributions of mitral from aortic, a first transducer64ais augmented by a second transducer64bthat is added to provide a second independent measurement from a slightly different angle, as illustrated inFIG.5. Each transducer64a,64bprovides an ultrasonic beam70a,70b, with the beams70a,70bat slightly different angles. The respective measured blood flow velocities from each transducer64a,64bare depicted in the blood flow charts82a,82b.

For every point in time, a set of two equations is solved to isolate the mitral contribution and the aortic contribution. The two transducers64a,64bare placed on the chest66to differ enough in their angles and distances to the aortic and mitral valves to produce an accurate separation between the two velocities. To add further accuracy or to isolate additional heart valves, more transducers can be added.

Once the two velocity signals (i.e., from the mitral and aortic valves) have been separated, the peak velocity of each signal represents the peak blood velocity through that particular valve, and the area under the curve can be correlated to the total volume flowing. For patients with aortic stenosis, the peak aortic blood velocity is related to the severity of stenosis. For mitral regurgitation patients, the regurgitation volume and flow are related to the severity of mitral regurgitation.

Because one or both of the blood jets (i.e., mitral and aortic) may be at an angle to the transducer(s), and not directly towards or away from the transducer(s), the absolute velocity of the blood jets may need to be calibrated. That can be easily achieved by measuring absolute velocity, one time, in a clinic using a phased array ultrasound system100operated by a skilled operator102as depicted inFIG.6. The phased array ultrasound system100includes a hand-held phased array transducer104providing data to a computer106that records and processes the echo Doppler data from the transducer104in order to generate an image108and/or other data regarding the absolute blood flow velocities. Using the absolute flow data provided by the phased array ultrasound system100, the skilled operator102can thus calibrate the readings from the transducers64a,64bof the portable worn device in order to provide accurate blood flow measurements from those transducers. Note that for calibration purposes the skilled operator can position the hand-held phased array transducer in a first position on the patient's chest, take blood flow measurements, then make sure the first transducer64ais properly secured (e.g., via pressure-sensitive adhesive) to the patient's chest at that first position. Similarly, the skilled operator can position the hand-held phased array transducer in a second position on the patient's chest, take blood flow measurements, then make sure the second transducer64ais properly secured (e.g., via pressure-sensitive adhesive) to the patient's chest at that second position. The process is repeated for any additional transducers. When the patient60goes home, as long as the transducers64a,64bdo not move relative to the patient's chest66the transducers64a,64bwould remain calibrated for weeks.

The present invention can be used for non-invasive left atrial blood pressure (LABP) measurement at home in heart failure patients that also have mitral regurgitation, which is a large portion of heart failure patients. Heart failure patients often have elevated blood pressure in the left atrium (LABP). Elevated LABP leads to pulmonary congestion, which is the leading cause for hospital admission in heart failure patients. Monitoring LABP has been shown to be a good indicator of the effectiveness of medical therapy and medication, and an upward trend in LABP is a good predictor of pulmonary congestion requiring hospitalization. LABP can be measured in a hospital by inserting a pressure measuring catheter to the left atrium. To monitor LABP at home using prior methods requires an implantable pressure sensor in the left atrium or in the pulmonary artery.

In severe mitral regurgitation patients, the peak LABP is actually in systole and not in diastole. The mitral regurgitation through the mitral valve allows the high left ventricular pressure to elevate the left atrial pressure. A way to measure LABP non-invasively is to measure arterial pressure non-invasively using a pressure-cuff on the arm or finger (or even using bio-impedance chest leads), then add the aortic valve gradient as measured by echo to deduce the left ventricular pressure, and then subtract the mitral valve gradient as measured by echo to deduce the left atrial pressure. This method does not provide LABP through the entire cardiac cycle, but it does provide peak pressure because in systole, during and around the peak pressure point, both the aortic valve and the regurgitant mitral valve are open and should allow for simultaneous measurements of pressure gradients.FIG.7illustrates a chart120showing the relationships of the arterial/aortic pressure122, the left ventricular pressure124, and the left atrial pressure126to the aortic pressure gradient128and the mitral pressure gradient130measured by echo at peak systole.

For the system of the present invention to be able to monitor peak LABP at home, components such as transducers, EKG electrodes, CPU processor, etc., may be provided in a wearable patch150, and two elements are added, as depicted inFIG.8: a non-invasive arterial blood pressure measurement, such as via a home cuff140a,140b; and a function in the CPU/processor to convert the peak velocities (aortic and mitral) and mitral regurgitation volume to aortic and mitral pressure gradients.

Home cuffs are commonly available for measuring arterial blood pressure, including arm cuffs140aand finger cuffs140bas depicted inFIG.8. The system can also use the EKG electrodes and/or additional electrodes to measure cardio-impedance and convert it to arterial blood pressure continuously. Measurements of blood pressure using cardio-impedance would typically need occasional calibration by an absolute blood pressure measurement with cuff.

Converting the velocity and flow to gradient is relatively complex. To do that conversion, the system requires an estimate of the effective orifice area of the valves involved. The effective orifice area of the aortic valve can be measure and stored during calibration (i.e., by skilled medical personnel in a clinical setting) by echo using the phased array transducers and systems discussed with respect toFIG.6. Note that the aortic effective orifice area typically does not change quickly with time and can be assumed to be constant for the few weeks of the monitoring period of the system. By contrast, the effective orifice area of the mitral valve changes dramatically with hemodynamic changes of a heart failure patient and cannot thus be assumed to be constant. Echo can measure the orifice area directly and can be used for calibration, although such echo will may require skilled medical personnel using a transducer such as a phased array transducer like that used for calibration of the system such as described with respect toFIG.6. Instead of a single number such as for the aortic valve, the changing effective orifice area of the mitral valve must be determined as a calibration curve. The system will need multiple calibration points in different hemodynamic conditions (rest vs. stress, or low vs. high heart rate, or low vs. high volume preload) to generate a calibration curve. Once a calibration curve is generated (e.g., in a clinical setting by skilled medical personnel), the home monitor can correlate the mitral regurgitation velocity and volume to a mitral gradient for that specific patient. This makes the calibration session a bit more complex, similar to a stress echo exam instead of a rest-only echo exam, but still less complex than implanting a sensor in a patient's heart.

Note that the system may include one or more alarm functions, such as where alarms are activated if the LABP or other heart function value reaches one or more designated values. For example, an emergency alarm value may be set, where if the calculated LABP or other heart function value reaches the emergency alarm value an emergency alarm is activated in the device, cell phone, and/or remote computer. When activated, the emergency alarm alerts the patient or his/her personal attendants (via the device or cell phone) to proceed to the hospital/emergency room. The emergency alarm may also alert designated medical personnel via the remote computer of the emergency LABP value (or other emergency heart function value) being reached, and may even activate the cell phone to call and/or text and/or email emergency personnel (e.g., paramedics and/or an ambulance) and/or the patient's designated physician/medical personnel to inform them of the emergency value being reached. A cautionary alarm value may be set (in addition to or instead of the emergency alarm value) for the LABP (or other emergency heart function value), which when reached instructs the patient/attendants (via activation of a cautionary alarm on the device and/or cell phone) to make an appointment for the patient to see his or her designated physician in the next day or so, and which may alert designated medical personnel (e.g., via the remote computer) of the cautionary LABP/heart function value being reached. The cautionary alarm may automatically call and/or text and/or email the designated physician/medical personnel with news of the cautionary LABP/heart function value being reached so that the medical personnel can contact the patient to discuss the patient's condition with the patient, schedule follow-up treatment and/or appointments, etc. The cautionary alarm and/or emergency alarm may when activated involve audio signals, such as from a speaker on the device or the cell phone, or other signals such as vibration or visual signals. Note that the emergency and/or cautionary LABP/heart function values may be pre-programmed into the device (and/or cell phone and/or remote computer) based on known emergency values of most patients, although it may be preferred that trained medical personnel program patient-specific emergency and/or cautionary LABP/heart function values into the device. Such patient-specific emergency/cautionary values can be determined by trained medical personnel based on the specific condition of the specific patient, and may be programmed into the device around the time of calibration when the device is applied to the patient's chest.

As depicted inFIGS.9A-9B and10A-10C, the two or more transducers can be mounted on an adhesive patch150with the necessary electronics160,162,164and EKG electrodes154and attached to a patient as one system. Additional sensors can also be added to the system to diagnose and document more symptoms of valve disease. For example, one important symptom is shortness of breath. To measure shortness of breath a microphone156may be added, and/or an accelerometer158, or both. The microphone156can record lung sounds to measure the frequency of breathing. The accelerometer158can measure the frequency of breathing by recording chest wall motion. Shortness of breath is characterized by fast shallow breathing. Correlation between shortness of breath and rise in aortic peak velocity is a clear indication of severe aortic stenosis. Correlation between shortness of breath and rise in mitral regurgitant volume is a clear indication of severe mitral regurgitation.

Elements of a patch150according to an embodiment of the invention are depicted inFIGS.9A-9B and10A-10C. The patch150is shaped and sized to be positioned (e.g., via adhesive) on the chest66of the patient60at a position adjacent the heart apex (not shown), such as being positioned on or adjacent the crease between the pectoral muscle/breast and the abdominal muscles as depicted inFIG.9B. The patch150includes transducers152a,152b, and may also include additional sensors such as EKG electrodes154, microphone156, and/or accelerometer158. A power supply160is included (e.g., a battery, such as an inductively rechargeable battery, and/or a small solar panel which may be on or in the patch or may be tethered thereto via a power conducting tether line and configured for securement to the patient's clothing), with a CPU and memory162configured to use the sensor data to calculate heart parameters such as aortic valve peak velocity and pressure gradient, mitral valve peak velocity and regurgitation volume, heart rate, and/or shortness of breath. Note that for a patient with substantial aortic valve regurgitation, the device may be configured to use the sensor data to calculate heart parameters such as aortic valve peak velocity and regurgitation volume, mitral valve peak velocity and pressure gradient, heart rate, and/or shortness of breath. A wireless transmitter164is configured to transmit the calculated heart parameters and/or raw sensor data via wireless (such as bluetooth) to a cell phone, which can then transmit the calculated heart parameters and/or raw sensor data to a remote location such as computer where skilled medical personnel (e.g., doctors/nurses) can review the parameters/data. The patch150may include an adhesive layer168(e.g., pressure-sensitive adhesive) on a back side thereof for easy attachment to the patient, and may include a waterproof cover170so that the patient can bathe without damaging the patch.

The monitor patch is placed on the patient's chest and calibrated, such as via the procedure described above with respect toFIG.6. The patient can go home, where any changes or severe episodes of heart valve function are recorded and transmitted to a cell phone and from the cellphone back to the physician in charge.

As depicted inFIGS.10A-10C, the patch150may be configured and dimensioned for easy attachment to the patient with the transducers spaced sufficiently apart for proper measurement of the respective valve flows. The patch150may have an overall length172of 5 cm to 20 cm, 8 to 17 cm, or 10 to 15 cm; an overall width174of 2 cm to 5 cm, 3 cm to 4 cm, or 5 cm or less; and/or an overall thickness176of 1 cm or less, 0.5 cm or less, or 0.25 cm or less. Note that other dimensions are within the scope of the invention. The transducers152a,152bmay be spaced apart a distance178of 2 cm to 15 cm, or 5 cm to 10 cm, to provide appropriate spacing between the transducer signals in order to separate the measured blood flows of the aortic and mitral valves. The patch150may be flexible to better conform to the surface of the patient's chest. Note that transducers for use with the invention may have diameters (if circular)/maximum dimension (if non-circular) of 3 cm or less, 2 cm or less, 1 cm or less.

The monitor patch150may be low cost and therefore disposable. After a few weeks, when the battery160is empty, the patch150may be taken off and disposed of. For patients requiring longer term monitoring, the patient may be able to self-apply a new patch when the old one is discarded, as long as care is taken to make sure that the transducers of the new patch are positioned at the same positions as the transducers of the old patch.

Note that the system may include multiple patches, such as a first patch having the transducers, a second patch having EKG electrodes, a third patch having the microphone or accelerometer, etc. The multiple patches may each have a dedicated battery and/or transmitter and/or processor/memory and may be linked via wireless transmissions, and/or may be linked via wires and may share power and/or transmitters and/or processors/memory.

Although the specific embodiments discussed above are directed toward mitral and aortic valve monitoring, the invention may also be applicable for use in monitoring other heart valves, including the tricuspid and pulmonary valves.

Unless otherwise noted, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. In order to facilitate review of the various embodiments of the disclosure, the following explanation of terms is provided:

The singular terms “a”, “an”, and “the” include plural referents unless context clearly indicates otherwise. The term “or” refers to a single element of stated alternative elements or a combination of two or more elements, unless context clearly indicates otherwise.

The term “includes” means “comprises.” For example, a device that includes or comprises A and B contains A and B, but may optionally contain C or other components other than A and B. Moreover, a device that includes or comprises A or B may contain A or B or A and B, and optionally one or more other components, such as C.

The term “subject” refers to both human and other animal subjects. In certain embodiments, the subject is a human or other mammal, such as a primate, cat, dog, cow, horse, rodent, sheep, goat, or pig. In a particular example, the subject is a human patient.

Although the operations of some of the disclosed methods are described in a particular, sequential order for convenient presentation, it should be understood that this manner of description encompasses rearrangement, unless a particular ordering is required by specific language. For example, operations described sequentially may in some cases be rearranged or performed concurrently. Moreover, for the sake of simplicity, the attached figures may not show the various ways in which the disclosed methods can be used in conjunction with other methods.

Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present disclosure, suitable methods and materials are described above. In case of conflict, the present specification, including terms, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.

In view of the many possible embodiments to which the principles of the disclosed invention may be applied, it should be recognized that the illustrated embodiments are only examples of the invention and should not be taken as limiting the scope of the invention. Rather, the scope of the invention is defined by the following claims. We therefore claim as our invention all that comes within the scope and spirit of these claims.