Ultrasound determination of ventricular volumes for pressure-volume loop

Abstract

An apparatus includes a processor configured for communication with an ultrasound transducer. The processor is configured to control the ultrasound transducer to obtain a first plurality of ultrasound images of a first heart valve of a heart chamber of a patient. The first plurality of ultrasound images may be a plurality of Doppler ultrasound frames. The processor is further configured to determine a first plurality of volume measurements of the heart chamber based on the first plurality of ultrasound images, wherein each volume measurement of the first plurality of volume measurements corresponds to an ultrasound image of the first plurality of ultrasound images. The processor is also configured to generate a pressure-volume (PV) loop of the heart chamber based on the first plurality of volume measurements without using a PV loop catheter and output the PV loop.

Description

ULTRASOUND DETERMINATION OF VENTRICULAR VOLUMES FORPRESSURE-VOLUME LOOPFIELD

[0001] The subject matter described herein relates to systems, devices, and methods for measuring the pressure-volume (PV) loop of a left or right ventricle of the heart. This PV loop measurement system has particular but not exclusive utility for diagnosing and monitoring health conditions of the heart.BACKGROUND

[0002] Pressure-volume loops (PV loops) are used to diagnose and monitor a number of heart conditions. However, in currently used methods, a specialized catheter is introduced into the heart to measure the “P” and “V” parts of the graph at that point in time. For any given point in time, the combination of the “P” and “V” values is charted, and over one cardiac cycle, forms a closed “loop”. The shape of the loop, and the angles formed by some sections of the graph and the axes provides information to the physician that can be used to diagnose or monitor progression of disease over time.

[0003] It is to therefore be appreciated that such commonly used left PV loop measurement procedures have numerous drawbacks, including the requirement for a specialized catheter designed for that purpose.

[0004] The information included in this Background section of the specification, including any references cited herein and any description or discussion thereof, is included for technical reference purposes only and is not to be regarded as subject matter by which the scope of the disclosure is to be bound.SUMMARY

[0005] In accordance with at least one aspect of the present disclosure, a pressure-volume (PV) loop measurement system is disclosed. The PV loop measurement system uses Doppler ultrasound imaging of heart valves (e.g., the aortic valve and / or the mitral valve) to calculate the change in volume of the heart ventricle (e.g., the left ventricle) at different points in the cardiac cycle. In some implementations, the same or similar Doppler data can be used to calculate the pressure within the ventricle. In other aspects, the pressure may be obtained invasively, or through ultrasound strain measurements of the wall of the heart. Plotting the pressure vs. volume change at different time points on a 2D graph yields a closed loop - the PV loop. It is noted that although the present disclosure is directed to measurement of PV loops for the left ventricle of the heart, the same principles can be used for measurement of a PV loop for the right ventricle, left atrium, right atrium,using Doppler ultrasound data from any associated heart valve(s) or blood vessel(s), which are the blood inflow and outflow sources for the given heart chamber.

[0006] The PV loop measurement system disclosed herein has particular, but not exclusive, utility for diagnosing and monitoring heart conditions, such as dilated or restrictive cardiomyopathy, left ventricular hypertrophy, valve stenoses or regurgitation, etc.

[0007] A system of one or more computers can be configured to perform particular operations or actions by virtue of having software, firmware, hardware, or a combination of them installed on the system that in operation causes or cause the system to perform the actions. One or more computer programs can be configured to perform particular operations or actions by virtue of including instructions that, when executed by data processing apparatus, cause the apparatus to perform the actions.

[0008] One general aspect includes a system that includes a processor configured for communication with an ultrasound transducer. The processor is configured to: control the ultrasound transducer to obtain a first plurality of ultrasound images of a first valve of a heart chamber of a patient; determine a first plurality of volume measurements of the heart chamber based on the first plurality of ultrasound images, wherein each volume measurement of the first plurality of volume measurements corresponds to an ultrasound image of the first plurality of ultrasound images; generate a PV loop of the heart chamber based on the first plurality of volume measurements; and output the PV loop. Other examples of this aspect include corresponding computer systems, apparatus, and computer programs recorded on one or more computer storage devices, each configured to perform the actions of the methods.

[0009] Implementations may include one or more of the following features. In some aspects, the first plurality of ultrasound images is a plurality of Doppler ultrasound frames. In some aspects, the heart chamber is a left ventricle, and the first heart valve is an aortic valve. In some aspects, the processor is further configured to: obtain a first plurality of pressure measurements corresponding to the first plurality of ultrasound images; and generate the PV loop based on the first plurality of pressure measurements. In some aspects, the first plurality of ultrasound images corresponds to a plurality of volume decreases of the heart chamber, and the processor is configured to determine the first plurality of volume measurements based on the plurality of volume decreases relative to a first initial volume of the heart chamber. In some aspects, the processor is configured to: control the ultrasound transducer to obtain a second plurality of ultrasound images of a second valve of the patient; determine a second plurality of volume measurements of the heart chamber based on the second plurality of ultrasound images, wherein each volume measurement of the second plurality of volume measurements corresponds to an ultrasound image of the second plurality of ultrasound images; and generate the PV loop based on the second plurality of volume measurements. In some aspects, the heart chamber is a left ventricle, the first heart valve is an aortic valve, and the secondheart valve is a mitral valve. In some aspects, the second plurality of ultrasound images corresponds to a plurality of volume increases of the heart chamber, and the processor is configmed to determine the second plurality of volume measurements based on the plurality of volume increases relative to a second initial volume of the heart chamber. In some aspects, the processor is further configmed to obtain a second plurality of pressure measmements corresponding to the second plurality of ultrasound images; and generate the PV loop based on the second plurality of pressure measmements.

[0010] In some aspects, the processor is further configmed to: control a pressme sensor to capture a plurality of pressme measurements; control the ultrasound transducer to obtain the first plurality of ultrasound images of the first valve of the heart chamber dming a first phase of a cardiac cycle; compute the first plurality of volume measurements of the heart chamber based on the first plurality of ultrasound images, each volume measmement of the first plurality of volume measmements corresponding to an image of the first plurality of ultrasound images and a pressme measmement of the plurality of pressme measurements; control the ultrasound transducer to obtain a second plurality of ultrasound images of a second valve of the heart chamber dming a second phase of the cardiac cycle; determine a second plurality of volume measurements of the heart chamber based on the second plurality of ultrasound images, each volume measurement of the second plurality of volume measmements corresponding to an image of the second plurality of images and a pressure measmement of the plurality of pressure measurements; generate a plot of the pressure measurements as a function of the first plurality of volume measurements and the second plurality of volume measmements; and display the plot. In some aspects, the apparatus includes the ultrasound transducer; and a pressme sensor configured to obtain a pressure measmement associated with the heart chamber. In some aspects, the pressure sensor comprises a pressure-sensing catheter or a guidewire. In some aspects, the pressme sensor is positioned in the heart chamber to capture the plurality of pressure measmements. In some aspects, the pressme sensor is located outside the heart chamber and the processor is further configmed to capture the plurality of pressme measurements by reading a pressme value from the pressure sensor; and at least one of: computing a pressme drop across the first heart valve based on the first plurality of ultrasound images; or computing a pressure drop across the second heart valve based on the second plurality of ultrasound images. In some aspects, an electrocardiogram sensor, and wherein the processor is further configured to, based on readings from the electrocardiogram sensor, synchronize the plurality of pressme measmements with the first plurality of volume measurements and the second plurality of volume measmements. In some aspects, the processor is further configured to generate a model of the heart chamber based on 3D imaging data. In some aspects, the model of the heart chamber includes a minimum volume of the heart chamber or a maximum volume of the heart chamber during a cardiac cycle. In some aspects, the 3D imaging data is obtained by at least one of the ultrasound transducer or an X-ray imaging device. In some aspects, the PV loop is generated as a graph that is output to a display. In some aspects, the ultrasound transducer is coupled to an intracardiac echography catheter, transesophagealechocardiography probe, or transthoracic echocardiography probe. In some aspects, the first phase is a systolic phase, and the second phase is a diastolic phase. Implementations of the described techniques may include hardware, a method or process, or computer software on a computer-accessible medium.

[0011] One general aspect includes an apparatus that includes a processor configured for communication with an ultrasound transducer and a display, where the processor is configured to: control the ultrasound transducer to obtain a first plurality of Doppler ultrasound frames of an aortic valve of a patient; determine a first plurality of volume measurements of a left ventricle based on the first plurality of Doppler ultrasound frames, where each volume measurement of the first plurality of volume measurements corresponds to a Doppler ultrasound frame of the first plurality of Doppler ultrasound frames; generate a graph of a PV loop of the left ventricle using the first plurality of volume measurements and without using a PV loop catheter; and output the graph of the PV loop to the display. Other examples of this aspect include corresponding computer systems, apparatus, and computer programs recorded on one or more computer storage devices, each configured to perform the actions of the methods.

[0012] Implementations may include one or more of the following features. In some aspects, the processor is configured to: receive a first plurality of pressure measurements corresponding to the first plurality of Doppler ultrasound frames; and use the first plurality of pressure measurements to generate the graph of the PV loop. In some aspects, the plurality of Doppler ultrasound frames corresponds to a plurality of volume decreases of the left ventricle, where, to determine the first plurality of volume measurements, the processor is configured to use the plurality of volume decreases relative to a first initial volume of the left ventricle. In some aspects, the processor is configured to: control the ultrasound transducer to obtain a second plurality of Doppler ultrasound frames of a mitral valve of the patient; determine a second plurality of volume measurements of the left ventricle based on the second plurality of Doppler ultrasound frames, where each volume measurement of the second plurality of volume measurements corresponds to a Doppler ultrasound frame of the second plurality of Doppler ultrasound frames; and use the second plurality of volume measurements to generate the graph of the PV loop. In some aspects, the second plurality of Doppler ultrasound frames corresponds to a plurality of volume increases of the left ventricle, where, to determine the second plurality of volume measurements, the processor is configured to use the plurality of volume increases relative to a second initial volume of the left ventricle. In some aspects, the processor is configured to: receive a second plurality of pressure measurements corresponding to the second plurality of Doppler ultrasound frames; and use the second plurality of pressure measurements to generate the graph of the PV loop. Implementations of the described techniques may include hardware, a method or process, or computer software on a computer-accessible medium.

[0013] One general aspect includes a system. The system includes an ultrasound transducer; a pressure sensor configured to obtain a pressure measurement associated with a heart chamber, aprocessor configured to: control the pressure sensor to capture a series of pressure measurements; control the ultrasound transducer to capture a first series of Doppler images of a first valve of the heart chamber during a first phase of a cardiac cycle; based on the first series of Doppler images, compute a first series of volume measurements of the heart chamber, each volume measurement corresponding to an image of the first series of images and a pressure measurement of the series of pressure measurements; control the ultrasound transducer to capture a second series of Doppler images of a second valve of the heart chamber during a second phase of the cardiac cycle; based on the second series of Doppler images, compute a second series of volume measurements of the heart chamber, each volume measurement corresponding to an image of the second series of images and a pressure measurement of the series of pressure measurements; generate a plot of the pressure measurements as a function of the first series of volume measurements and the second series of volume measurements; and display the plot to a user. Other examples of this aspect include corresponding computer systems, apparatus, and computer programs recorded on one or more computer storage devices, each configured to perform the actions of the methods.

[0014] Implementations may include one or more of the following features. In some aspects, the pressure sensor and the ultrasound transducer are different. In some aspects, the pressure sensor may include a pressure-sensing catheter or guidewire. In some aspects, the pressure sensor and the ultrasound transducer are the same. In some aspects, the pressure sensor is located in the heart chamber. In some aspects, the pressure sensor is located outside the heart chamber, and capturing the series of pressure measurements involves reading a pressure value from the pressure sensor; and computing a pressure drop across the first heart valve based on the first series of Doppler images; or computing a pressure drop across the second heart valve based on the second series of Doppler images. In some aspects, the processor is further configured to, based on readings from the electrocardiogram sensor, synchronize the series of pressure measurements with the first series of volume measurements and the second series of volume measurements. In some aspects, the processor is further configured to, based on 3D imaging data, generate a model of the heart chamber. In some aspects, the model of the heart chamber includes a minimum volume of the heart chamber or a maximum volume of the heart chamber during the cardiac cycle. In some aspects, the 3D imaging data is obtained by the ultrasound transducer. In some aspects, the 3D imaging data is obtained by an X-ray imaging device. In some aspects, the ultrasound transducer is coupled to an intracardiac echography catheter, transesophageal echocardiography probe, or transthoracic echocardiography probe. In some aspects, the heart chamber is a left ventricle, where the first heart valve is an aortic valve and the first phase is a systolic phase, and where the second heart valve is a mitral valve, and the second phase is a diastolic phase. In some aspects, the ultrasound transducer is positioned such that capturing the first series of Doppler images of the first valve and the second series of Doppler images of the second valve does not require repositioning of the ultrasound transducer.Implementations of the described techniques may include hardware, a method or process, or computer software on a computer-accessible medium.

[0015] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter. A more extensive presentation of features, details, utilities, and advantages of the PV loop measurement system, as defined in the claims, is provided in the following written description of various aspects of the disclosure and illustrated in the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Illustrative aspects of the present disclosure will be described with reference to the accompanying drawings, of which:

[0017] Figure 1A is a front view of a human heart according to aspects of the present disclosure.

[0018] Figure IB is a cross-sectional front view of a human heart according to aspects of the present disclosure.

[0019] Figure 2A is a graph showing ventricular volume as a function of time over one complete cardiac cycle, according to aspects of the present disclosure.

[0020] Figure 2B is a graph showing ventricular pressure as a function of time over one complete cardiac cycle, according to aspects of the present disclosure.

[0021] Figure 2C is a graph showing ventricular pressure as a function of ventricular volume over one complete cardiac cycle, according to aspects of the present disclosure.

[0022] Figure 3 is a schematic, diagrammatic view, in block diagram form, of a system 300 according to aspects of the present disclosure.

[0023] Figure 4 is a front cross-sectional view of a human heart being imaged by an intracardiac echography (ICE) catheter, according to aspects of the present disclosure.

[0024] Figure 5A is an en face ultrasound view of the aortic valve, according to aspects of the present disclosure.

[0025] Figure 5B is an en face ultrasound view of the aortic valve, according to aspects of the present disclosure.

[0026] Figure 6 is an en face color Doppler image of a heart valve at one time point during a cardiac cycle, according to aspects of the present disclosure.

[0027] Figure 7 is an enlarged view of the en face color Doppler image of Figure 6, according to aspects of the present disclosure.

[0028] Figure 8 is a schematic, diagrammatic representation, in block diagram form, of an example ventricular volume change measurement process, according to aspects of the present disclosure.

[0029] Figure 9 is a schematic, diagrammatic representation, in block diagram form, of an example per-segment volume change calculation process, according to aspects of the present disclosure.

[0030] Figure 10 is a schematic, diagrammatic representation, in block diagram form, of an example per-cardiac-cycle volume change calculation process, according to aspects of the present disclosure.

[0031] Figure 11 is a schematic, diagrammatic representation, in block diagram form, of an example minimum and maximum ventricular volume determination process, according to aspects of the present disclosure.

[0032] Figure 12 is a graph 1200 showing the reduction in ventricular volume as a function of time during the systolic portion of the heart cycle, according to aspects of the present disclosure.

[0033] Figure 13 is a schematic, diagrammatic representation, in block diagram form, of an example per-image-frame ventricular volume and pressure determination process, according to aspects of the present disclosure.

[0034] Figure 14 is a graph showing the changes in ventricular pressure as a function of time during the systolic portion of the heart cycle, according to aspects of the present disclosure.

[0035] Figure 15 is a graph showing the changes in ventricular pressure as a function of volume during the systolic portion of the heart cycle, according to aspects of the present disclosure.

[0036] Figure 16A is a front cross-sectional view of a human heart being imaged by an intracardiac echography (ICE) catheter, according to aspects of the present disclosure.

[0037] Figure 16B is a front cross-sectional view of a human heart being imaged by an intracardiac echography (ICE) catheter, according to aspects of the present disclosure.

[0038] Figure 17 is a B-mode ultrasound image of the heart showing both the aortic valve and the mitral valve, according to aspects of the present disclosure.

[0039] Figure 18 is a schematic, diagrammatic representation, in block diagram form, of an example per-image-frame ventricular volume and pressure determination process, according to aspects of the present disclosure.

[0040] Figure 19 is a schematic, diagrammatic representation, in block diagram form, of an example minimum and maximum ventricular volume determination process, according to aspects of the present disclosure.

[0041] Figure 20 is a graph showing the changes in ventricular pressure as a function of volume during the systolic and diastolic portions of the heart cycle (e.g., the entire heart cycle), according to aspects of the present disclosure.

[0042] Figure 21 is a graph showing changes in ventricular volume as a function of time during a complete heart cycle, according to aspects of the present disclosure.

[0043] Figure 22 is a graph showing the changes in ventricular pressure as a function of time during an entire cardiac cycle, according to aspects of the present disclosure.

[0044] Figure 23 is a schematic, diagrammatic representation, in flow diagram form, of an example PV loop generation method, according to aspects of the present disclosure.

[0045] Figure 24 is a graph of ventricular pressure as a function of ventricular volume, according to aspects of the present disclosure.

[0046] Figure 25 is a schematic diagram of a processor circuit, according to aspects of the present disclosure.DETAILED DESCRIPTION

[0047] Pressure-volume loops (PV loops) are used to diagnose and monitor a number of heart conditions, and can be performed on either the right or left side of the heart. The present disclosure avoids the need for a specialized catheter to be introduced into the heart on the desired side, spanning the ventricle and atria, where an electrical current is passed between electrodes on the catheter located at the very distal and a proximal location, and electrodes in between these outermost electrodes are used to measure the difference in electrical potential in pairs. This difference in electrical potential is directly proportional to the cross-sectional area of a cylinder at that segment of the catheter, so the composite cross-sectional area of all the segments can be summed up, giving a value for the “V” part of the graph at that point in time. The “P” part of the graph comes, for example, from a pressure sensor at the midpoint of the electrodes on the catheter.

[0048] A cardiac pressure-volume (PV) loop measurement system is disclosed. The systems, devices and methods described herein create the same PV loop by using data from an ultrasound probe. The probe may be a transesophageal echography (TEE) probe, a transthoracic echography (TTE) probe, or an intracardiac echocardiography (ICE) probe.

[0049] Using this method to generate a PV loop has several advantages. The first is that there is no need to use a specialized catheter, or the need to create an introduction site for it, especially when using a TEE or transthoracic probe. A second advantage is that there isn’t any interference with the normal heart function that could be introduced with a catheter across the valve between the ventricle and atria.

[0050] A third advantage is that the PV loop can be generated in real time during a procedure. Since a specialized catheter is not required, the PV loop can be generated at any point in a procedure as long as the ultrasound probe is able to gather data about the flow of blood across the orifice of the desired valve location.

[0051] One element of this invention is using the Doppler information from the flow of blood across a heart valve, and integrates that information over an area to generate a cumulative flowrate which can then be integrated over time to calculate a total volume of blood that has crossed the orifice of the valve in question. Since the blood can be considered as incompressible, the volume of blood flow is directly proportional to the change in volume of the heart chamber(s).

[0052] The pressure gradient across the valve is then calculated from the ultrasound Doppler data and / or pressure data can be obtained from an invasive blood pressure transducer (or from the transducer array itself) to further calculate the pressure portion of the PV Loop. Another method to calculate the pressure in the chamber is to use an ultrasound strain measurement of the heart wall, which is used in echocardiography.

[0053] Doppler data from the blood flow through the orifice of the valve of interest is used. The cross section of the orifice is broken into a number of discrete zones. The velocity data from the Doppler information, and the cross-sectional area of the zone can then be used to get an instantaneous flowrate through that area. Multiplying by the amount of time between such assessments then yields volume of blood that has passed through each zone during that time interval. When these volumes are summed across the entire cross-sectional area of the orifice, the change in volume of the heart chamber(s) can be determined.

[0054] This change in volume is the X-axis of the PV Loop. The Y-axis is determined by one of the three pressure measurement methods described above.

[0055] In addition to PV loop assessment, the method described above could also be used to better quantify both valve regurgitation and paravalvular leakage than just the velocity and visual assessments currently used.

[0056] The present disclosure aids substantially in diagnosing and monitoring health conditions of the heart, by allowing a clinician to compute and plot a PV loop without an invasive PV measurement catheter. Implemented on ultrasound console in communication with an ultrasound probe, the PV loop measurement system disclosed herein provides practical improvements in cardiology by allowing a single measuring device - the ultrasound probe - to provide the data from which the entire PV loop can be constructed (e.g., the shape of the PV loop. In some aspects, the PV loop that is generated only the Doppler ultrasound data and pressure data can provide a relative position of the PV loop (vs. an absolute position in the pressure-volume Cartesian coordinate system). This improved measurement technology transforms Doppler measurements of the heart valves into graphically represented PV loops, without the normally routine need to insert an invasive PV measurement catheter into the heart. This unconventional approach improves the functioning of the ultrasound console, by enabling it to calculate and display heart variables that previously required specialty hardware, and also improves the PV measurement process by not requiring a PV probe to be inserted partway through the aortic valve, potentially altering the function of the heart.

[0057] Imaging data of the heart (e.g., x-ray, ultrasound, etc.) can be used form a 3D reconstruction of the heart, from which volume measurements (e.g., maximum volume of heart chamber, such an initial volume or a final volume, or minimum volume of heart chamber, such as an initial volume or a final volume, etc.) can be determined. The volume measurements from 3D reconstruction can allow for the absolute position of the PV loop in the pressure-volume Cartesian coordinate system to be determined.

[0058] The PV loop measurement system may incorporate a process at least partially viewable on a display, and operated by a control process executing on a processor that accepts user inputs from a keyboard, mouse, or touchscreen interface, and that is in communication with an ultrasound probe. In that regard, the control process performs certain specific operations in response to different inputs or selections made at different times. Certain outputs of the PV loop measurement system may be printed, shown on a display, or otherwise communicated to human operators.

[0059] These descriptions are provided for exemplary purposes only, and should not be considered to limit the scope of the PV loop measurement system. Certain features may be added, removed, or modified without departing from the spirit of the claimed subject matter.

[0060] For the purposes of promoting an understanding of the principles of the present disclosure, reference will now be made to the aspects illustrated in the drawings, and specific language will be used to describe the same. It is nevertheless understood that no limitation to the scope of the disclosure is intended. Any alterations and further modifications to the described devices, systems, and methods, and any further application of the principles of the present disclosure are fully contemplated and included within the present disclosure as would normally occur to one skilled in the art to which the disclosure relates. In particular, it is fully contemplated that the features, components, and / or steps described with respect to one aspect may be combined with the features, components, and / or steps described with respect to other aspects of the present disclosure. For the sake of brevity, however, the numerous iterations of these combinations will not be described separately.

[0061] Figure 1A is a front view of a human heart 100 according to aspects of the present disclosure. Visible are an aorta 102 from which stems a right coronary artery 104 and a left main coronary artery 106. The left main coronary artery 106 branches into a left circumflex coronary artery 108 and a left anterior descending coronary artery 110. The right coronary artery 104, the left main coronary artery 106, the left circumflex coronary artery 108, and a left anterior descending coronary artery 110 are the arteries that provide oxygen-rich blood to muscles of the human heart 100.

[0062] Figure IB is a cross-sectional front view of a human heart 100 according to aspects of the present disclosure. Visible are a right atrium 112 and a right ventricle 114. In that regard, oxygenpoor blood enters the human heart 100 in the right atrium 112 and travels to the right ventricle 114 through the tricuspid valve 116. The oxygen-poor blood leaves the right ventricle 114 and travels tothe lungs. Also visible are a left atrium 118 and a left ventricle 120. In that regard, oxygen-rich blood is received from the lungs in the left atrium 118 and travels to the left ventricle 120 through the mitral valve 122. The oxygen-rich blood leaves the left ventricle 120 and goes out to the body through the aorta 102 via an aortic valve 124. The septum 130 separates the left ventricle 120 from the right ventricle 114.

[0063] Before continuing, it should be noted that the examples described above are provided for purposes of illustration, and are not intended to be limiting. Other devices and / or device configurations may be utilized to carry out the operations described herein.

[0064] Figure 2A is a graph 200 showing ventricular volume 210 as a function of time 220 over one complete cardiac cycle (e.g., a span of just over one second), according to aspects of the present disclosure. Six time points, A, B, C, D, E, and F, are marked. In an example, at time point A, systole begins. The mitral valve closes while the blood-filled left ventricle is at its maximum volume, and the left atrium now begins pressurizing. At time point B, the aortic valve opens, and the volume of the left atrium starts decreasing as the heart begins pumping blood into the aorta. At time point C, the left ventricle reaches its highest pressure while the volume of the left ventricle continues to decrease. At time point D, the blood has been pumped out of the left ventricle, which is now at its minimum volume. The left ventricle now depressurizes while at its minimum volume until, at point E, the mitral valve opens, systole ends, and diastole begins. The left atrium now expands (e.g., increases in volume) until, at point F, the left atrium is at its minimum pressure, and then continues expanding until it once again reaches point A, the maximum volume and the end of diastole. It is noted that volume is approximately constant between points A and B, and again between points D and E.

[0065] Figure 2B is a graph 230 showing ventricular pressure 240 as a function of time 220 over one complete cardiac cycle, according to aspects of the present disclosure. The six time points A, B, C, D, E, and F are marked. In an example, at time point A, systole begins. The mitral valve closes while the blood-filled left ventricle is at its maximum volume, and the left atrium now begins pressurizing. At time point B, the aortic valve opens, and the heart begins pumping blood into the aorta. At time point C, the left ventricle reaches its highest pressure and begins depressurizing. At time point D, the blood has been pumped out of the left ventricle, which is now at its minimum volume. The left ventricle now continues depressurizing while at its minimum volume until, at point E, the mitral valve opens, systole ends, and diastole begins. The left atrium now expands until, at point F, the left atrium is at its minimum pressure, and then continues expanding until it once again reaches point A, the maximum volume and the end of diastole.

[0066] Figure 2C is a graph 250 showing ventricular pressure 240 as a function of ventricular volume 210 over one complete cardiac cycle, according to aspects of the present disclosure. The six time points, A, B, C, D, E, and F, are marked. In an example, at time point A, systole begins. The mitral valve closes while the blood-filled left ventricle is at its maximum volume, and the left atriumnow begins pressurizing at constant volume. At time point B, the aortic valve opens, and the heart begins pumping blood into the aorta. At time point C, the left ventricle reaches its highest pressure. At time point D, the blood has been pumped out of the left ventricle, which is now at its minimum volume. The left ventricle now begins depressurizing while at constant volume until, at point E, the mitral valve opens, systole ends, and diastole begins. The left atrium now expands until, at point F, the left atrium is at its minimum pressure, and then continues expanding until it once again reaches point A, the maximum volume and the end of diastole. It is noted that volume is approximately constant between points A and B, and again between points D and E. The pressure and volume sketch out a closed figure in time, known as a PV loop 260.

[0067] Figure 3 is a schematic, diagrammatic view, in block diagram form, of a system 300 according to aspects of the present disclosure. Block diagrams are provided herein for exemplary purposes; a person of ordinary skill in the art will recognize myriad variations that nonetheless fall within the scope of the present disclosure. For example, any of the steps described herein may optionally include an output to a user of information relevant to the step, and may thus represent an improvement in the user interface over existing art by providing information not otherwise available. Block diagrams may show a particular arrangement of components, modules, services, steps, processes, or layers, resulting in a particular data flow. It is understood that some embodiments of the systems disclosed herein may include additional components, that some components shown may be absent from some aspects, and that the arrangement of components may be different than shown, resulting in different data flows while still performing the methods described herein.

[0068] The system 300 includes an ultrasound console 310, which includes a processor 312, input device 314, memory 316, and display 318. The ultrasound console 310 is coupled to an ultrasound probe 320, which includes a transducer array 322. Depending on the configuration of the ultrasound probe 320, it may include either or both of a flexible elongate member 342 (e.g., for an intracardiac echography (ICE) catheter or transesophageal echography (TEE) probe) or a handle 326 (e.g., for a handheld transthoracic echocardiography (TTE) probe or TEE probe).

[0069] Depending on the implementation, the system 300 may also include a computer 330, which serves to integrate data from multiple subsystems, and which includes a processor 332, memory 336, input device 334, and display 338.

[0070] Depending on the implementation, the system 300 may also include an intravascular pressure console 340, which includes a processor 342, input device 344, memory 346, and display 348. The intravascular pressure console 340 is coupled to an intravascular catheter or guidewire 350, which includes a pressure sensor 352 mounted on a flexible elongate member 354. The intravascular pressure console 340 may not be needed for implementations that calculate ventricular pressure exclusively from ultrasound data. In implementations that include the intravascular pressure console 340, the pressure sensor 352 may be positioned inside the left ventricle to directly obtain ventricularpressure readings, or may be positioned elsewhere (e.g., in the aorta or pulmonary artery) to obtain pressure readings that, while not equal to the ventricular pressure, can serve as proxy measurements representative of it. In still other aspects, both a pressure sensor 352 and the Doppler ultrasound data may be used to compute or deduce the intraventricular pressure at different times during the cardiac cycle.

[0071] Depending on the implementation, the system 300 may also include an electrocardiogram (ECG) console 360, to synchronize pressure and volume measurements. The ECG console 360 includes a processor 362, input device 364, memory 366, and display 268, and is coupled to ECG electrodes 370 that can be attached to the patient’s body to measure electrical signals generated by the heart over the course of a heartbeat cycle. The ECG console may not be needed for other implementations (e.g., such as those that calculate ventricular pressure exclusively from ultrasound data).

[0072] Depending on the implementation, the system 300 may include an X-ray imaging console 380, to image intravascular devices inserted into the patient’s body (including but not limited to an ICE catheter and / or pressure-sensing guidewire). The X-ray imaging console includes a processor 382, input device 384, memory 386, and display 388, and is coupled to an X-ray imaging device 390. More generally, the imaging console 380 can be any sort of external imaging system, including X-ray (e.g., fluoroscopic, angiographic, computed tomography (CT), etc.), MRI, external ultrasound, etc. In some aspects, external imaging may be used for 3D reconstruction of the left ventricle or other structures.

[0073] The processor and / or memory of the ultrasound console 310, the intravascular pressure console 340, the ECG console 360, the x-ray imaging console 380, and / or the computer 330 can be a processor circuit, such as described in Figure 25.

[0074] Figure 4 is a front cross-sectional view of a human heart 100 being imaged by an intracardiac echography (ICE) catheter 410, according to aspects of the present disclosure. Visible are the right atrium 112, right ventricle 114, tricuspid valve 116, left atrium 118, left ventricle 120, mitral valve 122, aorta 102, aortic valve 124, inferior vena cava (IVC) 1630, and superior vena cava (SVC) 1640. The ICE catheter 410 includes a flexible elongate member 324 and an ultrasound transducer array 322. In the example shown in Figure 4, the ICE catheter 410 is positioned such that the field of view 420 of the transducer array 322 has a central axis 430 that forms an en face view of the annulus of the aortic valve 124 (e.g., the central axis 430 is perpendicular (90 degrees) to a plane 440 extending through the annulus of the aortic valve 124). The ICE catheter 410 travels through the IVC 1630 and right atrium 112 into the SVC 1640, for imaging of the aortic valve 124 via the SVC 1640. The field of view 420 of the transducer array 322 can be selected based on the position and / or orientation (e.g., deflection) of the distal portion of the ICE catheter, and / or by beam steering.

[0075] It is understood that other types of probes can have different positions / orientations for an en face view of the aortic valve 124. It is understood that any kind of probe can have a different position and / or orientation for an en face view of the aortic valve 124 for 3D imaging and for 2D imaging.

[0076] Figure 5A is an en face ultrasound view 500 of the aortic valve 124, according to aspects of the present disclosure. In the example shown in Figure 5A, the aortic valve 124 is open, which happens at time point B (see Figure 2C), the beginning of systole. This view is a 3D B-mode image, but it is noted that a 2D B-mode image, or other imaging modality, can also clearly show an en face view of the aortic valve 124.

[0077] Figure 5B is an en face ultrasound view 500 of the aortic valve 124, according to aspects of the present disclosure. In the example shown in Figure 5B, the aortic valve 124 is closed, which happens at time point C (see Figure 2C), the before the start of diastole. This view is a 3D B-mode image, but it is noted that a 2D B-mode image, or other imaging modality, can also clearly show an en face view of the aortic valve 124.

[0078] Figure 6 is an en face color Doppler image 600 of a heart valve 610 at one time point during a cardiac cycle, according to aspects of the present disclosure. Colorless pixels 620 of the color Doppler image indicate there is no longitudinal motion with respect to the ultrasound transducer array. Blue pixels 630 of the color Doppler image 600 indicate longitudinal motion (e.g., blood flow) toward the ultrasound transducer array, and red pixels 640 of the color Doppler image 600 indicate longitudinal motion (e.g., blood flow) away from the ultrasound transducer array. The saturation of the red or blue color is proportional to the magnitude of the velocity toward or away from the ultrasound transducer array, as shown in the color key 650.

[0079] The example of Figure 6 shows Doppler image frame data overlaid on a 3D B-mode image. However, it is understood that the PV loop measurement system of the present disclosure can use Doppler image frame data alone, or Doppler image frame data overlaid on 2D B-mode images. The imaging plane for the Doppler image frame data can be along the valve annulus or along the vena contracta (above the valve annulus, in the direction of blood flow). In some cases, an angle correction may be required for the Doppler image data, as described below.

[0080] Figure 7 is an enlarged view 700 of the en face color Doppler image 600 of Figure 6, according to aspects of the present disclosure. In the example shown in Figure 7, the area of the heart valve 610 has been divided into a 4 x 5 grid 710 of segments 720. At any given time point in the cardiac cycle, each segment 720 can include colorless pixels 620, red pixels 640, and / or blue pixels 630, indicative of a direction and magnitude of blood flow toward or away from the ultrasound transducer. An average velocity can thus be computed for each segment 720, and an average velocity for flow through the heart valve 610 can be computed as the average of all of the segments 720.These velocity values can be used to compute volume changes of a heart chamber such as the left ventricle, as described below.

[0081] The 4 x 5 grid of Figure 7 is exemplary; other grid sizes, both larger and smaller (e.g., a x a, a x b, b x b, b x a), may be used instead or in addition. As will be appreciated by a person of ordinary skill in the art, a greater number of segments 720 (e.g., a 5 x 5 grid, a 10 x 10 grid, etc.) may result in a more accurate calculation or estimate of the average flow velocity through the heart valve 610, though at a greater real-time computational burden, whereas a smaller number of segments (e.g., a 4 x 4 grid, a 3 x 3 grid, etc.) may result in a less accurate but faster calculation or estimate of the average flow velocity through the heart valve 610.

[0082] Figure 8 is a schematic, diagrammatic representation, in block diagram form, of an example ventricular volume change measurement process 800, according to aspects of the present disclosure. In the example shown in Figure 8, the doppler image frame 600 of the heart valve 610 is divided into segments 720, each of which represents a computable contribution 810 to the change in ventricular volume due to blood flow. The sum of these contributions 810 is the volume change 820 of the ventricle (e.g., volume decrease, due to outflow of blood from the ventricle) between the current ultrasound image frame 600 and the next ultrasound image frame 600. This change in ventricular volume for time step i can be represented as DVi.

[0083] Figure 9 is a schematic, diagrammatic representation, in block diagram form, of an example per-segment volume change calculation process 900, according to aspects of the present disclosure. A particular segment 910 is an array of c x d pixels, each of which represents a different blood flow velocity 920. Averaging these blood flow velocities 920 yields an average velocity 930 for the segment (in units of distance or length over time). This can be multiplied by the cross- sectional area 940 of the segment (in units of length squared) and the frame rate 950 of the ultrasound imaging (in units of one over time) to yield that segment’s contribution to the change in volume of the ventricle for the current time step (DVi).

[0084] Figure 10 is a schematic, diagrammatic representation, in block diagram form, of an example per-cardiac-cycle volume change calculation process 1000, according to aspects of the present disclosure. Ultrasound image frames 600 of a heart valve (e.g. the aortic valve) are used to calculate the change in ventricular volume per image frame 820 (DV e.g., a decrease in volume due to the flow of blood out of the ventricle), as described above. These per-frame volume changes can then be summed to yield the total change (e.g., total decrease) in ventricular volume over the course of the cardiac cycle (equal to the difference between the maximum and minimum volumes of the ventricle).

[0085] Figure 11 is a schematic, diagrammatic representation, in block diagram form, of an example minimum and maximum ventricular volume determination process 1100, according to aspects of the present disclosure. Imaging data 1110, such as 3D B-mode ultrasound data, x-rayimaging data (e.g., multiple plane angiography, CT scan data, etc.), or other 2D or 3D imaging data, can be used to construct a 3D model 1115 of the ventricle, from which the maximum ventricular volume 1120 (Vmax) can be directly measured. The Doppler image frames 600 can also be used to compute the per-image-frame changes (e.g., decreases) in ventricular volume 820 (DVi), which can be summed to yield the total change (e.g., total decrease, DV) in ventricular volume 1010 over the course of the cardiac cycle. The minimum ventricular volume 1130 (Vmin) can then be computed as the maximum volume 1120 minus the change in volume 1010 (e.g., Vmin = Vmax - DV).

[0086] Figure 12 is a graph 1200 showing the reduction in ventricular volume 210 as a function of time 220 during the systolic portion of the heart cycle, according to aspects of the present disclosure. Visible are time points B, C, and D, as well as volumes Vi, V2, V3, V4, and V5 taken at exemplary imaging times Ti, T2, T3, T4, and T5(represented by circles along the graph). These volumes are related to the per-frame changes in volume DVi described above, such that: Vi = Vmax - DVi, and V2= Vi - DV2, etc. Thus, the volume of the ventricle at any given image time can be calculated based on the changes in volume from each previous image in the cycle.

[0087] Figure 13 is a schematic, diagrammatic representation, in block diagram form, of an example per-image-frame ventricular volume and pressure determination process 1300, according to aspects of the present disclosure. At each time point i, an ultrasound image frame 600-i of a heart valve (e.g., the aortic valve) can be used to compute the change in volume 820-i, DVi associated with that image frame, which can also be used to calculate the total current volume of the ventricle, as described above. At the same time, a pressure measurement 1310-i can be captured, by any of the methods described above, including direct measurement by a pressure sensor located in the left ventricle, indirect measurement by an intravascular pressure sensor located outside the left ventricle (e.g., in the aorta or pulmonary artery), pressure sensing by the ultrasound transducer array itself, a pressure computation based on the Doppler image data (e.g., pressure gradient across the valve), or combinations thereof.

[0088] In some aspects, the volume measurement DVi and the pressure measurement 1310-i may be synchronized by means of ECG data 1320, although in other aspects this may not be needed. When the cardiac cycle (e.g., cardiac cycle A) is complete, the same measurements can then be repeated during the next cardiac cycle (e.g., cardiac cycle B).

[0089] The result is, for each time point at which a Doppler image is captured, a volume measurement paired with a pressure measurement that can be used to populate the PV loop (see Figure 2C).

[0090] Figure 14 is a graph 1400 showing the changes in ventricular pressure 240 as a function of time 220 during the systolic portion of the heart cycle, according to aspects of the present disclosure. Visible are time points B, C, and D, as well as pressures Pi, P2, P3, P4, and P5 taken at exemplary imaging times Ti, T2, T3, T4, and T5(represented by squares along the graph). Coupledwith the volume data graphed in Figure 12, these pressure values can be used to populate a PV loop, as shown for example in Figure 2C, above, and Figure 15, below.

[0091] Figure 15 is a graph 1500 showing the changes in ventricular pressure 240 as a function of volume 210 during the systolic portion of the heart cycle, according to aspects of the present disclosure. Visible are time points B, C, and D, forming a portion of a PV loop 260. The volume measurements V1-V5 (circles) are now paired with the pressure measurements P1-P5 (squares) to create points in the pressure-volume plane that populate the systole portion of the PV loop 260.

[0092] Figure 16A is a front cross-sectional view of a human heart 100 being imaged by an intracardiac echography (ICE) catheter 410, according to aspects of the present disclosure. Visible are the right atrium 112, right ventricle 114, tricuspid valve 116, left atrium 118, left ventricle 120, mitral valve 122, aorta 102, aortic valve 124, left ventricular outflow tract 140, septum 130, inferior vena cava (IVC) 1630, and superior vena cava (SVC) 1640. The ICE catheter 410 includes a flexible elongate member 324 and an ultrasound transducer array 322. In the example shown in Figure 4, the ICE catheter 410 is positioned such that the field of view 420 of the transducer array 322 has a central axis 430 that forms a non-en face view of both the aortic valve 124 and the mitral valve 122. The central axis is at an angle 01 (generally not 90 degrees) with respect to the plane 1610 of the aortic valve and at an angle 02 (generally not 90 degrees) with respect to the plane 1620 of the mitral valve, such that an angle correction is needed to convert Doppler velocities (e.g., velocities parallel to the central axis) into flows through the valves (e.g., flows perpendicular to the plane of their respective valves). The field of view 420 of the transducer array 322 can be selected based on the position and / or orientation (e.g., deflection) of the distal portion of the ICE catheter 410. Instead or in addition, the field of view 420 of the transducer array 322 can be selected using beam steering.

[0093] The ICE catheter 410 travels through the IVC 1630, through the right atrium and into the SVC 1640, for imaging of the aortic valve 124 and mitral valve 122 via the SVC 1640. In this position and orientation, the ICE catheter 410 can image the aortic valve 124 and the mitral valve 122 simultaneously. However, it is noted that because the aortic valve 124 and mitral valve 122 are open at different times, a single Doppler image may not show flow through both valves simultaneously. Rather, some time points (e.g., those during diastole) may show flow through the mitral valve 122, while other time points (e.g., those during systole) may show flow through the aortic valve.

[0094] Figure 16B is a front cross-sectional view of a human heart 100 being imaged by an intracardiac echography (ICE) catheter 410, according to aspects of the present disclosure. Visible are the right atrium 112, right ventricle 114, tricuspid valve 116, left atrium 118, left ventricle 120, mitral valve 122, aorta 102, interatrial septum 130, inferior vena cava (IVC) 1630, and superior vena cava (SVC) 1640. In the example shown in Figure 16B, the ICE catheter 410 travels through the IVC 1630, into the right atrium 112, across the interatrial septum 130 into the left atrium 120, e.g., though a puncture in the interatrial septum made as part of a procedure to treat a heart condition, such as fordeployment of a treatment device. The field of view 420 of the ICE catheter 410 is such that the transducer array 322 images the mitral valve 122 while positioned in the left atrium, providing an en face view of the mitral valve and the inflow to the left ventricle.

[0095] In other aspects, the ICE catheter 410 can image the mitral valve 122 and aortic valve transeptally (e.g., while positioned inside left atrium). In such cases, the field of view 420 will be angled, similar to the configuration shown in Figure 16A. The field of view 420 of the transducer array 322 can be selected based on the position and / or orientation (e.g., deflection) of the distal portion of the ICE catheter 410, and / or via beam steering.

[0096] Figure 17 is a B-mode ultrasound image (e.g., from an ICE, TEE, or TCE probe) of the heart 100 showing both the aortic valve 124 and the mitral valve 122, according to aspects of the present disclosure. In the example of Figure 17, the aortic valve 124 is open and the mitral valve 122 is closed, indicating that the heart is in the systolic portion of its cycle. At other times (e.g., during diastole), the aortic valve 124 may be closed and the mitral valve 122 may be open.

[0097] Figure 18 is a schematic, diagrammatic representation, in block diagram form, of an example per-image-frame ventricular volume and pressure determination process 1300, according to aspects of the present disclosure. At each time point i, during systole, an ultrasound image frame 600- Ai of the aortic valve can be used to compute the decrease in left ventricular volume 820- Ai, D V, associated with that image frame, which can also be used to calculate the total current volume of the left ventricle, as described above. At the same time, a pressure measurement 1310-i can be captured, by any of the methods described above. In some aspects, the volume measurement DVi and the pressure measurement 1310-Ai may be synchronized by means of ECG data 1320, although in other aspects this may not be needed.

[0098] At each time point j during diastole, an ultrasound image frame 600-Mj of the mitral valve can be used to compute the increase in left ventricular volume 820-Mj, DVj associated with that image frame, which can also be used to calculate the total current volume of the left ventricle, as described above. At the same time, a pressure measurement 1310-Mj can be captured, by any of the methods described above.

[0099] When the cardiac cycle (e.g., cardiac cycle A) is complete, the same measurements can then be repeated during the next cardiac cycle (e.g., cardiac cycle B). The result is, for each time point at which a Doppler image is captured, a volume measurement paired with a pressure measurement that can be used to populate the PV loop (see Figure 2C).

[0100] Figure 19 is a schematic, diagrammatic representation, in block diagram form, of an example minimum and maximum ventricular volume determination process 1900, according to aspects of the present disclosure. Imaging data 1110, such as 3D B-mode ultrasound data, CT scan data, or other 2D or 3D imaging data, can be used to construct a 3D model 1115 of the left ventricle, from which the maximum ventricular volume 1120 (Vmax) can be directly measured. The Dopplerimage frames 600-A of the aortic valve during systole can also be used to compute the per-image- frame changes (e.g., decreases) in ventricular volume 820-A (DVi), which can be summed to yield the total change (e.g., total decrease, DV) in ventricular volume 1010-A over the course of the cardiac cycle. The minimum ventricular volume 1130 (Vmin) can then be computed as the maximum volume 1120 minus the change in volume 1010 (e.g., - DV).

[0101] The Doppler image frames 600-M of the mitral valve during diastole can also be used to compute the per-image-frame changes (e.g., increases) in ventricular volume 820-M (DVj), which can be summed to yield the total change (e.g., total increase, DV) in ventricular volume 1010-M over the course of the cardiac cycle, which should be equal to the total decrease 1010-A, and can thus also be used to validate the calculation of Vmax and Vmm.

[0102] Figure 20 is a graph 1900 showing the changes in ventricular pressure 240 as a function of volume 210 during the systolic and diastolic portions of the heart cycle (e.g., the entire heart cycle), according to aspects of the present disclosure. Visible are time points A, B, C, D, E, and F, forming a PV loop 260. Pressure measurements Pi -Pie (squares) may be captured using any of the methods described above. The volume measurements V1-V5 (circles) may be based on Doppler images of the aortic valve, captured during systole. Volume measurements V9-V13 (triangles) are based on Doppler images of the mitral valve, captured during diastole. Volume measurements Ve-Vs should be relatively constant and equal to the minimum volume Vmin, and may thus be based on Doppler images of either the aortic valve or the mitral valve. Volume measurements V14-V16 should be relatively constant and equal to the maximum ventricular volume Vmax, and may thus be based on Doppler images of either the aortic valve or the mitral valve.

[0103] The volume measurements Vi-Vie are paired with the pressure measurements P1-P16 to create points in the pressure-volume plane that populate the PV loop 260. Thus, the PV loop measurement system of the present disclosure has computed a complete PV loop, without the need for a specialized invasive catheter designed exclusively for that purpose.

[0104] Figure 21 is a graph 2100 showing changes in ventricular volume 210 as a function of time 220 during a complete heart cycle, according to aspects of the present disclosure. Visible are time points A, B, C, D, E, and F. Volumes Vi, V2, V3, V4, and V5 (represented by circles along the graph) are computed from aortic valve Doppler ultrasound images 600-A during systole. These volumes are related to the per-frame reductions in volume DVi described above, such that: Vi = Vmax - DVi, and V2= Vi - DV2, etc.

[0105] Volumes V9 - V13 (represented by triangles along the graph) are computed from mitral valve Doppler ultrasound images 600-M during diastole. These volumes are related to the per-frame increases in volume DVj described above, such that V9 = Vmm + DV9, V10 = V9 + DV10, etc. Thus, the volume of the left ventricle at any given image time can be calculated based on the changes in volume from each previous image in the cycle.

[0106] Volumes Ve - Vs (not shown) fall between points D and E, and should be relatively constant and equal to Vmm, and as such can be calculated from either the aortic valve Doppler images 600-A or the mitral valve Doppler images 600-M. Volumes Vi4 - Vie (not shown) fall between points A and B, and should be relatively constant and equal to Vmax, and as such can be calculated from either the aortic valve Doppler images 600-A or the mitral valve Doppler images 600-M.

[0107] Figure 22 is a graph 2200 showing the changes in ventricular pressure 240 as a function of time 220 during an entire cardiac cycle, according to aspects of the present disclosure. Visible are time points A, B, C, D, E and F, as well as pressures Pi-Pie (represented by squares along the graph), which can be measured, computed, or estimated by any of the methods described above, including direct measurement by a pressure sensor located in the left ventricle, indirect measurement by an intravascular pressure sensor located outside the left ventricle (e.g., in the aorta or pulmonary artery), pressure sensing by the ultrasound transducer array itself, a pressure computation based on the Doppler image data (e.g., pressure gradient across the valve), or combinations thereof. Coupled with the volume data graphed in Figure 21, these pressure values can be used to populate a PV loop, as shown for example in Figure 20, above.

[0108] Figure 23 is a schematic, diagrammatic representation, in flow diagram form, of an example PV loop generation method 2300, according to aspects of the present disclosure. It is understood that the steps of method 2300 may be performed in a different order than shown in Figure 23, additional steps can be provided before, during, and after the steps, and / or some of the steps described can be replaced or eliminated in other embodiments. One or more of steps of the method 2300 can be carried by one or more devices and / or systems described herein, such as components of the system 300, processor 312, processor 332, processor 342, processor 362, processor 382, and / or processor circuit 2550.

[0109] In step 2305, the method 2300 includes controlling one or more imaging devices to obtain imaging data of the left ventricle. Execution then proceeds to step 2310.

[0110] In step 2310, the method 2300 includes generating a 3D reconstruction or 3D model of the left ventricle. Execution then proceeds to steps 2315 and 2320.

[0111] In step 2315, the method 2300 includes using the 3D reconstruction or 3D model to compute or directly measure the minimum volume of the left ventricle (Vmm). The minimum volume can be considered an initial volume when going from minimum volume to maximum volume, with maximum volume being the final volume. The minimum volume can be considered a final volume when going from maximum volume to minimum volume, with maximum volume being the initial volume. Execution then proceeds to step 2365.

[0112] In step 2320, the method 2300 includes using the 3D reconstruction or 3D model to compute or directly measure the maximum volume of the left ventricle (Vmaz). The maximum volume can be considered an initial volume when going from maximum volume to minimum volume, withminimum volume being the final volume. The maximum volume can be considered a final volume when going from minimum volume to maximum volume, with minimum volume being the initial volume. Execution then proceeds to step 2345.

[0113] In step 2325, the method 2300 includes receiving ECG data. Execution then proceeds to step 2355.

[0114] In step 2330, the method 2300 includes controlling the ultrasound transducer to obtain Doppler image frames of the aortic valve for a given cardiac cycle. Execution then proceeds to step 2335, and thence to step 2340.

[0115] In step 2335, the method 2300 includes synchronizing the Doppler image frames and pressure measurements. Execution then proceeds to steps 2340, 2360, and 2375.

[0116] In step 2340, the method 2300 includes determining the change (e.g., the decrease) in ventricular volume for the aortic valve (AV) Doppler image frames. Execution then proceeds to step 2345.

[0117] In step 2345, the method 2300 includes generating a portion of the ventricular volume vs. time graph, wherein the volume of the left ventricle is decreasing. Execution then proceeds to step 2380.

[0118] In step 2350, the method 2300 includes controlling the ultrasound transducer array to obtain Doppler image frames of the mitral valve for the cardiac cycle. Execution then proceeds to step 2335, and thence to step 2360.

[0119] In step 2360, the method 2300 includes determining the change (e.g., the increase) in ventricular volume for the mitral valve (MV) image frames. Execution then proceeds to step 2365.

[0120] In step 2365, the method 2300 includes generating a portion of the ventricular volume vs. time graph, wherein the volume of the left ventricle is increasing. Execution then proceeds to step 2380.

[0121] In step 2370, the method 2300 includes controlling a pressure sensor and / or the ultrasound transducer array to obtain pressure measurements by any of the methods described above, including direct measurement by a pressure sensor located in the left ventricle, indirect measurement by an intravascular pressure sensor located outside the left ventricle (e.g., in the aorta or pulmonary artery), pressure sensing by the ultrasound transducer array itself, a pressure computation based on the Doppler image data (e.g., pressure gradient across the valve), or combinations thereof. Execution then proceeds to step 2335, and thence to step 2375.

[0122] In step 2375, the method 2300 includes generating a ventricular pressure vs. time graph. Execution then proceeds to step 2380.

[0123] In step 2380, the method 2300 includes using the data from the ventricular volume vs. time graph and the ventricular pressure vs. time graph to generate a ventricular volume vs. ventricular pressure graph (e.g., a PV loop). Execution then proceeds to step 2385.

[0124] In step 2385, the method 2300 includes outputting the PV loop, and possibly the ventricular pressure vs. time graph and / or the ventricular volume vs. time graph, to a display. Execution then proceeds to step 2390.

[0125] Steps 2390 and 2395 may be performed by a clinician rather than by the PV loop measurement system.

[0126] In step 2390, the method 2300 includes evaluating one or more health conditions of the heart based on the PV loop, the ventricular pressure vs. time graph, and / or the ventricular volume vs. time graph. Execution then proceeds to step 2395.

[0127] In step 2395, the method 2300 includes performing therapy based on the health condition(s) of the heart. The method 2300 is now complete.

[0128] Flow diagrams and block diagrams are provided herein for exemplary purposes; a person of ordinary skill in the art will recognize myriad variations that nonetheless fall within the scope of the present disclosure. For example, the logic of flow diagrams may be shown as sequential.However, similar logic could be parallel, massively parallel, object oriented, real-time, event-driven, cellular automation, or otherwise, while accomplishing the same or similar functions. In order to perform the methods described herein, a processor may divide each of the steps described herein into a plurality of machine instructions, and may execute these instructions at the rate of several hundred, several thousand, several million, or several billion per second, in a single processor or across a plurality of processors. Such rapid execution may be necessary in order to execute the method in real time or near-real time as described herein. For example, to update the PV loop in real time may involve measuring or estimating the ventricular volume and pressure, from the Doppler ultrasound data, dozens of times per cardiac cycle (e.g., 24 Hz, 36 Hz, 64 Hz, etc.).

[0129] Figure 24 is a graph 2400 of ventricular pressure 240 as a function of ventricular volume 210, according to aspects of the present disclosure. The graph 2400 shows four different PV loops 260, captured over four different (e.g., successive) cardiac cycles. Although the PV loops 260 differ in their precise size and shape, they share general characteristics and may thus be considered to have a similar shape. The shape of the PV loop is used by clinicians to diagnose and / or monitor various conditions of the heart, such as dilated or restrictive cardiomyopathy, left ventricular hypertrophy, valve stenoses or regurgitation, etc.

[0130] Figure 25 is a schematic diagram of a processor circuit 2550, according to aspects of the present disclosure. The processor circuit 2550 may be implemented in the system 300, the processor 312, the processor 332, the processor 342, the processor 362, the processor 382, or other devices or workstations (e.g., third-party workstations, network routers, etc.), or on a cloud processor or other remote processing unit, as necessary to implement the method. As shown, the processor circuit 2550 may include a processor 2560, a memory 2564, and a communication module 2568. These elements may be in direct or indirect communication with each other, for example via one or more buses.

[0131] The processor 2560 may include a central processing unit (CPU), a digital signal processor (DSP), an ASIC, a controller, or any combination of general-purpose computing devices, reduced instruction set computing (RISC) devices, application-specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or other related logic devices, including mechanical and quantum computers. The processor 2560 may also comprise another hardware device, a firmware device, or any combination thereof configured to perform the operations described herein. The processor 2560 may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[0132] The memory 2564 may include a cache memory (e.g., a cache memory of the processor 2560), random access memory (RAM), magnetoresistive RAM (MRAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), flash memory, solid state memory device, hard disk drives, other forms of volatile and non-volatile memory, or a combination of different types of memory. In an aspect, the memory 2564 includes a non-transitory computer- readable medium. The memory 2564 may store instructions 2566. The instructions 2566 may include instructions that, when executed by the processor 2560, cause the processor 2560 to perform the operations described herein. Instructions 2566 may also be referred to as code. The terms “instructions” and “code” should be interpreted broadly to include any type of computer-readable statement(s). For example, the terms “instructions” and “code” may refer to one or more programs, routines, sub-routines, functions, procedures, etc. “Instructions” and “code” may include a single computer-readable statement or many computer-readable statements.

[0133] The communication module 2568 can include any electronic circuitry and / or logic circuitry to facilitate direct or indirect communication of data between the processor circuit 2550, and other processors or devices. In that regard, the communication module 2568 can be an input / output (I / O) device. In some instances, the communication module 2568 facilitates direct or indirect communication between various elements of the processor circuit 2550 and / or the system 300. The communication module 2568 may communicate within the processor circuit 2550 through numerous methods or protocols. Serial communication protocols may include but are not limited to United States Serial Protocol Interface (US SPI), Inter-Integrated Circuit (I2C), Recommended Standard 232 (RS-232), RS-485, Controller Area Network (CAN), Ethernet, Aeronautical Radio, Incorporated 429 (ARINC 429), MODBUS, Military Standard 1553 (MIL-STD-1553), or any other suitable method or protocol. Parallel protocols include but are not limited to Industry Standard Architecture (ISA), Advanced Technology Attachment (ATA), Small Computer System Interface (SCSI), Peripheral Component Interconnect (PCI), Institute of Electrical and Electronics Engineers 488 (IEEE -488), IEEE-1284, and other suitable protocols. Where appropriate, serial and parallel communications maybe bridged by a Universal Asynchronous Receiver Transmiter (UART), Universal Synchronous Receiver Transmiter (USART), or other appropriate subsystem.

[0134] External communication (including but not limited to software updates, firmware updates, preset sharing between the processor and central server, or readings from associated devices) may be accomplished using any suitable wireless or wired communication technology, such as a cable interface such as a universal serial bus (USB), micro USB, Lightning, or FireWire interface, Bluetooth, Wi-Fi, ZigBee, Li-Fi, or cellular data connections such as 2G / GSM (global system for mobiles) , 3G / UMTS (universal mobile telecommunications system), 4G, long term evolution (LTE), WiMax, or 5G. For example, a Bluetooth Low Energy (BLE) radio can be used to establish connectivity with a cloud service, for transmission of data, and for receipt of software patches. The controller may be configured to communicate with a remote server, or a local device such as a laptop, tablet, or handheld device, or may include a display capable of showing status variables and other information. Information may also be transferred on physical media such as a USB flash drive or memory stick.

[0135] Accordingly, it can be seen that the PV loop measurement system advantageously provides means to generate a diagnostic PV loop of a patient’s heart using ultrasound data, which may in some cases require no invasive sensors to be placed within the patient’s body. A number of variations are possible on the examples and aspects described above. For example, the PV loop measurement system is described herein with regard to the left ventricle, but the principles described herein could also be used to generate PV loops for other heart chambers, such as the right ventricle, or even the left atrium or right atrium, using Doppler ultrasound data from the mitral valve, the aortic valve, the pulmonary valve, the tricuspid valve, the IVC, the SVC, the pulmonary veins, the pulmonary arteries, the aorta, etc.

[0136] Accordingly, the logical operations making up the aspects of the technology described herein are referred to variously as operations, steps, objects, elements, components, or modules. Furthermore, it should be understood that these may occur or be performed or arranged in any order, unless explicitly claimed otherwise or a specific order is inherently necessitated by the claim language.

[0137] All directional references e.g., upper, lower, inner, outer, upward, downward, left, right, lateral, front, back, top, botom, above, below, vertical, horizontal, clockwise, counterclockwise, proximal, and distal are only used for identification purposes to aid the reader’s understanding of the claimed subject mater, and do not create limitations, particularly as to the position, orientation, or use of the PV loop measurement system. Connection references, e.g., atached, coupled, connected, joined, or “in communication with” are to be construed broadly and may include intermediate members between a collection of elements and relative movement between elements unless otherwise indicated. As such, connection references do not necessarily imply that two elements are directlyconnected and in fixed relation to each other. The term “or” shall be interpreted to mean “and / or” rather than “exclusive or.” The word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. Unless otherwise noted in the claims, stated values shall be interpreted as illustrative only and shall not be taken to be limiting.

[0138] The above specification, examples and data provide a complete description of the structure and use of exemplary aspects of the PV loop measurement system as defined in the claims. Although various aspects of the claimed subject matter have been described above with a certain degree of particularity, or with reference to one or more individual aspects, those skilled in the art could make numerous alterations to the disclosed aspects without departing from the spirit or scope of the claimed subject matter.

[0139] Still other aspects are contemplated. It is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative only of particular aspects and not limiting. Changes in detail or structure may be made without departing from the basic elements of the subject matter as defined in the following claims.

Claims

CLAIMSWhat is claimed is:

1. A system, comprising: a processor configured for communication with an ultrasound transducer, the processor configured to: control the ultrasound transducer to obtain a first plurality of ultrasound images of a first valve of a heart chamber of a patient; determine a first plurality of volume measurements of the heart chamber based on the first plurality of ultrasound images, wherein each volume measurement of the first plurality of volume measurements corresponds to an ultrasound image of the first plurality of ultrasound images; generate a pressure-volume (PV) loop of the heart chamber based on the first plurality of volume measurements; and output the PV loop.

2. The system of claim 1, wherein the first plurality of ultrasound images is a plurality of Doppler ultrasound frames.

3. The system of claim 1, wherein the heart chamber is a left ventricle, and the first heart valve is an aortic valve.

4. The system of claim 1, wherein the processor is further configured to: obtain a first plurality of pressure measurements corresponding to the first plurality of ultrasound images; and generate the PV loop based on the first plurality of pressure measurements.

5. The system of claim 1, wherein the first plurality of ultrasound images corresponds to a plurality of volume decreases of the heart chamber, wherein the processor is configured to determine the first plurality of volume measurements based on the plurality of volume decreases relative to a first initial volume of the heart chamber.

6. The system of claim 1, wherein the processor is configured to: control the ultrasound transducer to obtain a second plurality of ultrasound images of a second valve of the patient;determine a second plurality of volume measurements of the heart chamber based on the second plurality of ultrasound images, wherein each volume measurement of the second plurality of volume measurements corresponds to an ultrasound image of the second plurality of ultrasound images; and generate the PV loop based on the second plurality of volume measurements.

7. The system of claim 6, wherein the heart chamber is a left ventricle, the first heart valve is an aortic valve, and the second heart valve is a mitral valve.

8. The system of claim 6, wherein the second plurality of ultrasound images corresponds to a plurality of volume increases of the heart chamber, and wherein the processor is configured to determine the second plurality of volume measurements based on the plurality of volume increases relative to a second initial volume of the heart chamber.

9. The system of claim 6, wherein the processor is further configured to: obtain a second plurality of pressure measurements corresponding to the second plurality of ultrasound images; and generate the PV loop based on the second plurality of pressure measurements.

10. The system of claim 1, wherein the processor is further configured to: control a pressure sensor to capture a plurality of pressure measurements; control the ultrasound transducer to obtain the first plurality of ultrasound images of the first valve of the heart chamber during a first phase of a cardiac cycle; compute the first plurality of volume measurements of the heart chamber based on the first plurality of ultrasound images, each volume measurement of the first plurality of volume measurements corresponding to an image of the first plurality of ultrasound images and a pressure measurement of the plurality of pressure measurements; control the ultrasound transducer to obtain a second plurality of ultrasound images of a second valve of the heart chamber during a second phase of the cardiac cycle; determine a second plurality of volume measurements of the heart chamber based on the second plurality of ultrasound images, each volume measurement of the second plurality of volume measurements corresponding to an image of the second plurality of images and a pressure measurement of the plurality of pressure measurements; generate a plot of the pressure measurements as a function of the first plurality of volume measurements and the second plurality of volume measurements; anddisplay the plot.

11. The system of claim 10, further comprising: the ultrasound transducer; and the pressure sensor configured to obtain a pressure measurement associated with the heart chamber.

12. The system of claim 11, wherein the pressure sensor comprises a pressure-sensing catheter or a guide wire.

13. The system of claim 11, wherein the pressure sensor is positioned in the heart chamber to capture the plurality of pressure measurements.

14. The system of claim 10, wherein the pressure sensor is located outside the heart chamber and the processor is further configured to capture the plurality of pressure measurements by: reading a pressure value from the pressure sensor; and at least one of: computing a pressure drop across the first heart valve based on the first plurality of ultrasound images; or computing a pressure drop across the second heart valve based on the second plurality of ultrasound images.

15. The system of claim 10, further comprising an electrocardiogram sensor, and wherein the processor is further configured to, based on readings from the electrocardiogram sensor, synchronize the plurality of pressure measurements with the first plurality of volume measurements and the second plurality of volume measurements.

16. The system of claim 1, wherein the processor is further configured to generate a model of the heart chamber based on 3D imaging data.

17. The system of claim 14, wherein the model of the heart chamber includes a minimum volume of the heart chamber or a maximum volume of the heart chamber during a cardiac cycle.

18. The system of claim 1, wherein the PV loop is generated as a graph that is output to a display.

19. The system of claim 11, wherein the ultrasound transducer is coupled to an intracardiac echography catheter, transesophageal echocardiography probe, or transthoracic echocardiography probe.

20. The system of claim 1, wherein the first phase is a systolic phase, and the second phase is a diastolic phase.

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