Methods for assessing fractional flow reserve

Abstract

A system for determining fractional flow reserve is disclosed. An example system may include: a pressure-sensing guidewire for measuring a first pressure; a second pressure-sensing medical device for measuring a second pressure; and a processor coupled to the pressure-sensing guidewire and to the second pressure-sensing medical device. The processor is configured to generate a plot of the magnitude of the second pressure over time, identify one or more time intervals in the plot where the slope is less than zero, determine an average value of the second pressure, and calculate a ratio of the first pressure to the second pressure during (a) the time interval when the second pressure is less than or equal to the average value of the second pressure and (b) the time interval when the slope of the curve is less than zero.

Description

[0001] This application is a divisional application of invention patent application number 201880064584.5.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims priority under 35 U.S.C. §119 to U.S. Provisional Patent Application No. 62 / 541,069, filed on August 3, 2017, which is hereby incorporated by reference in its entirety. Technical Field

[0004] The present invention relates to medical devices and methods of using medical devices. In particular, the present invention is applicable to methods for assessing fractional flow reserve. Background of the Invention

[0005] A variety of in-vivo medical devices have been developed for medical applications, such as intravascular use. Some of these devices include guidewires, catheters, and the like. These devices are manufactured using any of a variety of different manufacturing methods and can be used according to any of a variety of methods. Each of the known medical devices and methods has certain advantages and disadvantages. There is an ongoing need to provide alternative medical devices and alternative methods for manufacturing and using medical devices. Summary of the Invention

[0006] The present invention provides designs, materials, manufacturing methods, and use alternatives for medical devices. An exemplary medical device includes a system for determining blood flow reserve fraction. The system includes: a pressure-sensing guidewire for measuring a first pressure; a second pressure-sensing medical device for measuring a second pressure; a processor connected to the pressure-sensing guidewire and to the second pressure-sensing medical device; wherein the processor is designed to: generate a curve of the magnitude of the second pressure over time; identify one or more time intervals in the curve where the slope is less than zero, determine an average value of the second pressure, and calculate a ratio of the first pressure to the second pressure during (a) when the second pressure is less than or equal to the average value of the second pressure and (b) during one or more time intervals when the slope of the curve is less than zero.

[0007] Alternatively or additionally to any of the above embodiments, the pressure sensing guidewire includes an optical pressure sensor.

[0008] Alternatively or additionally to any of the above embodiments, the pressure sensing guidewire includes a tubular member including a proximal region having a first inner diameter and a distal region having a second inner diameter different from the first inner diameter.

[0009] Alternatively or additionally to any of the above embodiments, the second pressure sensing medical device includes a catheter having a pressure sensor.

[0010] Alternatively or additionally to any of the above embodiments, the first pressure, the second pressure, or both are wirelessly transmitted to the processor.

[0011] Alternatively or additionally to any of the above embodiments, the pressure sensing guidewire is designed to be deployed distally of an intravascular lesion.

[0012] Alternatively or additionally to any of the above embodiments, the second pressure sensing medical device is designed to be deployed proximal to the intravascular lesion.

[0013] Alternatively or additionally to any of the above embodiments, the processor is configured to calculate a ratio of the first pressure to the second pressure in the absence of a hyperemic agent.

[0014] Alternatively or additionally to any of the above embodiments, the processor is connected to the display.

[0015] Alternatively or additionally to any of the above-described embodiments, the display is designed to display a curve.

[0016] A system for determining fractional flow reserve is disclosed. The system includes: a pressure sensing guidewire for measuring distal pressure at a location distal to a lesion; a pressure sensing catheter for measuring aortic pressure; and a processor coupled to the pressure sensing guidewire and to the pressure sensing catheter. The processor is configured to generate a curve of aortic pressure magnitude over time, identify one or more time intervals in the curve where the slope is less than zero, determine an average value of the aortic pressure, and calculate a ratio of the distal pressure to the aortic pressure during (a) a time interval when the aortic pressure is less than or equal to the average value of the aortic pressure and (b) a time interval when the slope of the curve is less than zero.

[0017] Alternatively or additionally to any of the above embodiments, the pressure sensing guidewire includes an optical pressure sensor.

[0018] Alternatively or additionally to any of the above embodiments, the pressure sensing guidewire includes a tubular member including a proximal region having a first inner diameter and a distal region having a second inner diameter different from the first inner diameter.

[0019] Alternatively or additionally to any of the above embodiments, the processor is configured to calculate a ratio of distal pressure to aortic pressure in the absence of a hyperemic agent.

[0020] Alternatively or additionally to any of the above embodiments, the processor is connected to the display.

[0021] Alternatively or additionally to any of the above embodiments, the processor is designed to scale the mean aortic pressure by a scaling factor in the range of 0.75 to 1.25.

[0022] Alternatively or additionally to any of the above embodiments, the processor is configured to reject the time interval when the aortic pressure is less than a lower pressure limit.

[0023] A method for determining fractional flow reserve is disclosed. The method includes: deploying a pressure-sensing guidewire distal to a lesion within a blood vessel; measuring distal pressure with the pressure-sensing guidewire; deploying a pressure-sensing catheter within the vascular region; and measuring aortic pressure with the pressure-sensing catheter. A processor is coupled to the pressure-sensing guidewire and to the pressure-sensing catheter. The processor is configured to: generate a plot of aortic pressure magnitude over time, identify one or more time intervals where the plot has a slope less than zero, and determine an average value of the aortic pressure; and calculate a ratio of the distal pressure to the aortic pressure (a) when the aortic pressure is less than or equal to the average aortic pressure, and (b) during one or more time intervals where the slope of the plot is less than zero.

[0024] Alternatively or additionally to any of the above embodiments, measuring distal pressure with the pressure sensing guidewire includes measuring distal pressure without a hyperemic agent, wherein measuring aortic pressure with the pressure sensing catheter includes measuring aortic pressure without a hyperemic agent, or both.

[0025] Alternatively or additionally to any of the above embodiments, calculating the ratio of the distal pressure to the aortic pressure includes calculating the ratio of the distal pressure to the aortic pressure in the absence of a hyperemic agent.

[0026] The above summary of some embodiments is not intended to describe each disclosed embodiment or every implementation of the present invention. The following figures and detailed description more particularly exemplify these embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention may be more fully understood upon consideration of the following detailed description taken in conjunction with the accompanying drawings, in which:

[0028] Figure 1 An example system for assessing fractional flow reserve is schematically illustrated.

[0029] Figure 2 Blood pressure values ​​over time are depicted graphically.

[0030] Figure 3 is a partial cross-sectional side view of a portion of an example medical device.

[0031] While the present invention is susceptible to various modifications and alternative forms, details thereof have been shown by way of example in the drawings and will be described in detail. However, it should be understood that it is not intended to limit the invention to the particular embodiments described. On the contrary, it is intended to cover all modifications, equivalents, and alternative forms falling within the spirit and scope of the invention. DETAILED DESCRIPTION

[0032] For the following defined terms, these definitions shall apply unless a different definition is given in the claims or elsewhere in this specification.

[0033] All numerical values ​​herein are assumed to be modified by the term "about," whether or not expressly stated otherwise. The term "about" generally refers to a range of numbers that one skilled in the art would consider equivalent to the referenced value (i.e., having the same function or result). In many cases, the term "about" can include numbers that are rounded to the nearest significant figure.

[0034] The recitation of numerical ranges by endpoints includes all numbers within that range (eg, 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).

[0035] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term "or" is generally employed in its sense including "and / or" unless the content clearly dictates otherwise.

[0036] It should be noted that references in the specification to "one embodiment," "some embodiments," "other embodiments," etc., indicate that the described embodiments may include one or more particular characteristics, structures, or features. However, such recitation does not necessarily imply that all embodiments include the particular characteristics, structures, and / or features. Furthermore, when particular characteristics, structures, and / or features are described in conjunction with one embodiment, it should be understood that such characteristics, structures, and / or features may also be used in conjunction with other embodiments, regardless of whether such characteristics, structures, and / or features are explicitly described, unless expressly stated to the contrary.

[0037] The following detailed description should be read with reference to the accompanying drawings, in which similar elements in different drawings have the same reference numerals. The drawings, which are not necessarily drawn to scale, depict illustrative embodiments and are not intended to limit the scope of the invention.

[0038] During some medical interventions, it may be necessary to measure and / or monitor blood pressure within a blood vessel. For example, some medical devices may include a pressure sensor that allows a clinician to monitor blood pressure. Such devices are useful in determining fractional flow reserve (FFR), which can be understood as the pressure behind or distal to a stenosis (e.g., distal pressure P).d ) relative to the pre-stenotic pressure and / or aortic pressure (e.g., aortic pressure P a ). In other words, FFR can be understood as P d / P a .

[0039] exist Figure 1 An example system 100 for assessing / determining FFR is schematically shown in FIG. The system 100 may include a first pressure sensing medical device 10. In at least some cases, the first pressure sensing medical device 10 may take the form of a pressure sensing guidewire 10. Some additional details regarding the form of the guidewire 10 are disclosed herein, provided as examples. In other cases, the first pressure sensing medical device 10 may be a catheter or other type of pressure sensing medical device. The pressure sensing guidewire 10 may be used to measure blood pressure distal to a stenosis in a blood vessel, for example, distal pressure P d The first pressure sensing medical device 10 can be connected to a linking device 70. In some cases, this can include directly connecting the first pressure sensing medical device 10 to the linking device 70. In other cases, other structures, such as a connector cable (not shown), can be used to connect the first pressure sensing medical device 10 to the linking device 70. When the first pressure sensing medical device 10 is connected to the linking device 70, first pressure data 72 can be transmitted between the first pressure sensing medical device 10 and the linking device 70. Figure 1 As noted in FIG, a line is drawn between the first pressure sensing medical device 10 and the linking device 70 to indicate the connection of the first pressure sensing medical device 10 and the linking device 70. Additionally, the line between the first pressure sensing medical device 10 and the linking device 70 is labeled with reference numeral 72 to indicate the transmission of the first pressure data 72 (and / or the first pressure data 72 itself). In at least some cases, the first pressure data 72 is the distal pressure P d .

[0040] The system 100 may also include a second pressure sensing medical device 74. In at least some cases, the second pressure sensing medical device 74 may take the form of a pressure sensing catheter. However, other devices are contemplated, including a pressure sensing guidewire or other device. The second pressure sensing medical device 74 may be used to measure blood pressure and / or aortic pressure proximal to the stenosis within the vessel, e.g., aortic pressure P a The second pressure sensing medical device 74 may also be connected to the linking device 70 and second pressure data 76 may be communicated between the second pressure sensing medical device 74 and the linking device 70 . Figure 1, a line is drawn between the second pressure sensing medical device 74 and the linking device 70 to indicate the connection of the second pressure sensing medical device 74 and the linking device 70. Additionally, the line between the second pressure sensing medical device 74 and the linking device 70 is labeled with reference numeral 76 to indicate the transmission of the second pressure data 76 (and / or the second pressure data 76 itself). In at least some cases, the second pressure data 76 is the aortic pressure P a .

[0041] In some cases, the linking device 70 can communicate with the hemodynamic system 78 (eg, the hemodynamic display system 78). When doing so, the distal pressure P d The data (indicated by reference numeral 80) can be transmitted to the hemodynamic system 78 and represents the aortic pressure P a The data (indicated by reference numeral 82) can be transmitted to the hemodynamic system 78. In some cases, the two connections between the linking device 70 and the hemodynamic system 78 (e.g., for transmitting P d and P a ) can be wired connections. In other cases, one or both of the connections can be wireless connections. In still other cases, P d and P a can all be transmitted along a single wired connection.

[0042] In some cases, the linking device 70 may also communicate with the processing and / or display system 84. In doing so, the distal pressure P d The data and the representative aortic pressure P a Data (distal pressure P d and aortic pressure P a Data in Figure 1 In at least some cases, P d and P a A wireless connection may be used to communicate between the linking device 70 and the processing and / or display system 84. In other cases, P d and P a One or both of may be transmitted between the linking device 70 and the processing and / or display system 84 via a wired connection.

[0043] The processing and / or display system 84 may include a processor 88. The processor 88 may be an integrated component of the processing and / or display system 84 (e.g., the processor 88 may be configured within the same housing as the processing and / or display system 84) or the processor 88 may be a separate component of the processing and / or display system 84 and coupled thereto. The processor 88 may be coupled to the first pressure sensing medical device 10 and to the second pressure sensing medical device 74 so that pressure measurements (e.g., P d and P a ) can be received from the first pressure sensing medical device 10 and the second pressure sensing medical device 74 by the processor 88. The processor 88 can be designed and / or otherwise capable of performing a number of calculations, executing instructions, etc. For example, the processor can be designed to calculate / determine the average distal pressure P d (e.g., measured by the first pressure sensing medical device 10 during one or more cardiac cycles), calculate / determine the mean aortic pressure P a (e.g., as measured by the second pressure sensing medical device 74 during one or more cardiac cycles), plotting the distal pressure P d and / or aortic pressure P a Curve over time, calculate / determine distal pressure P d The slope of the curve and / or the aortic pressure P a The display 90 may be connected to or otherwise integrated with the processing and / or display system 84. The display 90 may display various data received from the first pressure sensing medical device 10 and the second pressure sensing medical device 74, the pressure data curves generated by the processor 80, etc.

[0044] When determining the fractional flow reserve, it may be desirable to measure the change or drop in pressure across the stenosis under a state of maximum flow (e.g., hyperemia). Therefore, many interventions are performed to assess the fractional flow reserve, including the administration of hyperemic agents, such as adenosine, to induce a state of maximum flow. For a variety of reasons (e.g., patient comfort, extended procedure time, technical challenges associated with admixed adenosine for intravascular administration, cost, etc.), it may be desirable to reduce the use of hyperemic agents. Pressure measurements performed under resting state conduction are often referred to as resting indexes. An example of such a measurement is the resting P d / P a , wherein the ratio is calculated using data from the entire cardiac cycle. Disclosed herein are methods of assessing / determining fractional flow reserve that can be performed in the absence of hyperemic agents including adenosine.

[0045] The maximum coronary blood flow occurs during the diastole of the cardiac cycle.d and P a Measurement of P can provide a ratio closer to the FFR than that obtained from the entire cardiac cycle (e.g., a better approximation of the FFR). d / P a In addition, some methods for evaluating fractional flow reserve can include calculating P in the diastolic time window. d and P a For example, some interventions, such as instantaneous waveform-free ratio and / or iFR TM , one may attempt to measure the fractional flow reserve during diastole. Such an approach may require precise measurement of the waveform and / or synchronization with the electrocardiogram, which may complicate the process of evaluating / determining the fractional flow reserve. This paper discloses a method for measuring the fractional flow reserve by monitoring P during a specific window during the diastole of the cardiac cycle. d and P a The method for assessing / determining the blood flow reserve fraction disclosed herein is relatively simple to implement, so that the blood flow reserve fraction can be assessed / determined in a timely manner, which can improve patient comfort and does not require unnecessary additional procedures and / or synchronization.

[0046] Figure 2 The pressure measurements over multiple cardiac cycles are graphically depicted (e.g., one complete cycle plus a portion of another cardiac cycle is depicted). In this example, P is shown over time. d (eg, as measured by the first pressure sensing medical device 10) and P a A graphical depiction of (eg, as measured by the second pressure sensing medical device 74). Also shown is mean aortic pressure 92.

[0047] To assess / determine Fractional Flow Reserve, processor 88 may be used to perform a number of tasks, including:

[0048] Generate distal pressure P d The size of (e.g., as measured by the first pressure sensing medical device 10 and as Figure 2 The curve over time is shown as

[0049] Generate aortic pressure P a The size of (e.g., as measured by the second pressure sensing medical device 74 and as Figure 2 The curve over time is shown as

[0050] Identify P a One or more time intervals of the curve where the slope of the curve is less than zero,

[0051] Calculate / determine mean aortic pressure 92,

[0052] one or more additional calculations, and / or

[0053] Its combination.

[0054] In one embodiment, regions of the cardiac cycle are identified where:

[0055] (a)P a Less than or equal to mean aortic pressure 92, and

[0056] (b) The slope of Pa is less than zero

[0057] In another embodiment, regions of the cardiac cycle are identified where:

[0058] (a)P a is less than or equal to the mean aortic pressure 92, which is scaled by a scaling factor in the range of 0.5 to 1.5, or about 0.75 to 1.25, or about 0.95 to 1.05 (e.g., regions of the cardiac cycle are identified where P a is less than or equal to the mean aortic pressure multiplied by the scaling factor 92), and

[0059] (b)P a The slope is less than zero.

[0060] In another embodiment, regions of the cardiac cycle are identified where:

[0061] (a)P a Less than or equal to mean aortic pressure 92, scaled by a scaling factor in the range of 0.5 to 1.5, or about 0.75 to 1.25, or about 0.95 to 1.05, and / or

[0062] (b)P a The slope of is less than zero, and / or

[0063] (c)P a Above the lower pressure limit, it can be determined by the first of the following methods:

[0064] i) a fixed negative offset from the mean aortic pressure 92 in the range of -10 mmHg to -100 mmHg,

[0065] ii) a relative negative offset from mean aortic pressure 92 calculated from 10%-100% of mean aortic pressure 92, and / or

[0066] iii) A fixed positive offset in the range of 10 mmHg - 100 mmHg from a minimum aortic pressure of 95 .

[0067] Mean aortic pressure 92 can be determined for each individual cardiac cycle or across multiple cardiac cycles. Time windows or regions that meet these criteria are considered to be during high flow (e.g., during diastole) and are considered suitable for use in assessing / determining fractional flow reserve. Thus, during these time periods when hyperemic agents are not present and / or unnecessary additional procedures and / or synchronization are not required, the system 100 can be used to assess / determine / calculate fractional flow reserve. Figure 2 As shown in the graph in FIG, three time zones 96a, 96b, and 96c are defined that meet these criteria. It will be appreciated that in other graphs / charts, fewer or more time zones may be identified. During these time zones 96a, 96b, and 96c, the processor 88 may be used to assess / determine / calculate the fractional flow reserve.

[0068] Figure 3 A portion of a first pressure sensing medical device 10 is shown, which can be part of the system 100. In this example, the first pressure sensing medical device 10 is a blood pressure sensing guidewire 10. However, this is not intended to limit other conceivable medical devices including, for example, catheters, rods, leads, wires, etc. The guidewire 10 can include a rod or tubular member 12. The tubular member 12 can include a proximal region 14 and a distal region 16. The materials of the proximal region 14 and the distal region 16 can vary and can include those disclosed herein. For example, the distal region 16 can include a nickel-cobalt-chromium-molybdenum alloy (e.g., MP35-N). The proximal region 14 can be made of the same material as the distal region 16 or a different material such as stainless steel. These are examples only. Other materials are contemplated.

[0069] In some embodiments, the proximal region 14 and the distal region 16 are formed from the same integral material. In other words, the proximal region 14 and the distal region 16 are portions of the same tube that define the tubular member 12. In other embodiments, the proximal region 14 and the distal region 16 are separate tubular members that are connected together. For example, a section of the outer surface of the portions 14 / 16 can be removed, and the sleeve 17 can be configured over the removed portion to connect the regions 14 / 16. Alternatively, the sleeve 17 can simply be configured over the regions 14 / 16. Other bonding methods can also be used, including welding, thermal bonding, adhesive bonding, etc. If used, the sleeve 17 used to connect the proximal region 14 to the distal region 16 can comprise a material that ideally combines both the proximal region 14 and the distal region 16. For example, the sleeve 17 can comprise a nickel-chromium-molybdenum alloy (e.g., Inconel).

[0070] A plurality of slots 18 may be formed in the tubular member 12. In at least some embodiments, the slots 18 are formed in the distal region 16. In at least some embodiments, the proximal region 14 lacks slots 18. However, the proximal region 14 may include slots 18. Slots 18 may be desirable for a number of reasons. For example, the slots 18 may provide the tubular member 12 (e.g., along the distal region 16) with a desired level of flexibility while also allowing for adequate torque transfer. The slots 18 may be arranged / distributed along the distal region 16 in a suitable manner. For example, the slots 18 may be arranged in opposing pairs of slots 18 distributed along the length of the distal region 16. In some embodiments, adjacent pairs of slots 18 may have a substantially constant spacing relative to one another. Alternatively, the spacing between adjacent pairs may vary. For example, more distal regions of the distal region 16 may have reduced spacing (and / or increased slot density), which may provide increased flexibility. In other embodiments, more distal regions of the distal region 16 may have increased spacing (and / or reduced slot density). These are examples only. Other arrangements are contemplated.

[0071] The pressure sensor 20 may be disposed within the tubular member 12 (e.g., within the lumen of the tubular member 12). Figure 3 The pressure sensor 20 is schematically shown in FIG. 1 , and it is understood that the structure and / or type of the pressure sensor 20 may vary. For example, the pressure sensor 20 may include a semiconductor (e.g., silicon wafer) pressure sensor, a piezoelectric pressure sensor, an optical fiber or optical pressure sensor, a Fabry-Perot pressure sensor, an ultrasonic transducer and / or an ultrasonic pressure sensor, a magnetic pressure sensor, a solid-state pressure sensor, or any other suitable pressure sensor.

[0072] As described above, the pressure sensor 20 may include an optical pressure sensor. In at least some of these embodiments, an optical fiber or fiber optic cable 24 (e.g., a multimode optical fiber) may be connected to the pressure sensor 20 and may thereby extend proximally. The optical fiber 24 may include a central core 60 and an outer cladding 62. In some cases, a sealing member (not shown) may connect the optical fiber 24 to the tubular member 12. Such a connecting member may be circumferentially arranged around and connected to the optical fiber 24 and may be fixed to the inner surface (e.g., distal region 16) of the tubular member 12. In addition, a center correction member 26 may also be incorporated into the optical fiber 24. In at least some embodiments, the center correction member 26 is spaced apart from the pressure sensor 20 proximally. Other arrangements may be considered. The center correction member 26 may help reduce the force that may be exposed to the pressure sensor 20 during navigation of the guidewire and / or during use.

[0073] In at least some embodiments, the distal region 16 can include an area having thinned walls and / or an increased inner diameter that defines a sensor housing region 52. Generally, the sensor housing region 52 is the area of ​​the distal region that ultimately "houses" the pressure sensor 20. Because a portion of the inner wall of the tubular member 12 is removed at the sensor housing region 52, additional space can be created or otherwise defined that can house the sensor 20. The sensor housing region 52 can include one or more openings, such as one or more distal porthole openings 66, that provide fluid access to the pressure sensor 20.

[0074] A tip member 30 can be connected to the distal region 16. The tip member 30 can include a core member 32 and a spring or coil member 34. A distal tip 36 can be connected to the core member 32 and / or the spring 34. In at least some embodiments, the distal tip 36 can take the form of a solder ball tip. The tip member 30 can be connected to the distal region 16 of the tubular member 12 via a bonding member 46, such as a weld.

[0075] The tubular member 12 may include an outer coating 19. In some embodiments, the coating 19 may extend along substantially the entire length of the tubular member 12. In other embodiments, one or more discrete portions of the tubular member 12 may include: the coating 19. The coating 19 may be a hydrophobic coating, a hydrophilic coating, or the like. The tubular member 12 may also include an inner coating 64 (e.g., a hydrophobic coating, a hydrophilic coating, or the like) disposed along its inner surface. For example, the hydrophilic coating 64 may be disposed along the inner surface of the housing region 52. In some of these and other cases, the core member 32 may include a coating (e.g., a hydrophilic coating). For example, the proximal region and / or the proximal end of the core member 32 may include a coating. In some of these and other cases, the pressure sensor 20 may also include a coating (e.g., a hydrophilic coating).

[0076] The materials that can be used for the various components of the system 100 and / or the guidewire 10 can include those materials commonly associated with medical devices. For simplicity, the following discussion refers to the tubular member 12 and other components of the guidewire 10. However, this is not intended to limit the devices and methods described herein, as the discussion can be applied to other tubular members and / or tubular member assemblies or devices disclosed herein.

[0077] The tubular member 12 and / or other components of the guidewire 10 can be made of metal, metal alloys, polymers (some examples of which are disclosed below), metal-polymer composites, ceramics, combinations thereof, etc., or other suitable materials. Some examples of suitable polymers can include polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP), polyoxymethylene (POM, e.g., available from DuPont), and polyoxymethylene (POM). ), polyether block esters, polyurethanes (e.g., polyurethane 85A), polypropylene (PP), polyvinyl chloride (PVC), polyether esters (e.g., available from DSM Engineering Plastics ), ether or ester based copolymers (e.g., butylene / poly(alkylene ether) phthalate and / or other polyester elastomers such as those available from DuPont ), polyamides (e.g., available from Bayer Or available from Elf Atochem ), elastomeric polyamides, block polyamide / ethers, polyether block amides (PEBA, such as can be ), ethylene vinyl acetate copolymer (EVA), silicone resin, polyethylene (PE), Marex high-density polyethylene, Marex low-density polyethylene, linear low-density polyethylene (e.g. ), polyester, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polytrimethylene terephthalate, polyethylene naphthalate (PEN), polyetheretherketone (PEEK), polyimide (PI), polyetherimide (PEI), polyphenylene sulfide (PPS), polyphenylene oxide (PPO), polyterephthalamide (e.g., ), polysulfone, nylon, nylon 12 (such as purchased from EMS American Grilon ), perfluoropropyl vinyl ether (PFA), ethylene vinyl alcohol, polyolefins, polystyrene, epoxy resins, polyvinylidene chloride (PVdC), poly(styrene-b-isobutylene-b-styrene) (e.g., SIBS and / or SIBS 50A), polycarbonate, ionomers, biocompatible polymers, other suitable materials, or mixtures, combinations, copolymers, polymer / metal composites, etc. thereof. In some embodiments, the sheath can be blended with a liquid crystal polymer (LCP). For example, the blend can contain up to about 6% liquid crystal polymer.

[0078] Some examples of suitable metals and metal alloys include stainless steel, such as 304V, 304L, and 316LV stainless steel; mild steel; nickel titanium alloys, such as linear elastic and / or superelastic nickel titanium alloys; other nickel alloys, such as nickel chromium molybdenum alloys (e.g., UNS: N06625, such as 625, UNS: N06022, such as UNS: N10276, such as other alloys, etc.), nickel-copper alloys (e.g., UNS: N04400, 400, 400, 400, etc.), nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035, etc.), nickel-molybdenum alloys (e.g., UNS: N10665, ), other nickel-chromium alloys, other nickel-molybdenum alloys, other nickel-cobalt alloys, other nickel-iron alloys, other nickel-copper alloys, other nickel-tungsten or tungsten alloys, etc.; cobalt-chromium alloys; cobalt-chromium-molybdenum alloys (e.g., UNS: R30003, such as etc.); platinum-rich stainless steel; titanium; combinations thereof; etc.; or any other suitable material.

[0079] In at least some embodiments, part or all of the guidewire 10 may also be doped, made of, or otherwise include a radiopaque material. Radiopaque materials should be understood as materials that are capable of producing a relatively bright image on a fluorescent screen or other imaging technology during medical procedures. This relatively bright image helps the user of the guidewire 10 determine its position. Some examples of radiopaque materials may include, but are not limited to, gold, platinum, palladium, tantalum, tungsten alloys, polymer materials loaded with radiopaque fillers, and the like. In addition, other radiopaque marker bands and / or coils may also be incorporated into the design of the guidewire 10 to achieve the same result.

[0080] In some embodiments, a degree of magnetic resonance imaging (MRI) compatibility is imparted to the guidewire 10. For example, the guidewire 10, or portions thereof, can be made of a material that does not substantially distort the image and produce substantial artifacts (e.g., gaps in the image). Certain ferromagnetic materials may not be suitable, for example, because they may produce artifacts in an MRI image. The guidewire 10, or portions thereof, can also be made of a material that can be imaged by an MRI machine. Some materials that exhibit these properties include, for example, tungsten, cobalt-chromium-molybdenum alloys (e.g., UNS: R30003, such as etc.), nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035, etc.), Nitinol, etc., and others.

[0081] It should be understood that this invention is in many respects merely illustrative. Changes may be made in detail, particularly in shape, size, and arrangement of steps, without exceeding the scope of the invention. This includes the ability to utilize any feature of one exemplary embodiment in other embodiments. The scope of the invention is, of course, defined by the language of the appended claims.

Claims

1. A system for determining fractional flow reserve, the system comprising: a processor configured to connect to a first pressure-sensing medical device and a second pressure-sensing medical device via a linking device, the first pressure-sensing medical device configured to measure a first pressure, and the second pressure-sensing medical device configured to measure a second pressure; and Wherein, the processor is configured to: generating a curve showing the magnitude of the second pressure over time; identifying one or more time intervals in the curve where the slope is less than zero, determining an average value of the second pressure, and A ratio of the first pressure to the second pressure is calculated during one or more of the time intervals when (a) the second pressure is less than or equal to an average value of the second pressure and (b) the slope of the curve is less than zero.

2. The system of claim 1, wherein the first pressure sensing medical device comprises an optical pressure sensor.

3. The system of any one of claims 1-2, wherein the first pressure-sensing medical device comprises a tubular member including a proximal region having a first inner diameter and a distal region having a second inner diameter different from the first inner diameter.

4. The system of any one of claims 1-2, wherein the second pressure-sensing medical device comprises a catheter having a pressure sensor.

5. The system of any one of claims 1-2, wherein the first pressure, the second pressure, or both are wirelessly transmitted to the processor.

6. The system of any one of claims 1-2, wherein the processor is configured to calculate a ratio of the first pressure to the second pressure in the absence of a hyperemic agent.

7. The system of any one of claims 1-2, wherein the processor is connected to a display.

8. The system of claim 7, wherein the display is designed to display the curve.

9. A system for determining fractional flow reserve, the system comprising: a processor configured to connect to the first pressure-sensing medical device and the second pressure-sensing medical device via a linking device; wherein the first pressure sensing medical device is configured to measure distal pressure at a location distal to a lesion, and the second pressure sensing medical device is configured to measure aortic pressure; and The processor is designed to: Generate a curve of the aortic pressure over time, identifying one or more time intervals in the curve where the slope is less than zero, determining the mean value of the aortic pressure, and The ratio of the distal pressure to the aortic pressure is calculated during one or more of the time intervals when (a) the aortic pressure is less than or equal to the average aortic pressure and (b) the slope of the curve is less than zero.

10. The system of claim 9, wherein the first pressure sensing medical device comprises an optical pressure sensor.

11. The system of any one of claims 9-10, wherein the first pressure sensing medical device comprises a tubular member including a proximal region having a first inner diameter and a distal region having a second inner diameter different from the first inner diameter.

12. The system of any one of claims 9-10, wherein the processor is configured to calculate the ratio of the distal pressure to the aortic pressure in the absence of a hyperemic agent.

13. The system of any of claims 9-10, wherein the processor is connected to a display.

14. The system of any one of claims 9-10, wherein the processor is designed to scale the mean aortic pressure by a scaling factor in the range of 0.75 to 1.

25.

15. The system of any one of claims 9-10, wherein the processor is configured to reject a time interval when the aortic pressure is less than a lower pressure limit.

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