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EP-4734829-A1 - METHOD OF DETERMINING MEAN TRANSIT TIME USING CORONARY PRESSURE MEASUREMENT

EP4734829A1EP 4734829 A1EP4734829 A1EP 4734829A1EP-4734829-A1

Abstract

A method includes acquiring, by one or more processing circuits, intravascular data, the intravascular data including a plurality of pressure measurements measured at a location within a blood vessel by an intravascular instrument, and determining, by the one or more processing circuits, a mean transit time parameter based on the plurality of pressure measurements. The mean transit time parameter is indicative of a mean transit time corresponding to a flow rate of blood in the blood vessel.

Inventors

  • CHIU, WEI C.
  • DOLATY, Amir
  • GOPINATH, AJAY

Assignees

  • St. Jude Medical Coordination Center BVBA

Dates

Publication Date
20260506
Application Date
20240625

Claims (20)

  1. 1. A method of determining a mean transit time parameter indicative of a mean transit time of blood in a blood vessel, the method comprising, by use of one or more processing circuits: acquiring intravascular data comprising a plurality of pressure measurements measured at a location within the blood vessel by an intravascular instrument during injection of a bolus of fluid; and determining, based on the plurality of pressure measurements, the mean transit time parameter.
  2. 2. The method of Claim 1, wherein: the mean transit time parameter is directly proportional to the mean transit time.
  3. 3. The method of Claim 1, wherein: the mean transit time parameter is not determined using temperature data.
  4. 4. The method of Claim 1, further comprising: determining at least one of a coronary flow reserve value or an index of microcirculatory resistance value based on the mean transit time parameter.
  5. 5. The method of Claim 4, wherein: the intravascular data includes (a) a first plurality of pressure measurements measured at rest and (b) a second plurality of pressure measurements measured at hyperemia, the step of determining the mean transit time parameter includes (a) determining a first mean transit time parameter based on the first plurality of pressure measurements and (b) determining a second mean transit time parameter based on the second plurality of pressure measurements, and the at least one of the coronary flow reserve value or the index of microcirculatory resistance value are determined based on the first mean transit time parameter and the second mean transit time parameter.
  6. 6. The method of Claim 1, wherein: the plurality of pressure measurements provide a raw pressure waveform, and the method further comprises filtering the raw pressure waveform by applying a moving average filter to the raw pressure waveform to generate a filtered pressure waveform, the filtered pressure waveform including a bolus injection portion associated with the injection of the bolus of fluid through the intravascular instrument as the plurality of pressure measurements are measured at the location within the blood vessel by the intravascular instrument, wherein the mean transit time parameter is determined based on the bolus injection portion of the filtered pressure waveform.
  7. 7. The method of Claim 6, further comprising: before acquiring the intravascular data, inserting the intravascular instrument into a test target until a portion of the intravascular instrument reaches the location within the blood vessel, and injecting the bolus of fluid through the intravascular instrument; and the step of acquiring the intravascular data comprises acquiring, by a sensor of the intravascular instrument, the plurality of pressure measurements prior to, during, and after the bolus of fluid being injected.
  8. 8. The method of Claim 6, wherein: the step of applying the moving average filter to the raw pressure waveform comprises: (a) determining a length of a single cardiac cycle based on the raw pressure waveform, (b) averaging a subset of the plurality of pressure measurements over a first portion of the raw pressure waveform having a window length equivalent to the length of the single cardiac cycle to determine a point of the filtered pressure waveform, (c) moving along the raw pressure waveform at an interval of a sample rate of the raw pressure waveform, and (d) repeating steps (b) and (c) across the raw pressure waveform to determine each subsequent point of the filtered pressure waveform associated with each subsequent portion of the raw pressure waveform.
  9. 9. The method of Claim 6, further comprising: determining a first point of interest along the bolus injection portion as a point where the pressure measurements begin to increase from a pre-bolus injection value, due to the injection of the bolus of fluid.
  10. 10. The method of Claim 9, further comprising determining, by the one or more processing circuits, a sub-portion of the bolus injection portion that is below the pre-bolus injection value and positioned after the first point of interest along the bolus injection portion.
  11. 11. The method of Claim 10, further comprising repositioning, by the one or more processing circuits, the bolus injection portion such that the first point of interest is positioned at zero along a y-axis, wherein the zero line represents the pre-bolus injection value.
  12. 12. The method of Claim 10, further comprising: determining an area of the sub-portion.
  13. 13. The method of Claim 12, further comprising: inverting the sub-portion, determining a start point of the sub-potion, determining an end point of the sub-portion, and determining the area of the sub-portion that is below the pre-bolus injection value and between the start point and the end point.
  14. 14. The method of Claim 13, wherein the step of determining the start point includes identifying where the sub-portion falls below the pre-bolus injection value following the first point of interest, and wherein determining the end point includes identifying either (a) where the sub-portion is greater than the pre-bolus injection value following the start point or (b) if the sub-portion is not greater than the pre-bolus injection value at any point following the start point, at a point closest to the pre-bolus injection value following a minimum point of the sub-portion.
  15. 15. The method of Claim 12, further comprising: determining, by the one or more processing circuits, a second point of interest by identifying a maximum value of the bolus injection portion; determining, by the one or more processing circuits, a third point of interest by identifying a minimum value of the bolus injection portion; and determining, by the one or more processing circuits, a sampling difference between the second point of interest and the third point of interest.
  16. 16. The method of Claim 15, wherein the mean transit time parameter is determined based on the area and the sampling difference.
  17. 17. A system comprising: an intravascular instrument configured to: be inserted into a test target to acquire measurements at a location within a blood vessel; facilitate injecting a bolus of fluid; and a data processing subsystem configured to: acquire intravascular data from the intravascular instrument, the intravascular data including a plurality of pressure measurements, wherein the plurality of pressure measurements provide a raw pressure waveform; apply a moving average filter to the raw pressure waveform to generate a filtered pressure waveform, the filtered pressure waveform including a bolus injection portion associated with an injection of the bolus of fluid through the intravascular instrument as the measurements are acquired by the intravascular instrument at the location within the blood vessel; and determine a mean transit time parameter based on the bolus injection portion of the filtered pressure waveform, the mean transit time parameter indicative of a mean transit time of blood in the blood vessel.
  18. 18. The system of Claim 17, wherein the mean transit time parameter is directly proportional to the mean transit time.
  19. 19. The system of Claim 17, wherein the mean transit time parameter is not determined using temperature measurements.
  20. 20. The system of Claim 17, wherein the data processing subsystem is configured to determine at least one of a coronary flow reserve value or an index of microcirculatory resistance value based on the mean transit time parameter.

Description

METHOD OF DETERMINING MEAN TRANSIT TIME USING CORONARY PRESSURE MEASUREMENT CROSS-REFERENCE TO RELATED PATENT APPLICATION [0001] This application claims the benefit of and priority to U.S. Provisional Patent Application No. 63/523,785, filed June 28, 2023, which is incorporated herein by reference in its entirety. BACKGROUND [0002] Identifying microvascular resistance in a patient may require one or more data collection systems. For example, a physician may use a pressure wire, angiography, intravascular imaging, etc., to collect data to identify microvascular disease. Angiography may provide an insight as to what is happening within a heart, while a pressure wire may be able to provide certain data measurements within a blood vessel. [0003] Mean transit time, corresponding to a flow rate of blood in a blood vessel, has traditionally been computed by passing a bolus of chilled saline through a blood vessel and measuring a temperature of the bolus as the bolus passes by a proximal and distal temperature sensor on a pressure wire, which is inserted separate from an optical coherence tomography (“OCT”) catheter. A thermodilution curve may then be plotted based on the temperature of the bolus as it passes the temperature sensors, providing an indication of the flow rate and, therefore, the mean transit time. This process, however, requires additional steps and instruments that can be cumbersome, and is susceptible to operator error due to the dependency on maintaining a certain temperature or temperature range of the bolus. SUMMARY [0004] One embodiment relates to a method of determining a mean transmit time parameter indicative of a mean transmit time of blood in a blood vessel. The method includes acquiring intravascular data comprising a plurality of pressure measurements measured at a location within the blood vessel by an intravascular instrument during injection of a bolus of fluid, and determining, based on the plurality of pressure measurements, the mean transit time parameter. [0005] Another embodiment relates to a system that includes an intravascular instrument and a data processing subsystem. The intravascular instrument is configured to be inserted into a test target to acquire measurements at a location within a blood vessel and facilitate injecting a bolus of fluid. The data processing subsystem is configured to acquire intravascular data from the intravascular instrument. The intravascular data includes a plurality of pressure measurements. The plurality of pressure measurements provide a raw pressure waveform. The data processing system is further configured to apply a moving average filter to the raw pressure waveform to generate a filtered pressure waveform. The filtered pressure waveform includes a bolus injection portion associated with an injection of the bolus of fluid through the intravascular instrument as the measurements are acquired by the intravascular instrument at the location within the blood vessel. The data processing system is further configured to determine a mean transit time parameter based on the bolus injection portion of the filtered pressure waveform. The mean transit time parameter is indicative of a mean transit time of blood in the blood vessel. [0006] Still another embodiment relates to a non-transitory computer-readable medium having computer-executable instructions encoded therein. The instructions, when executed by one or more processors, cause the one or more processors to acquire intravascular data including a plurality of pressure measurements measured at a location within a blood vessel by an intravascular instrument during injection of a bolus of fluid, and determine, based on the plurality of pressure measurements, a mean transit time parameter indicative of a mean transit time of blood in the blood vessel. The mean transit time parameter is directly proportional to the mean transit time. The mean transit time parameter is not determined using temperature data. [0007] This summary is illustrative only and is not intended to be in any way limiting. Other aspects, inventive features, and advantages of the devices or processes described herein will become apparent in the detailed description set forth herein, taken in conjunction with the accompanying figures, wherein like reference numerals refer to like elements. BRIEF DESCRIPTION OF THE DRAWINGS [0008] FIG. l is a schematic diagram of system for determining a mean transit time parameter based on pressure measurements acquired using an intravascular instrument, according to an exemplary embodiment. [0009] FIG. 2 is a schematic diagram of the system of FIG. 1 where the intravascular instrument includes a first catheter assembly, according to an exemplary embodiment. [0010] FIG. 3 is a schematic diagram of the system of FIG. 1 where the intravascular instrument includes a second catheter assembly, according to an exemplary embodiment. [0011] FIG. 4 is a detailed view of the second catheter assembly of FIG