WO2020028386A1

WO2020028386A1 - Systems and methods for hemodynamically evaluating peripheral artery stenoses

Info

Publication number: WO2020028386A1
Application number: PCT/US2019/044173
Authority: WO
Inventors: Anand Prasad
Original assignee: Boards Of Regents Of The University Of Texas System
Priority date: 2018-07-30
Filing date: 2019-07-30
Publication date: 2020-02-06

Abstract

In one embodiment, a system for hemodynamically evaluating a peripheral artery stenosis includes a pressure measurement device configured to measure hemodynamic pressure within a peripheral artery proximal of and distal to a stenosis; and a computing device that executes a stenosis evaluation program, the program including computer-executable instructions configured to receive hemodynamic pressure data measured by the pressure measurement device, calculate one or more diagnostic parameters that are indicative of the significance of the stenosis in terms of risk to the health of the patient, and generate an output useful to a physician in determining whether or not to perform an invasive procedure on the stenosis.

Description

SYSTEMS AND METHODS FOR HEMODYNAMICALLY EVALUATING PERIPHERAL ARTERY STENOSES Cross-Reference to Related Application

This application claims priority to co-pending U.S. Provisional Application Serial Number 62/711 ,871 , filed July 30, 2018, which is hereby incorporated by reference herein in its entirety. Background

Arterial stenosis is an abnormal narrowing in an artery, typically caused by a lesion within the artery that restricts blood flow through the artery, which can result in damage to an organ to which the artery supplies blood. There are various invasive procedures, such as stenting, angioplasty, and atherectomy, that can be performed to restore normal blood flow to arteries. Unfortunately, determining which specific stenoses need to be treated and which do not is challenging based on visual assessment of angiographic images.

In view of the fact that not all stenoses are responsible for symptoms for the patient, hemodynamic techniques have been developed to evaluate arterial stenoses to determine whether or not intervention is necessary. Fractional flow reserve (FFR) is one such technique used in coronary catheterization. FFR measures hyperemic pressure ratio differences across a coronary artery stenosis to determine the likelihood that the stenosis impedes oxygen delivery to the muscles of the heart. FFR involves use of a pressure wire or a small-diameter pressure catheter to measure a ratio of coronary pressure distal to a stenosis (Pd) versus aortic pressure (Pa) during distal vascular bed vasodilation, which causes hyperemia. Flyperemia is most often induced using pharmacologic administration, typically systemic or intracoronary adenosine.

Over the past decade, a technique referred to as instantaneous wave-free ratio (iFR) has been developed. Like FFR, iFR is also performed during cardiac catheterization using pressure wires or catheters that are placed in the coronary arteries to gather data about a lesion’s hemodynamic significance. In iFR, however, there is no need for pharmacologic hyperemia. Instead, iFR isolates a specific period in diastole, called the wave-free period, to measure Pd and Pa. During this wave-free period, the competing forces that affect coronary flow are quiescent such that pressure and flow are linearly related as compared to the rest of the cardiac cycle. In this respect, the wave-free period provides conditions similar to hyperemia.

While techniques such as FFR and iFR have proven to be useful in assessing stenoses of the coronary arteries, they have not been utilized to great effect in other vascular beds. As for FFR, there are various limitations when applied to non- coronary circulation, including challenges with using small diameter pressure wires for procedures, determining thresholds for stenosis significance, obtaining consistent effects from pharmacological agents for hyperemia, and obtaining certain dose responses to vasodilators. As for iFR, this technique has not been used in the non- coronary circulation. In view of the foregoing discussion, it can be appreciated that it would be desirable to have an effective system and method for hemodynamically evaluating peripheral artery stenoses.

Brief Description of the Drawings

The present disclosure may be better understood with reference to the following figures. Matching reference numerals designate corresponding parts throughout the figures, which are not necessarily drawn to scale.

Fig. 1 is a schematic diagram of a peripheral artery that has a stenosis to be evaluated.

Fig. 2 is a block diagram of an embodiment of a system for hemodynamically evaluating a peripheral artery stenosis

Fig. 3 is a flow diagram of an embodiment of a method for hemodynamically evaluating a peripheral artery stenosis.

Figs. 4A and 4B are schematic diagrams of a peripheral artery illustrating measurement of hemodynamic pressure within the artery proximal and distal of a stenosis, respectively.

Detailed Description

As described above, it can be appreciated that it would be desirable to have an effective system and method for hemodynamically evaluating peripheral artery stenoses. Disclosed herein are examples of such systems and methods. In some embodiments, a system and method for hemodynamically evaluating a peripheral artery stenosis relate to collecting pressure data proximal of and distal to a stenosis and calculating one or more parameters that are indicative of the significance of the stenosis in terms of patient health risk. In some embodiments, the method further comprises generating an output useful to a physician in determining whether or not to perform an invasive procedure.

In the following disclosure, various specific embodiments are described. It is to be understood that those embodiments are example implementations of the disclosed inventions and that alternative embodiments are possible. All such embodiments are intended to fall within the scope of this disclosure.

Fig. 1 schematically illustrates a peripheral artery 10 having a lesion 12 that has reduced the cross-sectional area of the artery in the location of the lesion. Presumably, the lesion 12 reduces blood flow through the artery. While a surgical procedure, such as stenting, angioplasty, or atherectomy, could be performed to remove or reduce the size of the lesion 12, the risks involved with such a procedure and/or later complications from such a procedure (e.g., clotting from an implanted stent) may outweigh the risks associated with the reduction in blood flow. In view of this fact, it is preferable to evaluate the hemodynamics of the artery 10 prior to performing an invasive procedure to determine whether or not such procedure is actually warranted. As disclosed below, the arterial hemodynamics can be evaluated by measuring the pressure gradient across the lesion 12. More particularly, the pressure proximal of the lesion 12, Pp, and the pressure distal of the lesion, Pd, can be measured and used in the evaluation of the lesion and the stenosis it is creating.

Fig. 2 illustrates an example system 14 for hemodynamically evaluating peripheral stenoses that can be used in such a capacity. As shown in the figure, the system 14 generally includes a cardiac monitor 16, a pressure measurement device 18, and a computing device 20. The cardiac monitor 16 is a device that is configured to monitor all aspects of the cardiac cycle. Such a cardiac monitor 16 can, for example, include an electrocardiography (ECG) machine that monitors and records the electrical activity of the heart over a period of time using electrodes placed on the skin.

The pressure measurement device 18 is a device that can be inserted into a peripheral artery and used to measure Pp and Pd at appropriate times during the cardiac cycle. Such a measurement device 18 can, for example, comprise a pressure wire and/or a pressure catheter that comprises a pressure sensor (e.g., pressure transducer) that can measure the pressure within the artery at the desired location.

The computing device 20 is in electrical communication with both the cardiac monitor 16 and the pressure measurement device 18. The computing device 20 receives data collected by the cardiac monitor 16 and the pressure measurement device 18. In some embodiments, the computing device 20 further controls operation of the pressure measurement device 18. As shown in Fig. 2, the computing device 20 includes a processing device 22, such as a microprocessor, and memory 24 (a non-transitory computer-readable medium) that stores software programs that can be executed by the processing device. These programs, which comprise computer- executable instructions that may form part of one or more software algorithms, include an operating system 26 that controls the overall operation of the computing device 20 and a stenosis evaluation program 28 that coordinates the collection of patient data and evaluates the collected patient data.

Notably, while “software” has been explicitly identified above, suitable hardware having integrated firmware, such as an application-specific integrated circuit (ASIC), could be used in lieu of actual software. Furthermore, while a “computing device” has been explicitly identified, it is noted that the computing device 20 need not be a conventional computer, such as a desktop or notebook computer. Instead, the computing device 20 can be a dedicated device that is specifically configured for evaluating peripheral artery stenosis. In other cases, the computing device 23 can be a smart phone or other portable and/or personal computing device that receives and processes the pressure data. It is also noted that, in some embodiments, a data acquisition (DAQ) device can be used to receive the raw pressure data from the pressure measurement device 18 and process the data (e.g., digitize it) for use by the computing device 20. As can be appreciated from this discussion, the configuration of the system 14 is not as important as the functionality it provides.

Fig. 3 provides an overview of a method for evaluating peripheral artery stenoses using a system such as that shown in Fig. 2. Beginning with block 30 of Fig. 3, a patient’s cardiac cycle is monitored. As noted above, this can involve ECG tracing. With reference to block 32, hemodynamic pressure data proximal of and distal to the peripheral artery stenosis (i.e. , Pp and Pd) is collected. Figs. 4A and 4B show an example of this. Beginning with Fig. 4A, a catheter 40 is passed through the peripheral artery 10 and a pressure measurement device, in the form of a pressure wire 42, is extended from a working channel of the catheter. The pressure wire 42 is equipped with a pressure sensor 44 that can measure the hemodynamic pressure within the artery 10 proximal (upstream) of the stenosis 12. Referring next to Fig. 4B, the catheter 40 can be further extended so that its pressure sensor 44 is positioned distal (downstream) of the stenosis 12.

In some embodiments, the pressure measurement device (e.g., pressure wire 42) collects these hemodynamic pressure measurements in the wave-free period during diastole. Notably, however, pressure measurements may be obtained at other times during the cardiac cycle if such measurements would be useful in evaluating the significance of the stenosis. For example, a vasodilator can be administered prior to collection of the pressure measurements, in which case the measurements can be taken at times other than the wave-fee period. In some embodiments, the specific times at which the pressure data most useful to the stenosis evaluation can be determined through clinical experimentation.

Referring next to block 34, one or more diagnostic parameters are calculated using the stenosis evaluation program 28 that are indicative of the significance of the stenosis in terms of risk to the patient’s health. Such risk can be a risk of damage to an organ to which the peripheral artery delivers blood and/or the risk of the stenosis rupturing and releasing plaque into the bloodstream. In the diagnostic parameters include a pressure ratio of Pd/Pp, in other words the ratio of the pressure distal to the stenosis to the pressure proximal of the stenosis. When these pressures are similar, and the ratio is near 1 , the hemodynamic effect of the stenosis may not be that significant, even if the stenosis appears to be significant to the naked eye. When these pressures are significantly different, however, and the ratio is significantly less than 1 , the hemodynamic effect of the stenosis might justify an invasive procedure to reduce the stenosis (e.g., remove or reduce a lesion in the artery). Notably, other parameters can be calculated. The significance of these other parameters can also be determined through clinical experimentation.

With reference to block 36, an output useful to the patient’s physician as to whether or not to perform an invasive procedure can be generated. In some embodiments, such an output may simply comprise the one or more calculated parameters, in which case the physician can draw his or her own conclusions as to whether or not to perform an invasive procedure. In other embodiments, the output can also comprise an indication as to the level of risk the stenosis poses and/or an indication of a recommended strategy. In some embodiments, the recommendation can be based upon statistical analysis that may or may not include other factors that should be considered, such as age, sex, health, and the like. Irrespective of the nature of the output, the physician can decide how to proceed at least in part based upon the information gleaned from the system 14. Such a decision may include omitting to perform an invasive procedure if the risks associated with such a procedure might outweigh the risks associated with the presence of the stenosis.

While the above method has focused on whether or not to perform an invasive procedure on a peripheral artery stenosis, it is noted that the method can be used to evaluate a peripheral artery after such a procedure has been performed.

Claims

CLAIMS Claimed are:

1. A system for hemodynamically evaluating a peripheral artery stenosis, the system comprising:

a pressure measurement device configured to measure hemodynamic pressure within a peripheral artery proximal of and distal to a stenosis; and

a computing device that executes a stenosis evaluation program, the program including computer-executable instructions configured to receive hemodynamic pressure data measured by the pressure measurement device, calculate one or more diagnostic parameters that are indicative of the significance of the stenosis in terms of risk to the health of the patient, and generate an output useful to a physician in determining whether or not to perform an invasive procedure on the stenosis.

2. The system of claim 1 , wherein the pressure measurement device comprises at least one of a pressure wire and catheter.

3. The system of claim 1 , wherein the pressure measurement device is configured to measure the hemodynamic pressures during the wave-free period of diastole.

4. The system of claim 1 , wherein the computer-executable instructions are configured to calculate a ratio of the distal pressure to the proximal pressure.

5. The system of claim 1 , wherein the computer-executable instructions are configured to calculate a ratio of the distal pressure to the proximal pressure during the wave-free period of diastole.

6. The system of claim 1 , further comprising a cardiac monitor configured to monitor a cardiac cycle of a patient.

7. The system of claim 6, wherein the cardiac monitor comprises an electrocardiogram machine.

8. A method for hemodynamically evaluating a peripheral artery stenosis, the method comprising:

monitoring the cardiac cycle of a patient;

measuring hemodynamic pressure within a peripheral artery of the patient proximal of and distal to a stenosis within the peripheral artery; and

calculating one or more diagnostic parameters that are indicative of the significance of the stenosis in terms of risk to the health of the patient.

9. The method of claim 8, wherein monitoring the cardiac cycle comprises monitoring the cardiac cycle using an electrocardiogram machine.

10. The method of claim 8, wherein measuring the hemodynamic pressure comprises measuring the hemodynamic pressure proximal of and distal of the stenosis using a pressure wire that is inserted within the peripheral artery.

11. The method of claim 10, wherein measuring the hemodynamic pressure comprise measuring the hemodynamic pressure in the wave-free period of diastole.

12. The method of claim 8, wherein calculating one or more parameters comprises calculating a ratio of the distal pressure to the proximal pressure.

13. The method of claim 12, further comprising generating an output useful to a physician in determining whether or not to perform an invasive procedure on the stenosis.

14. The method of claim 13, wherein generating an output comprises presenting the calculated ratio.

15. The method of claim 14, wherein generating an output further comprises presenting an indication as to the level of risk the stenosis poses to the patient’s health.