Devices, systems, and methods to determine fractional flow reserve

1. A method for determining a flow reserve within a luminal organ, the method comprising the steps of:

obtaining flow data comprising a flow velocity of a fluid within a luminal organ using an impedance device positioned within the luminal organ, a cross-sectional area at or near a stenosis within the luminal organ determined using conductance data obtained from the impedance device, and a pressure measurement indicative of the luminal organ, wherein the pressure measurement is determined using the flow velocity and the cross-sectional area by a data acquisition and processing system without the use of a pressure sensor; and

determining, using the data acquisition and processing system, a flow reserve within the luminal organ at or near the stenosis using the flow velocity, the cross-sectional area, and the pressure measurement.

2. The method of claim 1 , wherein the step of determining comprises determining a fractional flow reserve.

3. The method of claim 1 , wherein the flow velocity is obtained using the impedance device positioned within the luminal organ at or near the stenosis.

4. The method of claim 1 , wherein the flow velocity is obtained using the impedance device positioned within the luminal organ at or near the stenosis, the impedance device comprising at least two sensors separated a predetermined distance from one another.

5. The method of claim 4 , wherein the flow velocity is obtained by:

detecting a first fluid within the luminal organ using at least one of the at least two sensors, wherein the first fluid has a first parameter having a first value;

introducing the second fluid into the luminal organ, the second fluid temporarily displacing the first fluid within the luminal organ at the site of introduction, wherein the second fluid has a second parameter having a second value, the second value differing from the first value;

detecting the second value of the second parameter of the second fluid using the at least two sensors;

measuring time of detection of the second value of the second parameter of the second fluid by each of the at least two sensors; and

determining flow velocity of the second fluid within the luminal organ based upon the time of detection of the second value of the second parameter of the second fluid by each of the at least two sensors.

6. The method of claim 5 , wherein the first parameter and the second parameter are conductivity, pH, temperature, or an optically-detectable substance.

7. The method of claim 1 , wherein the conductance data is obtained using the impedance device when positioned within the luminal organ at or near the stenosis.

8. The method of claim 1 , wherein the cross-sectional area is obtained from the conductance data obtained using the impedance device positioned within the luminal organ at or near the stenosis, the conductance data obtained using (i) the at least two sensors of the impedance device separated a predetermined distance from one another, (ii) at least one additional sensor of the impedance device, or (iii) at least one of the at least two sensors and the at least one additional sensor.

9. The method of claim 1 , wherein the step of determining the flow reserve is further based upon a determination of volumetric flow between at least two sensors of an impedance device operated within the luminal organ.

10. The method of claim 1 , further comprising the step of:

diagnosing a disease based upon the determination of flow velocity within a luminal organ.

11. The method of claim 1 , wherein the determination of the flow reserve is indicative of a degree of stenosis within the luminal organ.

12. A method for determining a flow reserve within a luminal organ, the method comprising the steps of:

introducing an impedance device into a lumen of a luminal organ at or near a stenosis;

operating the impedance device to determine a flow velocity of a fluid within the luminal organ and to obtain conductance data useful to determine a cross-sectional area within the luminal organ;

determining a cross-sectional area within the luminal organ using the conductance data;

determining a pressure measurement indicative of the luminal organ using a data acquisition and processing system, wherein the pressure measurement is determined using the flow velocity and the cross-sectional area without the use of a pressure sensor; and

determining, using the data acquisition and processing system, a flow reserve at or near the stenosis using the flow velocity, the cross-sectional area, and the pressure measurement.

13. The method of claim 12 , wherein the step of determining comprises determining a fractional flow reserve.

14. The method of claim 12 , wherein the flow velocity is obtained by:

detecting a first fluid within the luminal organ using at least one of at least two sensors of the impedance device, wherein the first fluid has a first parameter having a first value;

introducing the second fluid into the luminal organ, the second fluid temporarily displacing the first fluid within the luminal organ at the site of introduction, wherein the second fluid has a second parameter having a second value, the second value differing from the first value;

detecting the second value of the second parameter of the second fluid using the at least two sensors;

measuring time of detection of the second value of the second parameter of the second fluid by each of the at least two sensors; and

determining flow velocity of the second fluid within the luminal organ based upon the time of detection of the second value of the second parameter of the second fluid by each of the at least two sensors.

15. The method of claim 14 , wherein the first parameter and the second parameter are conductivity, pH, temperature, or an optically-detectable substance.

16. The method of claim 12 , wherein the conductance data is obtained using (i) at least two sensors of the impedance device separated a predetermined distance from one another, (ii) at least one additional sensor of the impedance device, or (iii) at least one of the at least two sensors and the at least one additional sensor.

17. The method of claim 12 , wherein the step of determining the flow reserve is further based upon a determination of volumetric flow between at least two sensors of the impedance device.

18. The method of claim 12 , further comprising the step of:

diagnosing a disease based upon the determination of flow velocity within a luminal organ.

19. The method of claim 12 , wherein the determination of the flow reserve is indicative of a degree of stenosis within the luminal organ.

20. A system for determining a flow reserve within a luminal organ, the system comprising:

an impedance device comprising at least two sensors separated a predetermined distance from one another, the impedance device operable to (a) determine a flow velocity of a fluid within a mammalian luminal organ; and (b) obtain conductance data within the mammalian luminal organ useful to determine a cross-sectional area of the mammalian luminal organ, when at least part of the impedance device is positioned within the mammalian luminal organ; and

a data acquisition and processing system coupled to the impedance device, the data acquisition and processing system configured to (a) determine the cross-sectional area using the conductance data obtained from the impedance device, (b) determine a pressure measurement within the mammalian luminal organ using the flow velocity and the cross-sectional area, without the use of a pressure sensor, and (c) determine a flow reserve at or near a stenosis within the mammalian luminal organ using the cross-sectional area, the flow velocity, and the pressure measurement.