Method for determining the blood flow in a coronary artery

• US 20070078352A1
• Filed: 09/30/2005
• Published: 04/05/2007
• Est. Priority Date: 09/30/2005
• Status: Active Grant

• Current Assignee: St. Jude Medical Coordination Center BVBA (Abbott Laboratories Incorporated)
• Original Assignee: Radi Medical System AB
• Inventors: Pijls, Nico
• Granted Patent: US 7,775,988 B2
• Time in Patent Office: Days
• US Class Current: 600/504
• CPC Class Codes: A61B 5/028 by thermo-dilution

Abstract

The invention relates to a method and a system for determining the blood flow in an individual coronary artery of a patient, wherein the method comprises the steps of positioning a temperature sensor mounted at a distal portion of a guide wire at a distal position in the coronary artery, positioning an infusion catheter in the coronary artery such that the distal end of the infusion catheter is proximally of the temperature sensor, measuring the blood temperature with the temperature sensor, infusing cold indicator fluid with a known infusion rate and known or measurable temperature into the coronary artery by the infusion catheter, measuring the temperature of the mixture of blood and indicator fluid by the temperature sensor, and calculating the coronary blood flow by a formula based on the known and measured quantities. In an extended version, the method comprises steps for relating the calculated coronary flow value to related normal flow values, or related FFR values, or a related flow resistance.

Claims

1. A method for determining the blood flow in an individual coronary artery of a patient, comprising at least the following steps:

positioning a temperature sensor mounted at a distal portion of a guide wire at a distal position in the coronary artery;

positioning an infusion catheter in the coronary artery such that the distal end of the infusion catheter is proximally of the temperature sensor;

measuring blood temperature;

infusing cold indicator fluid with a known infusion rate and known or measurable temperature into the coronary artery using the infusion catheter;

measuring the temperature of the mixture of blood and indicator fluid using the temperature sensor; and

calculating the coronary blood flow by a formula based on the known and measured quantities.

2. The method according to claim 1, further comprising the step of retracting the temperature sensor until the temperature sensor is located inside the infusion catheter and measuring the indicator fluid temperature at the end of the infusion catheter.

3. The method according to claim 1, further comprising the step of inducing steady state hyperaemia in the patient before temperature measurement such that the calculated coronary blood flow is the maximum coronary blood flow.

4. The method according to claim 3, wherein the formula used for calculating the coronary blood flow is:

$Q_b=Q_k<br><br>\frac{T_k-T_b}{T-T_b}$

where Q_b is the coronary blood flow, Q_k is the infusion rate of the indicator fluid, T_k is the temperature of the indicator fluid, T_b is blood temperature, and T is the temperature of the mixture of blood and indicator fluid.

5. The method according to claim 1, wherein the formula used for calculating the coronary blood flow is:

$Q_b=Q_k<br><br>\frac{T-T_k}{T_b-T}$

where Q_b is the coronary blood flow, Q_k is the infusion rate of the indicator fluid, T_k is the temperature of the indicator fluid, T_b is blood temperature, and T is the temperature of the mixture of blood and indicator fluid.

13. The method according to claim 1, further comprising the step of measuring the blood temperature with the temperature sensor.

14. The method according to claim 1, wherein the infusing comprises continuous infusing.

6. A method for determining the blood flow in an individual coronary artery of a patient and for relating this blood flow to at least one related flow value or to at least one related FFR value, comprising at least the following steps:

positioning a temperature sensor mounted at a distal portion of a guide wire at a distal position in the coronary artery;

positioning an infusion catheter in the coronary artery such that the distal end of the infusion catheter is proximally of the temperature sensor;

inducing steady state hyperaemia in the patient;

measuring the blood temperature with the temperature sensor;

infusing cold indicator fluid with a known infusion rate and known or measurable temperature into the coronary artery using the infusion catheter;

measuring the temperature of the mixture of blood and indicator fluid using the temperature sensor;

calculating the maximum coronary blood flow by a formula based on the known and measured quantities;

positioning a pressure sensor mounted at a distal portion of a guide wire at a distal position in the coronary artery;

measuring a distal pressure by the pressure sensor;

measuring the aortic pressure;

calculating a first FFR value based on the measured aortic and distal pressures; and

calculating a related flow value, or a related FFR value, based on the calculated maximum coronary blood flow and the first FFR value, or a related flow resistance based on the measured pressures and a calculated flow value

7. The method according to claim 6, further comprising the step of retracting the temperature sensor until the temperature sensor is located inside the infusion catheter and measuring the indicator fluid temperature at the end of the infusion catheter.

8. The method according to claim 6, wherein the temperature measurements and the measurement of the distal pressure are executed with the same guide wire mounted sensor.

9. The method according to claim 6, wherein the temperature measurements, the measurement of the distal pressure, and the measurement of the aortic pressure are executed with the same guide wire mounted sensor.

10. The method according to claim 6, wherein the measurement of the aortic pressure is executed with a pressure transducer connected to a guide catheter inserted into the patient'"'"'s aorta.

11. The method according to claim 6, further comprising the step of inserting a catheter into the right atrium of the patient'"'"'s heart and measuring the venous pressure by a pressure transducer connected to the catheter.

12. The method according to claim 6, further comprising the step of positioning a balloon arranged at a catheter to a position proximally of the pressure sensor, inflating the balloon to completely occlude the coronary artery, and measuring the coronary wedge pressure using the pressure sensor.

15. A system for determining the blood flow in an individual coronary artery of a patient, comprising:

a sensor guide wire having a distal portion provided with a temperature sensor and being adapted for positioning in the individual coronary artery;

an infusion catheter adapted for positioning in a coronary artery and adapted for injecting an indicator fluid into the individual coronary artery;

a device for transforming an output signal from the temperature sensor into a temperature of the medium surrounding the sensor; and

a device adapted to be connected to the infusion catheter for continuously delivering a cold indicator fluid from a reservoir into the individual coronary artery.

16. The system according to claim 15, further comprising a sensor guide wire having a distal portion provided with a pressure sensor and being adapted for positioning in the individual coronary artery.

17. The system according to claim 16, wherein the pressure sensor and the temperature sensor are provided at the same guide wire.