AU2012329594B2

AU2012329594B2 - Medical system, and a method in relation to the medical system

Info

Publication number: AU2012329594B2
Application number: AU2012329594A
Authority: AU
Inventors: Johan Svanerudh
Original assignee: St Jude Medical Coordination Center BVBA
Current assignee: St Jude Medical Coordination Center BVBA
Priority date: 2011-10-28
Filing date: 2012-10-05
Publication date: 2015-07-30
Anticipated expiration: 2032-10-05
Also published as: EP2770903A1; AU2012329594A1; WO2013062464A1; JP2014519387A; SE537177C2; CA2835164A1; SE1151007A1; JP6077532B2

Abstract

A medical system for determining the individual Fractional Flow Reserve (FFR) value for one or many lesions of interest of a blood vessel, the system comprising an intravascular pressure measurement device for acquiring pressure measurements in the blood vessel during continuous blood flow there through. The pressure measurement device comprises a pressure sensor at its distal portion. The system further comprises an FFR processor adapted to determine the FFR value related to said lesion solely/only based upon the pressure measurements performed by said pressure sensor.

Description

1 Title Medical system, and a method in relation to the medical system Field of the invention 5 The present invention relates to a medical system, and to a method in relation to the medical system, according to the preambles of the independent claims. In particular the invention relates to a medical system including a pressure measurement system adapted to determine the Fractional Flow Reserve value. 10 Background of the invention In many medical procedures, various physiological conditions present within a body cavity need to be monitored. These physiological conditions are typically physical in nature - such as pressure, temperature, rate-of-fluid flow, and provide the physician or medical technician with critical information as to the status of a patient's condition. 15 One device that is widely used to monitor conditions is the blood pressure sensor. A blood pressure sensor senses the magnitude of a patient's blood pressure, and converts it into a representative signal that is transmitted to the exterior of the patient. 20 In the prior art, it is known to mount a sensor at a distal portion of a so-called sensor wire and to position the sensor by using the sensor wire in a blood vessel in a living body to detect a physical parameter, such as pressure or temperature. The sensor includes elements that are directly or indirectly sensitive to the parameter. 25 One known sensor wire has a typical length of 1.5-2 meter, and comprises a hollow tubing running along a major part of the wire and having an outer diameter in the range of 0.25 0.5 mm, typically approximately 0.35 mm. A core wire is arranged within the tubing and extends along the tubing and often extends out from a distal opening of the tubing. The sensor or sensors is/are preferably arranged in connection with the distal portion of the 30 core wire, e.g. at the distal end of the sensor wire. 6677265_1 (GHMatters) P95276.AU ROSG 2 The present invention is applicable e.g. in relation with a sensor wire of the type described above, but can also be applied to other types of sensor assemblies, e.g. where the sensor is arranged at the distal end of a catheter. 5 In one application the sensor wire of the type described above is used to measure pressure in blood vessels, and in particular in the coronary vessels of the heart, e.g. to identify constrictions in the coronary vessels. This may be performed by determining the so-called Fractional Flow Reserve (FFR) value related to the vessel. The sensor wire is typically inserted by use of an insertion catheter, which in turn is inserted via the femoral vein or 10 the radial artery, and guided by the inserted catheter to the measurement site. In order to power the sensor and to communicate signals representing the measured physiological variable to an external physiology monitor, one or more cables or leads, often denoted microcables, or optical cables, for transmitting the signals are connected to 15 the sensor, and are routed along the sensor wire to be passed out from the vessel to the external physiology monitor, via physical cables or wirelessly. The sensor element further comprises an electrical circuitry, which generally is connected in a Wheatstone bridge-type of arrangement to one or several piezoresistive elements 20 provided on a membrane. As is well known in the art, a certain pressure exerted on the membrane from the surrounding medium will thereby correspond to a certain stretching or deflection of the membrane and thereby to a certain resistance of the piezoresistive elements mounted thereon and, in turn, to a certain output from the sensor element. 25 In US-2006/0009817, which is incorporated herein in its entirety, and which is assigned to the present assignee, an example of such a sensor and guide wire assembly is disclosed. The system comprises a sensor arranged to be disposed in the body, a control unit arranged to be disposed outside the body and a wired connection between the sensor and the control unit, to provide a supply voltage from the control unit to the sensor and to 30 communicate a signal there between. The control unit further has a modulator, for modulating the received sensor signal and a communication interface for wireless communication of the modulated signal. 6677265_1 (GHMatters) P95276.AU ROSG 3 In US-7,724,148, which is incorporated herein in its entirety, and which also is assigned to the present assignee, another example of such a pressure measurement system is disclosed. The pressure sensor wire is adapted to be connected, at its proximal end, to a transceiver unit that is adapted to wirelessly communicate via a communication signal with a 5 communication unit arranged in connection with an external device. In US-6,112,598, which is incorporated herein in its entirety, and assigned to the present assignee, and also in US-7,207,227, further examples of such pressure sensors and guide wire assemblies are disclosed. 10 As briefly discussed above, the human vascular system may suffer from a number of problems. These may broadly be characterised as cardiovascular and peripheral vascular disease. Among the types of disease, atherosclerosis is a particular problem. Atherosclerotic plaque can develop in a patient's cardiovascular system. The plaque can 15 be quite extensive and occlude a substantial length of the vessel. A technique used to identify and measure the extent of a stricture, also denoted lesion, caused by plaque is to measure the pressure inside the vessel in the part of the vessel where the stricture is located. In the prior art there are numerous examples of catheters 20 suitable to perform pressure measurements. Among those may be mentioned US 6,615,667 related to a guidewire provided with a combined flow, pressure and temperature sensor. US-6,565,514 relates to an exemplary measurement system adapted to measure, calculate 25 and display physiological variables related to blood pressure and in particular for calculating the myocardial fractional flow reserve (FFR) being the ratio between the arterial pressure (Pa) and the distal coronary pressure (Pd). US-2006/0052700 relates to a pressure measurement system comprising a pressure sensor 30 guidewire provided with a pressure sensor at its distal end. The guidewire is adapted to be inserted into a vessel. The sensor is adapted to be drawn continuously along a section of 6677265_1 (GHMatters) P95276.AU ROSG 4 the vessel under examination, e.g. by a pull-back device, and the recorded pressure data is mapped on a displayed image of the vessel. Thus, FFR is a measure of coronary lesion severity and is defined as the ratio between 5 distal and aortic blood pressure during maximum hyperemia. In all known systems on the market FFR is calculated using simultaneous pressure readings from two transducers. A pressure guide wire provided with a distal pressure sensor at its distal end which is arranged to measure the pressure at a position distal to the lesion, and a fluid filled pressure catheter connected to an external pressure transducer. 10 Any FFR measurement system using this setup must allow for connection of both pressure transducers which makes the system design and setup complicated since the external pressure transducer must also be connected to the cathlab's own recording system. Any pressure difference between the two transducers must also be removed at the start of the procedure through an equalization procedure. 15 In view of the above reasoning, the inventor has identified a need for a less complicated but still a reliable system and method for determining FFR. Summary of the invention 20 In a first aspect, there is provided a medical system for determining the individual Fractional Flow Reserve (FFR) value for one or more lesions of interest of a blood vessel, the system comprising: an intravascular pressure measurement device for acquiring pressure measurements in the blood vessel during continuous blood flow there through, said 25 pressure measurement device comprising a pressure sensor at its distal portion, wherein said system further comprises an FFR processor adapted to determine the FFR value related to said lesion solely based upon the pressure measurements performed by said pressure sensor, and said intravascular pressure measurement device comprises: 30 an elongated sensor wire having an outer diameter of 0.3-0.5 mm or a catheter, provided with said pressure sensor at its distal end portion, and further provided with a proximal connector at its proximal end, and 6677265_1 (GHMatters) P95276.AU ROSG 5 said FFR processor is located in either: (i) a transceiver unit configured to connect to the elongated sensor wire or catheter via the proximal connector of the sensor wire or catheter, and to wirelessly transfer said FFR value to an external physiology monitor via a communication module, 5 the proximal connector being adapted to be inserted and attached to the transceiver unit, or (ii) a connector unit configured to connect to the elongated sensor wire or catheter via the proximal connector of the sensor wire or catheter, and to transfer said FFR value to an external physiology monitor via a communication cable, the proximal connector being adapted to be inserted and attached to the connector unit. 10 In a second aspect, there is provided a method for monitoring a physiological variable by determining the individual Fractional Flow Reserve (FFR) value for one or more lesions of interest of a blood vessel, the method comprising: a) deploying an intravascular pressure measurement device, provided with a 15 pressure sensor and an FFR processor, for acquiring pressure measurements in the blood vessel during continuous blood flow there through, wherein said intravascular pressure measurement device comprises: an elongated sensor wire having an outer diameter of 0.3-0.5 mm or a catheter, provided with said pressure sensor at its distal end portion, and further provided 20 with a proximal connector at its proximal end, and wherein said FFR processor is located in either: (i) a transceiver unit configured to connect to the elongated sensor wire or catheter via the proximal connector of the sensor wire or catheter, and to wirelessly transfer said FFR value to an external physiology monitor via a communication module, 25 the proximal connector being adapted to be inserted and attached to the transceiver unit, or (ii) a connector unit configured to connect to the elongated sensor wire or catheter via the proximal connector of the sensor wire or catheter, and to transfer said FFR value to an external physiology monitor via a communication cable, the proximal connector being adapted to be inserted and attached to the connector unit. 30 b) determining, using the FFR processor, the FFR value related to said lesion solely based upon the pressure measurements performed by said pressure sensor, and 6677265_1 (GHMatters) P95276.AU ROSG 6 c) using the transceiver unit or the connector unit to transfer the FFR value to the external physiology monitor. Preferred embodiments are set forth in the dependent claims. 5 The present invention relates to a system which only uses the pressure measurements from a single pressure transducer on a pressure guidewire or catheter as source for both the distal and the aortic pressures, enabling FFR calculation using only one transducer. FFR is measured during maximum hyperemia. 10 If hyperemia is induced using continuous intravenous adenosine infusion the ratio between distal and aortic pressure is stable as long as the infusion is running. Utilizing this steady state, FFR can be assessed by the system by first recording a pressure from a position distally to the lesion and to the aortic root, pulling back the transducer and then using the 15 pressure recorded by the same transducer now located in the aorta at the end of the pullback as reference pressure for the whole pullback. In this way FFR can be calculated by the system at the end of the pullback, assuming that the aortic pressure at the end of the pullback is representative for the whole pullback. In other words, a presumption is that the two measured pressure values are obtained essentially during similar states, i.e. the time 20 interval between the points of time when the measurements are performed must not be too long, such that the aortic pressure is relatively stable during the pullback procedure. Thus, the present invention relates to a medical system and a method for FFR measurement using only one pressure transducer. 25 The system and method offer a number of advantages. Among those may be mentioned that there is no need for connection to an aortic pressure transducer in order to perform the FFR measurements, and therefore there is no need for any distal/proximal pressure equalization. 30 It is a single transducer system, preferably without connection to any catheter-lab environment. 6677265_1 (GHMatters) P95276.AU ROSG 7 Thus, the present invention simplifies the procedure of determining FFR. In one advantageous setup the medical system and method according to the present invention may be used in combination with the wireless PressureWireTM AerisTM 5 (trademark owned by the present assignee) system where the proximal end of the pressure wire is connected to a transceiver unit that wirelessly communicates to a remote physiology monitor or a standard PC. Then a low cost, off the shelf, FFR measurement system is achieved. In such a set-up it would also be possible to present the FFR-value at a display provided at the transceiver unit. 10 The present invention is generally applicable for any type of pressure measurement device that comprises a pressure sensor at its distal portion. The pressure measurement device may e.g. be a pressure wire of the type referred to above, or a thin catheter provided with a pressure sensor at its distal portion, or a rapid-exchange catheter with a pressure sensor at 15 its distal end, to mention some examples. In one embodiment the pressure sensor comprises a piezoresistive element provided on a membrane on a chip arranged at the distal portion of the pressure measurement device. In another embodiment the pressure sensor is an optical sensor which is connected to an FFR 20 processor via optical cables. In still further embodiments the present invention may be embodied by using any kind of pressure sensor arranged at the distal end of a pressure measurement device provided that the distal end of the device has a sufficiently small dimension making it possible to insert it into the vessel of interest. 25 When the severity of a lesion has been identified the treatment of the area may be by any of the usual therapeutic procedures, including localised delivery of a therapeutic agent, delivery of a stent, brachy therapy, ablation of selected tissue etc. Furthermore, the pressure sensor guidewire may additionally comprise angioplasty balloons or sleeves. 30 Short description of the appended drawings Figure 1 is a block diagram schematically illustrating the present invention. 6677265_1 (GHMatters) P95276.AU ROSG 8 Figure 2 is a block diagram schematically illustrating a first embodiment of the present invention. Figure 3 is a block diagram schematically illustrating a second embodiment of the present invention. 5 Figure 4 is a block diagram schematically illustrating an embodiment of the present invention. Figure 5 is a diagram and a drawing illustrating the present invention. Figure 6 is a flow diagram illustrating the present invention. Figure 7 is a flow diagram illustrating an embodiment of the present invention. 10 Detailed description of preferred embodiments of the invention The present invention will now be described in detail with references to the appended drawings. 15 Figure 1 is a block diagram illustrating a medical system, according to the present invention, for determining the individual Fractional Flow Reserve (FFR) value for one or many lesions of interest of a blood vessel. The system comprises an intravascular pressure measurement device for acquiring pressure measurements in the blood vessel, e.g. a coronary vessel, during continuous blood flow there through. The pressure measurement 20 device comprises a pressure sensor at its distal portion. The system further comprises an FFR processor adapted to determine the FFR value related to said lesion solely based upon the pressure measurements performed by the pressure sensor. The pressure measurement device further comprises a timing unit adapted to control the 25 timing of the pressure measurements and the timing unit is adapted to control the pressure measurements such that a first pressure value (Pd) is measured distally said lesion, and a second pressure value (Pa) is measured proximally the lesion close to the aorta. Herein, the control of the pressure measurements should be interpreted as to ensure that corresponding first and second pressure values, Pd and Pa, respectively are related to each 30 other, i.e. obtained from the same measurement session (pullback procedure). The pullback procedure, which is to be discussed below, ends when it is determined that the pressure sensor is in the aorta which may be visible at X-ray when the X-ray opaque distal 6677265_1 (GHMatters) P95276.AU ROSG 9 end with the sensor element is just outside the opening of a guiding catheter placed in aorta. The first pressure value (Pd) is measured at a first point of time tI and the second pressure value (Pa) is measured at a second point of time t2, and that the time difference t2-t1 is 5 greater than a first predetermined time value but less than a second predetermined time value. The time difference is typically in the interval of 5-10 seconds. The FFR-processor preferably includes a memory where the measured pressure values are stored such that related values, i.e. values from the same measurement session, may be 10 retrieved. The FFR-processor may further include a calculating unit for calculating the FFR value, i.e. forming the quotient between related values of Pd and Pa. As described in the background section the intravascular pressure measurement device preferably may comprise an elongated sensor wire having an outer diameter of 0.3-0.5 mm 15 and provided with the pressure sensor at its distal end portion, and is further provided with a proximal connector at its proximal end. This is schematically illustrated in figures 2 and 3. As an alternative, as also discussed in the background section, the pressure measurement device may comprise a catheter, or a rapid-exchange catheter, provided with the pressure sensor at its distal end portion. 20 According to an embodiment of the invention, which is illustrated by figure 4, the pressure measurement device comprises a pull-back device adapted to pull-back the sensor wire from a first position (P1) where the pressure sensor senses a first pressure value (Pd) to a second position (P2) where the pressure sensor senses a second pressure value (Pa). The 25 pull-back speed may be adjusted such that the pull-back procedure lasts less than a second predetermined time value, which preferably is in the interval of 5-10 seconds. Whilst in normal circumstances the sensor guide wire provided with a pressure sensor is inserted manually, it is intended that when performing vascular measurements the pressure 30 sensor guide wire is pulled back relative to a predetermined start position, preferably by using an electro-mechanical pull-back device e.g. coupled directly, or indirectly, to the 6677265_1 (GHMatters) P95276.AU ROSG 10 sensor wire. EP-1291034 discloses a typical pull-back mechanism that may be used in connection with the sensor guide wire when implementing the present invention. The sensor guide wire is inserted such that a start position is reached when the pressure sensor is positioned distally the lesion to be measured. 5 The pull-back device may be controlled by a processing means (not shown) via a pull back device interface (not shown). The system software accesses user-defined configuration files to get the necessary information about controlling the pull-back interface. Data sampling rate, recording duration and pre-selected retraction rate are taken 10 into consideration for adjusting the pull-back speed. The speed may naturally be varied in dependence of the specific situation but as a general rule the speed is adjusted such that the pull-back procedure lasts for approximately 5-10 seconds. The medical system according to the present invention may also be applied by manually 15 pulling back the sensor wire (or catheter) from a first position (P1) where the pressure sensor senses a first pressure value (Pd) to a second position (P2) where the pressure sensor senses a second pressure value (Pa). The pull-back speed may such that the pull back procedure lasts less than a second predetermined time value, which preferably is in the interval of 5-10 seconds. 20 Figure 2 is a block diagram schematically illustrating a first embodiment of the present invention. According to the first embodiment the measurement device further comprises a transceiver unit into which the proximal connector is adapted to be inserted and attached, and that the transceiver unit comprises the FFR-processor. Preferably the transceiver unit 25 comprises a communication module (not shown in the figure) adapted to wirelessly transfer the FFR-value to an external device. The transceiver unit may include a presentation unit for displaying said FFR-value. As an alternative, the FFR-processor is arranged remote from the pressure measurement 30 device, e.g. in an external device, and the detected pressure values, Pa and Pd, are transmitted to the FFR-processor for further processing. 6677265_1 (GHMatters) P95276.AU ROSG 11 Figure 3 is a block diagram schematically illustrating a second embodiment of the present invention. According to the second embodiment the measurement device further comprises a connector unit into which the proximal connector of the sensor wire is adapted to be inserted and attached. The connector unit comprises the FFR-processor. The 5 connector unit comprises a communication cable adapted to transfer the FFR-value to an external device, and that the connector unit may comprise a presentation unit for displaying the FFR-value. As an alternative, the FFR-processor is arranged remote from the pressure measurement 10 device, e.g. in an external device, and the detected pressure values, Pa and Pd, are transmitted, via the cable, to the FFR-processor for further processing. Figure 5 is a diagram and a drawing illustrating the present invention. 15 The graph, above in figure 5, shows the pressure in relation to time, or in relation to the position of the pressure sensor. Below in figure 5 is shown a simplified drawing of a coronary vessel and aorta, and a sensor wire provided with a pressure sensor inserted into the vessel such that the pressure sensor is positioned distally a lesion. In the position P1, the pressure sensed by the 20 pressure sensor is Pd, which is denoted by an "X" in the graph. The pressure sensor is then pulled back to position P2. The pullback is started at the time tI and ends at time t2. In position P2, i.e. when the pressure sensor is in the aorta, or close to where the coronary vessel opens into the aorta, the pressure sensor senses the pressure, which is Pa, and which 25 also is denoted by an "X" in the graph. In some occasions it might be of interest to monitor how the pressure varies in the coronary vessel during the entire, or during parts of, the pullback procedure. This pressure profile could then be presented in the graph as a curve between Pd and Pa. 30 6677265_1 (GHMatters) P95276.AU ROSG 12 In the graph the aortic pressure Pa is denoted by a straight dashed line which essentially represents the mean aortic pressure. The aortic pressure naturally changes in dependence of the pumping action of the heart. 5 The present invention also relates to a method for determining the individual Fractional Flow Reserve (FFR) value for one or many lesions of interest of a blood vessel. The method is schematically illustrated by the flow diagram of figure 6. The method comprising: 10 a) deploying an intravascular pressure measurement device, provided with a pressure sensor, for acquiring pressure measurements in the blood vessel during continuous blood flow there through, b) determining the FFR value related to said lesion solely based upon the pressure measurements performed by said pressure sensor. 15 With references to figure 7 the method in particular comprises controlling the timing of the pressure measurements such that a first pressure value (Pd) is measured distally the lesion, and a second pressure value (Pa) is measured proximally the lesion close to Aorta. The first pressure value (Pd) is measured at a first point of time tI and the second pressure 20 value (Pa) is measured at a second point of time t2, and that the time difference t2-t1 is greater than a first predetermined time value but less than a second predetermined time value. Preferably, these time values are 5 seconds and 10 seconds, respectively. The method comprises pulling back the pressure sensor from a first position where the pressure sensor senses the first pressure value (Pd) to a second position where the pressure 25 sensor senses the second pressure value (Pa) and that the pull-back speed is adjusted such that the pull-back procedure lasts less than the second predetermined time value, which preferably is in the interval of 5-10 s. It should be noted that the described method is equally applicable as a manual method or 30 as a method where a pull-back device is used. If a manual method is used the physician manually pulls back the sensor wire. In that case the physician firstly inserts the sensor wire (or catheter) to a position where the pressure sensor is at a location distally the 6677265_1 (GHMatters) P95276.AU ROSG 13 suspected lesion. Thereafter Pd is registered, e.g. automatically or by manually pressing a button or similar, and the sensor wire is pulled-back at a pull-back speed such that the second pressure value (Pa) may be registered, automatically or manually, 5-10 seconds after the registration of Pd. Then, the FFR-value is calculated using the registered Pd and 5 Pa values as described above in connection with the description the medical system. The present invention is not limited to the above-described preferred embodiments. Various alternatives, modifications and equivalents may be used. Therefore, the above embodiments should not be taken as limiting the scope of the invention, which is defined 10 by the appending claims. In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive 15 sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention. It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general 20 knowledge in the art, in Australia or any other country. 6677265_1 (GHMatters) P95276.AU ROSG

Claims

1. A medical system for determining the individual Fractional Flow Reserve (FFR) value for one or more lesions of interest of a blood vessel, the system comprising: 5 an intravascular pressure measurement device for acquiring pressure measurements in the blood vessel during continuous blood flow there through, said pressure measurement device comprising a pressure sensor at its distal portion, wherein said system further comprises an FFR processor adapted to determine the 10 FFR value related to said lesion solely based upon the pressure measurements performed by said pressure sensor, said intravascular pressure measurement device comprises: an elongated sensor wire having an outer diameter of 0.3-0.5 mm or a catheter, provided with said pressure sensor at its distal end portion, and further provided 15 with a proximal connector at its proximal end, and said FFR processor is located in either: (i) a transceiver unit configured to connect to the elongated sensor wire or catheter via the proximal connector of the sensor wire or catheter, and to wirelessly transfer said FFR value to an external physiology monitor via a communication module, the proximal connector being adapted to be inserted and attached to the transceiver unit, or 20 (ii) a connector unit configured to connect to the elongated sensor wire or catheter via the proximal connector of the sensor wire or catheter, and to transfer said FFR value to an external physiology monitor via a communication cable, the proximal connector being adapted to be inserted and attached to the connector unit. 25

2. The system according to claim 1, wherein said pressure measurement device further comprises a timing unit adapted to control the timing of the pressure measurements. 30

3. The system according to claim 2, wherein said timing unit is adapted to control the pressure measurements such that a first pressure value is measured distally said lesion, and a second pressure value is measured proximally said lesion close to an aorta. 6677265_1 (GHMatters) P95276.AU ROSG 15

4. The system according to claim 3, wherein said first pressure value is measured at a first point of time tI and the second pressure value is measured at a second point of time t2, and that the time difference t2-t1 is greater than a first predetermined time value but less than a second predetermined time value. 5

5. The system according to claim 1 or 2, wherein said pressure measurement device is adapted to be manually pulled-back from a first position where said pressure sensor senses a first pressure value to a second position where the pressure sensor senses a second pressure value, and that said sensed pressure values are adapted to be registered by 10 said FFR processor.

6. The system according to claim 1 or 2, wherein said pressure measurement device comprises a pull-back device adapted to pull-back said sensor wire or catheter from a first position where said pressure sensor senses a first pressure value to a second 15 position where the pressure sensor senses a second pressure value.

7. The system according to claim 6, wherein a pull-back speed is adjusted at said pull-back device such that the pull-back procedure lasts less than 5 - 10 s. 20

8. The system according to any one of claims I to 7, wherein FFR processor is located in the transceiver unit.

9. The system according to claim 8, wherein said transceiver unit comprises a presentation unit for displaying said FFR value. 25

10. The system according to any one of claims I to 7, wherein said FFR processor is located in the connector unit.

11. The system according to claim 10, wherein said connector unit comprises a 30 presentation unit for displaying said FFR value.

12. A method for monitoring a physiological variable by determining the 6677265_1 (GHMatters) P95276.AU ROSG 16 individual Fractional Flow Reserve (FFR) value for one or more lesions of interest of a blood vessel, the method comprising: a) deploying an intravascular pressure measurement device, provided with a pressure sensor and an FFR processor, for acquiring pressure measurements in the blood 5 vessel during continuous blood flow there through, wherein said intravascular pressure measurement device comprises an elongated sensor wire having an outer diameter of 0.3-0.5 mm or a catheter, provided with said pressure sensor at its distal end portion, and further provided with a proximal connector at its proximal end, and 10 wherein said FFR processor is located in either: (i) a transceiver unit configured to connect to the elongated sensor wire or catheter via the proximal connector of the sensor wire or catheter, and to wirelessly transfer said FFR value to an external physiology monitor via a communication module, the proximal connector being adapted to be inserted and attached to the transceiver unit, or (ii) a connector unit configured to 15 connect to the elongated sensor wire or catheter via the proximal connector of the sensor wire or catheter, and to transfer said FFR value to an external physiology monitor via a communication cable, the proximal connector being adapted to be inserted and attached to the connector unit, b) determining, using the FFR processor, the FFR value related to said lesion 20 solely based upon the pressure measurements performed by said pressure sensor, and c) using the transceiver unit or the connector unit to transfer the FFR value to the external physiology monitor. 25

13. The method according to claim 12, wherein the method comprises controlling the timing of the pressure measurements such that a first pressure value is measured distally said lesion, and a second pressure value is measured proximally said lesion close to an aorta. 30

14. The method according to claim 13, wherein said first pressure value is measured at a first point of time tI and the second pressure value is measured at a second 6677265_1 (GHMatters) P95276.AU ROSG 17 point of time t2, and that the time difference t2-t1 is in the interval of 5-10 seconds.

15. The method according to any one of claims 12-14, wherein the method comprises pulling back said pressure sensor from a first position where said pressure 5 sensor senses a first pressure value to a second position where the pressure sensor senses a second pressure value.

16. The method according to claim 15, wherein the method further comprises monitoring a variation in pressure in the blood vessel during the entire, or during parts of, 10 the pullback procedure. 6677265_1 (GHMatters) P95276.AU ROSG