Patent Description:
The severity of a stenosis or lesion in a blood vessel may be assessed by obtaining proximal and distal pressure measurements relative to the given stenosis and using those measurements for calculating a value of the Fractional Flow Reserve (FFR). FFR is defined as the ratio of a first pressure measurement (Pd) taken on the distal side of the lesion to a second pressure measurement taken on the proximal side of the lesion usually within the aorta (Pa). Conventionally, a sensor is placed on the distal portion of a guidewire or FFR wire to obtain the first pressure measurement Pd, while an external pressure transducer is fluidly connected via tubing to a guide catheter for obtaining the second or aortic (AO) pressure measurement Pa. Calculation of the FFR value provides a lesion specific index of the functional severity of the stenosis in order to determine whether the blockage limits blood flow within the vessel to an extent that treatment is needed. An optimal or normal value of FFR in a healthy vessel is <NUM>, while values less than about <NUM> are generally deemed significant and in need of an interventional treatment. Common interventional treatment options include balloon angioplasty and/or stent implantation.

Conventional FFR devices require systems to process and display information received from the FFR device. Such systems generally include a processing system to process and record information and a console or display to display information to the physician. Such processing and display systems can be expensive and need to be integrated with hospital recording systems to keep accurate medical records. The cost of these separate systems used for FFR only can be prohibitive.

FFR procedures are generally performed in a catheterization laboratory ("cath-lab") of a hospital. A catheterization laboratory is an examination room in a hospital or clinic with diagnostic imaging equipment used to visualize the arteries of the heart and the chambers of the heart and treat any stenosis or abnormality found. A typical catheterization laboratory generally includes equipment, including a hemodynamic monitoring system. Hemodynamic monitoring systems directly measure blood pressure from inside the veins, heart and arteries. They also measure blood flow and how much oxygen is in the blood. In addition, these systems have interfaces to help document diagnostic catheterizations, coronary, peripheral and electrophysiology (EP) procedures. Standard processing systems for receiving data from a FFR device and communicating data to a conventional hemodynamic monitoring system with pressure displays are described in <CIT> and in <CIT>.

It would be desirable to use existing hemodynamic monitoring systems to record and display information from an FFR device, without the need for a software addition to the hemodynamic monitoring system.

Embodiments hereof relate to a processing system for receiving data from a Fractional Flow Reserve (FFR) device and communicating data to a conventional hemodynamic monitoring system having pressure displays. The processing system includes a first data input for receiving a proximal pressure measurement (PA) signal from an aortic pressure measurement device, a second data input for receiving a distal pressure measurement (PD) signal from a distal pressure measurement device, a processor for computing an FFR ratio from the proximal pressure measurement signal and the distal pressure measurement signal, and an FFR converter for converting the FFR ratio to a pressure format such that the FFR ratio reads on the conventional hemodynamic monitoring system as a pressure. The FFR converter in some embodiments multiplies the FFR ratio by <NUM> such that the pressure format is in a similar scale as the proximal pressure measurement and the distal pressure measurement. The processing system further includes a first data output signal for transmitting the proximal pressure measurement signal to the conventional hemodynamic monitoring system, a second data output signal for transmitting the distal pressure measurement signal to the conventional hemodynamic monitoring system, and a third data output signal for transmitting the FFR ratio in the pressure format to the conventional hemodynamic monitoring system. The processing system is separate from the conventional hemodynamic monitoring system.

Embodiments hereof also relate to a method of utilizing a conventional hemodynamic monitoring system to display data during a Fractional Flow Reserve (FFR) measurement procedure. The method includes receiving a proximal pressure measurement (PA) signal, receiving a distal pressure measurement (PD) signal, and processing the proximal pressure measurement signal and the distal pressure measurement signal to compute an FFR ratio. The method further includes converting the FFR ratio to a pressure format such that the FFR ratio reads on the conventional hemodynamic system as a pressure. In some embodiments, the converting step includes multiplying the FFR ratio in a decimal format by <NUM> such that the pressure format is in a similar scale as the proximal pressure measurement and the distal pressure measurement. The method further includes transmitting the proximal pressure measurement signal, the distal pressure measurement signal, and the converted FFR ratio in the pressure format to the conventional hemodynamic monitoring system.

Specific embodiments of the present invention are now described with reference to the figures, wherein like reference numbers indicate identical or functionally similar elements. The terms "distal" and "proximal" are used in the following description with respect to a position or direction relative to the treating clinician when describing an object or device manipulated by the clinician. "Distal" and "distally" are positions distant from or in a direction away from the clinician. "Proximal" and "proximally" are positions near or in a direction toward the clinician. The terms "distal" and "proximal", when used with respect to a position in a vessel refer to a position or direction relative to the direction of blood flow. Accordingly,
"distal" and "distally" are positions downstream of a reference position, and "proximal" and "proximally" are positions upstream of the reference position.

Although the description of the invention is in the context of treatment of blood vessels such as the coronary arteries, the invention may also be used in any other body passageways where it is deemed useful such as but not limited to peripheral arteries, carotid arteries, renal arteries, and/or venous applications.

With reference to <FIG>, a conventional catheterization laboratory generally may include, but is not limited to, a patient table <NUM>, an imaging device <NUM>, and a hemodynamic monitoring system <NUM>. Hemodynamic monitoring system <NUM> may include, for example and not by way of limitation, a data acquisition unit <NUM>, a processor <NUM>, display monitors <NUM>, and cath-lat) display monitors <NUM>, as shown in <FIG>. Other systems and sub-systems may also be included in a catheterization laboratory.

<FIG> shows a schematic illustration of some equipment in a catheterization laboratory of <FIG> according to an embodiment hereof. In particular, <FIG> shows patient table <NUM>, hemodynamic monitoring system <NUM>, an FFR measurement device <NUM> including a distal pressure measurement device <NUM>, a proximal or aortic pressure measurement device <NUM>, and a processing unit <NUM>. As in <FIG>, hemodynamic monitoring system <NUM> includes a data acquisition unit <NUM>, a processor <NUM>, display monitors <NUM>, and cath-lab display monitors <NUM>. Signals from distal pressure measurement device <NUM> and aortic pressure measurement device <NUM> as sent to processing unit <NUM> as indicated by arrows <NUM>, <NUM>, respectively, and as explained in more detail below. Output signals from processing unit <NUM> are sent to data acquisition unit <NUM> of hemodynamic monitoring system <NUM> as indicated by arrow <NUM>. Data acquisition unit <NUM> sends data to hemodynamic monitoring system <NUM>, as indicated by arrow <NUM>. Further, information from hemodynamic monitoring system <NUM> is displayed on cathlat) display monitors, as indicated by arrow <NUM>.

As explained above, hemodynamic monitoring systems <NUM> are conventional devices generally found in catheterization laboratories. Conventional hemodynamic monitoring systems include, but are not limited to MAC-LAB IT, XT, and XT1 available from GE Healthcare USA, McKesson Cardiology Hemo available from McKesson, Merge Hemo available from Merge Healthcare, Xper Physiomonitoring available from Phillips Healthcare, and AXIOM Sensis XP Hemo available from Siemens Healthcare. Hemodynamic monitoring system <NUM> is not limited to the listed examples. Data acquisition unit <NUM> is a data acquisition unit associated with hemodynamic monitoring system <NUM>. Data acquisition unit <NUM> provides ports for attachment to cables for devices which directly measure blood pressure from inside the veins, heart and arteries, and transmit such data to processor <NUM> of hemodynamic monitoring system <NUM>. For example, and not by way of limitation, the GE Healthcare MAC-LAB hemodynamic recording system may include a TRAM module data acquisition unit.

As explained above, conventional hemodynamic monitoring systems <NUM> are used to measure, record, and display intra-arterial blood pressure (IBP) and other properties, such as the amount of oxygen in the blood. However, conventional hemodynamic monitoring systems <NUM> cannot be used to measure and display FFR values during FFR procedures. Instead, either a separate system or a software upgrade to conventional systems is required. In the embodiment of <FIG>, however, a conventional hemodynamic monitoring system <NUM> receives data from interface or processing unit <NUM> such that FFR measurements may be recorded and displayed through hemodynamic monitoring system <NUM> and display monitors <NUM>, <NUM>. Accordingly, as shown schematically in <FIG>, processing unit <NUM> receives data from FFR measurement device <NUM>. Accordingly, for the purposes of this application, the term "conventional hemodynamic monitoring system" means a hemodynamic monitoring system that does not include specific FFR recording or displaying capabilities. Accordingly, hemodynamic systems that include such FFR recording or displaying capabilities or hemodynamic systems that have had a software upgraded to include such capabilities are not "conventional hemodynamic monitoring systems.

FFR measurement device <NUM> can be any device or system used to measure pressures to be used to calculate FFR. As explained above, FFR measurement device <NUM> generally includes distal pressure measurement (also referred to as Pd) device <NUM>. In some embodiments, FFR pressure measurement device may also include aortic or proximal pressure measurement (also referred to as Pa) device <NUM>. However, whether aortic pressure measurement device <NUM> is considered part of FFR pressure measurement device <NUM> or is considered a separate device does not affect the present disclosure. Aortic pressure measurement device <NUM> generally includes a guide catheter inserted into the aorta with an external AO pressure transducer. However, other devices can be used to for measuring the aortic or proximal pressure. Distal pressure measurement device <NUM> may be, for example and not by way of limitation, a guidewire with a pressure sensor disposed at a distal end thereof, a catheter configured to take a pressure measurement of blood distal to the target lesion, or any other device suitable to take the distal pressure measurement. For example, and not by way of limitation, distal pressure measurement device <NUM> may be any of the devices described in <CIT>; <CIT>; and <CIT>, each of which is incorporated by reference herein in its entirety.

<FIG> shows a block diagram of an embodiment of how processing unit <NUM> interacts with distal pressure measurement device <NUM>, aortic pressure measurement device <NUM>, and data acquisition unit <NUM> of hemodynamic monitoring system <NUM>. In particular, processing unit <NUM> receives inputs from distal pressure measurement device <NUM> and aortic pressure measurement device <NUM>. Processing unit <NUM> may receive such inputs by a cable connection to distal pressure measurement device <NUM> and aortic pressure measurement device <NUM>. Alternatively, one or both of distal pressure measurement device <NUM> and aortic pressure measurement device <NUM> may include a wireless transmitter to wirelessly transmit a signal to processing unit <NUM>, which in such an embodiment includes a wireless receiver (not shown).

After processing the data received from distal pressure measurement device <NUM> and aortic pressure measurement device <NUM>, described in more detail below, processing unit <NUM> outputs data to data acquisition unit <NUM> of hemodynamic monitoring system <NUM>. In particular, and as described in more detail below, a typical data acquisition unit <NUM> of hemodynamic monitoring system <NUM> includes at least three (<NUM>) pressure inputs or ports P1, P2, P3, as shown in <FIG>. Pressure ports P1, P2, P3 are configured to receive data regarding blood pressure from devices typically used in catheterization laboratories, for example, and not by way of limitation, devices which measure intra-arterial blood pressure. Data acquisition unit <NUM> and processor <NUM>, or, more generally, hemodynamic monitoring system <NUM>, process the pressure data and display such pressure data on cath-lab display monitors <NUM>. Accordingly, hemodynamic monitoring system <NUM> is configured to receive such pressure data from transducers in millivolts (mV) and to display such data as representative of pressure in millimeters of mercury (mmHg).

Accordingly, <FIG> shows a block diagram of the main elements of a processing unit <NUM> using a digital approach. <FIG> illustrates the steps in the general operation of processing unit <NUM>. Processing unit <NUM> includes a first input <NUM>a for receiving a signal from aortic pressure measurement device <NUM> and a second input <NUM>b for receiving signals from distal pressure measurement device <NUM>. However, the specific devices from which inputs receive signals may be varied depending on the FFR measurement device <NUM>. For example, and not by way of limitation, the distal pressure measurement device in some embodiments may also measure proximal pressure such that only a single input is needed in processing unit <NUM>. First input <NUM>a and second input <NUM>b may be any input suitable for use with aortic pressure measurement device <NUM> and distal pressure measurement device <NUM>. For example, and not by way of limitation, first input <NUM>a and second input <NUM>b may each be a receptacle, socket or port configured to receive a plug or prong at an end of a cable coupled to aortic pressure measurement device <NUM> and distal pressure measurement device <NUM>, respectively. In another non-limiting example, first input 131a and/or second input 131b may be a wireless receiver configured to receive a wireless signal from aortic pressure measurement device <NUM> and/or distal pressure measurement device <NUM>, respectively.

As shown in <FIG> and <FIG>, the following steps are taken by a controller <NUM> of processing unit <NUM>. In particular, in step <NUM>, controller <NUM> receives a signal (Pd) from distal pressure measurement device <NUM> through a distal pressure measurement signal conditioner <NUM> and an analog-to-digital converter <NUM>. Similarly, in step <NUM>, controller <NUM> receives a signal (Pa) from aortic pressure measurement device <NUM> through an aortic pressure measurement signal conditioner <NUM> and an analog-to-digital converter <NUM>. Analog-to-digital converters <NUM>, <NUM> may not be included in processing unit <NUM>. In particular, if the signals from distal pressure measurement device <NUM> and/or aortic pressure measurement device are received wirelessly, such signals may be converted to digital signals before being is sent to processing unit <NUM>. For example, and not by way of limitation, the signal from distal pressure measurement device <NUM> may be converted to a digital signal within FFR measurement device <NUM> and then sent wirelessly to processing unit <NUM>. Signal conditioners <NUM>, <NUM> may be any devices or processes used to make the signals received by processing unit suitable for processing. For example and not by way of limitation, signal conditioners <NUM>, <NUM> may condition the signals from distal pressure measurement device <NUM> and aortic pressure measurement device <NUM> through amplification, filtering, converting, range matching, isolation, and other similar processes or devices.

The signal from aortic pressure aortic pressure measurement device <NUM> is used both to calculate Pa, as described in more detail below (steps <NUM>, <NUM>), and to calculate FFR (step <NUM>). Similarly, the signal from distal pressure measurement device <NUM> is used both for Pd, as described in more detail below (steps <NUM>, <NUM>), and to calculate FFR (step <NUM>). In step <NUM>, controller <NUM> calculates the FFR ratio. As explained above, the FFR ratio is a ratio of the distal pressure in relation to the aortic pressure. Thus, FFR is calculated as Pd divided by Pa. Accordingly, FFR is a ratio without units. Further, since the distal pressure is generally less than the aortic pressure, the FFR ratio is generally between <NUM> and <NUM>, and more particularly, between <NUM> and <NUM>.

Step <NUM> shown in <FIG> is an optional step of applying a correction factor to the calculated FFR. Step <NUM> is optional because the correction factor is not needed for a guidewire-based distal pressure measurement device. However, in some instances, with a catheter based distal pressure measurement device <NUM>, it may be necessary to apply a correction factor to the FFR. This is due to the fact that a catheter-based distal pressure measurement device <NUM> may be larger in cross-section than a guidewire-based distal pressure measurement device <NUM>. In such a situation, the larger crossing profile of the device itself may cause an obstruction and artificially increase the pressure drop across the lesion. Accordingly, in such a situation, the distal pressure measured may be lower than the distal pressure measured across the identical lesion with a guidewire-based distal pressure measurement device <NUM>. Such an artificially lower distal pressure would also result in an artificially low FFR ratio. Thus, comparing an FFR measurement with a catheter-based distal pressure measurement device with traditional values of FFR with a guidewire-based distal pressure measurement device would result in interventional procedures for lesions that traditionally would not require intervention. Accordingly, in step <NUM>, a correction factor CF may be applied to the calculated FFR. Such a correction factor CF is calculated using clinical data, mathematical formulas, or a combination of both. In another embodiment, the correction factor may instead be applied to the distal pressure measurement Pd. Applying the correction factor to the distal pressure measurement Pd provides for the correct value for FFR and also provides a distal pressure Pd that is consistent with the distal pressure that would have been obtained with a guidewire-based distal pressure measurement device. In such a situation, the correction factor CFPd may be applied after the digital pressure signal is received but prior to calculating FFR, as indicated in step <NUM>a of <FIG>. If CFPd is used to correct the distal pressure measurement Pd, the following formula would be used:
<MAT>
<MAT>
<MAT>
<MAT>.

Many conventional hemodynamic monitoring systems do not include the ability to apply a correction factor to the FFR calculation or to the distal pressure measurement Pd. Thus, processing system <NUM> as described herein provides the additional benefit of being compatible with a catheter-based distal pressure measurement device <NUM> without the need for costly software upgrades to conventional hemodynamic monitoring systems or the purchase of a separate system just for FFR measurements.

As explained in more detail below, the present application describes displaying FFR on a device configured to display blood pressure. Accordingly, in order to be meaningfully displayed, FFR should be in the same range or scale as normally observed for blood pressure. Most conventional hemodynamic recording systems do not have the ability to individually control the scale of the displays for P1, P2, and P3. In such systems, the graph displayed by cath-lab monitors <NUM> is generally from <NUM> to <NUM>, as shown by the vertical axis in <FIG>. However, with FFR calculated as a ratio between <NUM> and <NUM>, displaying FFR on a scale of <NUM> to <NUM> would be hard to distinguish. Thus, in such cases, step <NUM> controller <NUM> converts FFR to a number from <NUM> to <NUM>, although generally it will be at least <NUM>. This is done by multiplying the FFR ratio by <NUM>. For example, and not by way of limitation, if the aortic pressure Pa is <NUM> mmHg and the distal pressure Pd is <NUM> mmHg, controller <NUM> will calculate FFR as <NUM> in step <NUM>. Controller <NUM> will further multiply <NUM> by <NUM> in optional step <NUM> such that FFR can be displayed as <NUM> mmHg in the same range as the aortic and distal pressures, as explained in more detail below. If FFR were displayed as <NUM>, the FFR value would not be distinguishable in the graph of FFR on the cath-lab display monitors <NUM> due to the scale used for pressure readings, as will be apparent below. Some conventional hemodynamic recording systems allow a user to select individual scales for P1, P2, and P3. In such a situation, a scale of <NUM> to <NUM> can be used for P3 while the conventional scale of <NUM> to <NUM>, as shown in <FIG>, can be used for P1 and P2. In such a situation, step <NUM> is not necessary.

In step <NUM>, the converted FFR value is converted to a "pressure format". The term "pressure format" as used herein means the format that conventional hemodynamic monitoring systems use to record and display pressures in mmHg. Thus, for example, the FFR ratio (which does not have a unit of measure) will be displayed on cath-lab monitors <NUM> as <NUM> mmHg on P3 (or <NUM> mmHg if step <NUM> is not utilized). Most pressure transducers in use conform to the ANSI/AAMI BP22-<NUM> standard for blood pressure transducers, accepting an excitation voltage of <NUM> to <NUM> VRM5 at a frequency of <NUM> to <NUM>, and having a sensitivity of <NUM>µV/V/mmHg (<NUM>µV output per volt of excitation voltage per mmHg of pressure), an input impedance greater than <NUM> ohms, an output impedance smaller than <NUM>,<NUM> ohms, and a zero balance within ±<NUM> mmHg. Accordingly, the transducer aortic pressure measurement device <NUM> generally will conform to ANSI/AAMI BP22-<NUM>. The transducers used in distal pressure measurement device <NUM> may conform to ANSI/AAMI BP22-<NUM>, but need not. In particular, if controller <NUM> knows the pressure that corresponds to the signal it receives from distal pressure measurement device <NUM>, then that is sufficient for performing the functions of controller <NUM>. However, in order to properly communicate with hemodynamic monitoring system <NUM>, the outputs from processing unit <NUM> must be in the above-referenced "pressure format", and such conventional hemodynamic monitoring systems <NUM> generally use this ANSI/AAMI BP22-<NUM>. Thus, the outputs from processing unit <NUM> are in mV such that they can be recorded and displayed as mmHg in hemodynamic monitoring system <NUM>. Thus, for the FFR ratio to be displayed in "pressure format", the signal sent to hemodynamic monitoring system <NUM> needs to be the signal that would have been produced by a pressure transducer detecting a blood pressure of the value of the converted FFR. For example, and not by way of limitation, for a transducer sensitivity of <NUM>µV/V/mmHg, an excitation voltage of <NUM> V and a pressure of <NUM> mmHg, a pressure transducer will output a differential voltage of (<NUM>µV/V/mmHg)×(<NUM> V)×(<NUM> mmHg), or <NUM> mV. For the same combination of sensitivity, excitation voltage and pressure, the interface will also output the same differential voltage of <NUM> mV. This differential voltage can be expressed algebraicly as: VEXC×SENS×FFR, where VEXC is the root-mean-square (RMS) differential voltage across the excitation terminals, SENS is the transducer sensitivity which the hemodynamic monitoring system <NUM> is configured to work with, and FFR is the converted FFR value. Controller <NUM> also emulates the input and output impedances of a pressure transducer. In summary, in step <NUM>, controller <NUM> computes the equivalent differential pressure transducer output voltage as the product of the transducer sensitivity, excitation voltage and converted FFR value, and computes an appropriate digital value that is proportional to the equivalent differential voltage.

After controller <NUM> has converted the FFR value to a pressure format, controller <NUM> sends the digital value to a digital-to-analog converter <NUM>, as shown in <FIG> and step <NUM> in <FIG>.

As described above, in step <NUM>, controller <NUM> receives a signal from distal pressure measurement device <NUM> through distal pressure measurement signal conditioner <NUM> and analog-to-digital converter <NUM> (if necessary, see paragraph <NUM> above). In step <NUM>, controller <NUM> computes the digital value for the measured distal blood pressure. Step <NUM> is similar to step <NUM>, except that instead of an FFR value, the measured distal blood pressure from distal pressure measurement device <NUM> is used. Controller <NUM> then sends this digital value to a digital-to-analog converter <NUM>, as shown in <FIG> and step <NUM> in <FIG>.

Similarly, and also as described above, in step <NUM>, controller <NUM> receives a signal from aortic pressure measurement device <NUM> through aortic pressure measurement signal conditioner <NUM> and analog-to-digital converter <NUM>. In step <NUM>, controller <NUM> computes the digital value for the measured aortic blood pressure. Step <NUM> is similar to step <NUM>, except that instead of an FFR value, the measured aortic pressure value from aortic pressure measurement device <NUM> is used. Controller <NUM> then sends this digital value to a digital-to-analog converter <NUM>, as shown in <FIG> and step <NUM> in <FIG>.

In step <NUM>, the signals from digital-to-analog converters <NUM>, <NUM>, and <NUM> are sent to hemodynamic monitoring system <NUM>. In an embodiment, the signals from digital-to-analog converters <NUM>, <NUM>, and <NUM> are sent to receptacles or ports P3, P2, and P1 of data acquisition unit <NUM>, respectively, such as through outlets, plugs, or prongs <NUM>, <NUM>, and <NUM>, as shown in <FIG>. Data from data acquisition unit <NUM> is then utilized by the remainder of hemodynamic monitoring system <NUM>, such as but not limited to, processor <NUM> and cath-lab display monitor <NUM>, as shown in <FIG>.

The resulting display on cath-lab display monitor <NUM> may be as depicted in <FIG>. As can be seen in <FIG>, the proximal or aortic pressure measurement is shown as P1, the distal pressure measurement is shown as P2, and the FFR value is shown in pressure format as mmHg as P3. A clinician viewing cath-lab display monitor <NUM> knows that the P3 reading of <NUM> mmHg in <FIG> means an FFR of <NUM>.

Processing system <NUM> hereof may also include other features and devices as needed or desired. For example, and not by way of limitation, a power source <NUM> may be provided as part of processing system <NUM>. Power source <NUM> may be a battery or a receptacle configured to receive power from another source, such as a power outlet. Other devices or features, such as but not limited to, wireless receivers and transmitters, indicators such as lights, alarms, and other similar features.

<FIG> shows a processing system <NUM>a similar to processing system of <FIG>. However, in processing system <NUM>a, the aortic pressure signal from aortic pressure measurement device <NUM> is not converted to a digital signal and then converted back to an analog signal before being sent to port P1. Instead, second input <NUM>b of processing unit <NUM> receives a signal from aortic pressure measurement device <NUM>. The signal is conditioned by aortic pressure measurement signal conditioner <NUM> and is sent to receptacle or port P1 through outlet plug, or prong <NUM>, as shown in <FIG>. Further, the signal is split and sent to controller <NUM> through analog-digital converted <NUM>, as shown in <FIG>. The remainder of the processing through controller <NUM> and to ports P2 and P3 is as described above with respect to <FIG> and <FIG>.

<FIG> shows an embodiment of a method of preparing and using the systems described above for an FFR procedure. In particular, in step <NUM>, processing system <NUM> is connected to conventional hemodynamic monitoring system <NUM>. In the embodiment described above, step <NUM> may be accomplished by connecting outlets, plugs, or prongs <NUM>, <NUM>, and <NUM> of processing system <NUM> to inputs P3, P2, P1 of data acquisition unit <NUM> of conventional hemodynamic monitoring system <NUM>.

With processing system <NUM> connecting to conventional hemodynamic monitoring system <NUM>, channels for P1, P2, P3 are "zeroed". The conventional hemodynamic monitoring system <NUM> may prompt the user to zero the channels. "Zeroing" the channels sets "zero" for each port P1, P2, and P3. Since processing system <NUM> is not yet connected to aortic pressure measurement device <NUM> or distal pressure measurement device <NUM>, ports P1, P2, and P3 should be recording a pressure of zero. Step <NUM> sets this zero.

Step <NUM> is inserting aortic pressure measurement device <NUM> into the blood stream. As noted above, aortic pressure measurement device <NUM> generally includes a guide catheter (not shown) inserted into the aorta with an external AO pressure transducer. In step <NUM>, the guide catheter is advanced through the vasculature such that the guide catheter is disposed within the aorta with a distal end thereof disposed within the aorta at an ostium of the aorta adjacent the branch vessel within which a target lesion is located. Although step <NUM> is shown and described prior to steps <NUM>-<NUM>, step <NUM> does not necessarily need to be before steps <NUM>-<NUM>.

in step <NUM>, aortic pressure measurement device <NUM> is connected to processing system <NUM> and activated. As explained above, aortic pressure measurement device <NUM> may be connected to processing system <NUM> by a cable or by a wireless connection. If a wireless connection is used, the wireless connection between aortic pressure measurement device <NUM> and processing system <NUM> is made automatically when aortic pressure measurement device <NUM> is activated, such as by turning aortic pressure measurement device "on". With aortic pressure measurement device <NUM> activated, hemodynamic monitoring system <NUM> displays the AO pressure as trace <NUM> on display monitor <NUM> of conventional hemodynamic monitoring system <NUM> at port P1 through processing system <NUM>, as shown in <FIG>. As also described in step <NUM>, aortic pressure measurement device <NUM> is flushed. Aortic pressure measurement device <NUM> can be flushed with saline or other fluids. Pressure wave <NUM> represents the pressure recorded by the external AO pressure transducer of aortic pressure measurement device <NUM>. Distal pressure measurement device <NUM> is not yet connected to the system. Accordingly, ports P2 and P3 are not recording any data.

Step <NUM> of shown in <FIG> is to open the stopcock of the AO pressure transducer of aortic pressure measurement device <NUM>. With the AO pressure transducer opened to atmosphere, the pressure recorded by port P1 connected to aortic pressure measurement device <NUM> drops near zero, as shown by trace <NUM> in <FIG>. Trace <NUM> may not drop all the way to <NUM> mmHg because aortic pressure measurement device <NUM> has not yet been "zeroed".

Step <NUM> shown in <FIG> is to activate distal pressure measurement device <NUM>. Distal pressure measurement device <NUM> is activated while it is still outside of the body. Distal pressure measurement device <NUM> is also connected to processing system <NUM> and, because processing system <NUM> is connected to hemodynamic monitoring system <NUM>, as explained above, distal pressure measurement device <NUM> is connected to hemodynamic monitoring system <NUM> through processing system <NUM>. As explained above, distal pressure measurement device <NUM> may be connected to processing system <NUM> by a cable or by a wireless connection. If a wireless connection is used, the wireless connection between distal pressure measurement device <NUM> and processing system <NUM> is made automatically when activating distal pressure measurement device <NUM>, such as by turning distal pressure measurement device "on". With distal pressure measurement device <NUM> activated and not inserted into the body, hemodynamic monitoring system <NUM> displays the AO pressure as trace <NUM>, the pressure from distal pressure measurement device <NUM> as trace <NUM> through port P2, and trace <NUM> through port P3, as shown in <FIG>. As explained above, port P3 is the FFR calculation converted to a pressure format. For the purposes of the example screens shown in the Figures, the FFR value has also been multiplied by <NUM> to put it the range from <NUM>-<NUM>. However, as seen in <FIG>, pressure trace <NUM> for port P3/FFR reads zero. This is a safety feature than may incorporated into controller <NUM> such that FFR is not outputted to hemodynamic system <NUM> until after the ports have been equalized, as explained in more detail below.

The user then flushes distal pressure measurement device <NUM>, as shown in step <NUM>. Distal pressure measurement device <NUM> can be flushed with saline or other fluids. Other steps to prepare distal pressure measurement device for insertion into the patient can also be performed, as necessary.

Ports P1, P2, and P3 are then "zeroed" in controller <NUM>, as shown in step <NUM> of <FIG>. To "zero" ports P1, P2, and P3, both the aortic transducer of aortic pressure measurement device <NUM> and distal pressure measurement device <NUM> are opened to atmosphere, such as by opening a stopcock of each device, as described above. Buttons or other devices on the distal pressure measurement device <NUM>, aortic pressure measurement device <NUM>, processing system <NUM>, external interface <NUM> or other devices connected to controller <NUM> may be activated. "Zeroing" of the ports gives controller <NUM> control of the zero level for each device. Thus, the pressures for ports P1, P2, and P3 are all calibrated to zero when measuring atmospheric pressure. As shown in <FIG>, the traces <NUM> for all three ports P1, P2, and P3 reflect a pressure of zero. Also, the pressures for each read zero at <NUM>, as also shown in <FIG>.

Step <NUM> of <FIG> is to insert distal pressure measurement device <NUM> in the patient and advance distal pressure measurement device <NUM> in the guide catheter of aortic pressure measurement device <NUM>. Distal pressure measurement device <NUM> is generally advanced to a distal end of the guide catheter, which is where aortic pressure measurement device <NUM> is reading the aortic or proximal pressure. Accordingly, at this location, distal pressure measurement device <NUM> and aortic pressure measurement device <NUM> should read the same blood pressure. However, as shown in <FIG>, the pressure trace <NUM> from the aortic pressure measurement device <NUM> and the pressure trace <NUM> from the distal pressure measurement device <NUM> often do not match up. Also, at this time, port P3 is not registering a pressure. As explained above, port P3, which is supposed to display the FFR value in pressure format, is not displaying a pressure despite port P1 (Pa) and port P2 (Pd) registering pressures. This is a safety feature that may be incorporated into controller <NUM> such that FFR is not outputted to hemodynamic system <NUM><NUM> until after the ports have been equalized.

Accordingly, aortic pressure measurement device <NUM> and distal pressure measurement device <NUM> are "equalized", as shown in step <NUM> of <FIG>. This is accomplished by processing system <NUM> by calculating the average difference between the pressure measured by aortic pressure measurement device <NUM> and the pressure measured by distal pressure measurement device <NUM>, and offsetting or applying a correction factor to the pressure measured by distal pressure measurement device <NUM> to equalize it with the pressure measured by aortic pressure measurement device. <FIG> and <FIG> show an external interface <NUM> used to equalize the values for Pa and Pd when the distal pressure measurement device <NUM> and aortic pressure measurement device <NUM> are measuring pressure at the same location. In particular, external interface <NUM> may be a controller, such as an HIB controller, that is connected to controller <NUM> of processing unit <NUM>. External interface <NUM> may be part of processing unit <NUM> or may be couple thereto.

After the equalization step, with distal pressure measurement device <NUM> still located at the location where aortic pressure measurement device <NUM> takes the aortic pressure measurement (e.g., the distal end of the guide catheter), the pressure trace <NUM>a aortic pressure measurement device <NUM> (Pa) and <NUM>b for distal pressure measurement device <NUM> (P2) are the same, as shown in <FIG>. Further, the pressures for both shown at <NUM> are the same. For clarity of visualization purposes, traces <NUM>a/<NUM>b are shown side-by-side in <FIG> to represent P1 and P2. However, the traces would be nearly identical due the equalization step.

With the equalization step completed, controller <NUM> permits FFR to be calculated and displayed. Therefore, with distal pressure measurement device <NUM> still located at the location where aortic pressure measurement device <NUM> measures the aortic pressure, the FFR is also recorded and displayed through port P3, as explained above. Accordingly, with the distal pressure measurement device <NUM> and aortic pressure measurement device <NUM> measuring the same pressure, port P3 shows a pressure of <NUM> mmHg. However, as explained in detail above, while P3 displays a pressure, its value is not actually a pressure, but instead is FFR x <NUM>. Thus, as would be expected, when aortic pressure measurement device <NUM> and distal pressure measurement device <NUM> are measuring the same pressure, FFR would be <NUM>. As explained above, in the embodiment where a separate scale is not used for port P3, FFR is multiplied by <NUM> in order to be within the same scale range as the measured pressures, and is converted to a pressure format. Thus, as shown in <FIG>, FFR is displayed at trace <NUM> as <NUM> mmHg. However, a user knows that this trace is an FFR of <NUM>. Further, P3 shows the FFR x <NUM>, as shown at <NUM> of <FIG>.

Claim 1:
A processing system for receiving data from pressure measurement devices and communicating data to a conventional hemodynamic monitoring system (<NUM>) having pressure displays, the processing system comprising:
a first data input for receiving a proximal pressure measurement (Pa) signal from an aortic pressure measurement device (<NUM>);
a second data input for receiving a distal pressure measurement (Pd) signal from a distal pressure measurement device (<NUM>);
a controller (<NUM>) configured to:
compute a Fractional Flow Reserve (FFR) ratio from the proximal pressure measurement signal and the distal pressure measurement signal;
convert the FFR ratio to a pressure format such that the FFR ratio reads on the conventional hemodynamic system (<NUM>) as a pressure in units of pressure;
transmit a first data output signal representing the proximal pressure measurement signal to the conventional hemodynamic monitoring system (<NUM>);
transmit a second data output signal representing the distal pressure measurement signal to the conventional hemodynamic monitoring system (<NUM>); and
transmit a third data output signal representing the FFR ratio in the pressure format to the conventional hemodynamic monitoring system (<NUM>),
wherein the processing system is separate from the conventional hemodynamic monitoring system (<NUM>).