Fractional Flow Reserve Measurement Technique
- Author: Eiman Jahangir, MD, FACC; Chief Editor: Karlheinz Peter, MD, PhD more...
Typically, conscious sedation is administered as part of the cardiac catheterization. Unless the patient is uncomfortable, no other anesthesia is required. The patient is placed in the supine position.
To measure fractional flow reserve (FFR), the operator crosses the coronary stenosis with an FFR-specific guide wire designed to record the coronary arterial pressure distal to the stenosis. The pressure transducer is located approximately 20 mm proximal to the distal tip of the wire, and it can be seen fluoroscopically.
Once the transducer is distal to the stenosis, a hyperemic stimulus is administered by injection through the guide catheter, and the FFR is monitored for a significant change. To achieve maximum hyperemia, adenosine is typically used: a 15-30 µg bolus in the right coronary artery, a 20-40 µg bolus in the left coronary artery, or intravenous (IV) infusion for 3-4 minutes at 140 µg/kg/min. The mean arterial pressures from the pressure wire transducer and from the guide catheter are then used to calculate FFR.
An FFR value lower than 0.75 indicates a hemodynamically significant stenosis. An FFR value higher than 0.8 indicates a stenosis that is not hemodynamically significant. Values between 0.75 and 0.80 are indeterminate and should be considered in the context of patient’s clinical history to determine if revascularization is necessary.
Specific Approaches to FFR Measurement
Open the product packaging with sterile technique, and place the spiral on the sterile field. With the wire in the spiral, remove the cable from the spiral by pulling on the plug, and connect it to a compatible instrument. Verify that the nose is rotated to the locked position.
After the wire has been zeroed, carefully remove the connector body from the spiral clip, and withdraw the guide wire from the spiral. At this time, the guide wire tip may be shaped with standard tip-shaping practices, if desired.
Wet the working length of the guide wire with normal saline, and insert the wire through the appropriate introducer components and guiding catheter into the desired blood vessel. Slowly advance the guide wire tip under fluoroscopic guidance, using contrast injections to verify its location. Be careful not to kink the proximal contact bands of the wire. Ensure that the tip is rotating freely and that no resistance is felt when torque is applied.
Locate the pressure sensor adjacent to the tip of the guide catheter, and perform a normalization procedure with the instrument. Advance the sensor to the desired measurement location, and perform measurements with the instrument. If the FFR is greater than 0.75 at baseline, proceed with administering a hyperemic stimulus (eg, intracoronary adenosine in a dose of 15-40 µg or IV adenosine at 140 µg/kg/min), and monitor measurements.
Finally, withdraw the pressure sensor and verify that pressures are equal.
St Jude Medical system
Open the product packaging with sterile technique, and place the PressureWire on the sterile field. Remove the gray connector from its holder and connect it to the RadiAnalyzer Xpress. Place the coil flat, and flush with 10 mL of saline. Press Enter on the RadiAnalyzer Xpress to calibrate the PressureWire (see the video below).
Advance the sensor element so that it is just outside the guide catheter opening (see the first image below). Verify that aortic pressure and PressureWire pressure are equal at that position (see the second image below). If the 2 pressures are not equal, position the aortic transducer at the level of the patient’s heart, remove the guide wire introducer needle, close the valve tightly, flush any contrast remnants, press Equalize, and hold for 3 seconds.
Advance the sensor element to a point distal to the stenosis of interest (see the image below). Wait for stable baseline pressure values to be obtained.
Induce maximum hyperemia with intracoronary adenosine (15-40 µg) or IV adenosine (140 µg/kg/min). When maximum hyperemia is reached, press Stop/View to stop recording. The instrument then calculates the FFR automatically (see the image below).
Complications associated with cardiac catheterization include the following:
Coronary vessel dissection, occlusion, or perforation
Embolism (coronary, cerebral, or other arterial)
Coronary artery spasm
Local or systemic infection
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