(MACEs) related to coronary stents. As the performance of these stents improved, the interest in tackling more complex anatomies of coronary artery disease (CAD) became greater and moved the procedure forward to where we are today.
that have used two different FFR criteria for defining hemodynamically significant lesions: 0.75 or 0.80. The different choice of dichotomous cutoffs has its origin in early validation studies, which demonstrated that an FFR <0.75 has 100% specificity to identify stenosis with inducible ischemia, whereas an FFR >0.80 has a sensitivity of more than 90% to exclude stenoses that cause ischemia. Recent developments spurred by wire-based FFR include other coronary functional indexes such as instantaneous wave-free ratio (iFR) and resting distal-to-aortic coronary pressure ratio (Pd/Pa), which can be performed without hyperemic agents as well as angiography-based FFR, which utilizes computational flow dynamics to estimate FFR by contrast flow16 (Figure 43.1A-D and Table 43.3).
TABLE 43.1 Hyperemic Agents Used in Coronary Fractional Flow Reserve Measurements
TABLE 43.2 Landmark Studies Demonstrate Improved Patient Outcomes by Selecting Patients for PCI with FFR
rest with stenosis severity, a resting index should be sufficient to quantify severity, provided there is sufficient flow velocity to distinguish between stenoses. During diastole, the competing waves are quiescent, and during the wave-free period, microcirculatory resistance is at its lowest and most stable compared to the rest of the cardiac cycle. At this time, the pressure and flow velocity are linearly related, and pressure ratios can assess the flow limitation imposed by a stenosis.
FIGURE 43.1 Angiogram and FFR of a patient with multivessel coronary artery disease (CAD). A. Patient with multivessel CAD undergoing PCI with an FFR-guided approach. The LAD lesion (1) is judged to be severe and matched with stress test result and symptoms. The mid-LAD lesion (2) is clearly intermediate, as is the lesion in the LCx (3). B. FFR is obtained in the LCX, with the wire positioned as shown, and is 0.88. This lesion is physiologically insignificant and is not treated with PCI. C. A stent is placed in the proximal LAD lesion and then FFR is performed to assess the significance of the more distal LAD lesion originally judged to be intermediate. The FFR of the LAD is 0.68, and the more distal lesion is subsequently stented as well, secondary to this significant FFR finding. D. Final angiogram showing the treated proximal and mid-LAD lesions with the intermediate LCX lesion left untreated. FFR, fractional flow reserve; LAD, left anterior descending; LCx, left circumflex artery; PCI, percutaneous coronary intervention.
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