Given its cost and commonality, the appropriate application of percutaneous coronary intervention (PCI) in treating coronary artery disease is justifiably a health care policy priority. Understanding the limitations of the subjective assessment and treatment of coronary stenosis through coronary angiography alone has led to many changes, including greater incorporation of stress testing and intracoronary imaging devices into the cardiac catheter laboratory in recent years. Routine use of fractional flow reserve (FFR) (where a sensor-equipped guidewire is passed across a coronary lesion to assess intracoronary hemodynamics) and intravascular ultrasonography (IVUS) (where a miniature ultrasonographic probe allows imaging of a cross-section of the coronary artery) for contemporary PCI in the United States is estimated at 6.1% and 20.3%, respectively.1 The use of FFR to assess the functional significance of a coronary plaque to guide PCI to reduce major adverse cardiac events has been supported by randomized clinical trials.2,3 Subsequently, American Heart Association guidelines now recommend that FFR should be used for assessing plaques of intermediate severity (50%-70%).4 In this issue of JAMA Internal Medicine, Fröhlich et al5 conclude that the use of FFR-guided PCI and IVUS-guided PCI is not associated with improved long-term survival compared with standard angiography-guided PCI in a large London, England, observational study involving 41 688 patients, including those who were stable and those who were initially seen with non–ST-segment acute coronary syndrome. These real-world data provide useful additional information to the randomized clinical trials of FFR in the Fractional Flow Reserve Versus Angiography in Multivessel Evaluation (FAME) and FAME 2 studies.2,3 FAME 2 randomized patients to PCI guided by FFR or to optimal medical therapy without revascularization. The trial was terminated early because of a significant reduction in the composite primary end point (of death, myocardial infarction, or urgent revascularization) in the FFR-guided PCI group. However, this reduction was primarily driven by the need for urgent revascularization. Neither FAME nor FAME 2 found a mortality benefit for FFR-guided PCI.