Why is this study important?

• Visual estimation of the degree of coronary artery stenosis and the effects on flow are known to be imprecise and wire-based pressure assessment remains underutilized in part due to convenience, time, and cost. The inaccurate identification and intervention on non-significant stenosis and/or deferring significant stenosis may contribute to worse patient outcomes.  
• Alternative methods to assess the physiologic significance of coronary stenosis, including use of angiographically derived quantitative flow ratio (QFR), are appealing.  

What question was this study supposed to answer?  

Angiography based and computational derived quantitative flow ratio (QFR) has been validated to have high clinical accuracy and reproducibility as compared with wire-based pressure measurements and is associated with improved 1-year clinical outcomes as compared with conventional angiographic guidance. However, the effect on longer term outcomes remains unclear. 

What did the study show?

In this multicenter, randomized, sham-controlled trial of 3,847 patients with predominantly unstable angina or chronic stable angina, the use of QFR-guided PCI was associated with a decreased risk of a MACE composite (death, MI, or ischemia-driven revascularization) as compared with angiographic guided PCI at 2 years (8.5% vs 12.5%, HR 0.66, 95% CI 0.54-0.81;P<0.001). The between group differences in MACE were driven by lower rates of MI (4.0% vs 6.8%, HR 0.58, 95% CI 0.44-0.77;p=0.002) and ischemia driven revascularization (4.2% vs 5.8%, HR 0.71, 95% CI 0.53-0.95;p=0.02), and the composite remained significant when periprocedural MIs were excluded. 

As compared with the revascularization plan devised at the time of angiography, QFR was associated with a change in revascularization strategy in 23.3% of subjects- primarily due to the deferral of at least one vessel initially intended for PCI (19.6%) but also identification of a target lesion not originally intended to be treated (4.4%). The greatest reduction in the primary MACE outcome was among patients in whom the revascularization strategy was altered by QFR assessment, driven predominantly by improved outcomes among patients in whom intended vessels to be treated were deferred.  

All editors: Timothy F. Simpson, MD, PharmD