Fractional flow reserve (FFR) value between 0.75 and 0.80 is considered the ‘gray zone.’ There is a scarcity of outcomes data relative to treatment strategy (revascularization vs medical therapy alone [deferral]) for this group.

A study published in J Invasive Cardiol followed 238 patients (64.3 ± 8.6 years; 97% male; 45% diabetic) with gray-zone FFR for the primary endpoint of major adverse cardiovascular event (MACE), defined as a composite of death, myocardial infarction (MI), and target-vessel revascularization. Deferred patients were found to have a higher prevalence of smoking and chronic kidney disease compared with the PCI group. Patients who underwent PCI had significantly lower MACE compared with the deferred patients (16% vs 40%; log rank P<.01). The composite of death or MI was significantly lower in the PCI group (9% vs 27%; P<.01). Multivariate Cox proportional hazards regression analysis revealed that PCI was associated with lower MACE (hazard ratio, 0.5; 95% confidence interval, 0.27-0.95; P=.03). Revascularization for patients with gray-zone FFR was thus shown to be associated with a significantly reduced risk of MACE compared with medical therapy alone.

A study presented at EuroPCR 2018 revealed that among 104 patients randomly assigned in the single-center, unblinded, prospective Gray Zone Fractional-Flow Reserve (GZ-FFR) trial to PCI or optimal medical therapy (OMT), patients assigned to receive PCI had less frequent angina and larger improvements in quality-of-life (QoL) measures at 2 months compared with patients assigned to OMT.