Is Instantaneous Wave-Free Ratio a New Standard of Care for Physiologic Assessment of Coronary Lesions?
More Questions Than Answers
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After >20 years since the proof of concept, fractional flow reserve (FFR) has become an invasive standard for lesion assessment in the cath laboratory. The fundamental premise that allowed for the transition from traditional coronary flow reserve to a pressure-only flow reserve (ie, fraction of normal flow or FFR) required maximal hyperemia to create a linear relationship between pressure and flow.1 Compared with resting pressure ratios, hyperemia produces better separation of the families of pressure/flow curves characterizing obstructive from nonobstructive stenotic lesions. Validation of FFR against multiple stress test modalities demonstrated that regionally specific myocardial ischemia could be identified. The proof of clinical value came from favorable randomized trial results with reduced adverse event rates and costs for FFR-directed PCI (FAME I [Fractional Flow Reserve versus Angiography for Guiding PCI in Patients with Multivessel Coronary Artery Disease trial I]) and the superiority of FFR-guided revascularization over medical therapy for FFR obstructive lesions (FAME II [Fractional Flow Reserve versus Angiography for Guiding PCI in Patients with Multivessel Coronary Artery Disease trial II]).
Despite its strengths for lesion assessment over angiography alone, the interventional community was slow to adopt FFR for reasons, either perceived or real, that included additional time, cost, loss of procedural reimbursement, and use of adenosine. Nonetheless, FFR use has continued to grow as clinical studies covered new areas such as non–ST-segment elevation myocardial infarction …