Rise of the Machines: Where Virtual Processing Meets Percutaneous Coronary Intervention

The evidence base supporting the incorporation of intracoronary physiology into decision making in the cardiac catheterization laboratory has accumulated for more than 3 decades. The Deferral vs Performance of Percutaneous Coronary Intervention in Patients Without Documented Ischemia (DEFER), ^,  Fractional Flow Reserve vs Angiography for Multivessel Evaluation (FAME), and FAME 2 trials have solidified the foundation of use of fractional flow reserve (FFR) in clinical decision making to help guide revascularization decisions. Additional nonhyperemic invasive methods of assessing coronary physiology, such as instantaneous wave-free ratio (iFR), have subsequently been developed to determine the physiological significance of coronary lesions without the need for potent vasodilators such as adenosine. Specifically, the Functional Lesion Assessment of Intermediate Stenosis to Guide Revascularization (DEFINE-FLAIR) and Instantaneous Wave-Free Ratio vs Fractional Flow Reserve in Patients With Stable Angina Pectoris or Acute Coronary Syndrome (iFR-SWEDEHEART) studies both demonstrated that iFR-guided revascularization was noninferior to FFR-guided revascularization for the primary outcome of major adverse cardiovascular events at 1 year. These data are reflected in the most recent major guideline recommendations supporting the use of invasive functional testing for intermediate-grade stenoses to help guide revascularization decisions (American College of Cardiology/American Heart Association/Society for Cardiovascular Angiography [ACC/AHA/SCAI] class IIA; European Society for Cardiology/European Association for Cardio-Thoracic Surgery [ESC/EACTS] class IA), with the ACC/AHA guidelines giving a class Ia recommendation for revascularization of functionally significant coronary lesions. More recently, the routine use of intracoronary imaging, including intravascular ultrasound (IVUS) and optical coherence tomography (OCT), has garnered support, particularly in complex interventions such as left main coronary artery intervention and bifurcation disease as well as in ACS. Intracoronary imaging can inform more precise stent sizing while helping to identify incomplete stent apposition/expansion, which is associated with adverse clinical outcomes. Despite the importance of these assessments, both coronary physiology and imaging remain woefully underused in clinical practice. ^, Barriers to increased use of these technologies include the inconvenience and potentially higher risk of additional coronary instrumentation, prolonged procedural times, cost and reimbursement concerns, limited availability, and variable comfort with the necessary equipment and interpretation depending on the operator and clinical centre.