Conversation in cardiology: Is there a need for clinical trials for the nonhyperemic pressure ratios?

In the last decade, coronary physiologic measurements in the cath lab have undergone dramatic advances in both techniques and outcomes for clinical practice. Moving from a dominant technique of fractional flow reserve (FFR) with its requirement for adenosine-induced hyperemia to a specific diastolic nonhyperemic pressure ratio (NHPR) during the wave-free period (WFP), called the instantaneous wave-free ratio (iFR), the field now enjoys at least five NHPRs (see Table 1 and Figure 1). Recall that in March 2017, the Coronary Revascularization Writing Group on behalf of the American College of Cardiology (ACC), American Association Thoracic Surgery (AATS), American Heart Association (AHA), American Society of Echocardiography (ASE), American Society of Nuclear Medicine (ASNC), Society of Cardiac Angiography and Intervention (SCAI), Society of Coronary Computer Tomography (SCCT), Society of Thoracic Surgery (STS), chaired by Patel et al, authored the 2017 Appropriate Use Criteria for Coronary Revascularization in Patients with Stable Ischemic Heart Disease, which changed the language from only iFR to more generic NHPRs, specifically, in page 2218, Section 3, “Assumptions,” “General Assumptions” added that