Resting (ie, no adenosine) instantaneous pressure during wave-free period = iFR

Reproduced from: Sen S, Escaned J, Malik IS, et al. Development and validation of a new adenosine-independent index of stenosis severity from coronary wave-intensity analysis: results of the ADVISE (ADenosine Vasodilator Independent Stenosis Evaluation) study. J Am Coll Cardiol 2012; 59:1392. Illustration used with the permission of Elsevier Inc. All rights reserved.