Fractional Flow Reserve: Who Needs the Pressure Wire?

Abstract

Recently, the interest in coronary pressure measurements has been revived thanks to technical innovations (the development of pressure‐measuring angioplasty guidewire) and theoretical progress (the concept of pressure derived fractional flow reserve). Fractional flow reserve (FFR) is the ratio of maximal flow in the myocardial region depending on a stenosis to maximal flow in that same region if the stenosis were absent. With the development of pressure guidewires, fractional flow reserve can be calculated rapidly and safely in the diagnostic and interventional setting. It has been shown that pressure derived FFR can be used as a surrogate for a stress test for on‐line clinical decision making in the catheterization laboratory. Values < 0.75 are most often associated with exercise‐inducible myocardial ischemia, while values > 0.75 exclude objective signs of ischemia during exercise. The accuracy of FFR for that purpose is approximately 95% and higher than that of any single noninvasive test taken alone. Of note, it has been shown that prognosis is favorable in patients in whom a planned angioplasty was deferred on the basis of a myocardial fractional flow reserve > 0.75. After regular balloon angioplasty, the combination of a good angiographic result and a FFR > 0.90 is associated with an event rate during a 2‐year follow‐up, which is similar to that after stenting. After stent implantation, FFR should normalize. A FFR < 0.94 after stent implantation appears to be as accurate as intravascular ultrasound (IVUS) to detect stent malposition. Thus, pressure derived FFR is a well‐validated index of stenosis severity that has evolved from a physiological index to a clinical tool.