In 1995 Topol first described what vascular surgeons have known for many years:
The pressure drop in a fluid flowing through a long cylindrical pipe such as a stenotic artery becomes functionally significant when the obstruction exceeds 70%, first described in the Poiseuille law in 1846.
As was stated in Topol’s paper: “Accordingly, before the residual stenosis in an infarct vessel is addressed, there should be demonstration of either spontaneous or provocable signs of ischemia… clinicians and investigators rely excessively on angiography for clinical decision-making… Procedures should not be performed solely to improve the luminal appearance—so-called coronary “cosmetology”.
- PCI was superior to Optimal Medical Therapy only in stenotic lesions with hemodynamically significant flow restrictions (FFR<80%).
- Among patients with stenoses that were not functionally significant (FFR >0.80), the best available medical therapy alone resulted in an excellent outcome, regardless of the angiographic appearance of the stenoses.
A strategy of reflex PCI during routine coronary angiogaraphy has only recently become less common. It is not known how many non-ischemic lesions are stented in day-to-day practice, but these results suggest a high percentage!
 Fractional Flow Reserve Versus Angiography for Guiding Percutaneous Coronary Intervention in Patients With Multivessel Coronary Artery Disease, Nico H.J. Pijls, MD et al; J Am Coll Cardiol. 2010;56(3):177-184.