Читать книгу Interventional Cardiology - Группа авторов - Страница 182

Fractional flow reserve (FFR) is recognized as the reference standard for coronary physiology in the catheter laboratory. FFR, conceptually, is defined as the maximum myocardial blood flow in the presence of an epicardial stenosis divided by the theoretical maximum flow in the absence of a stenosis [7,50]. In reality, FFR does not measure flow, instead measuring intracoronary pressure and draws an inference to flow. Pressure and flow are not linearly related and thus a constant relationship can only be inferred if coronary microcirculatory resistance is minimal as is theoretically the case during maximal arteriolar vasodilatation during adenosine infusion. Hyperemic agents reduce microvascular resistance and increase coronary flow, thereby magnifying a trans‐stenotic pressure gradient that is often present at rest. FFR is defined as a ratio of the distal to proximal coronary pressures (Pd/Pa) during hyperemia. In common parlance, a vessel with FFR of 0.80 has 80% of the blood flow it should have if the stenosis was absent.

FFR is usually accepted as the lowest Pd/Pa during stable hyperemia; high quality traces must be assessed [51]. When using short‐lived intracoronary vasodilators, the lowest Pd/Pa ratio achieved may be used. Automated calculation may make errors as port opening, ectopy or a cardiac pause can erroneously generate a low Pd/Pa.