Standardized Hyperemic Stress for Fractional Flow Reserve
The article by Tarkin et al1 in this issue of Circulation: Cardiovascular Interventions adds interesting details to the extensive, well-established basis for assessing stenosis severity at maximal coronary flow induced by pharmacological vasodilation. As the authors state, all the major clinical trials of fractional flow reserve (FFR) as the basis for percutaneous coronary angioplasty were made under conditions of stable hyperemia as defined in the original protocol. Their data in this article reinforce that requirement by showing the errors in FFR if measured during initial hemodynamic changes of the systemic and coronary circulation after intravenous adenosine before stable hyperemia is reached.
Article see p 654
The authors display 7 arbitrarily chosen patterns of aortic (Pa) and distal coronary pressures (Pd) all showing larger peak stenosis gradient than the steady-state hyperemic gradient. Pd and the ratio Pd/Pa after adenosine (FFR) were related to but did not exactly parallel the stenosis gradient. Moreover, Pd and FFR paralleled to some extent Pa reflecting systemic hemodynamics as well as stenosis fluid dynamics, thereby raising the question of which provides the truth about stenosis severity.
The answer is that stenosis gradient, Pd, and FFR all tell the truth but respond to different questions. The stenosis gradient reflects the fluid dynamic characteristics of the stenosis depending on flow. Pd reflects pressure that the …