Pd/Pa fluctuation with continuous ATP administration indicates inaccurate FFR measurement caused by insufficient hyperemia.

Continuous intravenous adenosine triphosphate (ATP) administration is the standard method for inducing maximal hyperemia in fractional flow reserve (FFR) measurements. Several cases have demonstrated fluctuations in the ratio of mean distal coronary pressure to mean arterial pressure (Pd/Pa) value during ATP infusion, which raised our suspicions of FFR value inaccuracy. This study aimed to investigate our hypothesis that Pd/Pa fluctuations may indicate inaccurate FFR measurements caused by insufficient hyperemia. We examined 57 consecutive patients with angiographically intermediate coronary lesions who underwent fractional flow reverse (FFR) measurements in our hospital between November 2016 and September 2018. Pd/Pa was measured after continuous ATP administration (150 μg/kg/min) via a peripheral forearm vein for 5 min (FFR _A ); and we analyzed the FFR value variation in the final 20 s of the 5 min, defining 'Fluctuation' as variation range > 0.03. Then, 2 mg of nicorandil was administered into the coronary artery during continued ATP infusion, and the Pd/Pa was remeasured (FFR _A+N ). Fluctuations were observed in 23 of 57 patients. The cases demonstrating discrepancies of > 0.05 between FFR _A and FFR _A+N were observed more frequently in the fluctuation group than in the non-fluctuation group (12/23 vs. 1/34; p < 0.0001). The discrepancy between FFR _A and FFR _A+N values was smaller in the non-fluctuation group (mean difference ± SD; -0.00026 ± 0.04636 vs. 0.02608 ± 0.1316). Pd/Pa fluctuation with continuous ATP administration could indicate inaccurate FFR measurements caused by incomplete hyperemia. Additional vasodilator administration may achieve further hyperemia when Pd/Pa fluctuations are observed.
Competing Interests: Declarations. Conflict of interest: The authors have no conflicts of interest to declare. Authorship inclusion criteria: This manuscript has been read and approved by all the authors, the requirements for authorship as stated above have been met, and each author believes that this manuscript represents honest work.
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