Increased dose of adenosine and the relationship between the resting full-cycle ratio and fractional flow reserve

• Fractional flow reserve (FFR) and resting full-cycle ratio (RFR) have shown discordance. • FFR decreases with increased adenosine dose. • Increased adenosine doses results in a higher number FFR-positive lesions. • Microvascular function influence on FFR reduction with increased adenosine dose. • Area under the curve were similar for RFR compared to FFR 140 and FFR 200. Intermediate coronary artery stenosis can be evaluated with fractional flow reserve (FFR) and resting full-cycle ratio (RFR) to determine if the stenosis is functionally significant. However, RFR and FFR have shown discordance in around 20% of examinations. One explanation could be that maximal hyperemia was not achieved during adenosine infusion. The aim was to investigate if increased doses of adenosine would reduce FFR further, and if the agreement between RFR and FFR would improve. Two hundred patients underwent physiological assessment of an intermediate stenosis with RFR and FFR at 140 µg/kg/min (FFR 140 ) and 200 µg/kg/min (FFR 200 ) of adenosine infusion. The microcirculation function was assessed using the index of microvascular resistance (IMR). Median RFR was 0.89 (interquartile range [IQR] 0.85–0.93). Median FFR decreased significantly during increased adenosine doses: FFR 140 = 0.85 (IQR 0.77–0.90) versus FFR 200 = 0.82 (IQR 0.75–0.87), p < 0.001. Reduction in FFR during increased adenosine doses was higher in patients with IMR ≥ 24 (FFR 140 0.85 [IQR 0.78–0.92] versus FFR 200 0.82 [IQR 0.75–0.86], p < 0.001) compared to patients with IMR < 24 (FFR 140 0.83 [IQR 0.77–0.89] versus FFR 200 0.81 [IQR 0.75–0.87], p < 0.001) with an absolute difference of −0.03 (−0.05, −0.01) versus −0.01 (−0.02, 0.0), p < 0.001. Area under the curve (AUC) of RFR compared to FFR 140 was 0.88 (95 % confidence interval [CI] 0.84–0.93), and for FFR 200, AUC was 0.88 (CI: 0.84–0.93). Increased doses of adenosine significantly reduced FFR values, whereas the correlation agreement between RFR and FFR was not improved.