Effect of caffeine on intravenous adenosine-induced hyperemia in fractional flow reserve measurement.

BACKGROUND: The interaction between caffeine and adenosine is still a matter of debate. AIMS: We examined whether caffeine attenuated intravenous adenosine-induced hyperemia in the measurement of fractional flow reserve (FFR) and whether an increased dose of adenosine overcame the caffeine antagonism. METHODS: FFR was measured using different adenosine doses (140, 175, and 210 μg/kg/min) and papaverine as a reference standard in patients with intermediate coronary stenoses, who refrained from caffeine for >24 h (no-caffeine group; n = 14) and those who consumed caffeine (caffeine group; n = 28). RESULTS: The median caffeine level in the caffeine group was 2.9 mg/L (interquartile range, 1.8-4.6 mg/L). In the no-caffeine group, FFR with adenosine did not decrease above the dose of 140 μg/kg/min (0.769, 0.771, and 0.770 at 140, 175, and 210 μg/kg/min, respectively) and was not significantly different from that with papaverine (0.765). In the caffeine group, adenosine overestimated FFR (140 μg/kg/min: 0.813, P<.001; 175 μg/kg/min: 0.806, P<.01; 210 μg/kg/min: 0.794, P=.01) compared with papaverine (0.779). The difference in FFR between papaverine and 140 μg/kg/min dose of adenosine was significantly greater in the caffeine group than in the no-caffeine group (0.034 vs 0.004; P<.05). CONCLUSION: Caffeine attenuates intravenous adenosine-induced hyperemia in FFR measurement. Even increased adenosine doses up to 210 μg/kg/min cannot fully surmount the antagonism.