title: Effect of caffeine intake on myocardial hyperemic flow induced by adenosine triphosphate and dipyridamole.
abstract: The aims of this study were (a). to compare absolute myocardial blood flow (MBF) during adenosine triphosphate (ATP) infusion with that after dipyridamole administration without caffeine intake and (b). to evaluate the effect of caffeine intake on the hyperemic flow induced by these coronary vasodilator agents.
  
  
  METHODS
  MBF was quantified with (15)O-labeled water and PET at rest, during ATP infusion (0.16 mg/kg/min for 9 min), and after dipyridamole administration (0.56 mg/kg over 4 min) after a 24-h abstinence from caffeine (baseline evaluation) in 10 healthy volunteers. Within 2 wk, the same PET studies were repeated after caffeine intake to evaluate the effect of caffeine on the hyperemic flow induced by these pharmacologic agents (caffeine study). Myocardial flow reserve (MFR), defined as the ratio of hyperemic to resting blood flow, was also evaluated.
  
  
  RESULTS
  Resting MBF in baseline and caffeine studies did not differ significantly (0.79 +/- 0.29 vs. 0.75 +/- 0.31 mL/min/g, P = 0.88). Without caffeine intake, MBF during ATP infusion was significantly higher than that after dipyridamole administration (3.70 +/- 0.67 vs. 3.00 +/- 0.79 mL/min/g, P = 0.003), whereas there was no significant difference in MFR between ATP and dipyridamole stress (5.15 +/- 1.64 vs. 4.11 +/- 1.44, P = 0.07). After caffeine intake, the hyperemic flows induced by ATP and dipyridamole were not significantly different (1.68 +/- 0.37 vs. 1.52 +/- 0.40 mL/min/g, P = 0.50). MFR estimated by ATP and dipyridamole also did not differ significantly in the caffeine studies (2.44 +/- 0.88 vs. 2.25 +/- 0.94, P = 0.73). MBF during ATP infusion and after dipyridamole administration were significantly lower in the caffeine studies than that in the baseline evaluation (1.68 +/- 0.37 vs. 3.70 +/- 0.67 mL/min/g, P < 0.0001, and 1.52 +/- 0.40 vs. 3.00 +/- 0.79 mL/min/g, P < 0.0001, respectively).
  
  
  CONCLUSIONS
  This study demonstrates that ATP has the potential to induce greater hyperemia than dipyridamole, whereas hyperemic responses to ATP and dipyridamole are similarly attenuated after caffeine intake. These findings suggest that abstinence from caffeine before ATP stress testing may be needed.
authors.affiliation: Department of Nuclear Medicine and Diagnostic Imaging, Kyoto University Graduate School of Medicine, Kyoto, Japan. kub@kuhp.kyoto-u.ac.jp
authors.forename: Shigeto
authors.initials: S
authors.lastname: Kubo
authors.forename: Eiji
authors.initials: E
authors.lastname: Tadamura
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Toyoda
authors.forename: Marcelo
authors.initials: M
authors.lastname: Mamede
authors.forename: Masaki
authors.initials: M
authors.lastname: Yamamuro
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Magata
authors.forename: Takahiro
authors.initials: T
authors.lastname: Mukai
authors.forename: Haruhiro
authors.initials: H
authors.lastname: Kitano
authors.forename: Nagara
authors.initials: N
authors.lastname: Tamaki
authors.forename: Junji
authors.initials: J
authors.lastname: Konishi
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000328:Adult; D002110:Caffeine / Q000494:pharmacology*; D003326:Coronary Circulation / Q000187:drug effects*; D004176:Dipyridamole / Q000494:pharmacology*; D006321:Heart / Q000000981:diagnostic imaging*; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D006940:Hyperemia / Q000139:chemically induced*; D007262:Infusions, Intravenous; D008297:Male; D010104:Oxygen Radioisotopes; D014055:Tomography, Emission-Computed; D014665:Vasodilator Agents / Q000494:pharmacology*; D014867:Water
chemical_list: D010104:Oxygen Radioisotopes; D014665:Vasodilator Agents; D014867:Water; D002110:Caffeine; D004176:Dipyridamole; D000255:Adenosine Triphosphate