Assessment of the reproducibility of baseline and hyperemic myocardial blood flow measurements with O-15-labeled water and PET

PET with O-15-labeled water allows noninvasive quantification of myocardial blood flow (MBF) at baseline and during pharmacologically induced hyperemi a to assess the coronary vasodilator reserve (CVR = hyperemic/baseline MBF) . Despite widespread use of PET, its reproducibility during one study sessi on has not been tested. Intravenous adenosine (Ado), a powerful coronary va sodilator with a very short decay time, is commonly used for the induction of hyperemia. However, it is not known whether Ado can induce tachyphylaxis after short-term repetitive administration. In this study, we aimed to tes t the reproducibility of PET assessment of CVR during Ado-induced hyperemia . Methods: In 21 healthy volunteer men, baseline and Ado MBF were measured twice using PET with O-15-labeled water to obtain two CVR assessments withi n 1 h. Results: There was no significant difference between the two baselin es (0.89 +/- 0.14 versus 0.99 +/- 0.15 mL/min/g, mean difference 13% +/- 11 %) or between the two hyperemic MBFs (3.51 +/- 0.45 versus 3.83 +/- 0.49 mL /min/g, mean difference 10% +/- 14%), resulting in comparable values of CVR (4.05 +/- 0.75 versus 3.93 +/- 0.72, mean difference 2% +/- 15%), The repe atability coefficient for MBF was 0.17 mL/min/g at baseline and 0.94 mL/min /g during hyperemia. The repeatability coefficient of the rate pressure pro duct (RPP) was lower at baseline (1,304 mm Hg x beat/min) than during hyper emia (3,448 mm Hg x beat/min). Conclusion: Repeated measurements of MBF and CVR during the same study session were not significantly different, demons trating the validity of the technique. The larger variability of hyperemic flow, as indicated by the larger repeatability coefficient, was paralleled by a greater variability of the RPP. This could mean that the greater varia bility of MBF during stress is more likely due to a variable response to Ad o rather than to a measurement error.