Abstract 2428: Reproducibility of PET-Measured Myocardial Blood Flow Responses to Cold-Pressor-Testing.
Background: Despite an increasing use of PET measurements of MBF combined with CPT to non-invasively probe endothelium-dependent coronary vasomotor function, its intraobserver reproducibility has not been tested in a prospective fashion. Therefore, we aimed to determine the short- and long-term intraobserver reproducibility of PET-measured myocardial blood flow (MBF) at rest and during cold-pressor-test (CPT).
Methods: Twenty healthy volunteers (10 without and 10 with coronary risk factors) were studied. MBF was measured in repeat assessment at rest and during CPT with a two-compartment model for 13N-ammonia in a one day session (short-term reproducibility; SR). After a follow-up of two weeks, MBF was measured again at rest and during CPT and compared to the initial baseline measurement (long-term reproducibility; LR).
Results: The assessment of the SR did not show a significant absolute difference of MBF at rest, MBF during CPT and the endothelium-related change in MBF from rest to CPT (ΔMBF) (Table⇓), and they were linearely correlated (r=0.72, SEE=0.14; r=0.76, SEE=0.14 and r=0.84, SEE=0.09;p<0.0001). The corresponding short-term MBF repeatability coefficient were 0.26, 0.28 and 0.18 ml/g/min. The LR yielded relative higher but non-significant absolute differences of the MBF at rest, MBF during CPT and ΔMBF (Table⇓). Corresponding paired MBFs also significantly correlated (r=0.75, SEE=0.13; r=0.71, SEE=0.15 and r=60, SEE=0.17; p<0.001) and the corresponding lon-term MBF repeatability coefficients were 0.26, 0.31 and 0.27 ml/g/min. The absolute difference of the change in rate-pressure product (RPP= heart rate x systolic blood pressure) from rest to CPT(ΔRPP), as index for the sympathetic stimulation with CPT, was non-significantly lower at SR than at LR (Table⇓) .
Conclusion: Short- and long-term MBF responses to CPT, as an index of endothelium-dependent coronary vasomotor function, can be measured reproducibly with 13N-ammonia PET.