In conclusion, flow velocity measurements repeated after a 6-month interval show a variability, which is larger for baseline velocity and coronary flow reserve. This variability is correlated with the changes in heart rate and can be reduced by a normalization for the cross-sectional area at the site of the measurement (coronary flow) and for the aortic pressure at the time of the measurement (flow resistance).

doi.org/10.1016/S0002-9149(99)80755-3, hdl.handle.net/1765/52722
The American Journal of Cardiology
Department of Cardiology

di Mario, C., Gil, R., & Serruys, P. (1995). Long-term reproducibility of coronary flow velocity measurements in patients with coronary artery disease. The American Journal of Cardiology, 75(16), 1177–1180. doi:10.1016/S0002-9149(99)80755-3