Hyperaemic blood-flow velocities in systole and diastole relate to coronary risk in divergent ways

Background: A recent study suggested blood-flow velocity in diastole during reactive hyperaemia as a major driver of flow-mediated vasodilation (FMD) of the brachial artery, also being related to cardiovascular risk factors. The present study aimed to investigate the relative importance of hyperaemic systolic and diastolic blood-flow velocity in the forearm regarding both FMD and cardiovascular risk factors. Methods: In the Prospective Investigation of the Vasculature in Uppsala Seniors study, conducted in 1016 subjects aged 70 years, FMD, systolic and diastolic blood hyperaemic flow velocities in the brachial artery were evaluated by ultrasound. Results: Hyperaemic blood-flow velocity both in systole and diastole were related to FMD (r = 0.14-0.19, P < 0.0001). However, while hyperaemic systolic blood-flow velocity was related to coronary risk (Framingham risk score) in a positive way (r = 0.08, P = 0.013), diastolic blood-flow velocity was inversely related to coronary risk (r = -0.08, P = 0.016). Therefore, the systolic to diastolic hyperaemic blood-flow velocity ratio was more powerful related to coronary risk (r = 0.23, P = 0.0001). In a multiple regression model, both FMD and the systolic to diastolic hyperaemic blood-flow velocity ratio were independent predictors of coronary risk (P = 0.018 and P = 0.0001). Conclusion: As hyperaemic blood-flow velocities in systole and diastole in the brachial artery were related to coronary risk in divergent ways, the ratio thereof is a promising index of vascular function providing independent information regarding coronary risk when compared with FMD.