INTEGRATIVE RESPONSE PROFILES FOR FLOW-MEDIATED SLOWING OF BRACHIAL-RADIAL PULSE WAVE VELOCITY: TOWARDS CLINICAL INTERPRETATION OF A NON-INVASIVE VASOREACTIVITY TEST

Objective: Flow-mediated slowing (FMS) quantifies the decline in brachial-radial pulse wave velocity (PWV) during reactive hyperaemia as a non-invasive marker of macrovascular reactivity. We studied abnormal FMS profiles using reference values and integrative algorithmic analyses.Design and method: In 408 individuals (mean age, 62 years; 45% women; 65% hypertensive), we assessed FMS after 5 minutes of upper arm occlusion. We calculated the relative PWV change at 30 second interval over 4 minutes post-occlusion. From a healthy subsample (n=76), we extracted age-specific reference limits for peak PWV change, defining an abnormal peak FMS response if peak FMS was above -9.4% (if younger than 60 years) or above -4.6% (if 60 years or older). Group-based trajectory modelling (GBTM) categorized the study sample into distinct FMS response trajectories. Clinical correlates of the FMS response profiles were identified through multivariable regression. Results: Higher age related independently to smaller decline in PWV in the early phase (P<0.0076 for 0-30 seconds), while lower systolic blood pressure (SBP) and beta blocker use were linked to stronger decline in overall response (SBP: P<0.048 for 0- 210 seconds; beta blockers: P<0.014 until 180 seconds). The risk for an abnormal peak FMS (n=79, 19.4%) increased with higher SBP (adjusted OR: 1.31, P=0.0017) and decreased with the use of beta blockers (adjusted OR: 0.44, P=0.041). A 3-trajectory GBTM model identified a low, moderate and high FMS response group, while a 7-trajectory model provided more granular response categories. The risk for a low FMS response increased with age (adjusted OR: 1.58) and SBP (adjusted OR: 1.33) but decreased with beta blockers (adjusted OR: 0.46) (P<0.038). Conclusions: Integrative FMS response profiles were linked to cardiovascular risk factors such as ageing and hypertension. Beta blocker use enhanced FMS, potentially affecting clinical interpretation. Algorithmic profiling may facilitate the clinical interpretation of FMS test results.